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| 1/14 www.rohm.com 2010.08 - rev.c ? 2010 rohm co., ltd. all rights reserved. single-chip type with built- in fet switching regulators simple step-down switching regulators with built-in power mosfet BD9325FJ,bd9326 efj,bd9327efj description the BD9325FJ, bd9326efj and bd9327efj are step-down regulators t hat integrate a low resistance high side n-channel mosfet. it achieves 2a / 3a / 4a continuous output current over a wide input supply range. current mode operation provides fast transie nt response and easy phase compensation. features 1) wide operating input range 4.75v 18.0v 2) selectable 2a / 3a / 4a output current 3) selectable 0.16 ? / 0.12 ? / 0.11 ? internal mosfet switch 4) low esr output ceramic capacitors are available 5) low stanby current during shutdown mode 6) 380khz operating frequency 7) feedback voltage 0.9v 1.5% accuracy at room temp. (3.0% for -40 to 85 temperature range) 8) protection circuit: undervoltage lockout protection circuit thermal shutdown circuit overcurrent protection circuit 9) sop-j8 package for 2a model, htsop-j8 packa ge for 3a, 4a models (with exposed thermal pad) applications distributed power system pre-regulator for linear regulator line up matrix line-up BD9325FJ bd9326efj bd9327efj fet on-resistance 0.16 ? 0.12 ? 0.11 ? output current 2.0 a 3.0a 4.0 a package sop-j8 htsop-j8 htsop-j8 no.10027ect06
technical note BD9325FJ, bd9326efj, bd9327efj 2/14 www.rohm.com 2010.08 - rev.c ? 2010 rohm co., ltd. all rights reserved. absolute maximum ratings (ta = 25c) parameter symbol ratings unit supply voltage v in 20 v switch voltage v sw 20 v power dissipation for htsop-j8 pd1 3760 *1 mw power dissipation for sop-j8 pd2 675 *2 mw operating temperature range topr -40 +85 storage temperature range tstg -55 +150 junction temperature tjmax 150 bst voltage v bst v sw +7 v en voltage v en 20 v all other pins v oth 7 v *1 derating in done 30.08 mw/ for operating above ta R 25 (mount on 4-layer 70.0mm 70.0mm 1.6mm board) *2 derating in done 5.4 mw/ for operating above ta R 25 (mount on 1-layer 70.0mm 70.0mm 1.6mm board) operation range (ta= -40 85) parameter symbol ratings unit min typ max supply voltage v in 4.75 12 18 v sw voltage v sw -0.5 - 18 v output current for BD9325FJ i sw2 - - 2** a output current for bd9326efj i sw3 - - 3** a output current for bd9327efj i sw4 - - 4** a ** pd, aso should not be exceeded electrical characteristics (unless otherwise specified v in =12v ta=25 ) parameter symbol limits unit conditions min typ max error amplifier block fb input bias current i fb - 0.1 2 a feedback voltage1 v fb1 0.886 0.900 0.914 v voltage follower feedback voltage2 v fb2 0.873 0.900 0.927 v ta=-40 85 sw block ? sw hi-side fet on-resistance for BD9325FJ r on2 - 0.16 - ? i sw = -0.8a *** hi-side fet on-resistance for bd9326efj r on3 - 0.12 - ? i sw = -0.8a *** hi-side fet on-resistance for bd9327efj r on4 - 0.11 - ? i sw = -0.8a *** lo-side fet on-resistance r onl - 10 - ? i sw = 0.1a leak current n-channel i leakn - 0 10 a v in = 18v, v sw = 0v switch current limit for BD9325FJ i limit2 2.5 - - a *** switch current limit for bd9326efj i limit3 3.5 - - a *** switch current limit for bd9327efj i limit4 4.5 - - a *** maximum duty cycle m duty - 90 - % v fb = 0v general enable sink current i en 86 181 275 a v en = 12v enable threshold voltage v en 1.1 1.18 1.4 v under voltage lockout threshold v uvlo 4.05 4.40 4.75 v v in rising under voltage lockout hysteresis v hys - 0.1 - v soft start current i ss 23 41 62 ua v ss = 0 v soft start time t ss - 1.6 - ms c ss = 0.1 f operating frequency f osc 300 380 460 khz circuit current i cc - 2.1 4.3 ma v fb = 1.5v, v en = 12v quiescent current i qui - 80 170 a v en = 0v *** see the series line-up table below. technical note BD9325FJ, bd9326efj, bd9327efj 3/14 www.rohm.com 2010.08 - rev.c ? 2010 rohm co., ltd. all rights reserved. block diagram typical application circuit fig.1 block diagram en;pull up to vin en fb vref tsd uvlo ibias err soft start slope + pwm vreg osc 5v lvs gnd sw vin bst ss vin s drv logic r comp lvs ocp output 12v + fi g .2 a pp lication circuit c_co1 r_pc 15k r_dw r_up c_bs 0.1 f 10 h c_vc1 10 f c_pc1 3300pf 10k 27k 20 f c_ss 0.1 f l ss en comp fb bst vin gnd sw d thermal pad (for bd9326efj, bd9327efj) vin 12v v out 3.3v technical note BD9325FJ, bd9326efj, bd9327efj 4/14 www.rohm.com 2010.08 - rev.c ? 