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1 2270f ltc2270 typical application features applications description 16-bit, 20msps low noise dual adc n low power instrumentation n software defined radios n portable medical imaging n multi-channel data acquisition n two-channel simultaneously sampling adc n 84.1db snr (46v rms input referred noise) n 99db sfdr n 2.3lsb inl(max) n low power: 160mw total, 80mw per channel n single 1.8v supply n cmos, ddr cmos, or ddr lvds outputs n selectable input ranges: 1v p-p to 2.1v p-p n 200mhz full power bandwidth s/h n shutdown and nap modes n serial spi port for configuration n pin compatible with ltc2180: 16-bit, 25msps, 78mw ltc2140-14: 14-bit, 25msps, 50mw n 64-lead (9mm 9mm) qfn package the ltc ? 2270 is a two-channel simultaneous sampling 16-bit a/d converter designed for digitizing high frequency, wide dynamic range signals. it is perfect for demanding applications with ac performance that includes 84.1db snr and 99db spurious free dynamic range (sfdr). dc specs include 1lsb inl (typ), 0.2lsb dnl (typ) and no missing codes over temperature. the transition noise is 1.44lsb rms . the digital outputs can be either full rate cmos, double data rate cmos, or double data rate lvds. a separate output power supply allows the cmos output swing to range from 1.2v to 1.8v. the enc + and enc C inputs may be driven differentially or single-ended with a sine wave, pecl, lvds, ttl, or cmos inputs. an optional clock duty cycle stabilizer al- lows high performance at full speed for a wide range of clock duty cycles. l , lt, ltc, ltm, linear technology and the linear logo are registered trademarks of linear technology corporation. all other trademarks are the property of their respective owners. integral non-linearity (inl) cmos, ddr cmos or ddr lvds outputs 1.8v v dd 1.8v ov dd clock control d1_15 d1_0 2270 ta01 ch 1 analog input output drivers t t t gnd ognd s/h 16-bit adc core ch 2 analog input s/h 16-bit adc core d2_15 d2_0 t t t 20mhz clock output code 0 C2.0 C1.5 C1.0 inl error (lsb) C0.5 0.5 0.0 1.0 1.5 2.0 16384 32768 49152 65536 2270 ta02
ltc2270 2 2270f absolute maximum ratings supply voltages (v dd , ov dd ) ....................... C0.3v to 2v analog input voltage (a in + , a in C , par/ ser , sense) (note 3) .......... C0.3v to (v dd + 0.2v) digital input voltage (enc + , enc C , cs , sdi, sck) (note 4) .................................... C0.3v to 3.9v sdo (note 4) ............................................. C0.3v to 3.9v (notes 1, 2) pin configurations digital output voltage ................ C0.3v to (ov dd + 0.3v) operating temperature range ltc2270c ................................................ 0c to 70c ltc2270i ............................................. C40c to 85c storage temperature range .................. C65c to 150c full-rate cmos output mode double data rate cmos output mode top view up package 64-lead (9mm s 9mm) plastic qfn v dd 1 v cm1 2 gnd 3 a in1 + 4 a in1 C 5 gnd 6 refh 7 refl 8 refh 9 refl 10 par/ ser 11 a in2 + 12 a in2 C 13 gnd 14 v cm2 15 v dd 16 48 d1_5 47 d1_4 46 d1_3 45 d1_2 44 d1_1 43 d1_0 42 ov dd 41 ognd 40 clkout + 39 clkout C 38 d2_15 37 d2_14 36 d2_13 35 d2_12 34 d2_11 33 d2_10 65 gnd 64 v dd 63 sense 62 v ref 61 sdo 60 of1 59 of2 58 d1_15 57 d1_14 56 d1_13 55 d1_12 54 d1_11 53 d1_10 52 d1_9 51 d1_8 50 d1_7 49 d1_6 v dd 17 enc + 18 enc C 19 cs 20 sck 21 sdi 22 d2_0 23 d2_1 24 d2_2 25 d2_3 26 d2_4 27 d2_5 28 d2_6 29 d2_7 30 d2_8 31 d2_9 32 t jmax = 150c, ja = 20c/w exposed pad (pin 65) is gnd, must be soldered to pcb top view up package 64-lead (9mm s 9mm) plastic qfn v dd 1 v cm1 2 gnd 3 a in1 + 4 a in1 C 5 gnd 6 refh 7 refl 8 refh 9 refl 10 par/ ser 11 a in2 + 12 a in2 C 13 gnd 14 v cm2 15 v dd 16 48 d1_4_5 47 dnc 46 d1_2_3 45 dnc 44 d1_0_1 43 dnc 42 ov dd 41 ognd 40 clkout + 39 clkout C 38 d2_14_15 37 dnc 36 d2_12_13 35 dnc 34 d2_10_11 33 dnc 65 gnd 64 v dd 63 sense 62 v ref 61 sdo 60 of2_1 59 dnc 58 d1_14_15 57 dnc 56 d1_12_13 55 dnc 54 d1_10_11 53 dnc 52 d1_8_9 51 dnc 50 d1_6_7 49 dnc v dd 17 enc + 18 enc C 19 cs 20 sck 21 sdi 22 dnc 23 d2_0_1 24 dnc 25 d2_2_3 26 dnc 27 d2_4_5 28 dnc 29 d2_6_7 30 dnc 31 d2_8_9 32 t jmax = 150c, ja = 20c/w exposed pad (pin 65) is gnd, must be soldered to pcb
3 2270f ltc2270 order information lead free finish tape and reel part marking* package description temperature range ltc2270cup#pbf ltc2270cup#trpbf ltc2270up 64-lead (9mm 9mm) plastic qfn 0c to 70c ltc2270iup#pbf ltc2270iup#trpbf ltc2270up 64-lead (9mm 9mm) plastic qfn C40c to 85c consult ltc marketing for parts specified with wider operating temperature ranges. *the temperature grade is identified by a label on the shipping container. consult ltc marketing for information on non-standard lead based finish parts. for more information on lead free part marking, go to: http://www.linear.com/leadfree/ for more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/ double data rate lvds output mode top view up package 64-lead (9mm s 9mm) plastic qfn v dd 1 v cm1 2 gnd 3 a in1 + 4 a in1 C 5 gnd 6 refh 7 refl 8 refh 9 refl 10 par/ ser 11 a in2 + 12 a in2 C 13 gnd 14 v cm2 15 v dd 16 48 d1_4_5 + 47 d1_4_5 C 46 d1_2_3 + 45 d1_2_3 C 44 d1_0_1 + 43 d1_0_1 C 42 ov dd 41 ognd 40 clkout + 39 clkout C 38 d2_14_15 + 37 d2_14_15 C 36 d2_12_13 + 35 d2_12_13 C 34 d2_10_11 + 33 d2_10_11 C 65 gnd 64 v dd 63 sense 62 v ref 61 sdo 60 of2_1 + 59 of2_1 C 58 d1_14_15 + 57 d1_14_15 C 56 d1_12_13 + 55 d1_12_13 C 54 d1_10_11 + 53 d1_10_11 C 52 d1_8_9 + 51 d1_8_9 C 50 d1_6_7 + 49 d1_6_7 C v dd 17 enc + 18 enc C 19 cs 20 sck 21 sdi 22 d2_0_1 C 23 d2_0_1 + 24 d2_2_3 C 25 d2_2_3 + 26 d2_4_5 C 27 d2_4_5 + 28 d2_6_7 C 29 d2_6_7 + 30 d2_8_9 C 31 d2_8_9 + 32 t jmax = 150c, ja = 20c/w exposed pad (pin 65) is gnd, must be soldered to pcb pin configurations
ltc2270 4 2270f analog input the l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at t a = 25c. (note 5) symbol parameter conditions min typ max units v in analog input range (a in + C a in C ) 1.7v < v dd < 1.9v l 1 to 2.1 v p-p v in(cm) analog input common mode (a in + + a in C )/2 differential analog input (note 8) l 0.65 v cm v cm + 200mv v v sense external voltage reference applied to sense external reference mode l 0.625 1.250 1.300 v i incm analog input common mode current per pin, 20msps 32 a i in1 analog input leakage current (no encode) 0 < a in + , a in C < v dd l C1 1 a i in2 par/ ser input leakage current 0 < par/ ser < v dd l C1 1 a i in3 sense input leakage current 0.625 < sense < 1.3v l C2 2 a t ap sample-and-hold acquisition delay time 0 ns t jitter sample-and-hold acquisition delay jitter single-ended encode differential encode 85 100 fs rms fs rms cmrr analog input common mode rejection ratio 80 db bw-3b full-power bandwidth figure 5 test circuit 200 mhz converter characteristics the l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at t a = 25c. (note 5) parameter conditions min typ max units resolution (no missing codes) l 16 bits integral linearity error differential analog input (note 6) l C2.3 1 2.3 lsb differential linearity error differential analog input l C0.8 0.2 0.8 lsb offset error (note 7) l C7 1.3 7 mv gain error internal reference external reference l C1.6 1.2 C0.3 1 %fs %fs offset drift 10 v/c full-scale drift internal reference external reference 30 10 ppm/c ppm/c gain matching l C0.2 0.06 0.2 %fs offset matching l C10 1.5 10 mv transition noise 1.44 lsb rms
