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general description the max6920 is a 12-output, 76v, vacuum fluorescent display (vfd) tube driver that interfaces a multiplexed vfd tube to a vfd controller such as the max6850?ax6853 or to a microcontroller. the max6920 is also ideal for driving either static vfd tubes or telecom relays. data is inputted using an industry-standard 4-wire serial interface (clock, data, load, blank) for compatibili- ty with both industry-standard drivers and maxim? vfd controllers. for easy display control, the active-high blank input forces all driver outputs low, turning the display off, and automatically puts the max6920 into shutdown mode. display intensity may also be controlled by pulse-width modulating the blank input. the max6920 has a serial interface data output pin, dout, allowing any number of devices to be cascaded on the same serial interface. the max6920 is available in a 20-pin so package. maxim also offers vfd drivers with either 20 (max6921/max6931) or 32 outputs (max6922 and max6932). applications white goods industrial weighing gaming machines security automotive telecom avionics features 5mhz industry-standard 4-wire serial interface 3v to 5.5v logic supply range 8v to 76v grid/anode supply range push-pull cmos high-voltage outputs outputs can source 40ma, sink 4ma continuously outputs can source 75ma repetitive pulses outputs can be paralleled for higher current drive any output can be used as a grid or an anode driver blank input simplifies pwm intensity control small 20-pin so package -40? to +125? temperature range max6920 12-output, 76v, serial-interfaced vfd tube driver ________________________________________________________________ maxim integrated products 1 ordering information 19-3061; rev 0; 10/03 for pricing, delivery, and ordering information, please contact maxim/dallas direct! at 1-888-629-4642, or visit maxim? website at www.maxim-ic.com. part temp range pin-package max6920awp -40 c to +125 c 20 wide so max6920 din clk load out0 ?out11 vfd tube vfdout vfload vfclk blank vfblank 1 20 19 12 11 9 10 12 v cc gnd v bb +60v +5v c1 100nf c2 100nf c typical operating circuit top view 20 19 18 17 16 15 14 13 12 11 1 2 3 4 5 6 7 8 9 10 v cc din out0 out1 out2 out3 out4 out5 load clk gnd blank out6 out7 out8 out9 out10 out11 dout v bb max6920awp pin configuration
max6920 12-output, 76v, serial-interfaced vfd tube driver 2 _______________________________________________________________________________________ absolute maximum ratings electrical characteristics (typical operating circuit, v bb = 8v to 76v, v cc = 3v to 5.5v, t a = t min to t max , unless otherwise noted.) (note 1) stresses beyond those listed under ?bsolute maximum ratings?may cause permanent damage to the device. these are stress rating s only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specificatio ns is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability. voltage (with respect to gnd) v bb ................................................................................. -0.3v to +80v v cc .......................................................................-0.3v to +6v out_.......................................................-0.3v to (v bb + 0.3v) all other pins..........................................-0.3v to (v cc + 0.3v) out_ continuous source current ....................................-45ma out_ pulsed (1ms max, 1/4 max duty) source current ...-80ma total out_ continuous source current .........................-540ma total out_ continuous sink current .................................60ma total out_ pulsed (1ms max, 1/4 max duty) source current ............................................................ -960ma out_ sink current .............................................................. 15ma clk, din, load, blank, dout current .......................10ma continuous power dissipation 20-pin wide so (derate 10mw/ c over t a = +70 c) ..800mw operating temperature range (t min to t max ) .-40 c to +125 c junction temperature ......................................................+150 c storage temperature range .............................-65 c to +150 c lead temperature (soldering, 10s) .................................+300 c parameter symbol conditions min typ max units logic supply voltage v cc 3 5.5 v tube supply voltage v bb 876v t a = +25 c 72 170 all outputs out_ low, clk = idle t a = -40 c to +125 c 200 t a = +25 c 350 650 logic supply operating current i cc all outputs out_ high, clk = idle t a = -40 c to +125 c 700 a t a = +25 c12 all outputs out_ low t a = -40 c to +125 c 4.2 t a = +25 c 0.53 0.85 tube supply operating current i bb all outputs out_ high t a = -40 c to +125 c 0.9 ma t a = +25 cv bb - 1.1 t a = -40 c to +85 cv bb - 2 v bb 15v, i out = -25ma t a = -40 c to +125 cv bb - 2.5 t a = -40 c to +85 cv bb - 3.5 v bb 15v, i out = -40ma t a = -40 c to +125 cv bb - 4.0 t a = +25 cv bb - 1.2 t a = -40 c to +85 cv bb - 2.5 high-voltage out_ v h 8v < v bb < 15v, i out = -25ma t a = -40 c to +125 cv bb - 3.0 v t a = +25 c 0.75 1 t a = -40 c to +85 c 1.5 v bb 15v, i out = 1ma t a = -40 c to +125 c 1.9 t a = +25 c 0.8 1.1 t a = -40 c to +85 c 1.6 low-voltage out_ v l 8v < v bb < 15v, i out = 1ma t a = -40 c to +125 c 2.0 v
