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1 high efficiency 5v, 10a buck regulator ISL95210 the ISL95210 is a high-efficiency step-down regulator that can deliver 10a of output current from a 5v input. the small 4mmx6mm qfn package and only four external components provide a very small total solution size. low resistance internal mosfets deliver excellent efficiency and permit full power operation in a +90c ambient without airflow. the regulator operates from an input voltage of 2.97v to 5.5v, and provides a 0.6% accurate output voltage over the full operating temperature range. intersil's patented r4? control architecture provides exceptiona l transient response with no external compensation componen ts. the output voltage may be programmed by an internal dac or by an external resistor divider (see ?output voltage programming? on page 11 for more details). several digital control signals provide flexibility for users that want additional features. switch ing frequency, switching mode, output voltage margining and daisy-chained power-good functions are all programmed by these pins. the ISL95210 also includes comprehensive internal protection for overvoltage, undervoltage, overcurrent and over-temperature conditions. related literature ?see an1485 , ?ISL95210 10a integrated fet regulator evaluation board setup procedure? features ? 10a continuous output current ? 2.97v to 5.5v input voltage range ?up to 95% efficiency ? full power operation in +9 0c ambient without airflow ? r4? control architecture delivers excellent transient response without compensation ? pin selectable output voltage programming ? 0.6% output voltage accuracy over full operating temperature range ? programmable enhanced light- load efficiency operation ? output voltage margining and power-good monitor ?small 6mmx4mm qfn package applications ? point-of-load power supplies ? notebook computer power ? general purpose power rail generation figure 1. 10a dc/dc converter using only 4 external components figure 2. efficiency of circuit shown in figure 1 (includes inductor losses) vin pvcc en pg_in vsel1 fset mpct msel vsel0 fccm t-pad vout vcc agnd pgnd pgood phase vout = 1.2v vin = 5v lout 420nh cout 220f 1f 10f cin control signals power good vcc + ISL95210 lout cout = mpc0740lr42c (nec/tokin) = 2tplf220m5 (sanyo) fsw= 800khz 100 95 90 85 80 75 70 65 60 55 50 012345678910 iout (a) efficiency (%) vin = 5v vout = 1.2v fsw = 800khz december 15, 2011 fn6938.4 caution: these devices are sensitive to electrostatic discharge; follow proper ic handling procedures. 1-888-intersil or 1-888-468-3774 | copyright intersil americas inc. 2011. all rights reserved intersil (and design) is a trademark owned by intersil corporation or one of its subsidiaries. all other trademarks mentioned are the property of their respective owners.
ISL95210 2 fn6938.4 december 15, 2011 functional block diagram dac and margin logic soft-start por bandgap r4 ? modulator frequency control pgood monitor dead-time control & adaptive shoot- through protection undervoltage overvoltage protection pg_in pgood pgnd phase vin vout fset thermal monitor & protection overcurrent protection vsel0 vsel1 msel mpct vcc en fccm agnd pvcc pvcc vcc 10 ?
ISL95210 3 fn6938.4 december 15, 2011 pin configuration ISL95210 (32 ld qfn) top view 1 2 34 5 6 78 910 27 26 25 24 23 22 21 20 19 18 16 15 14 13 12 11 28 29 30 31 32 17 msel mpct vcc vout agnd vsel0 vsel1 pgood pg_in pgnd pgnd pgnd pgnd pgnd vin vin dnc pgnd pgnd pvcc pvcc vin fccm fset en phase phase phase phase phase phase phase t-pad (pgnd) functional pin descriptions pin name function t-pad (thermal pad) pgnd power ground. this thermal pad provides a return path for power stage and switching currents, as well as a thermal path for removing heat from the ic into the board. place thermal vias in the pad to the pgnd plane. 1 fccm logic input for operating mode selection. connect this pin to vcc for ccm regulation only. connect this pin to agnd to all ow discontinuous conduction mode for lig ht-load efficiency. float this pin for audio mode light-load switching. 2 fset tri-state digital input for programmin g the regulator switching frequency. pull th is pin to vcc for 800khz switching. pull this pin to gnd for 400khz switching. leave th is pin floating for 533khz switching. 3 en logic input for enabling and disabling output voltage regulati on. pull this pin to vcc to begin regulation. pull this pin to agnd to disable regulation. 4, 5, 6, 7, 8, 9, 10 phase power stage switching node for output voltage regulation. connect to the output inductor. all phase pins must be electrically connected together on the printed circuit board. 11 dnc do not connect. this pin must be left floating under all conditions. 12, 13, 19, 20, 21, 22, 23 pgnd power ground. this pin provides a return path fo r power stage and switching currents. all pgnd pins must be electrically connected together on the printed circuit board. 14, 15 pvcc power input for the integrated mosfet gate drivers. connect to a 5v (10%) supply. both pvcc pins must be shorted on the printed circuit board. vin and pvcc may be tied together (see figure 1) when operat ing from a nominal 5v supply. however, pvcc requires a 5v (10%) supply irrespective of vin. it is connected to vcc through an integrated 10 resistor and therefore doubles as the power supply for ic bias. if vin is below 4.5v, pvcc must receive a separate power supply input and decoupling capacitor (1f typical). 16, 17, 18 vin power input for buck regulation stage. bypass to pg nd with one 10f or 22f ceramic capacitor. connect to a 2.97v to 5.5v supply. all vin pins must be electrically connected together on the printed circuit board. 24 pg_in input voltage for the power-good cmos output. co nnect this pin to the desired pgood output high level. 25 pgood active cmos output for power-good indication. high state is indicated when the output voltage is in regulation, and outp ut is logic low otherwise. logic high level is set by the voltage on the pg_in pin. 26 vsel1 dac logic msb input. used to program preset output voltages of 0.60v, 0.75v, 0.90v, 1.00v, 1.05v, 1.10v, 1.20v, 1.50v, and 1.80v. 27 vsel0 dac logic lsb input. used to program preset output voltages of 0.60v, 0.75v, 0.90v, 1.00v, 1.05v, 1.10v, 1.20v, 1.50v, and 1.80v.