5 2270f ltc2270 internal reference characteristics the l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at t a = 25c. (note 5) parameter conditions min typ max units v cm output voltage i out = 0 l 0.5 ? v dd C 25mv 0.5 ? v dd 0.5 ? v dd + 25mv v v cm output temperature drift 25 ppm/c v cm output resistance C600a < i out < 1ma 4 v ref output voltage i out = 0 l 1.230 1.250 1.270 v v ref output temperature drift 25 ppm/c v ref output resistance C400a < i out < 1ma 7 v ref line regulation 1.7v < v dd < 1.9v 0.6 mv/v dynamic accuracy the l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at t a = 25c. a in = C1dbfs. (note 5) symbol parameter conditions min typ max units snr signal-to-noise ratio 1.4mhz input 5mhz input 30mhz input 70mhz input l 82.3 84.1 84.1 83.8 82.7 dbfs dbfs dbfs dbfs sfdr spurious free dynamic range, 2nd harmonic 1.4mhz input 5mhz input 30mhz input 70mhz input l 90 99 98 98 90 dbfs dbfs dbfs dbfs spurious free dynamic range, 3rd harmonic 1.4mhz input 5mhz input 30mhz input 70mhz input l 92 99 98 98 96 dbfs dbfs dbfs dbfs spurious free dynamic range, 4th harmonic or higher 1.4mhz input 5mhz input 30mhz input 70mhz input l 95 110 110 105 100 dbfs dbfs dbfs dbfs s/(n+d) signal-to-noise plus distortion ratio 1.4mhz input 5mhz input 30mhz input 70mhz input l 81.9 83.9 83.9 83.7 82.0 dbfs dbfs dbfs dbfs crosstalk 10mhz input C110 dbc
ltc2270 6 2270f digital inputs and outputs the l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at t a = 25c. (note 5) symbol parameter conditions min typ max units encode inputs (enc + , enc C ) differential encode mode (enc C not tied to gnd) v id differential input voltage (note 8) l 0.2 v v icm common mode input voltage internally set externally set (note 8) l 1.1 1.2 1.6 v v v in input voltage range enc + , enc C to gnd l 0.2 3.6 v r in input resistance (see figure 10) 10 k c in input capacitance (note 8) 3.5 pf single-ended encode mode (enc C tied to gnd) v ih high level input voltage v dd = 1.8v l 1.2 v v il low level input voltage v dd = 1.8v l 0.6 v v in input voltage range enc + to gnd l 0 3.6 v r in input resistance (see figure 11) 30 k c in input capacitance (note 8) 3.5 pf digital inputs ( cs, sdi, sck in serial or parallel programming mode. sdo in parallel programming mode) v ih high level input voltage v dd = 1.8v l 1.3 v v il low level input voltage v dd = 1.8v l 0.6 v i in input current v in = 0v to 3.6v l C10 10 a c in input capacitance (note 8) 3 pf sdo output (serial programming mode. open-drain output. requires 2k pull-up resistor if sdo is used) r ol logic low output resistance to gnd v dd = 1.8v, sdo = 0v 200 i oh logic high output leakage current sdo = 0v to 3.6v l C10 10 a c out output capacitance (note 8) 3 pf digital data outputs (cmos modes: full data rate and double data rate) ov dd = 1.8v v oh high level output voltage i o = C500a l 1.750 1.790 v v ol low level output voltage i o = 500a l 0.010 0.050 v ov dd = 1.5v v oh high level output voltage i o = C500a 1.488 v v ol low level output voltage i o = 500a 0.010 v ov dd = 1.2v v oh high level output voltage i o = C500a 1.185 v v ol low level output voltage i o = 500a 0.010 v digital data outputs (lvds mode) v od differential output voltage 100 differential load, 3.5ma mode 100 differential load, 1.75ma mode l 247 350 175 454 mv mv v os common mode output voltage 100 differential load, 3.5ma mode 100 differential load, 1.75ma mode l 1.125 1.250 1.250 1.375 v v r term on-chip termination resistance termination enabled, ov dd = 1.8v 100
7 2270f ltc2270 power requirements the l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at t a = 25c. (note 9) symbol parameter conditions min typ max units cmos output modes: full data rate and double data rate v dd analog supply voltage (note 10) l 1.7 1.8 1.9 v ov dd output supply voltage (note 10) l 1.1 1.8 1.9 v i vdd analog supply current dc input sine wave input l 89 89.5 100 ma ma i ovdd digital supply current sine wave input, ov dd = 1.2v 2 ma p diss power dissipation dc input sine wave input, ov dd = 1.2v l 160 164 180 mw mw lvds output mode v dd analog supply voltage (note 10) l 1.7 1.8 1.9 v ov dd output supply voltage (note 10) l 1.7 1.8 1.9 v i vdd analog supply current sine input, 1.75ma mode sine input, 3.5ma mode l 91 93 105 ma ma i ovdd digital supply current (0v dd = 1.8v) sine input, 1.75ma mode sine input, 3.5ma mode l 38 73 82 ma ma p diss power dissipation sine input, 1.75ma mode sine input, 3.5ma mode l 232 299 337 mw mw all output modes p sleep sleep mode power 0.5 mw p nap nap mode power 12 mw p diffclk power increase with differential encode mode enabled (no increase for nap or sleep modes) 20 mw timing characteristics the l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at t a = 25c. (note 5) symbol parameter conditions min typ max units f s sampling frequency (note 10) l 1 20 mhz t l enc low time (note 8) duty cycle stabilizer off duty cycle stabilizer on l l 23.5 2 25 25 500 500 ns ns t h enc high time (note 8) duty cycle stabilizer off duty cycle stabilizer on l l 23.5 2 25 25 500 500 ns ns t ap sample-and-hold acquisition delay time 0 ns symbol parameter conditions min typ max units digital data outputs (cmos modes: full data rate and double data rate) t d enc to data delay c l = 5pf (note 8) l 1.1 1.7 3.1 ns t c enc to clkout delay c l = 5pf (note 8) l 1 1.4 2.6 ns t skew data to clkout skew t d C t c (note 8) l 0 0.3 0.6 ns pipeline latency full data rate mode double data rate mode 6 6.5 6 6.5 cycles cycles
ltc2270 8 2270f symbol parameter conditions min typ max units digital data outputs (lvds mode) t d enc to data delay c l = 5pf (note 8) l 1.1 1.8 3.2 ns t c enc to clkout delay c l = 5pf (note 8) l 1 1.5 2.7 ns t skew data to clkout skew t d C t c (note 8) l 0 0.3 0.6 ns pipeline latency 6.5 6.5 cycles spi port timing (note 8) t sck sck period write mode readback mode, c sdo = 20pf, r pullup = 2k l l 40 250 ns ns t s cs to sck setup time l 5n s t h sck to cs setup time l 5n s t ds sdi setup time l 5n s t dh sdi hold time l 5n s t do sck falling to sdo valid readback mode, c sdo = 20pf, r pullup = 2k l 125 ns timing characteristics the l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at t a = 25c. (note 5) note 1: stresses beyond those listed under absolute maximum ratings may cause permanent damage to the device. exposure to any absolute maximum rating condition for extended periods may affect device reliability and lifetime. note 2: all voltage values are with respect to gnd with gnd and ognd shorted (unless otherwise noted). note 3: when these pin voltages are taken below gnd or above v dd , they will be clamped by internal diodes. this product can handle input currents of greater than 100ma below gnd or above v dd without latchup. note 4: when these pin voltages are taken below gnd they will be clamped by internal diodes. when these pin voltages are taken above v dd they will not be clamped by internal diodes. this product can handle input currents of greater than 100ma below gnd without latchup. note 5: v dd = ov dd = 1.8v, f sample = 20mhz, lvds outputs, differential enc + /enc C = 2v p-p sine wave, input range = 2.1v p-p with differential drive, unless otherwise noted. note 6: integral nonlinearity is defined as the deviation of a code from a best fit straight line to the transfer curve. the deviation is measured from the center of the quantization band. note 7: offset error is the offset voltage measured from C0.5 lsb when the output code flickers between 0000 0000 0000 0000 and 1111 1111 1111 1111 in 2s complement output mode. note 8: guaranteed by design, not subject to test. note 9: v dd = 1.8v, f sample = 20mhz, cmos outputs, enc + = single-ended 1.8v square wave, enc C = 0v, input range = 2.1v p-p with differential drive, 5pf load on each digital output unless otherwise noted. the supply current and power dissipation specifications are totals for the entire ic, not per channel. note 10: recommended operating conditions.
