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november 2013 rev. 1.3 www.microsemi .com 1 ? 2013 microsemi corporation 5 a const a nt fre que ncy h yst e re t ic synchronous re gulat or d1 vin bst s1 sw ocp d2 fb comp rt vcc 5vreg s2 gnd nx9415 0.1f 0.56h 220pf v in +12v 768 2*(10f/16v/x5r) 5k 15.8k 22f/6.3v/x5r 0.1f v out1 +5v,5a 3.01k 330pf 15k 4.7f 1f 10 4.22k 10pf figure 1 typical application of nx9415 features ? single supply voltage from 8v to 22v ? internal 5v regulator ? programmable frequency up to 2.2mhz ? internal digital soft start function ? internal boost schottky diode ? prebias startup ? less than 50 ns adaptive deadband ? current limit triggers hiccup by sensing r dson of synchronous mosfet ? pb - free and rohs compliant applications ? low profile on board dc to dc application ? lcd tv ? hard disk drive ? adsl modem description the nx9415 is synchronous buck switching converter in a multi chip module designed for step - down dc to dc converter applications. it is optimized to convert bus voltages from 8v to 22v to as low as 0.8v output voltage. the output current can be up to 5a. an internal regulator converts bus voltage to 5v, which provides a voltage supply to the internal logic and driver circuits. the nx9415 operates from 200 khz to 2.2mhz and employs loss - less current limiting by sensing the r dson of synchronous mosfet followed by hiccup feature. feedback under voltage protection triggers hiccup. other features of the device are: internal schottky diode, thermal shutdown, 5v gate drive, adaptive deadband control, internal digital soft start, 5vreg under - voltage lock out and shutdown capability via the comp pin. nx9415 is available in 4x4 mcm package . nx9415 downloaded from: http:///
5a constant frequency hysteretic synchronous regulator 2 pin configuration and pinout 1 2 5 8 17 3 1615 14 4 9 6 7 10 11 12 13 18 19 20 22 21 23 24 pad1 pad2 pad3 s1 s2s2 d1 s1 s2 d2 d1 d2 s1d1 d2 nc nc fb comp gndrt vin nc 5vreg vcc ocpbst 24-lead plastic mcm 4x4 figure 2 pinout ordering information ambient temperature type package part number packaging type 0c to 70c rohs compliant pb-free 4x4 mcm - 24l nx9415cm bulk / tube NX9415CMTR tape and reel downloaded from: http:///
pin description 3 pin description pin number pin designator description 1, 23 - 24 s2 source of low side mosfet and needs to be connected to power ground. 2- 3,22, pad2 d2 drain of low side mosfet. 4 , 12, 15, pad3 nc not used pin. connecting these pins to ground is recommended. 5 vcc voltage supply for internal analog circuit and driver 6 5vreg an internal 5v regulator. a high frequency 4.7f/x5r ceramic capacitor must be connected from this pin to the gnd pin as close as possible. 7 vin voltage supply for the internal 5v regulator. 8 rt oscillator's frequency can be set by using an external resistor from this pin to gnd. 9 gnd ground. 10 comp this pin is the output of the error amplifier and is used to compensate the voltage control feedback loop. this pin is also used as a shut down pin. when this pin is pulled below 0.3v, both drivers are turned off and internal soft start is reset. 11 fb this pin is the error amplifier inverting input. this pin is connected via resistor divider to the output of the switching regulator to set the output dc voltage. 13 bst this pin supplies voltage to the high side driver. a high frequency ceramic capacitor of 0.1 to 1f must be connected from this pin to sw pin. 14 ocp this pin is connected to the d2 of the low side mosfet and is the input of the over current protection (ocp) comparator. a fixed internal current flows to the external resistor which sets the ocp voltage across the r dson of the low side mosfet. current limit point is this voltage divided by the r dson . 16, 21 - 20, pad1 d1 drain of high side mosfet 17 - 19 s1 source of high side mosfet and provides return path for the high side driver. downloaded from: http:///
5a constant frequency hysteretic synchronous regulator 4 block diagram pwm logic ocp 5 vreg vcc comp fb rt gnd hiccup set osc vcc uvlo 5 v ldo vin bst d1 s1 sw soft start ramp + - ocp gate control logic s2 d2 0.3v + 0. 56 v fb + bias generator 0.8v( ref ) 1. 25 v thermal shutdown figure 3 simplified block diagram of nx9 415 downloaded from: http:///