ISL95210 4 fn6938.4 december 15, 2011 28 agnd ground reference for analog signals. connect this pin to the ground plane. 29 vout sense point for output voltage regulati on and output soft-discharge. connect to the desired regulation point. a resistor divider can be used to program vout away from preset dac and margin values. however, the divider must not set vout more than 5% from the programmed value. see ?output voltage programmi ng? on page 11 and figure 34 for more information on this implementation. 30 vcc power supply input used for regulator bias and precision re ferences. place a high frequency ceramic capacitor (0.1f to 1f) to agnd. pvcc provides power to vcc through an integrated 10 resistor. 31 mpct 3-state logic input for programming the amount of output voltage ma rgining as controlled by the msel pin. pull the pin to gnd for 15% margining, to vcc for 20% marg ining, and float the pin for 10% margining. 32 msel digital input for control of output voltage margining. pull this pin to vcc to margin the output voltage to the high valu e. leave this pin floating to margin the output voltage low. pull this pin to agnd to regulate the nominally programmed output voltage value. the margin amount is dictated by the mpct pin. functional pin descriptions (continued) pin name function ordering information part number (notes 1, 2, 3) part marking temp range (c) package (pb-free) pkg. dwg. # ISL95210hrz 95210 hrz -10 to +100 32 ld 6x4 qfn l32.6x4b ISL95210irz 95210 irz -40 to +100 32 ld 6x4 qfn l32.6x4b ISL95210eval1z evaluation board notes: 1. add ?-t*? suffix for tape and reel. please refer to tb347 for details on reel specifications. 2. these intersil pb-free plastic packaged products employ specia l pb-free material sets, molding compounds/die attach materials , and 100% matte tin plate plus anneal (e3 termination finish, which is rohs complian t and compatible with both snpb and pb-free soldering operation s). intersil pb-free products are msl classified at pb-free peak reflow temperatures th at meet or exceed the pb-free requirements of ipc/jedec j std -020. 3. for moisture sensitivity level (msl), please see device information page for ISL95210 . for more information on msl please see techbrief tb363 .
ISL95210 5 fn6938.4 december 15, 2011 absolute maximum rating s thermal information all pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3v to +6v (dc) phase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -2v to +10v (< 10ns) vin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3v to 8v (< 10ns) recommended operating conditions vcc supply voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .+5v 10% pvcc supply voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .+5v 10% vin supply voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +2.97v to +5.5v junction temperature (ISL95210hrz) . . . . . . . . . . . . . . .-10c to +125c junction temperature (ISL95210irz) . . . . . . . . . . . . . . . .-40c to +125c thermal resistance (typical) ja (c/w) jc (c/w) 32 ld qfn package (notes 4, 5) . . . . . . . . 40 4 maximum junction temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . .+150c maximum storage temperature range . . . . . . . . . . . . . .-65c to +150c pb-free reflow profile . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . see link below http://www.intersil.com/ pbfree/pb-freereflow.asp caution: do not operate at or near the maximum ratings listed for extended periods of time. exposure to such conditions may adv ersely impact product reliability and result in failures not covered by warranty. notes: 4. ja is measured in free air with the componen t mounted on a high effective thermal conduc tivity test board with ?direct attach? fe atures. see tech brief tb379 . 5. for jc , the ?case temp? location is the center of the exposed metal pad on the package underside. electrical specifications recommended operating conditions, unless otherwise specified. boldface limits apply over the operating temperature range (-10c to +100c for ISL95210hrz; -40c to +100c for ISL95210irz). parameter test conditions min (note 7) typ max (note 7) units bias supplies shutdown supply current [pvcc] en = low, vin = pvcc = high 0.4 10 a switching supply current [pvcc] en = high, vcc = high, fset = gnd(400khz), fccm = high 7.2 ma en = high, vcc = high, fset = float (533khz), fccm = high 8.9 ma en = high, vcc = high, fset = high (800khz), fccm = high 12.2 ma standby supply current [pvcc] en = high, vcc = high, fccm = low, iout = 0a 1.9 2.7 ma vcc por (power-on reset) threshold vcc rising 4.25 4.50 v vcc falling 4.00 4.25 v pwm modulator oscillator frequency accuracy, f sw (ISL95210hrz) fset = gnd (400khz)/float (533khz)/vcc (800khz), t a = +25c -5 5 % fset = gnd (400khz)/float (533khz)/vcc (800khz), -10c to +100c -10 10 % oscillator frequency accuracy, f sw (ISL95210irz) fset = gnd (400khz)/float (533khz)/vcc (800khz), -40c to +100c -15 15 % control thresholds en rising threshold 2.0 v en falling threshold 1.0 v fccm, mpct, msel, fset, vsel_ input low threshold 1.20 1.50 1.80 v fccm, mpct, msel, fset, vsel_ input floating voltage input impedance > 1m 1.85 2.00 2.15 v fccm, mpct, msel, fset, vsel_ input high threshold 2.2 2.50 2.8 v