9 2270f ltc2270 typical performance characteristics integral non-linearity (inl) differential non-linearity (dnl) 64k point fft, f in = 1.4mhz, C1dbfs, 20msps output code 0 C2.0 C1.5 C1.0 inl error (lsb) C0.5 0.5 0.0 1.0 1.5 2.0 16384 32768 49152 65536 2270 g01 output code C1.0 C0.4 C0.2 C0.6 C0.8 dnl error (lsb) 0.0 0.4 0.2 0.6 0.8 1.0 2270 g02 0 16384 32768 49152 65536 frequency (mhz) C100 C140 C120 C60 C80 amplitude (dbfs) C40 0 C20 2270 g03 0 2 6 410 8 64k point fft, f in = 5.1mhz, C1dbfs, 20msps 64k point fft, f in = 10.1mhz, C1dbfs, 20msps 64k point fft, f in = 30.3mhz, C1dbfs, 20msps 64k point fft, f in = 70.3mhz, C1dbfs, 20msps 64k point 2-tone fft, f in = 14.8, 15.2mhz, C7dbfs, 20msps frequency (mhz) C100 C140 C120 C60 C80 amplitude (dbfs) C40 C20 0 2270 g04 024 6 810 frequency (mhz) C100 C140 C120 C60 C80 amplitude (dbfs) C40 C20 0 2270 g05 0 2 86 41 0 frequency (mhz) C100 C120 C140 C60 C80 amplitude (dbfs) C40 C20 0 2270 g06 0 2 6 410 8 frequency (mhz) 0 C120 C140 C80 C100 amplitude (dbfs) C60 0 C20 C40 246810 2270 g08 output code n-6 10000 5000 0 40000 35000 30000 25000 20000 15000 count n-5 n-4 n-3 n-2 n-1 n+6 n+5 n+4 n+3 n+2 n+1 n 2270 g09 shorted input histogram frequency (mhz) 0 C100 C120 C140 C60 C80 amplitude (dbfs) C40 C20 0 2 6 410 8 2270 g07
ltc2270 10 2270f typical performance characteristics sfdr vs input level, f in = 5mhz, 20msps, 2.1v range input frequency (mhz) 0 85 80 75 70 90 2nd and 3rd harmonic (dbfs) 95 105 100 20 40 60 80 100 120 140 2270 g12 2nd 3rd input level (dbfs) C80 40 60 50 80 70 130 120 110 100 90 sfdr (dbc and dbfs) C70 C40C50C60 0C10C20C30 2270 g13 dbfs dbc 0 20 40 60 80 100 120 140 input frequency (mhz) 83 82 81 80 79 85 84 snr (dbfs) 2270 g10 single-ended encode differential encode snr vs input frequency, C1dbfs, 20msps, 2.1v range i vdd vs sample rate, 5mhz, C1dbfs sine wave input on each channel i ovdd vs sample rate, 5mhz, C1dbfs sine wave input on each channel snr, sfdr vs sample rate, f in = 5mhz, C1dbfs sfdr vs analog input common mode, f in = 9.7mhz, 20msps, 2.1v range snr vs sense, f in = 5mhz, C1dbfs sample rate (msps) 0 80 70 90 100 i vdd (ma) 5 101520 2270 g14 3.5ma lvds outputs cmos outputs sample rate (msps) 0 10 0 20 30 80 70 60 50 40 i ovdd (ma) 5 101520 2270 g15 3.5ma lvds 1.75ma lvds 1.8v cmos sense pin (v) 0.6 77 78 79 80 snr (dbfs) 81 82 85 84 83 0.80.7 1 1.21.1 0.9 1.3 2270 g16 80 85 sfdr (dbfs) 90 95 100 2270 g17 input common mode (v) 0.6 0.80.7 0.9 1.11 1.2 v dd 1.9v v dd 1.7v sample rate (msps) 0 80 90 snr, sfdr (dbfs) 100 110 10 51520 2270 g18 sfdr snr 020 60 40 80 100 120 140 input frequency (mhz) 95 90 85 80 75 70 105 100 2nd and 3rd harmonic (dbfs) 2270 g11 2nd 3rd 2nd, 3rd harmonic vs input frequency, C1dbfs, 20msps, 2.1v range 2nd, 3rd harmonic vs input frequency, C1dbfs, 20msps, 1.05v range
11 2270f ltc2270 pins that are the same for all digital output modes v dd (pins 1, 16, 17, 64): analog power supply, 1.7v to 1.9v. bypass to ground with 0.1f ceramic capacitors. adjacent pins can share a bypass capacitor. v cm1 (pin 2): common mode bias output, nominally equal to v dd /2. v cm1 should be used to bias the common mode of the analog inputs to channel 1. bypass to ground with a 1f ceramic capacitor. gnd (pins 3, 6, 14): adc power ground. a in1 + (pin 4): channel 1 positive differential analog input. a in1 C (pin 5): channel 1 negative differential analog input. refh (pins 7, 9): adc high reference. see the applica- tions information section for recommended bypassing circuits for refh and refl. refl (pins 8, 10): adc low reference. see the applica- tions information section for recommended bypassing circuits for refh and refl. par/ ser (pin 11): programming mode selection pin. con- nect to ground to enable the serial programming mode. cs , sck, sdi, sdo become a serial interface that control the a/d operating modes. connect to v dd to enable the parallel programming mode where cs, sck, sdi, sdo become parallel logic inputs that control a reduced set of the a/d operating modes. par/ ser should be connected directly to ground or v dd and not be driven by a logic signal. a in2 + (pin 12): channel 2 positive differential analog input. a in2 C (pin 13): channel 2 negative differential analog input. v cm2 (pin 15): common mode bias output, nominally equal to v dd /2. v cm2 should be used to bias the common mode of the analog inputs to channel 2. bypass to ground with a 1f ceramic capacitor. enc + (pin 18): encode input. conversion starts on the rising edge. enc C (pin 19): encode complement input. conversion starts on the falling edge. tie to gnd for single-ended encode mode. cs (pin 20): in serial programming mode, (par/ser = 0v), cs is the serial interface chip select input. when cs is low, sck is enabled for shifting data on sdi into the mode control registers. in the parallel programming mode (par/ ser = v dd ), cs controls the clock duty cycle stabilizer (see table 2). cs can be driven with 1.8v to 3.3v logic. sck (pin 21): in serial programming mode, (par/ser = 0v), sck is the serial interface clock input. in the parallel programming mode (par/ ser = v dd ), sck controls the digital output mode. (see table 2). sck can be driven with 1.8v to 3.3v logic. sdi (pin 22): in serial programming mode, (par/ser = 0v), sdi is the serial interface data input. data on sdi is clocked into the mode control registers on the rising edge of sck. in the parallel programming mode (par/ ser = v dd ), sdi can be used together with sdo to power down the part (see table 2). sdi can be driven with 1.8v to 3.3v logic. ognd (pin 41): output driver ground. must be shorted to the ground plane by a very low inductance path. use multiple vias close to the pin. ov dd (pin 42): output driver supply. bypass to ground with a 0.1f ceramic capacitor. sdo (pin 61): in serial programming mode, (par/ser = 0v), sdo is the optional serial interface data output. data on sdo is read back from the mode control regis- ters and can be latched on the falling edge of sck. sdo is an open-drain nmos output that requires an external 2k pull-up resistor to 1.8v C 3.3v. if read back from the mode control registers is not needed, the pull-up resistor is not necessary and sdo can be left unconnected. in the parallel programming mode (par/ ser = v dd ), sdo can be used together with sdi to power down the part (see table 2). when used as an input, sdo can be driven with 1.8v to 3.3v logic through a 1k series resistor. pin functions
ltc2270 12 2270f pin functions v ref (pin 62): reference voltage output. bypass to ground with a 2.2f ceramic capacitor. the output voltage is nominally 1.25v. sense (pin 63): reference programming pin. connecting sense to v dd selects the internal reference and a 1.05v input range. connecting sense to ground selects the internal reference and a 0.525v input range. an external reference between 0.625v and 1.3v applied to sense selects an input range of 0.84 ? v sense . ground (exposed pad pin 65): the exposed pad must be soldered to the pcb ground. full-rate cmos output mode all pins below have cmos output levels (ognd to ov dd ) d2_0 to d2_15 (pins 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38): channel 2 digital outputs. d2_15 is the msb. clkout C (pin 39): inverted version of clkout + . clkout + (pin 40): data output clock. the digital outputs normally transition at the same time as the falling edge of clkout + . the phase of clkout + can also be delayed relative to the digital outputs by programming the mode control registers. d1_0 to d1_15 (pins 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58): channel 1 digital outputs. d1_15 is the msb. of2 (pin 59): channel 2 over/under