absolute maximum ratings 5 absolute maximum ratings note: stresses above those listed in absolute maximum ratings, may cause permanent damage to the device. this is a stress only rating and operation of the device at these or any other conditions above those indicated in the operational sections of this specification is not implied. parameter min max units 5vreg,vcc to gnd & bst to sw voltage - 0.3 6.5 v vin to gnd voltage - 25 v s1 to gnd -2 30 v d1 to s1, d2 to s2 - 30 v all other pins - 0.3 vcc +0.3 , or 6.5 v storage temperature range - 65 150 c operating junction temperature range - 40 125 c peak reflow temperature (40 seconds) 260 (+0, - 5) c esd susceptibility 2 kv power dissipation internally limited by otp thermal properties thermal resistance typ units ja 30 c/w jc 2.5 c/w note: the ja numbers assume no forced airflow. junction temperature is calculated using t j = t a + (pd x ja ). in particular, ja is a function of the pcb construction. the stated number above is for a four - layer board in accordance with jesd - 51 (jedec). electrical characteristics unless otherwise specified, these specifications apply over v in = 12v, and t a = 0 to 70 c. following are the bypass capacitors: c vin = 1f, c 5vreg = 4.7f, and all x5r ceramic capacitors. typical values refer to t a = 25 c. low duty cycle pulse testing is used which keeps junction and case temperatures equal to the ambient temperature. symbol parameter test condition min typ max units reference vo ltage vref ref voltage 0.8 v ref voltage line regulation vin= 9v to 22v 0.4 % 5vreg 5vreg voltage range 4.75 5 5.25 v 5vreg line regulation vin= 9v to 22v 10 mv 5vreg max current 50 ma downloaded from: http:///
5a constant frequency hysteretic synchronous regulator 6 electrical characteristics - continued unless otherwise specified, these specifications apply over v in = 12v, and t a = 0 to 70 c. following are the bypass capacitors: c vin = 1f, c 5vreg = 4.7f, and all x5r ceramic capacitors. typical values refer to t a = 25 c. low duty cycle pulse testing is used which keeps junction and case temperatures equal to the ambient temperature. symbol parameter test condition min typ max units supply voltage (v in ) v in v in voltage range 9 22 v input voltage current (static) no switching 4.8 ma input voltage current ( dynamic ) r rt = 4.22k ? 10 ma v in uvlo v in _uvlo v in - threshold v in rising 6.5 v v in _hyst v in - hysteresis v in falling 0.6 v unde r vol tage lockout v cc _uvlo v cc threshold v cc rising 3.9 v v cc _hyst v cc hysteresis v cc falling 0.2 v ss t ss soft start time f s = 2.2mhz 400 s oscillato r (rt) f s frequency r rt = 4.22 k ? 2250 khz v ramp ramp amplitud e voltage 1.5 v ma x dut y cycle f s = 2.2mhz 71 % min controllable on time 150 ns erro r amplifiers transconductance 2000 mho i b inpu t bia s current 10 na c omp sd threshold 0.3 v fbuvlo feedbac k uvlo threshold 0.6 v ove r temperature threshold 150 c hysteresis 20 c ocp ocp current 37 a internal schottky diode forward voltage drop f orward current = 20ma 350 mv ou t put stage high side mosfet rdson 31 m ? low side mosfet rdson 31 m ? output current 5 a downloaded from: http:///
typical application 7 typical application ? input voltage = 12v, output voltage ~ 5v@ 5a, working frequency ~ 2.2mhz u1 d1 vin bst s1 sw ocp d2fb comp rt vcc 5vreg s2 gnd nx9415 c2 0.1f l1 0.56h v out1 c5 220pf v in +12v r4 768 c in 2*(10f/16v/x5r) r7 5k r515.8k c out 22f/6.3v/x5r c3 0.1f +5v, 5a r63.01k c6330pf r3 15k c4 4.7f c1 1f r1 10 r2 4.22k 10pf figure 4 demo board schematic bill of materials item quantity reference value manufacturer 1 1 c1 1f 2 2 c2,c3 0.1f 3 1 c4 4.7f/6.3v/x5r 4 1 c5 220pf 5 1 c6 330pf 6 2 cin 10f/16v/x5r 7 1 cout 22f/6.3v/x5r 8 1 l1 do1813p - 561hc coilcraft 9 1 r1 10 ? 10 1 r2 4.22k ? 11 1 r3 15k ? 12 1 r4 768 ? 13 1 r5 15.8k ? 14 1 r6 3.01k ? 15 1 r7 5k ? 16 1 u1 nx9415cm microsemi downloaded from: http:///