2010 rohm co., ltd. all rights reserved. block operation ? vreg a block to generate constant-voltage for dc/dc boosting. ? vref a block that generates internal reference voltage of 2.9 v (typ.). ? tsd/uvlo tsd (thermal shutdown)/uvlo (under voltage lockout) prot ection block. the tsd circuit shuts down ic at 175 (typ.) the uvlo circuit shuts down the ic when the vcc is low voltage. ? error amp block (err) this is the circuit to compare the reference voltage and the feedback voltage of output voltage. the comp pin voltage resulting from this comparison determines the switching duty. at the time of start up, since the soft start is operated by the ss pin voltage, the comp pin voltage is limited to the ss pin voltage. ? oscillator block (osc) this block generates the oscillating frequency. ? slope block this block generates the triangular waveform from the clock created by osc. generated trian gular waveform is sent to the pwm comparator. ? pwm block the comp pin voltage output by the error amp is compared to the slope block's triangular waveform to determine the switching duty. since the switching duty is limited by the maximum duty ratio which is determined internally, it does not become 100%. ? drv block a dc/dc driver block. a signal from the pwm is input to drive the power fets. ? soft start circuit since the output voltage rises gradually while restricting the current at the time of startup, it is possible to prevent the output voltage overshoot or the rush current. pin assignment and pin function pin no. pin name function 1 bst high-side gate drive boost input 2 vin power input 3 sw power switching output 4 gnd ground 5 fb feed back input 6 comp compensation node 7 en enable input 8 ss soft start control input technical note BD9325FJ, bd9326efj, bd9327efj 5/14 www.rohm.com 2010.08 - rev.c ? 2010 rohm co., ltd. all rights reserved. typical performance characteristics (unless otherwise specified, v in = 12v ta = 25 ) fig.3 circuit current (no switching) 1.5 1.6 1.7 1.8 1.9 2 2.1 2.2 2.3 2.4 2.5 4 6 8 1012141618 vin : [v] icc [ma] 0 20 40 60 80 100 120 140 160 4 6 8 10 12 14 16 18 vin : [v] icc [ua] 0.873 0.883 0.893 0.903 0.913 0.923 -40-20 0 20406080100 temperature : [c] feedback voltage [v] fig.4 quiescent current (ic not active) fig.5 input bias current fig.6 feedback voltage 300 310 320 330 340 350 360 370 -40 -20 0 20 40 60 80 temperature : [c] operating frequency [khz] fig.8 operating frequency fig.9 step down efficiency (vin= 12v v out = 3.3v l=10h) v out v ss v sw i out fig.10 overcurrent protection (v out is shorted to gnd) 0.01 0.1 1 10 100 0.001 0.01 0.1 1 c ss [uf] softstart time [ms] fig.11 soft start time -0.1 -0.08 -0.06 -0.04 -0.02 0 0.02 0.04 0.06 0.08 0.1 0 0.5 1 1.5 2 v fb [v] ifb [ua] 50 55 60 65 70 75 80 85 90 95 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 iout [a] efficiency [%] BD9325FJ bd9326efj 0 0.05 0.1 0.15 0.2 0.25 -40-200 20406080 ta [ ] ron [ ] bd9326efj BD9325FJ fig.7 hi-side on-resistance technical note BD9325FJ, bd9326efj, bd9327efj 6/14 www.rohm.com 2010.08 - rev.c ? 2010 rohm co., ltd. all rights reserved. fig.16 start up waveform (vin= 12v vout= 3.3v l= 22h css= 0.1f iout= 0a) fig.12 transient response (vin= 12v vout= 3.3v l= 10h cout =22f iout= 0.2-1.0a ) fig.13 output ripple voltage (vin= 12v vout= 3.3v l= 10h cout =22f i out= 1.0a ) fig.14 transient response (vin= 12v v out = 3.3v l= 10h cout =22f iout= 0.2-3.0a) fig.15 output ripple voltage (vin= 12v vout= 3.3v l= 10 h cout =22f iout= 3.0a) v out v out i out i out v out : 100 mv / d i out : 1.0 a / div v out : 10.0 mv / div i out : 1.0 a / div v out - max : +100mv v out - min : -100m v v out v out i out i out : 1.0 a / div i out v out - max : +460mv v out - min : -240mv v out : 10.0 mv / div i out : 1.0 a / div i out v out en v out : 1.0v / div i out : 1.0 a / div en: 10v / div : 10.4 mv :11.8 mv technical note BD9325FJ, bd9326efj, bd9327efj 7/14 www.rohm.com 2010.08 - rev.c ? 2010 rohm co., ltd. all rights reserved. selecting application components (1) output lc constant (buck converter) the inductance l to use for output is decided by the rated current ilr and input current maximum value iomax of the inductance. fig.17 fig.18 adjust so that iomax + ? il does not reach the rated curre nt value ilr. at this time, ? il can be obtained by the following equation. ? i l = 1 ? (v cc - vo) ? vo ? 1 [a] l v cc f set with sufficient margin because the induct ance l value may have the dispersion of 30%. for the capacitor c to use for the output, select the capa citor which has the larger value in the ripple voltage v pp permissible value and the drop voltage permissible value at the time of sudden load change. output ripple voltage is decid ed by the following equation. ? v pp = ? i l ? r esr + ? i l ? vo ? 