flow digital output. of2 is high when an overflow or underflow has occurred. of1 (pin 60): channel 1 over/under flow digital output. of1 is high when an overflow or underflow has occurred. double data rate cmos output mode all pins below have cmos output levels (ognd to ov dd ) d2_0_1 to d2_14_15 (pins 24, 26, 28, 30, 32, 34, 36, 38): channel 2 double data rate digital outputs. two data bits are multiplexed onto each output pin. the even data bits (d0, d2, d4, d6, d8, d10, d12, d14) appear when clkout + is low. the odd data bits (d1, d3, d5, d7, d9, d11, d13, d15) appear when clkout + is high. dnc (pins 23, 25, 27, 29, 31, 33, 35, 37, 43, 45, 47, 49, 51, 53, 55, 57, 59): do not connect these pins. clkout C (pin 39): inverted version of clkout + . clkout + (pin 40): data output clock. the digital outputs normally transition at the same time as the falling and ris- ing edges of clkout + . the phase of clkout + can also be delayed relative to the digital outputs by programming the mode control registers. d1_0_1 to d1_14_15 (pins 44, 46, 48, 50, 52, 54, 56, 58): channel 1 double data rate digital outputs. two data bits are multiplexed onto each output pin. the even data bits (d0, d2, d4, d6, d8, d10, d12, d14) appear when clkout + is low. the odd data bits (d1, d3, d5, d7, d9, d11, d13, d15) appear when clkout + is high. of2_1 (pin 60): over/under flow digital output. of2_1 is high when an overflow or underflow has occurred. the over/under flow for both channels are multiplexed onto this pin. channel 2 appears when clkout + is low, and channel 1 appears when clkout + is high.
13 2270f ltc2270 double data rate lvds output mode all pins below have lvds output levels. the output current level is programmable. there is an optional internal 100 termination resistor between the pins of each lvds output pair. d2_0_1 C /d2_0_1 + to d2_14_15 C /d2_14_15 + (pins 23/24, 25/26, 27/28, 29/30, 31/32, 33/34, 35/36, 37/38): chan- nel 2 double data rate digital outputs. two data bits are multiplexed onto each differential output pair. the even data bits (d0, d2, d4, d6, d8, d10, d12, d14) appear when clkout + is low. the odd data bits (d1, d3, d5, d7, d9, d11, d13, d15) appear when clkout + is high. clkout C /clkout + (pins 39/40): data output clock. the digital outputs normally transition at the same time as the falling and rising edges of clkout + . the phase of clkout + can also be delayed relative to the digital outputs by programming the mode control registers. d1_0_1 C /d1_0_1 + to d1_14_15 C /d1_14_15 + (pins 43/44, 45/46, 47/48, 49/50, 51/52, 53/54, 55/56, 57/58): chan- nel 1 double data rate digital outputs. two data bits are multiplexed onto each differential output pair. the even data bits (d0, d2, d4, d6, d8, d10, d12, d14) appear when clkout + is low. the odd data bits (d1, d3, d5, d7, d9, d11, d13, d15) appear when clkout + is high. of2_1 C /of2_1 + (pins 59/60): over/under flow digital output. of2_1 + is high when an overflow or underflow has occurred. the over/under flow for both channels are multiplexed onto this pin. channel 2 appears when clkout + is low, and channel 1 appears when clkout + is high. pin functions
ltc2270 14 2270f functional block diagram diff ref amp ref buf 2.2f 1f 1f internal clock signals refh refl clock/duty cycle control range select 1.25v reference enc + refh refl enc C correction logic sdo cs ognd of1 ov dd d1_15 clkout C clkout + d1_0 2270 f01 sense v ref ch 1 analog input 2.2f v cm1 1f v dd /2 output drivers mode control registers sck par/ ser sdi t t t gnd s/h 16-bit adc core ch 2 analog input s/h 16-bit adc core v cm2 1f of2 d2_15 d2_0 t t t v dd figure 1. functional block diagram
15 2270f ltc2270 full-rate cmos output mode timing all outputs are single-ended and have cmos levels timing diagrams t h t d t c t l b C 6 b C 5 b C 4 b C 3 b C 2 t ap a + 1 a + 2 a + 4 a + 3 a ch 1 analog input enc C enc + clkout + clkout C d2_0 - d2_15, of2 t ap b + 1 b + 2 b + 4 b + 3 b ch 2 analog input a C 6 a C 5 a C 4 a C 3 a C 2 d1_0 - d1_15, of1 2270 td01
ltc2270 16 2270f timing diagrams double data rate cmos output mode timing all outputs are single-ended and have cmos levels t d t t t t d t c t c t l bit 0 a-6 bit 1 a-6 bit 0 a-5 bit 1 a-5 bit 0 a-4 bit 1 a-4 bit 0 a-3 bit 1 a-3 bit 0 a-2 bit 14 a-6 bit 15 a-6 bit 14 a-5 bit 15 a-5 bit 14 a-4 bit 15 a-4 bit 14 a-3 bit 15 a-3 bit 14 a-2 enc C enc + d1_0_1 d1_14_15 t t t bit 0 b-6 bit 1 b-6 bit 0 b-5 bit 1 b-5 bit 0 b-4 bit 1 b-4 bit 0 b-3 bit 1 b-3 bit 0 b-2 bit 14 b-6 bit 15 b-6 bit 14 b-5 bit 15 b-5 bit 14 b-4 bit 15 b-4 bit 14 b-3 bit 15 b-3 bit 14 b-2 of b-6 of a-6 of b-5 of a-5 of b-4 of a-4 of b-3 of a-3 of b-2 d2_0_1 d2_14_15 clkout + clkout C of2_1 2270 td02 t h t ap a + 1 a + 2 a + 4 a + 3 a ch 1 analog input t ap b + 1 b + 2 b + 4 b + 3 b ch 2 analog input
17 2270f ltc2270 timing diagrams double data rate lvds output mode timing all outputs are differential and have lvds levels t d t t t t d t c t c t l bit 0 a-6 bit 1 a-6 bit 0 a-5 bit 1 a-5 bit 0 a-4 bit 1 a-4 bit 0 a-3 bit 1 a-3 bit 0 a-2 bit 14 a-6 bit 15 a-6 bit 14 a-5 bit 15 a-5 bit 14 a-4 bit 15 a-4 bit 14 a-3 bit 15 a-3 bit 14 a-2 enc C enc + d1_0_1 + d1_14_15 + t t t bit 0 b-6 bit 1 b-6 bit 0 b-5 bit 1 b-5 bit 0 b-4 bit 1 b-4 bit 0 b-3 bit 1 b-3 bit 0 b-2 bit 14 b-6 bit 15 b-6 bit 14 b-5 bit 15 b-5 bit 14 b-4 bit 15 b-4 bit 14 b-3 bit 15 b-3 bit 14 b-2 of b-6 of a-6 of b-5 of a-5 of b-4 of a-4 of b-3 of a-3 of b-2 d2_0_1 + d2_14_15 + clkout + clkout C of2_1 + d1_0_1 C d1_14_15 C d2_0_1 C d2_14_15 C of2_1 C 2270 td03 t h t ap a + 1 a + 2 a + 4 a + 3 a ch 1 analog input t ap b + 1 b + 2 b + 4 b + 3 b ch 2 analog input
ltc2270 18 2270f a6 t s t ds a5 a4 a3 a2 a1 a0 xx d7 d6 d5 d4 d3 d2 d1 d0 xx xx xx xx xx xx xx cs sck sdi r/w sdo high impedance spi port timing (readback mode) spi port timing (write mode) t dh t do t sck t h a6 a5 a4 a3 a2 a1 a0 d7 d6 d5 d4 d3 d2 d1 d0 2270 td04 cs sck sdi r/w sdo high impedance timing diagrams
19 2270f ltc2270 converter operation the ltc2270 is a low power, two-channel, 16-bit, 20msps a/d converter that is powered by a single 1.8v supply. the analog inputs must be driven differentially. the encode input can be driven differentially, or single ended for lower power consumption. the digital outputs can be cmos, double data rate cmos (to halve the number of output lines), or double data rate lvds (to reduce digital noise in the system.) many additional features can be chosen by programming the mode control registers through a serial spi port. analog input the analog inputs are differential cmos sample-and-hold circuits (figure 2). the inputs should be driven differen- tially around a common mode voltage set by the v cm1 or v cm2 output pins, which are nominally v dd /2. for the 2.1v input range, the inputs should swing from v cm C 525mv to v cm + 525mv. there should be 180 phase difference between the inputs. the two channels are simultaneously sampled by a shared encode circuit (figure 2). input drive circuits input filtering if possible, there should be an rc lowpass filter right at the analog inputs. this lowpass filter isolates the drive circuitry from the a/d sample-and-hold switching, and also limits wideband noise from the drive circuitry. figure 3 shows an example of an input rc filter. the rc component values should be chosen based on the applications input frequency. transformer coupled circuits figure 3 shows the analog input being driven by an rf transformer with a center-tapped secondary. the center tap is biased with v cm , setting the a/d input at its optimal dc level. at higher input frequencies a transmission line balun transformer (figure 4 to figure 5) has better balance, resulting in lower a/d distortion. c sample 17pf r on 24 r on 24 v dd v dd ltc2270 a in + 2270 f02 c sample 17pf v dd a in C enc C enc + 1.2v 10k 1.2v 10k c parasitic 1.8pf c parasitic 1.8pf 10 10 25 25 25 25 50 0.1f a in + a in C 12pf 1f v cm ltc2270 analog input 0.1f t1 1:1 t1: ma/com mabaes0060 resistors, capacitors are 0402 package size 2270 f03 figure 2. equivalent input circuit. only one of the two analog channels is shown figure 3. analog input circuit using a transformer. recommended for input frequencies from 1mhz to 40mhz applications information