5a constant frequency hysteretic synchronous regulator 8 theory of operation over current protection over current protection is achieved by sensing current through the low side mosfet. a ty pical internal current source of 37a flowing through an external resistor connected f rom ocp pin to sw node sets the over current pro tection threshold. when synchron ous fet is on, the voltage at node sw is given as ? ?? = ?? ? ? ???? the voltage at pin ocp is given as ? ????? ? ??? + ? ?? when the voltage is below zero, the over - current occurs. ocpcomparator i ocp r ocp ocp sw v bus figure 5 over current protection the over current limit can be set by the following equation: ? ??? = ? ??? ? ??? ? ? ???? k is temperature coefficient of r dson , the recommended value is 1.4 . downloaded from: http:///
demoboard waveforms 9 demoboard waveforms figure 6 output ripple (ch1 sw 10v/div, ch2 vout ac 50mv/div, ch4 output current 5a/div) figure 7 output voltage transient response ( ch2 vout ac 50mv/div, ch4 output current 5a /div) downloaded from: http:///
5a constant frequency hysteretic synchronous regulator 10 figure 8 over current protection(ch4 output current 5 a/div) figure 9 startup (ch2 vout 2v/div, ch4 current 2 a/div) downloaded from: http:///
application information 11 70.00% 90.00% 100.00% 80.00%60.00% 50.00% 40.00% 20.00% 10.00% 0.00% 1000 2000 5000 4000 3000 6000 30.00% 0 efficiency vs. i out efficiency (%) i out (ma) figure 10 output efficiency @v out =5v, v in =12v a pplication information symbol used in application information: symbol description v in input voltage v out output voltage i out output current ? v ripple output voltage ripple f s working frequency ? i ripple inductor current ripple output inductor selection the selection of inductor value is based on inductor ripple current, power rating, working f requency and efficiency. larger inductor value normally means smaller ripple current. however if the inductance is chosen too large, it brings slow response and lower efficiency . usually the ripple current ranges from 20% to 40% of the output current. this is a design freedom which can be decided by design engineer according to various application requirements. the inductor value can be calculated by using the following equations: ? ??? = ??? ? ? ??? ?? ?????? ? ??? ? ?? 1 ? ? ? ?????? = ? ? ?????? where k is between 0.2 to 0.4. downloaded from: http:///
5a constant frequency hysteretic synchronous regulator 12 output capacitor selection output capacitor is basically decided by the amount of the output voltage ripple allowed during steady state (dc) load condition as well as specification for the load transient. the optim um design may require a couple of iterations to satisfy both conditions . the amount of voltage ripple during the dc load condition is determined by the following equation: ?? ?????? = ??? ?? ?????? + ?? ?????? 8 ? ? ? ??? where esr is the output capacitors' equivalent series resistance, c out is the value of output capa citors. typically when ceramic capacitors are selected as output capacitors, dc ripple spec i s easy to be met, but multiple ceramic capacitors are required at the output to meet transient requirement. compensator design due to the double pole generated by lc filter of the power stage, the power system has 180 phase shift, and therefore, is unstable by itself. in order to achieve accurate output voltage and fast transient response, compensator is employed to provide highest possible bandwidth and enough p hase margin . ideally, the bode plot of the closed loop system has crossover frequency between 1/10 and 1/5 of the switching f requency, phase margin greater than 50 and the gain crossing 0db with 20db/decade. power stage output capacitors usually decide the compensator type. if electrolytic capa citors are chosen as output capacitors, type ii compensator can be used to compensate t he system, because the zero caused by output capacitor esr is lower than crossover frequency. otherwise type iii compensator s hould be chosen. a. type iii compensator design for low esr output capacitors, typically such as sanyo os - con and poscap , the frequency of esr zero caused by output capacitors is higher than the crossover frequency. in thi s case, it is necessary to compens ate the system with type iii compensator. the following figures and equations show how to realize the type iii compensator by transconductance amplifier. ? ?1 = 1 2 ? ? 