ISL95210 6 fn6938.4 december 15, 2011 reference and dac system accuracy ISL95210hrz -10c to +100c vout = {0.700v to 2.1625v}, vin = 5v -0.60 0.60 % vout = {0.48125v to 0.700v}, vin = 5v -0.75 0.75 % system accuracy ISL95210irz -40c to +100c vout = {0.700v to 2.1625v}, vin = 5v -0.75 0.75 % vout = {0.48125v to 0.700v}, vin = 5v -1 1 % line regulation accuracy 4.5v < vin < 5.5v 0.05 % load regulation accuracy fccm = high, inductor dcr = 2m 0.08 % soft-start ramp soft-start and vsel slew rate 1.6 2.3 3.0 mv/s protection overcurrent trip level valley cu rrent limit (8 pwm pulse count) 10 12.5 14 a peak way-overcurrent (~1s delay) 28 35 43 a undervoltage threshold vout:vdac 81 84 87 % overvoltage rising threshold vout:vdac 112 116 120 % overvoltage falling threshold vout:vdac 99 102 106 % power-good pull-up resistance 1.8 2.3 2.8 k power-good pull-down resistance 30 50 70 vout soft-discharge resistance all shutdown conditions 25 45 65 power mosfet on-resistance high-side pmos +25c only 16.52 m high-side pmos 14.8 19.5 m low-side nmos +25c only 4.28 m low-side nmos 3.8 5.7 m over-temperature shutdown (note 6 ) thermal shutdown setpoint 150 c thermal recovery setpoint 125 c notes: 6. thermal impedance measured in still air on the isl952 10eval1z rev b evaluation board with 800khz setup. see an1485 . 7. compliance to datasheet limits is assured by one or more methods: production test, characterization and/or design. electrical specifications recommended operating conditions, unless otherwise specified. boldface limits apply over the operating temperature range (-10c to +100c for ISL95210hrz; -40c to +100c for ISL95210irz). (continued) parameter test conditions min (note 7) typ max (note 7) units
ISL95210 7 fn6938.4 december 15, 2011 typical performance curves figure 3. 800khz efficiency fccm = low figure 4. 800khz efficiency fccm = float figure 5. 800khz efficiency fccm = high figure 6. normal start-up figure 7. pre-biased start-up figure 8. ccm output voltage load regulation 0 10 20 30 40 50 60 70 80 90 100 0.01 0.10 1.00 10.00 iout (a) efficiency (%) 0.60 0.75 0.90 1.00 1.05 1.10 1.20 1.50 1.80 vout (v) 0 10 20 30 40 50 60 70 80 90 100 0.01 0.10 1.00 10.00 efficiency (%) iout (a) 0.60 0.75 0.90 1.00 1.05 1.10 1.20 1.50 1.80 vout (v) 50 55 60 65 70 75 80 85 90 95 100 012345678910 efficiency (%) iout (a) 0.60 0.75 0.90 1.00 1.05 1.10 1.20 1.50 1.80 vout (v) pgood 5v/div en 5v/div iin 200ma/div vout 0.5v/div 0.1ms/div pgood 5v/div en 5v/div iin 200ma/div vout 0.5v/div 0.1ms/div -0.5 -0.4 -0.3 -0.2 -0.1 0.0 0.1 0.2 0.3 0.4 0.5 0.01 0.10 1.00 10.00 accuracy (%) iout (a) vout = 1.10v high vout ripple with high esr high vout ripple with low esr low vout ripple
ISL95210 8 fn6938.4 december 15, 2011 figure 9. output voltage load regulation (log scale) figure 10. ccm steady-state figure 11. audio mode steady-state figu re 12. audio mode steady-state (zoom) figure 13. dcm steady-state (100ma) figure 14. 10a load transient 50a/s typical performance curves (continued) -1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0 0.01 0.10 1.00 10.00 accuracy (%) iout (a) vout = 1.10v audio dcm audio dcm high vout ripple with low esr high vout ripple with high esr phase 2v/div vout (ac) 20mv/div 1s/div phase 2v/div vout (ac) 20mv/div 20s/div phase 2v/div vout (ac) 20mv/div 1s/div phase 2v/div 20mv/div 10s/div vout (ac) iout 5a/div 100mv/div 5s/div vout (ac)
ISL95210 9 fn6938.4 december 15, 2011 figure 15. 10a load transient 50a/s (zoom rising edge) figure 16. 10a load transient 50a/s (zoom falling edge) figure 17. 10a load transient 5a/s fig ure 18. vsel1 transitions 0.90v to 1.80v figure 19. normal shut-down figure 20. overvoltage shut-down (vdac = 1.00v) typical performance curves (continued) iout 5a/div 50mv/div phase 5v/div 1s/div vout (ac) iout 5a/div 50mv/div phase 5v/div 2s/div vout (ac) iout 5a/div 100mv/div vout (ac) 5s/div 0.2ms/div vsel1 2v/div vout 500mv/div pgood 5v/div en 5v/div vout 0.5v/div 5ms/div pgood 5v/div vout 200mv/div 10s/div phase 2v/div
ISL95210 10 fn6938.4 december 15, 2011 figure 21. undervoltage shut-down (vdac = 1.00v) figure 22. overcurrent shutdown figure 23. current derating over-temperature figure 24. current derating over-temperature (zoom) note: figures 23 and 24 were generated on the ISL95210eval1z rev b evaluation board (4-layers/2oz. copper). the test conditions were 5vin and 1.8vout. the junction temperature was characterized by measuring the shift over-temperature of an integrated polysilicon resist or. all other above figures were generated with the typical application schematic found in fi gure 1, unless otherwise specified. for more details on the la yer stack up of the evaluation board, please see the ISL95210 application note ( an1485 ). typical performance curves (continued) pgood 5v/div vout 200mv/div 10s/div phase 2v/div phase 5v/div pgood 5v/div il 5a/div 0 2 4 6 8 10 12 25 50 75 100 125 ambient temperature (c) maximum continuous 85 output current (a) 200 lfm 100 lfm 300 lfm air flow 0 lfm 0 2 4 6 8 10 12 85 90 95 100 105 110 115 120 125 ambient temperature (c) maximum continuous output current (a) 200 lfm 100 lfm 300 lfm air flow 0 lfm
ISL95210 11 fn6938.4 december 15, 2011 theory of operation the following sections will provide a detailed description of the inner workings of the ISL95210 10a integrated fet regulator. start -up the ISL95210 will not respond to any logic inputs until vcc and pvcc are above the power-on reset (por) level as described in the ?electrical specifications? table on page 5. once the por condition is achieved, the ISL95210 will then acknowledge the states of its logic inputs. if the en pin is pulled above the rising threshold, the regulator is co mmanded on and the soft-start sequence is initiated. during soft-start, the programmed output voltage set point is determined by the logic states of vsel0, vsel1, mpct and msel. the output then ramps digitally to the regulation voltage in 2.5mv/s steps. once the output voltage achieves regulation, the power-good monitor output (pgood) is toggled high to the voltage provided on the pg_in pin. figure 25 illustrates the ideal soft-start behavior. using the values in tables 1 and 2, the soft-start interval can be easily calculated by equation 1. the units of equation 1 are in microseconds. for example: - vdac = 1.200v -t ss = 1.200v / 0.0025 = 480s the fixed soft-start slew rate of 2.5mv/s allows for easy calculation of the in-rush current. consequently, the in-rush is manageable for all practical values of output capacitance. for example: - cout = 330f - inrush current = 2500*330f = 0.825a output voltage programming the highly integrated nature of the ISL95210 simplifies design and reduces component count. the vsel0 and vsel1 pins are 3-state logic inputs to an integrated dac that controls the output voltage set point