ltc2270 20 2270f applications information figure 5. recommended front-end circuit for input frequencies above 80mhz amplifier circuits figure 6 shows the analog input being driven by a high speed differential amplifier. the output of the amplifier is ac-coupled to the a/d so the amplifiers output common mode voltage can be optimally set to minimize distortion. if dc coupling is necessary, use a differential amplifier with an output common mode set by the ltc2270 v cm pin (figure 7). figure 4. recommended front-end circuit for input frequencies from 5mhz to 80mhz reference the ltc2270 has an internal 1.25v voltage reference. for a 2.1v input range using the internal reference, connect sense to v dd . for a 1.05v input range using the internal reference, connect sense to ground. for a 2.1v input range with an external reference, apply a 1.25v reference voltage to sense (figure 9). the input range can be adjusted by applying a voltage to sense that is between 0.625v and 1.30v. the input range will then be 1.68 ? v sense . the v ref , refh and refl pins should be bypassed as shown in figure 8. a low inductance 2.2f interdigitated capacitor is recommended for the bypass between refh and refl. this type of capacitor is available at a low cost from multiple suppliers. 25 12 12 25 50 0.1f a in + a in C 8.2pf 1f v cm analog input 0.1f 0.1f t1 t2 t1: ma/com maba-007159-000000 t2: coilcraft wbc1-1tl resistors, capacitors are 0402 package size 2270 f04 ltc2270 25 25 50 0.1f a in + a in C 1.8pf 1f v cm analog input 0.1f 0.1f t1 t2 t1: ma/com maba-007159-000000 t2: coilcraft wbc1-1tl resistors, capacitors are 0402 package size 2270 f05 ltc2270 25 25 200 200 0.1f a in + a in C 1f 12pf 12pf v cm ltc2270 2270 f06 C C + + analog input high speed differential amplifier 0.1f 25 25 a in + a in C 1f 25pf 25pf v cm ltc2270 2270 f07 C + + C analog input cm figure 6. front-end circuit using a high speed differential amplifier figure 7. dc-coupled amplifier
21 2270f ltc2270 applications information v ref refh refh sense c1 tie to v dd for 2.1v range; tie to gnd for 1.05v range; 3"/(&t7 sense for 0.625v < v sense < 1.300v 1.25v refl refl internal adc high reference buffer 2270 f08a ltc2270 5 0.84x diff amp internal adc low reference c1: 2.2f low inductance interdigitated capacitor tdk clle1ax7s0g225m murata lla219c70g225m avx w2l14z225m or equivalent 1.25v bandgap reference 0.625v range detect and control 2.2f c2 1 f c3 1f + + C C C C + + figure 8a. reference circuit sense 1.25v external reference 2.2f 1f v ref 2270 f09 ltc2270 figure 9. using an external 1.25v reference refh refh refl refl 2270 f08b ltc2270 capacitors are 0402 package size c3 1f c1 2.2f c2 1f figure 8b. alternative refh/refl bypass circuit figure 8c. recommended layout for the refh/refl bypass circuit in figure 8a alternatively c1 can be replaced by a standard 2.2f capacitor between refh and refl (see figure 8b). the capacitors should be as close to the pins as possible (not on the back side of the circuit board). figure 8c and figure 8d show the recommended circuit board layout for the refh/refl bypass capacitors. note that in figure 8c, every pin of the interdigitated capacitor (c1) is connected since the pins are not internally connected in some vendors capacitors. in figure 8d the refh and figure 8d. recommended layout for the refh/refl bypass circuit in figure 8b encode inputs the signal quality of the encode inputs strongly affects the a/d noise performance. the encode inputs should be treated as analog signals C do not route them next to digital traces on the circuit board. there are two modes of operation for the encode inputs: the differential encode mode (figure 10), and the single-ended encode mode (figure 11). the differential encode mode is recommended for si- nusoidal, pecl, or lvds encode inputs (figure 12 and figure 13). the encode inputs are internally biased to 1.2v through 10k equivalent resistance. the encode inputs can be taken above v dd (up to 3.6v), and the common mode range is from 1.1v to 1.6v. in the differential encode refl pins are connected by short jumpers in an internal layer. to minimize the inductance of these jumpers they can be placed in a small hole in the gnd plane on the second board layer. ltc2270 f08c ltc2270 f08d
ltc2270 22 2270f 50 100 0.1f t1 = ma/com etc1-1-13 resistors and capacitors are 0402 package size 50 ltc2270 2270 f12 enc C enc + 0.1f 0.1f t1 figure 12. sinusoidal encode drive enc + enc C pecl or lvds clock 0.1f 0.1f 2270 f13 ltc2270 figure 13. pecl or lvds encode drive v dd ltc2270 2270 f10 enc C enc + 15k v dd differential comparator 30k figure 10. equivalent encode input circuit for differential encode mode 30k enc + enc C 2270 f11 0v 1.8v to 3.3v ltc2270 cmos logic buffer figure 11. equivalent encode input circuit for single-ended encode mode mode, enc C should stay at least 200mv above ground to avoid falsely triggering the single ended encode mode. for good jitter performance enc + and enc C should have fast rise and fall times. the single-ended encode mode should be used with cmos encode inputs. to select this mode, enc C is connected to ground and enc + is driven with a square wave encode input. enc + can be taken above v dd (up to 3.6v) so 1.8v to 3.3v cmos logic levels can be used. the enc + threshold is 0.9v. for good jitter performance enc + should have fast rise and fall times. if the encode signal is turned off or drops below approxi- mately 500khz, the a/d enters nap mode. clock duty cycle stabilizer for good performance the encode signal should have a 50% (5%) duty cycle. if the optional clock duty cycle stabilizer circuit is enabled, the encode duty cycle can vary from 10% to 90% and the duty cycle stabilizer will maintain a constant 50% internal duty cycle. if the encode signal changes frequency, the duty cycle stabilizer circuit requires one hundred clock cycles to lock onto the input clock. the duty cycle stabilizer is enabled by mode control register a2 (serial programming mode), or by cs (parallel programming mode). for applications where the sample rate needs to be changed quickly, the clock duty cycle stabilizer can be disabled. if the duty cycle stabilizer is disabled, care should be taken to make the sampling clock have a 50% (5%) duty cycle. the duty cycle stabilizer should not be used below 2msps. digital outputs digital output modes the ltc2270 can operate in three digital output modes: full rate cmos, double data rate cmos (to halve the number of output lines), or double data rate lvds (to reduce digital noise in the system.) the output mode is set by mode control register a3 (serial programming mode), or by sck (parallel programming mode). note that double data rate cmos cannot be selected in the parallel programming mode. applications information