max6920 12-output, 76v, serial-interfaced vfd tube driver _______________________________________________________________________________________ 3 electrical characteristics (continued) (typical operating circuit, v bb = 8v to 76v, v cc = 3v to 5.5v, t a = t min to t max , unless otherwise noted.) (note 1) parameter symbol conditions min typ max units rise time out_ (20% to 80%) t r v bb = 60v, c l = 50pf, r l = 2.3k ? 0.9 2 s fall time out_ (80% to 20%) t f v bb = 60v, c l = 50pf, r l = 2.3k ? 0.6 1.5 s serial interface timing characteristics load rising to out_ falling delay (notes 2, 3) 0.9 1.8 s load rising to out_ rising delay (notes 2, 3) 1.2 2.4 s blank rising to out_ falling delay (notes 2, 3) 0.9 1.8 s blank falling to out_ rising delay (notes 2, 3) 1.3 2.5 s input leakage current clk, din, load, blank i ih , i il 0.05 10 a logic-high input voltage clk, din, load, blank v ih 0.8 x v cc v logic-low input voltage clk, din, load, blank v il 0.3 x v cc v hysteresis voltage din, clk, load, blank ? v i 0.6 v high-voltage dout v oh i source = -1.0ma v cc - 0.5 v low-voltage dout v ol i sink = 1.0ma 0.5 v 3v to 4.5v 60 100 rise and fall time dout c dout = 10pf (note 2) 4.5v to 5.5v 30 80 ns clk clock period t cp 200 ns clk pulse-width high t ch 90 ns clk pulse-width low t cl 90 ns clk rise to load rise hold t csh (note 2) 100 ns din setup time t ds 5ns 3v to 4.5v 20 din hold time t dh 4.5v to 5.5v 15 ns 3.0v to 4.5v 25 120 240 dout propagation delay t do c dout = 10pf 4.5v to 5.5v 20 75 150 ns load pulse high t csw 55 ns note 1: all parameters are tested at t a = +25 c. specifications over temperature are guaranteed by design. note 2: guaranteed by design. note 3: delay measured from control edge to when output out_ changes by 1v.
max6920 12-output, 76v, serial-interfaced vfd tube driver 4 _______________________________________________________________________________________ typical operating characteristics (v cc = 5.0v, v bb = 76v, and t a = +25 c, unless otherwise noted.) tube supply current (i bb ) vs. temperature (outputs low) max6920 toc01 temperature ( c) supply current (ma) 110 60 85 10 35 -15 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 0 -40 v bb = 76v v bb = 40v v bb = 8v tube supply current (i bb ) vs. temperature (outputs high) max6920 toc02 temperature ( c) supply current (ma) 100 80 40 60 020 -20 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 0 -40 120 v bb = 76v v bb = 40v v bb = 8v logic supply current (i cc ) vs. temperature (outputs low) max6920 toc03 temperature ( c) supply current ( a) 100 80 40 60 020 -20 50 100 150 200 250 300 350 400 0 -40 120 v cc = 5v, clk = 5mhz v cc = 3.3v, clk = 5mhz v cc = 5v, clk = idle v cc = 3.3v, clk = idle supply current (i cc ) vs. temperature (outputs high) max6920 toc04 temperature ( c) supply current ( a) 60 10 300 350 400 450 500 550 600 250 -40 110 v cc = 5v, clk = 5mhz v cc = 3.3v, clk = 5mhz v cc = 5v, clk = idle v cc = 3.3v, clk = idle output voltage (v bb - v h ) vs. temperature (output high) max6920 toc05 temperature ( c) output voltage (v) 100 80 40 60 020 -20 0.5 1.0 1.5 2.0 2.5 3.0 3.5 0 -40 120 v bb = 76v v bb = 40v v bb = 8v i out = -40ma output voltage vs. temperature (output low) max6920 toc06 temperature ( c) output voltage (v) 100 80 40 60 020 -20 2 4 6 8 10 12 14 0 -40 120 v bb = 40v v bb = 8v v bb = 76v i out = 4ma output rise and fall waveform max6920 toc11 1 s/div blank 2v/div out_ 20v/div
max6920 12-output, 76v, serial-interfaced vfd tube driver _______________________________________________________________________________________ 5 pin name function 1v bb vfd tube supply voltage 2 dout serial-clock output. data is clocked out of the internal shift register to dout on clk s rising edge. 3 8, 13 18 out0 to out11 vfd anode and grid drivers. out0 to out11 are push-pull outputs swinging from v bb to gnd. 9 blank blanking input. high forces outputs out0 to out11 low, without altering the contents of the output latches. low enables outputs out0 to out11 to follow the state of the output latches. 10 gnd ground 11 clk serial-clock input. data is loaded into the internal shift register on clk s rising edge. 12 load load input. data is loaded transparently from the internal shift register to the output latch while load is high. data is latched into the output latch on load's rising edge, and retained while load is low. 19 din serial-data input. data is loaded into the internal shift register on clk s rising edge. 20 v cc logic supply voltage pin description serial-to-parallel shift register latches clk din load blank out0 out1 out2 out11 dout max6920 figure 1. max6920 functional diagram