as prescribed in table 1. this allows the user to progra m the output voltage without the use of a resistor divider network. however, if the user wishes to program values of vout away from the dac values, a resistor divider can be used. however, because the input impedance of the vout pin is relatively low, the top resistor in the divider stack (r1 in figure 31) must be kept small to minimize regulation error as the internal resistance chan ges over-temperature and process tolerances. a 100 resistor is recommended. the bottom resistor in the divider stack (r2 in figure 31) can be derived from equation 3: for example: - desired vout = 1.35v - vdac = 1.32v (1.2v +10% margin) -r1 = 100 - r2 = 4.351k (select nearest standard value) note: the resistor divider should not be used to program vout more than 5% away from any preset dac value. if this limit is exceeded, the modulator will be severely imbalanced and may result in loop instabilit y and regulator shutdown. the use of a resistor network also limits the soft discharge feature of the ISL95210. more detail on this operation can be found in the ?soft-discharge? on page 15. in addition to digitally controlled output voltage programming, the ISL95210 includes the ability to margin the output voltage up and down from the set point for use in end-of-line manufacturing reliability tests. the mpct pin controls the amount of margining desired by the user and the msel pin determines when margining is engaged. in all margining conditions, the output voltage is slewed to the new value at the soft-start rate of figure 25. idealized soft-start waveform pg_out en vout 1us 2.5mv dac voltage t ss en dac voltage vout 2.5mv 1s t ss pgood t ss v dac 0.0025 ----------------- - = (eq. 1) i inrush 2500 c out ? () = (eq. 2) table 1. dac controlled output voltage settings vsel1 vsel0 vout (v) 0 0 0.600 0 float 0.750 0 1 0.900 float 0 1.000 float float 1.050 float 1 1.100 1 0 1.200 1 float 1.500 1 1 1.800 note: 1 = input high, 0 = input low, float = input unconnected or high-z (see ?electrical specifications? table for details). r2 r1 v dac ? v out 2r1 ? 205k --------------- ?? ?? 205k r 1 + 205k -------------------------- - ?? ?? ? + v dac ? ------------------------------------------------------------------------------------------------------- = (eq. 3)
ISL95210 12 fn6938.4 december 15, 2011 2.5mv/s. table 2 shows the output voltage as dictated by mpct and msel. each of the margin targets represents the dac code nearest to the desired value. table 3 shows the actual targets for each margin setting (see table 4 on pa ge 17 for the full output truth table). both the dac and margining features can be used ?on the fly?, meaning the voltage can be chan ged during normal operation. regulation r4 ? modulator the r4 modulator is an advanced current-mode hysteretic control scheme that generates a sy nthetic current signal on chip instead of measuring real current. this has the benefit of producing a cleaner and lower jitt er system versus conventional current-mode hysteretic architectures. r4? also employs a highly balanc ed architecture that greatly reduces the need for high dc loop gain traditionally required for output voltage regulation accuracy. this allows the r4? modulator to accurately regulate without the need for an integrator in the feedback loop. another benefit of the balanced system is that it does not requir e compensation for stability over a wide range of designs. the result is a power solution that is flexible and easy to design with minimal components. a complete point of load regula tor can be designed with the ISL95210 using only 4 external components. figure 26 shows the basic error-amplifier configuration for the r4? controller. a hysteretic comparator monitors the synthetic current signal against the er ror voltage and corresponding window voltage to determine the pwm switching events. stability the r4? balanced architecture creates a control loop that does not require compensation for an extremely wide range of output filters (lout, cout). however, there are corners of operation that will destabilize the loop and result in oscillatory behavior in vout. the filters that push the control loop toward instability are ones that add a considerable amount of phase delay to the output voltage. in general, phase delay increases as output capacitance decreases in conjunction with reduced output capacitor equivalent series resistance (esr). for this reason, output filters that are all-ceramic based have the most difficulty achieving stable regulation. the first indication that the ISL95210 is nearing instability is when its step load response begi ns to have ring-back. ring-back occurs when the pwm on pulse in response to a sharp increase in output load is so long as to cause the output voltage to overshoot the regulation point befo re fully recovering. equation 4 approximates the boundary cond ition between normal recovery and ring-back as a function of operating parameters where: - cout = total output capacitance in farads - lout = output inductance in henries - d = steady-state duty cycle (vout / vin) - esr = output capacitor equivalent series resistance - istep = expected load step (worst case is preferred) - il = inductor ripple current - fsw = switching frequency -k = modulator factor: - 3700 for 400khz fsw - 4933 for 533khz fsw - 7400 for 800khz fsw as good design practices dictate, a system should be designed safely away from this boundary to cover any tolerance shifts that may occur. for example, if the output capacitor in figure 1 is replaced with low-esr ceramics and reduced until the inequality table 2. output voltage margining control msel mpct result 0 0 no margining 0 float no margining 0 1 no margining float 0 margin down dac - 15% float float margin down dac - 10% float 1 margin down dac - 20% 1 0 margin up dac + 15% 1 float margin up dac + 10% 1 1 margin up dac + 20% note: 1 = input high, 0 = input low, float = input unconnected or high-z (see ?electrical specifications? table for details). table 3. output voltage margin targets vout -20% -15% -10% +10% +15% +20% 0.600 0.481 0.513 0.538 0.663 0.688 0.719 0.750 0.600 0.638 0.675 0.825 0.863 0.900 0.900 0.719 0.763 0.813 0.988 1.038 1.081 1.000 0.800 0.850 0.900 1.100 1.150 1.200 1.050 0.838 0.894 0.944 1.156 1.206 1.263 1.100 0.881 0.938 0.988 1.213 1.263 1.325 1.200 0.963 1.019 1.081 1.319 1.381 1.438 1.500 1.200 1.275 1.350 1.650 1.7250 1.800 1.800 1.438 1.531 1.619 1.981 2.069 2.163 figure 26. basic r4 ? pwm signal generation vout vdac + vw - error- amplifier hysteretic window voltage comp voltage synthetic current pwm (eq. 4 ) cout esr ? k lout cout ?? + [] istep dd ? fsw il ? --------------------------- - ? >