4 ? 2 ? ?2 = 1 2 ? ( ? 2 + ? 3 ) ? 3 ? ?1 = 1 2 ? ? 3 ? 3 ? ?2 = 1 2 ? ? 4 ? 1 ? 2 ? 1 + ? 2 w here , f z1 , f z2 , f p1 , and f p2 are poles and zeros in the compensator. their locations are shown in figure 10. the transfer function of type iii compensator for transconductance amplifier is given by: ? ? ? ??? = 1 ? ? ? ? ? 1 + ? ? ? ?? + ? ?? / ? 1 for the voltage amplifier, the transfer function of compensator is ? ? ? ??? = ?? ? ? ?? downloaded from: http:///
applicati on information 13 to achieve the same effect as voltage amplifier, the compensator of transconductance amplifier must satisfy this condition: r 4 >>2/gm. and it would be desirable if r 1 ||r 2 ||r 3 >> 1/gm can be met at the same time. z in v out zf r3 r2r1 vref fb c1 gm r4 c3 c2 + - figure 11 type iii compensator using transconductance amplifier power stage 40db/decade f lc loop gain gain (db) 20db/decade f esr f o f z1 f p2 f s f p1 f z2 compensator figure 12 bode plot of type iii compensator downloaded from: http:///
5a constant frequency hysteretic synchronous regulator 14 b. type ii compensator design type ii compensator can be realized by simple rc circuit without feedback as shown in figure 12. r 3 and c 1 introduce a zero to cancel the double pole effect. c 2 introduces a pole to suppress the switching noise. the following equations show the compensator pole zero location and constant gain. ???? = ? ? ? 1 ? 1 + ? 2 ? 3 ? ? = 1 2 ? ? 3 ? 1 ? ? 1 2 ? ? 3 ? 2 for this type of compensator, fo has to satisfy f lc application information 15 output voltage calculation output voltage is set by reference voltage and external voltage divider. the reference voltage is fixed at 0.8v. the divider consists of two ratioed resistors so that the output volta ge applied at the fb pin is 0.8v when the output voltage is at the desired value. the following equation and picture show the relationship between v out , v ref , and voltage divider. ? 1 = ? 2 ? ??? ? ??? ? ? ??? where , r 2 is part of the compensator, and the value of r 1 value can be set by voltage divider. see compensator design for r 1 and r 2 selection. v out fb vref voltage divider r2r1 -+ figure 15 voltage d ivider frequency selection the frequency can be set by external rt resistor. the relationship between frequency and rt pin is shown as follows: 25002000 1500 500 0 1000 3 13 23 33 rt(kohm) nx9415 frequency vs r rt frequency(khz) figure 16 frequency versus rt resistor downloaded from: http:///
5a constant frequency hysteretic synchronous regulator 16 mcm 24 pin 4 x 4 package outline dimensions by marking 4.000 0.050 0.400 0.050 4.000 0.050 top view side view bottom view 2.600 0.050 1.125 2.500ref. 0.500 bsc 0.050 0.250 0.050 pin #1 identificationchamfer 0.300 x 45 0.900 0.000-0.050 0.203 ref. exp.dap exp.dap figure 17 package dimensions note: all dimensions are displayed in millimeters. downloaded from: http:///
nx9415.0/ 01.3 microsemi corporation (nasdaq: mscc) offers a comprehensive portfolio of semiconductor solutions for: aerospace, defense and security; en terprise and communications; and industrial and alternative energy markets. products include high - performance, high - reliability analog and rf devices, mixed signal and rf integrated circuits, customizable socs, fpgas, and complete subsystems. microsemi is headquartered in aliso viejo, calif. learn more at www.microsemi.com . ? 2013 microsemi corporation. all rights reserved. microsemi and the microsemi l ogo are trade marks of microsemi corporation. all other trademarks and service marks are the prop erty of their respective owners . microsemi corporate headquarters one enterprise, aliso viejo ca 92656 usa within the usa: +1(949) 380 - 6100 sales: +1 (949) 380 - 6136 fax : +1 (949) 215 - 4996 downloaded from: http:///

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