max6920 12-output, 76v, serial-interfaced vfd tube driver 6 _______________________________________________________________________________________ detailed description the max6920 is a vfd tube driver comprising a 4-wire serial interface driving 12 high-voltage rail-to-rail output ports. the driver is suitable for both static and multiplexed displays. the output ports feature high current-sourcing capabili- ty to drive current into grids and anodes of static or multiplex vfds. the ports also have active current sink- ing for fast discharge of capacitive display electrodes in multiplexing applications. the 4-wire serial interface comprises a 12-bit shift reg- ister and a 12-bit transparent latch. the shift register is written through a clock input clk and a data input din and the data propagates to a data output dout. the data output allows multiple drivers to be cascaded and operated together. the output latch is transparent to the shift register outputs when load is high, and latch- es the current state on the falling edge of load. each driver output is a slew-rated controlled cmos push-pull switch driving between v bb and gnd. the output rise time is always slower than the output fall time to avoid shoot-through currents during output tran- sitions. the output slew rates are slow enough to mini- mize emi, yet are fast enough so as not to impact the typical 100s digit multiplex period and affect the dis- play intensity. initial power-up and operation an internal reset circuit clears the internal registers of the max6920 on power-up. all outputs out0 to out11 and the interface output dout initialize low regardless of the initial logic levels of the clk, din, blank, and load inputs. 4-wire serial interface the max6920 uses a 4-wire serial interface with three inputs (din, clk, load) and a data output (dout). this interface is used to write output data to the max6920 ( figure 3) ( table 1). the serial interface data word length is 12 bits, d0 d11. the functions of the four serial interface pins are: clk input is the interface clock, which shifts data into the max6920 s 12-bit shift register on its rising edge. load input passes data from the max6920 s 12- bit shift register to the 12-bit output latch when load is high (transparent latch), and latches the data on load s falling edge. slew- rate control v bb out_ 40 ? typical 750 ? typical figure 2. max6920 cmos output driver structure load t csw t cp t csh t ch t dh t do t ds d11 d10 d1 d0 d11 t cl clk din dout figure 3. 4-wire serial interface timing diagram rail-to-rail is a registered trademark of nippon motorola, ltd.
max6920 12-output, 76v, serial-interfaced vfd tube driver _______________________________________________________________________________________ 7 din is the interface data input, and must be stable when it is sampled on the rising edge of clk. dout is the interface data output, which shifts data out from the max6920 s 12-bit shift register on the falling edge of clk. data at din is propa- gated through the shift register and appears at dout (20 clk cycles + t do ) later. a fifth input pin, blank, can be taken high to force out- puts out0 to out11 low, without altering the contents of the output latches. when the blank input is low, outputs out0 to out11 follow the state of the output latches. a common use of the blank input is pwm intensity control. the blank input s function is independent of the oper- ation of the serial interface. data can be shifted into the serial interface shift register and latched regardless of the state of blank. writing device registers using the 4-wire serial interface the max6920 is written using the following sequence: 1) take clk low. 2) clock 12 bits of data in order d11 first to d0 last into din, observing the data setup and hold times. 3) load the 12 output latches with a falling edge on load. load may be high or low during a transmission. if load is high, then the data shifted into the shift regis- ter at din appears at the out0 to out11 outputs. clk and din may be used to transmit data to other peripherals. activity on clk always shifts data into the max6920 s shift register. however, the max6920 only updates its output latch on the rising edge of load, and the last 12 bits of data are loaded. therefore, multi- ple devices can share clk and din as long as they have unique load controls. determining driver output voltage drop the outputs are cmos drivers, and have a resistive characteristic. the typical and maximum sink and source output resistances can be calculated from the v h and v l electrical characteristics. use this calculated resistance to determine the output voltage drop at dif- ferent output currents. output current ratings the continuous current source capability is 40ma per output. outputs may drive up to 75ma as a repetitive peak current, subject to the on time (output high) being no longer than 1ms, and the duty cycle being such that the output power dissipation is no more than the dissipa- tion for the continuous case. the repetitive peak rating allows outputs to drive a higher current in multiplex grid driver applications, where only one grid is on at a time, and the multiplex time per grid is no more than 1ms. clock input shift register contents load input latch contents blanking input output contents serial data input din clk d0 d1 d2 dn-1 dn load d0 d1 d2 dn-1 dn blank d0 d1 d2 dn-1 dn h h r0 r1 rn-2 rn-1 l l r0 r1 rn-2 rn-1 xr0r1r2 rn-1 rn xxx xx lr0r1r2 rn-1 rn p0 p1 p2 pn-1 pn h p0 p1 p2 pn-1 pn l p0 p1 p2 pn-1 pn xxx xx h lll ll table 1. 4-wire serial interface truth table l = low logic level. h = high logic level. x = don? care. p = present state (shift register). r = previous state (latched).