23 2270f ltc2270 applications information full rate cmos mode in full rate cmos mode the data outputs (d1_0 to d1_15 and d2_0 to d2_15), overflow (of2, of1), and the data output clocks (clkout + , clkout C ) have cmos output levels. the outputs are powered by ov dd and ognd which are isolated from the a/d core power and ground. ov dd can range from 1.1v to 1.9v, allowing 1.2v through 1.8v cmos logic outputs. for good performance the digital outputs should drive minimal capacitive loads. if the load capacitance is larger than 10pf a digital buffer should be used. double data rate cmos mode in double data rate cmos mode, two data bits are multi- plexed and output on each data pin. this reduces the num- ber of digital lines by seventeen, simplifying board routing and reducing the number of input pins needed to receive the data. the data outputs (d1_0_1, d1_2_3, d1_4_5, d1_6_7, d1_8_9, d1_10_11, d1_12_13, d1_14_15, d2_0_1, d2_2_3, d2_4_5, d2_6_7, d2_8_9, d2_10_11, d2_12_13, d2_14_15), overflow (of2_1), and the data output clocks (clkout + , clkout C ) have cmos output levels. the outputs are powered by ov dd and ognd which are isolated from the a/d core power and ground. ov dd can range from 1.1v to 1.9v, allowing 1.2v through 1.8v cmos logic outputs. note that the overflow for both adc channels is multiplexed onto the of2_1 pin. for good performance the digital outputs should drive minimal capacitive loads. if the load capacitance is larger than 10pf a digital buffer should be used. double data rate lvds mode in double data rate lvds mode, two data bits are multi- plexed and output on each differential output pair. there are eight lvds output pairs per adc channel (d1_0_1 + / d1_0_1 C through d1_14_15 + /d1_14_15 C and d2_0_1 + / d2_0_1 C through d2_14_15 + /d2_14_15 C ) for the digital output data. overflow (of2_1 + /of2_1 C ) and the data output clock (clkout + /clkout C ) each have an lvds output pair. note that the overflow for both adc channels is multiplexed onto the of2_1 + /of2_1 C output pair. by default the outputs are standard lvds levels: 3.5ma output current and a 1.25v output common mode volt- age. an external 100 differential termination resistor is required for each lvds output pair. the termination resistors should be located as close as possible to the lvds receiver. the outputs are powered by ov dd and ognd which are isolated from the a/d core power and ground. in lvds mode, ov dd must be 1.8v. programmable lvds output current in lvds mode, the default output driver current is 3.5ma. this current can be adjusted by serially programming mode control register a3. available current levels are 1.75ma, 2.1ma, 2.5ma, 3ma, 3.5ma, 4ma and 4.5ma. optional lvds driver internal termination in most cases using just an external 100 termination resistor will give excellent lvds signal integrity. in addi- tion, an optional internal 100 termination resistor can be enabled by serially programming mode control register a3. the internal termination helps absorb any reflections caused by imperfect termination at the receiver. when the internal termination is enabled, the output driver current is doubled to maintain the same output voltage swing. overflow bit the overflow output bit outputs a logic high when the analog input is either over-ranged or under-ranged. the overflow bit has the same pipeline latency as the data bits. in full-rate cmos mode each adc channel has its own overflow pin (of1 for channel 1, of2 for channel 2). in ddr cmos or ddr lvds mode the overflow for both adc channels is multiplexed onto the of2_1 output.
ltc2270 24 2270f applications information phase shifting the output clock in full rate cmos mode the data output bits normally change at the same time as the falling edge of clkout + , so the rising edge of clkout + can be used to latch the output data. in double data rate cmos and lvds modes the data output bits normally change at the same time as the falling and rising edges of clkout + . to allow adequate set-up and hold time when latching the data, the clkout + signal may need to be phase shifted relative to the data output bits. most fpgas have this feature; this is generally the best place to adjust the timing. the ltc2270 can also phase shift the clkout + /clkout C signals by serially programming mode control register a2. the output clock can be shifted by 0, 45, 90, or 135. to use the phase shifting feature the clock duty cycle stabilizer must be turned on. another control register bit can invert the polarity of clkout + and clkout C , independently of the phase shift. the combination of these two features enables phase shifts of 45 up to 315 (figure 14). data format table 1 shows the relationship between the analog input voltage, the digital data output bits and the overflow bit. by default the output data format is offset binary. the 2s complement format can be selected by serially program- ming mode control register a4. table 1. output codes vs input voltage a in + C a in C (2v range) of d15-d0 (offset binary) d15-d0 (2s complement) >1.000000v +0.999970v +0.999939v 1 0 0 1111 1111 1111 1111 1111 1111 1111 1111 1111 1111 1111 1110 0111 1111 1111 1111 0111 1111 1111 1111 0111 1111 1111 1110 +0.000030v +0.000000v C0.000030v C0.000061v 0 0 0 0 1000 0000 0000 0001 1000 0000 0000 0000 0111 1111 1111 1111 0111 1111 1111 1110 0000 0000 0000 0001 0000 0000 0000 0000 1111 1111 1111 1111 1111 1111 1111 1110 C0.999939v C1.000000v 25 2270f ltc2270 digital output randomizer interference from the a/d digital outputs is sometimes unavoidable. digital interference may be from capacitive or inductive coupling or coupling through the ground plane. even a tiny coupling factor can cause unwanted tones in the adc output spectrum. by randomizing the digital output before it is transmitted off chip, these unwanted tones can be randomized which reduces the unwanted tone amplitude. the digital output is randomized by applying an exclusive- or logic operation between the lsb and all other data output bits. to decode, the reverse operation is applied C an exclusive-or operation is applied between the lsb and all other bits. the lsb, of and clkout outputs are not affected. the output randomizer is enabled by serially programming mode control register a4. alternate bit polarity another feature that reduces digital feedback on the circuit board is the alternate bit polarity mode. when this mode is enabled, all of the odd bits (d1, d3, d5, d7, d9, d11, d13, d15) are inverted before the output buffers. the even bits (d0, d2, d4, d6, d8, d10, d12, d14), of and clkout are not affected. this can reduce digital currents in the circuit board ground plane and reduce digital noise, particularly for very small analog input signals. when there is a very small signal at the input of the a/d that is centered around mid-scale, the digital outputs toggle between mostly 1s and mostly 0s. this simultaneous switching of most of the bits will cause large currents in the ground plane. by inverting every other bit, the alternate bit polarity mode makes half of the bits transition high while half of the bits transition low. this cancels current flow in the ground plane, reducing the digital noise. the digital output is decoded at the receiver by inverting the odd bits (d1, d3, d5, d7, d9, d11, d13, d15.) the alternate bit polarity mode is independent of the digital output randomizer C either, both or neither function can be on at the same time. the alternate bit polarity mode is enabled by serially programming mode control register a4. applications information clkout clkout of d15/d0 d14/d0 t t t d2/d0 d1/d0 d0 2270 f15 of d15 d14 d2 d1 d0 randomizer on d15 fpga pc board d14 t t t d2 d1 d0 2270 f16 d0 d1/d0 d2/d0 d14/d0 d15/d0 of clkout ltc2270 figure 15. functional equivalent of digital output randomizer figure 16. decoding a randomized digital output signal