1 [v] 2co v cc f perform setting so that the voltage is within the permissible ripple voltage range. for the drop voltage vdr during sudden load change, please perform the rough calculation by the following equation. v dr = ? i l ? 10 s [v] co however, 10 s is the rough calculation value of the dc/dc response speed. make co settings so that these two va lues will be within the limit values. i l t i omax + ? i l should not reach the rated value level i lr i omax mean current vo l vcc i l co technical note BD9325FJ, bd9326efj, bd9327efj 8/14 www.rohm.com 2010.08 - rev.c ? 2010 rohm co., ltd. all rights reserved. (2) loop compensation choosing compensation capacitor c 1 and resistor r 3 the example of dc/dc converter application bode plot is shown below. the compensat ion resistor r3 will set the cross over frequency fc that decides the stability and response speed of dc/dc converter. so compensation resistor r3 has to be adjusted to adequate value for good stability and response speed. the cross over frequency f c can be adjusted by changing the compensati on resistor r3 connected to comp terminal. the higher cross over frequency achieves good response spee d, but less stability. and the lower cross over frequency shows good stability, but worse response speed. usually, the 1/10 of dc/dc converter operating fr equency is used for cross over frequency f c . so please decide the compensation resistor and capacitor using the followi ng formula on setting f c to 1/10 of operating frequency at first. after that, please measure and adjust the cr oss over frequency on your set (on the actu al application) to meet the enough response speed and phase-margin. ( i ) choosing phase comp ensation resistor r3 please decide the compensation resistor r3 on following formula. compensation resistor r3= 5800 c out f c v out [ ? ] where c out : output capacitor connected to dc/dc output v out : output voltage f c : desired cross over frequency (38khz) ( ii ) choosing phase comp ensation capacitor c1 the stability of dc/dc converter needs to cancel the phase delay that is from output lc f ilter by inserting the phase advance. the phase advance can be added by the zero on compensation resistor and capacitor. the lc resonant frequency flc and the zero on compensat ion resistor and capacitor are expressed below. lc resonant frequency f lc = 1 [hz] 2 lc out zero by c 1 and r 3 f z = 1 [hz] 2 c 1 r 3 please choose c1 to make fz to 1 / 3 of flc . compensation capacitor c 1 = 3 [f] 2 f lc r 3 ( iii ) the condition of the loop compensation stability the stability of dc/dc converter is important. to secure th e operating stability, please check the loop compensation has the enough phase-margin. for the condition of loop co mpensation stability, the phase-delay must be less than 150 degree where gain is 0 db. namely over 30 degree phase-margin is needed. lastly after the calculation above, please measure and adjust the phase-margin to secure over 30 degree. phase margin 180 90 180 90 0 0 a (a) gbw(b) f f gain [db] phase f c v out r1 r2 c1 comp r3 fb technical note BD9325FJ, bd9326efj, bd9327efj 9/14 www.rohm.com 2010.08 - rev.c ? 2010 rohm co., ltd. all rights reserved. (3) design of feedback resistance constant set the feedback resistance as shown below. v out = r1 + r2 ? reference voltage [v] r2 soft start function the buck converter has an adjustable soft start function to prevent high inrush current during start up. the soft-start time is set by th e external capaci tor connected to ss pin. the soft start time is given by; tss [ms] = 16.2 ?c [f] please confirm the overshoot of the output voltage and inrush current when deciding the ss capacitor value. en function the en terminal controls ic?s shut down. leaving en terminal open makes ic shutdown. to start the ic, en terminal should be connected to v in or the other power source output. when the en voltage exceed 1.2v (typ.), the ic start operating. fig.19 the equivalent internal circuit. css ss 2.9v(typ) + - comp 70k(typ) erramp vin en 66k ? (typ.) 60k ? (typ.) v out r1 r2 err reference voltage fb technical note BD9325FJ, bd9326efj, bd9327efj 10/14 www.rohm.com 2010.08 - rev.c ? 