max6920 12-output, 76v, serial-interfaced vfd tube driver 8 _______________________________________________________________________________________ since dissipation is proportional to current squared, the maximum current that can be delivered for a given mul- tiplex ratio is given by: i peak = (grids x 1600) 1/2 ma where grids is the number of grids in a multiplexed display. this means that a duplex application (two grids) can use a repetitive peak current of 56.5ma, a triplex application (three grids) can use a repetitive peak current of 69.2ma, and higher multiplex ratios are limited to 75ma. paralleling outputs any number of outputs within the same package may be paralleled in order to raise the current drive or reduce the output resistance. only parallel outputs directly (by shorting outputs together) if the interface control can be guaranteed to set the outputs to the same level. although the sink output is relatively weak (typically 750 ? ), that resistance is low enough to dissi- pate 530mw when shorted to an opposite level output at a v bb voltage of only 20v. a safe way to parallel out- puts is to use diodes to prevent the outputs from sink- ing current ( figure 4). because the outputs cannot sink current from the vfd tube, an external discharge resis- tor, r, is required. for static tubes, r can be a large value such as 100k ? . for multiplexed tubes, the value of the resistor can be determined by the load capaci- tance and timing characteristics required. resistor rl discharges tube capacitance c to 10% of the initial voltage in 2.3 x rc seconds. so, for example, a 15k ? value for r discharges 100pf tube grid or anode from 40v to 4v in 3.5s, but draws an additional 2.7ma from the driver when either output is high. power dissipation take care to ensure that the maximum package dissi- pation ratings for the chosen package are not exceed- ed. over dissipation is unlikely to be an issue when driving static tubes, but the peak currents are usually higher for multiplexed tubes. when using multiple dri- ver devices, try to share the average dissipation evenly between the drivers. determine the power dissipation (p d ) for the max6920 for static tube drivers with the following equation: p d = (v cc x i cc ) + (v bb x i bb ) + ((v bb - v h ) x i anode x a)) where: a = number of anodes driven (a max6920 can drive a maximum of 12). i anode = maximum anode current. (v bb - v h ) is the output voltage drop at the given maxi- mum anode current i out . a static tube dissipation example follows: v cc = 5v 5%, v bb = 10v to 18v, a = 12, i out = 2ma p d = (5.25v x 0.7ma) + (18v x 0.9ma) + ((2.5v x 2ma/25ma) x 2ma x 12) = 24.7mw determine the power dissipation (p d ) for the max6920 for multiplex tube drivers with the following equation: p d = (v cc x i cc ) + (v bb x i bb ) + ((v bb - v h ) x i anode x a) + ((v bb - v h ) x i grid )) where: a = number of anodes driven g = number of grids driven i anode = maximum anode current i grid = maximum grid current the calculation presumes all anodes are on but only one grid is on. the calculated p d is the worst case, presuming one digit is always being driven with all its anodes lit. actual p d can be estimated by multiplying this p d figure by the actual tube drive duty cycle, taking into account interdigit blanking and any pwm intensity control. a multiplexed tube dissipation example follows: v cc = 5v 5%, v bb = 36v to 42v, a = 6, g = 6, i anode = 0.4ma, i grid = 24ma p d = (5.25v x 0.7ma)+ (42v x 0.9ma) + ((2.5v x 0.4ma/25ma) x 0.4ma x 6) + ((2.5v x 24ma/25ma) x 24ma) = 99mw thus, for a 20-pin wide so package (t ja = 1 / 0.01 = +100 c/w from absolute maximum ratings ), the maxi- mum allowed ambient temperature t a is given by: t j(max) = t a + (p d x t ja ) = +150 c = t a + (0.099 x +100 c/w) so t a = +140 c. max6920 out0 out1 d1 d2 r output figure 4. paralleling outputs