ISL95210 13 fn6938.4 december 15, 2011 in equation 4 is not met, transi ent ring-back performance similar to what is shown in figure 27 will occur. in this example, the total output capacitance was 76f with an esr of approximately 1m . when the values are put into equation 4, the inequality is not met: x 3.1210 -7 > 3.2510 -7 if additional ceramics are added to increase cout to 120f with an esr of approximately 0.67m , the ring-back condition is eliminated, providing the transient results seen in figure 28. when the new values are evaluated in equation 4, the following results are observed: 4.5310 -7 > 3.2510 -7 this result shows a clean, stable solution when the inequality is satisfied. it should be noted that when the capacitance in this example is decremented between 120f and 76f, the severity and frequency of ring-back increases. it can occur prior to violating equation 4. this is due to the non-idealities that exist in real systems and some simplificati ons in the derivation process. care should be taken to design away from the boundary condition. the above example became fully stable (zero ring-back) when the inequality?s percentage difference was ~35%. transient response as with all current-mode hysteretic style controllers, the ISL95210 will increase and de crease switching frequency in response to load transient even ts. this oversampling quickens the converters response and minimizes output voltage deviation. the change in frequency is achieved by the movement on the comp voltage seen in figure 26. when the load current changes up or down, there is an proportional movement on comp. the movement on comp naturally changes the hysteretic window size for both pwm edges. upwa rd swings in comp (due to increasing load current) make the effective hysteretic window larger during pwm on times and smaller during pwm off times. the result is increased switching frequency. conversely, downward swings in comp (due to decreasing load current) make the effective hysteretic window smaller during pwm on times and larger during pwm off times. switching frequency is reduced in this scenario. figure 29 illustrates the idealized effect on switching frequency from movements in comp in response to load transient events. unlike more traditional current-mode hysteretic architectures, r4? does not require an error-integrating capacitor in the feedback loop. this removes significant delay in the control loop and produces extremely fast tran sient response to changes in load current. the speed of response allows system designers to use less output capacitance and save on board area and cost. figure 30 depicts a comparison of the r4? modulator vs. various classic architectures in response to a load step-up transient. the figure 27. ISL95210 load transient response with ring-back conditions from excessive vout phase delay figure 28. ISL95210 load transient response without ring-back conditions 20mv/div 2s/div vout (ac) vin = 5v vout = 1.2v istep = 0-6a fsw = 800khz 20mv/div 2s/div vout (ac) vin = 5v vout = 1.2v istep = 0-6a fsw = 800khz 3 figure 29. idealized effect of load transients on switching frequency iout synthetic current hysteretic window voltage comp voltage pwm vout both pwm edges are modulated during load transient
ISL95210 14 fn6938.4 december 15, 2011 dotted red and blue lines represent the time delayed behavior of vout and vcomp when an integrator is used. the solid red and blue lines illustrate the incr eased response of r4? in the absence of the integrating capacitor. discontinuous conduction modes the ISL95210 supports two power saving modes of operation during light load conditions. if fccm is asserted high, the regulator remains in continuous conduction mode (ccm) which offers the best transient response and the most stable operating frequency. if the fccm pin is pulled to gr ound potential, the regulator is allowed to operate in full discon tinuous conducti on mode (dcm) when the load becomes sufficiently low. in this mode, the inductor current is monitored and prohibited from going negative. when the inductor current reaches zero, both internal power mosfets are turned off. the output voltage then decays solely as a function of load. th e power fets remain off until the output voltage droops enough to trigger a pwm on pulse. because the rate of decay of vout scales proportionally with load, so does the switching frequency. this increases efficiency as the relatively fixed power loss associated with switching the power fets is averaged over the switching period. if the fccm pin is left floating, the ISL95210 will operate in audio mode dcm. this mode operates largely the same as full dcm mode with one exception; the swit ching period is monitored cycle by cycle. if the load diminishes to a point where the switching frequency begins to drop belo w ~28khz, the ISL95210 control loop will issue a pwm on pulse to ensure the frequency remains above the upper threshold for human hearing. this allows flexibility for designs that are sensitive to audio frequency interference. the r4? architecture seamlessly enters and exits all power saving modes to ensure accurate regulation. protection and shutdown features the ISL95210 offers a full suite of protection features to reduce the risk of damage to the ic and load. they include under and overvoltage