ltc2270 26 2270f allowed so the on-chip references can settle from the slight temperature shift caused by the change in supply current as the a/d leaves nap mode. either channel 2 or both channels can be placed in nap mode; it is not possible to have channel 1 in nap mode and channel 2 operating normally. sleep mode and nap mode are enabled by mode control register a1 (serial programming mode), or by sdi and sdo (parallel programming mode). device programming modes the operating modes of the ltc2270 can be programmed by either a parallel interface or a simple serial interface. the serial interface has more flexibility and can program all available modes. the parallel interface is more limited and can only program some of the more commonly used modes. parallel programming mode to use the parallel programming mode, par/ ser should be tied to v dd . the cs , sck, sdi and sdo pins are binary logic inputs that set certain operating modes. these pins can be tied to v dd or ground, or driven by 1.8v, 2.5v, or 3.3v cmos logic. when used as an input, sdo should be driven through a 1k series resistor. table 2 shows the modes set by cs, sck, sdi and sdo. table 2. parallel programming mode control bits (par/ ser = v dd ) pin description cs clock duty cycle stabilizer control bit 0 = clock duty cycle stabilizer off 1 = clock duty cycle stabilizer on sck digital output mode control bit 0 = full-rate cmos output mode 1 = double data rate lvds output mode (3.5ma lvds current, internal termination off) sdi/sdo power down c ontrol bit 00 = normal operation 01 = channel 1 in normal operation, channel 2 in nap mode 10 = channel 1 and channel 2 in nap mode 11 = sleep mode (entire device powered down) applications information digital output test patterns to allow in-circuit testing of the digital interface to the a/d, there are several test modes that force the a/d data outputs (of, d15-d0) to known values: all 1s: all outputs are 1 all 0s: all outputs are 0 alternating: outputs change from all 1s to all 0s on alternating samples. checkerboard: outputs change from 10101010101010101 to 01010101010101010 on alternating samples. the digital output test patterns are enabled by serially programming mode control register a4. when enabled, the test patterns override all other formatting modes: 2s complement, randomizer, alternate bit polarity. output disable the digital outputs may be disabled by serially program- ming mode control register a3. all digital outputs including of and clkout are disabled. the high-impedance disabled state is intended for in-circuit testing or long periods of inactivity C it is too slow to multiplex a data bus between multiple converters at full speed. when the outputs are disabled both channels should be put into either sleep or nap mode. sleep and nap modes the a/d may be placed in sleep or nap modes to conserve power. in sleep mode the entire device is powered down, resulting in 0.5mw power consumption. the amount of time required to recover from sleep mode depends on the size of the bypass capacitors on v ref , refh, and refl. for the suggested values in fig. 8, the a/d will stabilize after 2ms. in nap mode the a/d core is powered down while the internal reference circuits stay active, allowing faster wakeup than from sleep mode. recovering from nap mode requires at least 100 clock cycles. if the application demands very accurate dc settling then an additional 50s should be
27 2270f ltc2270 serial programming mode to use the serial programming mode, par/ ser should be tied to ground. the cs, sck, sdi and sdo pins become a serial interface that program the a/d mode control registers. data is written to a register with a 16-bit serial word. data can also be read back from a register to verify its contents. serial data transfer starts when cs is taken low. the data on the sdi pin is latched at the first 16 rising edges of sck. any sck rising edges after the first 16 are ignored. the data transfer ends when cs is taken high again. the first bit of the 16-bit input word is the r/ w bit. the next seven bits are the address of the register (a6:a0). the final eight bits are the register data (d7:d0). if the r/w bit is low, the serial data (d7:d0) will be writ- ten to the register set by the address bits (a6:a0). if the r/w bit is high, data in the register set by the address bits (a6:a0) will be read back on the sdo pin (see the timing diagrams). during a read back command the register is not updated and data on sdi is ignored. the sdo pin is an open drain output that pulls to ground with a 200 impedance. if register data is read back through sdo, an external 2k pull-up resistor is required. if serial data is only written and read back is not needed, then sdo can be left floating and no pull-up resistor is needed. table 3 shows a map of the mode control registers. software reset if serial programming is used, the mode control registers should be programmed as soon as possible after the power supplies turn on and are stable. the first serial command must be a software reset which will reset all register data bits to logic 0. to perform a software reset, bit d7 in the reset register is written with a logic 1. after the reset spi write command is complete, bit d7 is automatically set back to zero. grounding and bypassing the ltc2270 requires a printed circuit board with a clean unbroken ground plane. a multilayer board with an in- ternal ground plane in the first layer beneath the adc is recommended. layout for the printed circuit board should ensure that digital and analog signal lines are separated as much as possible. in particular, care should be taken not to run any digital track alongside an analog signal track or underneath the adc. high quality ceramic bypass capacitors should be used at the v dd , ov dd , v cm , v ref , refh and refl pins. bypass capacitors must be located as close to the pins as possible. size 0402 ceramic capacitors are recommended. the traces connecting the pins and bypass capacitors must be kept short and should be made as wide as possible. of particular importance is the capacitor between refh and refl. this capacitor should be on the same side of the circuit board as the a/d, and as close to the device as possible. the analog inputs, encode signals, and digital outputs should not be routed next to each other. ground fill and grounded vias should be used as barriers to isolate these signals from each other. heat transfer most of the heat generated by the ltc2270 is transferred from the die through the bottom-side exposed pad and package leads onto the printed circuit board. for good electrical and thermal performance, the exposed pad must be soldered to a large grounded pad on the pc board. this pad should be connected to the internal ground planes by an array of vias. applications information
ltc2270 28 2270f applications information table 3. serial programming mode register map (par/ ser = gnd) register a0: reset register (address 00h) d7 d6 d5 d4 d3 d2 d1 d0 resetxxxxxxx bit 7 reset software reset bit 0 = not used 1 = software reset. all mode control registers are reset to 00h. the adc is momentarily placed in sleep mode. this bit is automatically set back to zero at the end of the spi write command. the reset register is write-only. data read back from the reset register will be random. bits 6-0 unused, dont care bits. register a1: power-down register (address 01h) d7 d6 d5 d4 d3 d2 d1 d0 xxxxxxp wroff1 pwroff0 bits 7-2 unused, dont care bits. bits 1-0 pwroff1:pwroff0 power down control bits 00 = normal operation 01 = channel 1 in normal operation, channel 2 in nap mode 10 = channel 1 and channel 2 in nap mode 11 = sleep mode register a2: timing register (address 02h) d7 d6 d5 d4 d3 d2 d1 d0 xxxxc lkinv clkphase1 clkphase0 dcs bits 7-4 unused, dont care bits. bit 3 clkinv output clock invert bit 0 = normal clkout polarity (as shown in the timing diagrams) 1 = inverted clkout polarity bits 2-1 clkphase1:clkphase0 output clock phase delay bits 00 = no clkout delay (as shown in the timing diagrams) 01 = clkout + /clkout C delayed by 45 (clock period ? 1/8) 10 = clkout + /clkout C delayed by 90 (clock period ? 1/4) 11 = clkout + /clkout C delayed by 135 (clock period ? 3/8) note: if the clkout phase delay feature is used, the clock duty cycle stabilizer must also be turned on bit 0 dcs clock duty cycle stabilizer bit 0 = clock duty cycle stabilizer off 1 = clock duty cycle stabilizer on