max6920 12-output, 76v, serial-interfaced vfd tube driver _______________________________________________________________________________________ 9 this means that the driver can be operated in this application up to the max6920 s +125 c maximum operating temperature. power-supply considerations the max6920 operates with multiple power-supply volt- ages. bypass the v cc and v bb power-supply pins to gnd with a 0.1f capacitor close to the device. for multiplex applications, it may be necessary to add an additional 1f bulk electrolytic capacitor, or greater, to the v bb supply. power-supply sequencing the order of the power-supply sequencing is not impor- tant. the max6920 will not be damaged if either v cc or v bb is grounded (or maintained at any other voltage below the data sheet minimum), while the other supply is maintained up to its maximum rating. however, as with any cmos device, do not drive the max6920 s logic inputs if the logic supply v cc is not operational because the input protection diodes clamp the signals. max6920 din clk load blank max685x vfdout vfclk vfload vfblank dout vfd tube max6920 din clk load blank dout max6920 din clk load blank dout typical application circuit chip information transistor count: 2743 process: bicmos
max6920 12-output, 76v, serial-interfaced vfd tube driver maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a maxim product. no circu it patent licenses are implied. maxim reserves the right to change the circuitry and specifications without notice at any time. 10 ____________________maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 ? 2003 maxim integrated products printed usa is a registered trademark of maxim integrated products. package information (the package drawing(s) in this data sheet may not reflect the most current specifications. for the latest package outline info rmation, go to www.maxim-ic.com/packages .) package information (the package drawing(s) in this data sheet may not reflect the most current specifications. for the latest package outline info rmation, go to www.maxim-ic.com/packages .) soicw.eps package outline, .300" soic 1 1 21-0042 b rev. document control no. approval proprietary information title: top view front view max 0.012 0.104 0.019 0.299 0.013 inches 0.291 0.009 e c dim 0.014 0.004 b a1 min 0.093 a 0.23 7.40 7.60 0.32 millimeters 0.10 0.35 2.35 min 0.49 0.30 max 2.65 0.050 0.016 l 0.40 1.27 0.512 0.496 d d min dim d inches max 12.60 13.00 millimeters min max 20 ac 0.447 0.463 ab 11.75 11.35 18 0.398 0.413 aa 10.50 10.10 16 n ms013 side view h 0.419 0.394 10.00 10.65 e 0.050 1.27 d 0.614 0.598 15.20 24 15.60 ad d 0.713 0.697 17.70 28 18.10 ae h e n d a1 b e a 0-8 c l 1 variations:
e nglish ? ???? ? ??? ? ??? what's ne w p roducts solutions de sign ap p note s sup p ort buy comp any me mbe rs max6920 part number table notes: see the max6920 quickview data sheet for further information on this product family or download the max6920 full data sheet (pdf, 192kb). 1. other options and links for purchasing parts are listed at: http://www.maxim-ic.com/sales . 2. didn't find what you need? ask our applications engineers. expert assistance in finding parts, usually within one business day. 3. part number suffixes: t or t&r = tape and reel; + = rohs/lead-free; # = rohs/lead-exempt. more: see full data sheet or part naming c onventions . 4. * some packages have variations, listed on the drawing. "pkgc ode/variation" tells which variation the product uses. 5. part number free sample buy direct package: type pins size drawing code/var * temp rohs/lead-free? materials analysis max6920awp+ soic ;20 pin;.300" dwg: 21-0042b (pdf) use pkgcode/variation: w20+2 * -40c to +125c rohs/lead-free: yes materials analysis max6920awp+t soic ;20 pin;.300" dwg: 21-0042b (pdf) use pkgcode/variation: w20+2 * -40c to +125c rohs/lead-free: yes materials analysis max6920awp soic ;20 pin;.300" dwg: 21-0042b (pdf) use pkgcode/variation: w20-2 * -40c to +125c rohs/lead-free: no materials analysis max6920awp-t -40c to +125c rohs/lead-free: no max6920atp+ thin qfn;20 pin;5x5x0.8mm dwg: 21-0140k (pdf) use pkgcode/variation: t2055+4 * -40c to +125c rohs/lead-free: yes materials analysis max6920atp+t -40c to +125c rohs/lead-free: yes didn't find what you need?
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