monitoring and protec tion as well as protection against excessive current and thermal operating conditions. undervoltage protection if the output voltage dips too lo w during normal operation, the ISL95210 recognizes a fault co ndition and shuts down. when vout goes 16% below vdac, the power-good monitor flags pgood low and tri-states the phase node by turning off both integrated power mosfets. in addition, the soft-discharge mosfet is turned on to gently pull the output voltage to ground potential for the next restart. the undervoltage fault remains latched until a por event or en is toggled. overvoltage protection during normal operation, the outp ut voltage is monitored at all times to ensure it does not exceed the set point by more than 16%. excessively high voltages can cause failure to output capacitors as well as the load. if vout goes above 116% of dac, the power-good monitor is flagged by toggling pgood low and the ic enters overvoltage protection mode. in overvoltage protection mode, the upper p-channel mosfet is latched off until the fault is cleared. in addition, vout is compared against the reference da c voltage. if vout is above dac, the lower n-channel mosfet is turned on to pull vout down. if vout falls below dac, the lower n-channel mosfet is turned off. this process repeat s until the fault condition is cleared through vcc/pvcc por or a recycling of the en pin. this produces a soft-crowbar action that can effectively pull the output away from dangerously high voltage levels without causing the negative voltage swings on vout that are present with full crowbar implementations of overvoltage protection. overcurrent protection if the current draw from the load becomes too high during operation, the ic protects itself and the load by latching off. the overcurrent mechanism is implemented as a two-fold protection scheme. the ISL95210 continuously monitors the lower n-channel mosfet current. it stores the va lley of the inductor current each cycle and compares it against th e lower overcurrent protection (ocp) threshold of 11a nominally. if the ocp threshold is achieved for 8 consecutive pwm cycles, an overcurrent fault is detected and the ic is shutdown. in this event, power-good monitor flags pgood low and tri-states both switching power mosfets and turns on the soft-discharge fet. inductor valley current is used to ensure that the minimum ocp threshold is above the maximum ISL95210?s normal maximum load of 10a regardless of chosen inductor value. in addition to valley current limit, the upper p-channel mosfet current is continuously monitored. if a catastrophic overcurrent event is encountered (e.g. short circuit on vout), the ISL95210 immediately responds to protect the output by latching both mosfets off and engaging the soft-discharge fet. the power-good monitor flags pgood low and the ic remains latched off until por or en is toggled. thermal protection the ISL95210 actively monitors the die temperature to protect against harmful thermal operatin g conditions. if the silicon temperature exceeds +150c, the controller will suspend figure 30. classic architectures vs r4 ? idealized transient response classic voltage-mode or t r4? vout vcomp iout current-mode architecture
ISL95210 15 fn6938.4 december 15, 2011 operation and shut down until th e ic junction temperature falls below +135c. once the temperatur e has fallen below the lower protection threshold, the ic will resume normal operation following a por event or toggling of the en input. power-good monitor a status indicator is provided to inform the system whether or not the ISL95210 output voltage is in regulation or if a fault has occurred. if vcc and pvcc are above the por threshold, the part is enabled, and no faults have been detected, pgood will toggle high. the power-good monitor is a cmos configuration (refer to the ?functional block diagram? on page 2). this allows the user to provide any voltage to indicate when power is good. the voltage provided on to the pg_in pin will be used as the logic high value for pgood. this has the advantage over open-drain configurations of saving a pull-u p resistor. a pull-up resistor on pgood can still be used if desired. in this configuration, the pg_in pin needs to be floated. soft-discharge to ensure a known operating cond ition when the ISL95210 is in a standby state, the vout pin is actively discharged to pgnd through an integrated 45 mosfet. the mosfet is commanded on if the en pin is pulled low or if any of the previously mentioned fault conditions are achieved with the exception of overvoltage, which actively pulls down on vo ut as a matter of protection. it should be noted that if an exte rnal resistor divider is used to program vout to values not found in the dac table, the soft-discharge feature will be negatively impacted. figure 31 illustrates this condition. the discharge resistance is increased by the presence of the resistor divider. the total discha rge resistance is expressed in equation 5: general application design guide this design guide is intended to provide a high-level explanation of the steps necessary to design a single-phase power converter. it is assumed that the reader is familia r with many of the basic skills and techniques referenced in the following section. in addition to this guide, intersil provides complete reference designs that include schematics, bills of materials, and example board layouts. selecting the lc output filter the duty cycle of an ideal buck converter is a function of the input and the output voltage. th is relationship is written as equation 6: the output inductor peak-to-peak ripple current is written as equation 7: a typical step-down dc/dc converter will have an i p-p of 20% to 40% of the maximum dc output load current. the value of i p-p is selected based upon several crit eria such as mosfet switching loss, inductor core loss, and the resistive loss of the inductor winding. the dc copper loss of the inductor can be estimated by equation 8: where i