29 2270f ltc2270 register a3: output mode register (address 03h) d7 d6 d5 d4 d3 d2 d1 d0 x ilvds2 ilvds1 ilvds0 termon outoff outmode1 outmode0 bit 7 unused, dont care bit. bits 6-4 ilvds2:ilvds0 lvds output current bits 000 = 3.5ma lvds output driver current 001 = 4.0ma lvds output driver current 010 = 4.5ma lvds output driver current 011 = not used 100 = 3.0ma lvds output driver current 101 = 2.5ma lvds output driver current 110 = 2.1ma lvds output driver current 111 = 1.75ma lvds output driver current bit 3 termon lvds internal termination bit 0 = internal termination off 1 = internal termination on. lvds output driver current is 2 the current set by ilvds2:ilvds0 bit 2 outoff output disable bit 0 = digital outputs are enabled 1 = digital outputs are disabled and have high output impedance note: if the digital outputs are disabled the part should also be put in sleep or nap mode (both channels). bits 1-0 outmode1:outmode0 digital output mode control bits 00 = full-rate cmos output mode 01 = double data rate lvds output mode 10 = double data rate cmos output mode 11 = not used register a4: data format register (address 04h) d7 d6 d5 d4 d3 d2 d1 d0 x x outtest2 outtest1 outtest0 abp rand twoscomp bit 7-6 unused, dont care bits. bits 5-3 outtest2:outtest0 digital output test pattern bits 000 = digital output test patterns off 001 = all digital outputs = 0 011 = all digital outputs = 1 101 = checkerboard output pattern. of, d15-d0 alternate between 1 0101 0101 0101 0101 and 0 1010 1010 1010 1010 111 = alternating output pattern. of, d15-d0 alternate between 0 0000 0000 0000 0000 and 1 1111 1111 1111 1111 note: other bit combinations are not used bit 2 abp alternate bit polarity mode control bit 0 = alternate bit polarity mode off 1 = alternate bit polarity mode on. forces the output format to be offset binary bit 1 rand data output randomizer mode control bit 0 = data output randomizer mode off 1 = data output randomizer mode on bit 0 twoscomp twos complement mode control bit 0 = offset binary data format 1 = twos complement data format applications information
ltc2270 30 2270f silkscreen top typical applications top side
31 2270f ltc2270 typical applications inner layer 2 gnd inner layer 3
ltc2270 32 2270f typical applications inner layer 4 inner layer 5 power
33 2270f ltc2270 typical applications bottom side
ltc2270 34 2270f 48 47 46 45 44 43 42 41 40 39 38 37 36 35 34 33 d1_4_5 + d1_4_5 C d1_2_3 + d1_2_3 C d1_0_1 + d1_0_1 C ov dd ognd clkout + clkout C d2_14_15 + d2_14_15 C d2_12_13 + d2_12_13 C d2_10_11 + d2_10_11 C 65 pad 64 63 62 61 60 59 58 57 56 55 54 53 52 51 50 49 v dd sense v ref sdo of2_1 + of2_1 C d1_14_15 + d1_14_15 C d1_12_13 + d1_12_13 C d1_10_11 + d1_10_11 C d1_8_9 + d1_8_9 C d1_6_7 + d1_6_7 C 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 v dd enc + enc C cs sck sdi d2_0_1 C d2_0_1 + d2_2_3 C d2_2_3 + d2_4_5 C d2_4_5 + d2_6_7 C d2_6_7 + d2_8_9 C d2_8_9 + 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 c19 0.1f sdo v dd v dd v cm1 gnd a in1 + a in1 C gnd refh refl refh refl par/ ser a in2 + a in2 C gnd v cm2 v dd c20 1f c18 0.1f v dd par/ ser c17 1f c23 2.2f c37 0.1f digital outputs digital outputs ov dd spi bus c67 1f c78 0.1f c79 0.1f r51 100 ltc2270 encode clock cn1 a in2 + a in2 C a in1 + a in1 C c15 1f c21 1f + + C C C C + + sense 2270 ta03 typical applications ltc2270 schematic
35 2270f ltc2270 package description information furnished by linear technology corporation is believed to be accurate and reliable. however, no responsibility is assumed for its use. linear technology corporation makes no representa- tion that the interconnection of its circuits as described herein will not infringe on existing patent rights. 9 .00 0.10 (4 sides) note: 1. drawing conforms to jedec package outline mo-220 variation wnjr-5 2. all dimensions are in millimeters 3. dimensions of exposed pad on bottom of package do not include mold flash. mold flash, if present, shall not exceed 0.20mm on any side, if present 4. exposed pad shall be solder plated 5. shaded area is only a reference for pin 1 location on the top and bottom of package 6. drawing not to scale pin 1 top mark (see note 5) 0.40 0.10 6463 1 2 bottom viewexposed pad 7.15 0.10 7.15 0.10 7.50 ref (4-sides) 0.75 0.05 r = 0.10 typ r = 0.115 typ 0.25 0.05 0.50 bsc 0.200 ref 0.00 C 0.05 (up64) qfn 0406 rev c recommended solder pad pitch and dimensions apply solder mask to areas that are not soldered 0.70 0.05 7.50 ref (4 sides) 7.15 0.05 7.15 0.05 8.10 0.05 9.50 0.05 0.25 0.05 0.50 bsc package outline pin 1 chamfer c = 0.35 up package 64-lead plastic qfn (9mm w 9mm) (reference ltc dwg # 05-08-1705 rev c)
ltc2270 36 2270f linear technology corporation 1630 mccarthy blvd., milpitas, ca 95035-7417 (408) 432-1900 fax: (408) 434-0507 www.linear.com linear technology corporation 2012 lt 0812 ? printed in usa related parts part number description comments adcs ltc2160 16-bit 25msps 1.8v adc, ultralow power 45mw, 77db snr, 90db sfdr, ddr lvds/ddr cmos/cmos outputs, 7mm 7mm qfn-48 ltc2180 16-bit 25msps 1.8v dual adc, ultralow power 39mw/ch, 77db snr, 90db sfdr, ddr lvds/ddr cmos/cmos outputs, 9mm 9mm qfn-64 ltc2188 16-bit 20msps 1.8v dual adc, ultralow power 38mw/ch, 77db snr, 90db sfdr, ddr lvds/ddr cmos/cmos outputs, 9mm 9mm qfn-64 ltc2190 16-bit 25msps 1.8v dual adc, ultralow power 52mw/ch, 77db snr, 90db sfdr, serial lvds outputs, 7mm 8mm qfn-52 ltc2202/ltc2203 16-bit 10msps/25msps 3.3v adcs 140mw/220mw, 81.6db snr, 100db sfdr, cmos outputs, 7mm 7mm qfn-48 plls LTC6946-X ultralow noise and spurious integer-n synthesizer with integrated vco 3.7mhz to 5.7ghz, C226dbc/hz normalized in-band phase noise floor C157dbc/hz wideband output phase noise floor ltc6945 ultralow noise and spurious 0.35ghz to 6ghz integer-n synthesizer 3.5ghz to 6ghz, C226dbc/hz normalized in-band phase noise floor C157dbc/hz wideband output phase noise floor signal chain receivers ltm9002 14-bit, dual channel if/baseband module receiver dual adc, dual amplifiers, anti-alias filters and a dual trim dac in 15mm 11.25mm lga ltm9004 14-bit, direct conversion module receiver i/q demodulator, baseband amplifiers, lowpass filters up to 20mhz, dual 14-bit 125msps adc in 22mm 15mm lga rf mixers/demodulators ltc5569 300mhz to 4ghz dual active downconverting mixer high iip3: 26.8dbm, 2db conversion gain, low power: 3.3v/600mw, integrated rf transformer for compact footprint ltc5584 30mhz to 1.4ghz wideband i/q demodulator i/q demodulation bandwidth >530mhz, 31dbm iip3, iip2 adjustable to >80dbm, dc offset adjustable to zero, 45db image rejection ltc5585 700mhz to 3ghz wideband i/q demodulator i/q demodulation bandwidth >530mhz, 25.7dbm iip3, iip2 adjustable to >80dbm, dc offset adjustable to zero, 43db image rejection integral non-linearity (inl) output code 0 C2.0 C1.5 C1.0 inl error (lsb) C0.5 0.5 0.0 1.0 1.5 2.0 16384 32768 49152 65536 2270 ta05 typical application

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