load is the converter output dc current. the copper loss can be significant so attention has to be given to the dcr selection. another factor to consider when choosing the inductor is its saturation characte ristics at elevated temperature. a saturated inductor could cause destruction of circuit components, as well as nuisance ocp faults. a dc/dc buck regulator must have output capacitance c o into which ripple current i p-p can flow. current i p-p develops a corresponding ripple voltage v p-p across c o, which is the sum of the voltage drop across the capa citor esr and of the voltage change stemming from charge moved in and out of the capacitor. these two voltages are written as equation 9: and equation 10: if the output of the converter ha s to support a load with high pulsating current, several capacitors will need to be paralleled to reduce the total esr until the required v p-p is achieved. the inductance of the capacitor can cause a brief voltage dip if the load transient has an extremely high slew rate. low inductance capacitors should be considered in this scenario. a capacitor dissipates heat as a function of rms current and frequency. be sure that i p-p is shared by a sufficient quantity of paralleled capacitors so that they operate below the maximum rated rms current at f sw . take into account that the rated value of a capacitor can fade as much as 50 % as the dc voltage across it increases. figure 31. simplified soft-discharge circuit v out soft-discharge vout r1 r2 ISL95210 45 r dchrg 45 r2 ? 45 r2 + ------------------------- - r1 + = (eq. 5) d v o v in --------- = (eq. 6) (eq. 7 ) i pp v o 1d ? () ? f sw l ? ----------------------------- - = (eq. 8) p copper i load 2 dcr ? = v esr i p-p e ? sr = (eq. 9) v c i p-p 8c o f ? sw ? ------------------------------- = (eq. 10)
ISL95210 16 fn6938.4 december 15, 2011 selection of the input capacitor the important parameters for the bulk input capacitance are the voltage rating and the rms current rating. for reliable operation, select bulk capacitors with voltage and current ratings above the maximum input voltage and capable of supplying the rms current required by the switching circuit. their voltage rating should be at least 1.25x greater than the maximum input voltage, while a voltage rating of 1.5x is a preferred rating. figure 32 is a graph of the input rms ripple current, normalized relative to output load current, as a function of duty cycle and is adjusted for a converter efficiency of 80%. the ripple current calculation is written as equation 11: where: - x is a multiplier (0 to 1) corresponding to the inductor peak-to-peak ripple amplitude expressed as a percentage of i max (0% to 100%) - d is the duty cycle that is adjusted to take into account the efficiency of the converter, which is written as equation 12: in addition to the bulk capacitance, some low esl ceramic capacitance is recommended to decouple between the drain of the high-side mosfet and the so urce of the low-side mosfet. typical applications circuits there are two main variants to typical application schematic shown in figure 1. the first of these is when an input voltage lower than 5v is desired. this requires the designer to provide separate power supplies to vin and pvcc as the ISL95210 requires a 5v bias to operate properly. figure 33 illustrates this configuration for a vin of 3.3v. the second typical application variant is when the designer wishes to program vout to a value not available in the dac table. the component selection for this configuration is described in detail in ?output voltage prog ramming? on page 11. figure 34 shows a resistor divider programm ed configuration for an output voltage of 2.25v. layout considerations it is important to place power co mponents as close as possible to the devices they decouple. figure 35 provides an example of proper power component placement for the ISL95210. input capacitors are placed directly across vin and pgnd to filter switching currents between the pmos and nmos power fets. the output inductor is placed directly adjacent to the phase pins. its ?north-south? arrangements easily allow for the output voltage decoupling capacitor to be placed with its ground terminal very near the input capacitors grounds and the pgnd pins of the ISL95210. this provides a low impedance return path for the inductor ripple current. this is one possible arrangement that will result in a good layout. the analog ground connection (not shown) should be connected directly to the ground plane through a via. the vcc decoupling capacitor should be placed next to the vcc and agnd pins for optimal noise rejection. figure 32. normalized rms input current (eq. 11) i in_rms normalized , dd 2 ? () d x 2 12 ------ ? ?? ?? + = d v o v in eff ? -------------------------- = (eq. 12) 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 0 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 0.60 normalized input duty cycle rms ripple current x = 1 x = 0.75 x = 0.50 x = 0.25 x = 0 figure 33. ISL95210 typical application with vin < 5v figure 34. ISL95210 typical application with vout = 2.5v vin pvcc en pg_in vsel1 fset mpct msel vsel0 fccm t-pad vout vcc agnd pgnd pgood phase vout = 1.2v vin = 3.3v lout 420nh cout 220f 1f 10f cin control signals power good vcc + ISL95210 lout cout = mpc0740lr42c (nec/tokin) = 2tplf220m5 (sanyo) 1f fsw = 800khz pvcc = 5v vin pvcc en pg_in vsel1 fset mpct msel vsel0 fccm t-pad vout vcc agnd pgnd pgood phase vout = 2.25v vin = 5v lout 420nh cout 220f 1f 10f cin control signals power good vcc + ISL95210 lout cout = mpc0740lr42c (nec/tokin) = 2tplf220m5 (sanyo) 100 2.49k fsw = 800khz
ISL95210 17 fn6938.4 december 15, 2011 the colored shapes represent the following power planes: copper size for the phase node the parasitic capacitance and parasitic inductance of the phase node should be kept very low to minimize ringing. it is best to limit the size of the phase node copper in strict accordance with the current and thermal management of the application. an mlcc should be connected directly between vin and pgnd to suppress the turn-off voltage spike. this is achieved by placing the mlcc as close to the ic as possible and adjacent to vin and pgnd. full output voltage truth table pgnd phase vin vout figure 35. ISL95210 power component layout example lout (7x7mm) cout (d-case) cin (1206) ISL95210 (4x6mm) table 4. output voltage truth table msel mpct vsel1 vsel0 vout float1000.48125 float0000.51250 float float 0 0 0.53750 00000.60000 0 float 0 0 0.60000 01000.60000 float 1 0 float 0.60000 float 0 0 float 0.63750 1 float 0 0 0.66250 float float 0 float 0.67500 10000.68750 float1010.71875 11000.71875 0 0 0 float 0.75000 0float0float0.75000 0 1 0 float 0.75000 float0010.76250 float 1 float 0 0.80000 float float 0 1 0.81250 1float0float0.82500 float 1 float float 0.83750 float 0 float 0 0.85000 1 0 0 float 0.86250 float 1 float 1 0.88125 float 0 float float 0.89375 00010.90000 0 float 0 1 0.90000 01010.90000 float float float 0 0.90000 1 1 0 float 0.90000 float 0 float 1 0.93750 float float float float 0.94375 float 1 1 0 0.96250 float float float 1 0.98750 1 float 0 1 0.98750 0 0 float 0 1.00000 0 float float 0 1.00000 0 1 float 0 1.00000 float0101.01875 10011.03750 0 0 float float 1.05000 0 float float float 1.05000 0 1 float float 1.05000 float float 1 0 1.08125 11011.08125 00float11.10000 0floatfloat1 1.10000
ISL95210 18 fn6938.4 december 15, 2011 01float11.10000 1floatfloat0 1.10000 1 0 float 0 1.15000 1 float float float 1.15625 00101.20000 0 float 1 0 1.20000 01101.20000 float 1 1 float 1.20000 1 1 float 0 1.20000 1 0 float float 1.20625 1floatfloat1 1.21250 1 0 float 1 1.26250 1 1 float float 1.26250 f01float1.27500 1float1 0 1.31875 1 1 float 1 1.32500 float float 1 float 1.35000 10101.38125 float1111.43750 11101.43750 0 0 1 float 1.50000 0float1float1.50000 0 1 1 float 1.50000 float0111.53125 float float 1 1 1.61875 1float1float1.65000 1 0 1 float 1.72500 00111.80000 0 float 1 1 1.80000 01111.80000 1 1 1 float 1.80000 1float1 1 1.98125 10112.06875 11112.16250 note: 1 = input high, 0 = input low, float = input unconnected or high-z (see ?electrical specifications? table for details). table 4. output voltage truth table (continued) msel mpct vsel1 vsel0 vout
ISL95210 19 intersil products are manufactured, assembled and tested utilizing iso9000 quality systems as noted in the quality certifications found at www.intersil.com/design/quality intersil products are sold by description only. intersil corporat ion reserves the right to make changes in circuit design, soft ware and/or specifications at any time without notice. accordingly, the reader is cautioned to verify that data sheets are current before placing orders. information furnished by intersil is believed to be accurate and reliable. however, no responsi bility is assumed by intersil or its subsid iaries for its use; nor for any infringem ents of patents or other rights of third parties which may result from its use. no license is granted by implication or otherwise under any patent or patent rights of i ntersil or its subsidiaries. for information regarding intersil corporation and its products, see www.intersil.com fn6938.4 december 15, 2011 for additional products, see www.intersil.com/product_tree products intersil corporation is a leader in the design and manufacture of high-performance analog semico nductors. the company's product s address some of the industry's fastest growing markets, such as , flat panel displays, cell phones, handheld products, and noteb ooks. intersil's product families address power management and analog sign al processing functions. go to www.intersil.com/products for a complete list of intersil product families. for a complete listing of applications, rela ted documentation and related parts, please see the respective device information p age on intersil.com: ISL95210 to report errors or suggestions for this datasheet, please go to: www.intersil.com/askourstaff fits are available from our website at: http://rel.intersil.com/reports/sear revision history the revision history provided is for informat ional purposes only and is believed to be accurate, but not warranted. please go t o web to make sure you have the latest rev. date revision change december 6, 2011 fn6938.4 in the?recommended operating conditions? on page 5, changed the following from: vcc supply voltage?..41+5v 10% vin supply voltage?..+2.97v to +5v to: vcc supply voltage?..+5v 10% vin supply voltage?..+2.97v to +5.5v november 1, 11 fn6938.3 "pg_out" pin renamed to "pgood." multiple sections rewritten for clarity, specifically ?regulation? on pa ge 12 to page 14. may 18, 2011 fn6938.2 added ?32 lead, 6mmx4mm qfn package? to ?features? on page 1. may 10, 2011 fn6938.1 initial release to web.
ISL95210 20 fn6938.4 december 15, 2011 package outline drawing l32.6x4b 32 lead quad flat no-lead plastic package rev 0, 09/08 located within the zone indicated. the pin #1 identifier may be unless otherwise specified, tolerance : decimal 0.05 tiebar shown (if present) is a non-functional feature. the configuration of the pin #1 identifier is optional, but must be between 0.15mm and 0.30mm from the terminal tip. dimension applies to the metallized terminal and is measured dimensions in ( ) for reference only. dimensioning and tolerancing conform to amse y14.5m-1994. 6. either a mold or mark feature. 3. 5. 4. 2. dimensions are in millimeters. 1. notes: bottom view detail "x" side view typical recommended land pattern top view 110 11 16 17 26 27 32 2x 6.00 pin 1 index area 4.00 b a 0.10 c 0 . 2 ref 0-0.05 5 see detail "x" 0.10 max. 1.00 c c seating plane 0.08 c 16 (11x 0.50) 6.40 (14x 0.25) package boundary (11x 0.45) 3x 0.95 (4.40) (1.80) (2.5) (2x 4.7) (2x 1.12) 18x 0.55 (2.64) (18x 0.25) (14x 0.50) 18x 0.55 2x 1.12 0.50 11x 14x 0.25 2x 4.70 chamfer 0.300 x45 pin #1 identification 11x 0.25 1.80 3x 0.75 2.50 2x 2.64 (2.50) 0.50 14x 18x 0.35 18x 0.25 b mc 0.10 a 4 m 4 0.10 c a b

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