2010 rohm co., ltd. all rights reserved. layout pattern consideration two high pulsing current flowing loops exist in the buck regulator system. the first loop, when fet is on, starts from the input capacito rs, to the vin terminal, to the sw terminal, to the inductor, to the output capacitors, and then returns to the input capacitor through gnd. the second loop, when fet is off, starts from the shotkey diode, to the inductor, to the output capacitor, and then returns to the shotkey diode through gnd. to reduce the noise and improve the efficiency, please minimize these two loop area. especially input capacitor, output capacitor and s hotkey diode should be connected to gnd plain. pcb layout may affect the thermal perf ormance, noise and efficiency greatly. so please take extra care when designing pcb layout patterns. ? the thermal pad on the back side of ic has the great thermal conduction to the chip. so using the gnd plain as broad and wide as possible can help thermal dissipation. and a lot of the rmal via for helping the spread of heat to the different layer i s also effective. ? the input capacitors should be connected as close as possible to the vin terminal. ? keep sensitive signal traces such as trace connected fb and comp away from sw pin. ? the inductor, the shot key diode and the output capacitors s hould be placed close to sw pin as much as possible. c in fet di c out l v out vin fig.20 current loop in buck regulator system fig.21 the example of pcb layout pattern ss bst vin sw gnd fb comp en c in c out l di fet vin sw v out technical note BD9325FJ, bd9326efj, bd9327efj 11/14 www.rohm.com 2010.08 - rev.c ? 2010 rohm co., ltd. all rights reserved. operation notes 1) absolute maximum ratings use of the ic in excess of absolute maximum ratings such as the applied voltage or op erating temperature range may result in ic damage. assumptions should not be made regardin g the state of the ic (short mode or open mode) when such damage is suffered. a physical safety measure such as a fuse should be implemented when use of the ic in a special mode where the absolute maximum ratings may be exceeded is anticipated. 2) gnd potential ensure a minimum gnd pin potentia l in all operating conditions. 3) setting of heat use a thermal design that allows for a suffic ient margin in light of the power dissipa tion (pd) in actual operating conditions. 4) pin short and mistake fitting use caution when orienting and positioning the ic for mounting on printed circuit boards. improper mounting may result in damage to the ic. shorts between output pins or between output pins and the po wer supply and gnd pins caused by the presence of a foreign object may result in damage to the ic. 5) actions in strong magnetic field use caution when using the ic in the pres ence of a strong magnetic field as doi ng so may cause the ic to malfunction. 6) testing on application boards when testing the ic on an application boar d, connecting a capacitor to a pin with low impedance subjects the ic to stress. always discharge capacitors after each process or step. ground the ic during assembly steps as an antistatic measure, and use similar caution when transporting or st oring the ic. always turn the ic's power supply off before connecting it to or removing it from a jig or fixtur e during the inspection process. 7) ground wiring patterns when using both small signal and large current gnd pattern s, it is recommended to isolate the two ground patterns, placing a single ground point at the application's referenc e point so that the pattern wiring resistance and voltage variations caused by large currents do not cause variations in the small signal ground voltage. be careful not to change the gnd wiring patterns of any external components. 8) regarding input pin of the ic this monolithic ic contains p+ isolation and p substrate layers between adjacent el ements in order to keep them isolated. p/n junctions are formed at the intersecti on of these p layers with the n layers of other elements to create a variety of parasitic elements. for example, when the resistors and transistors are connected to the pins as shown in fig.22 , a parasitic diode or a transistor operates by invertin g the pin voltage and gnd voltage. the formation of parasitic elements as a result of the relationships of the potentials of different pins is an inevitable resul t of the ic's architecture. the operation of parasitic elements c an cause interference with circuit operation as well as ic malfunction and damage. for these reasons, it is necessary to use caution so that the ic is not used in a way that will trigger the operation of parasitic elements such as by the a pplication of voltages lower than the gnd (p substrate) voltage to input and output pins. fig.22 example of a simple monolithic ic architecture 9) overcurrent protection circuits an overcurrent protection circuit designed according to the out put current is incorporated fo r the prevention of ic damage that may result in the event of load sh orting. this protection circuit is effect ive in preventing damage due to sudden and unexpected accidents. however, the ic should not be used in applications characterized by the continuous operation or transitioning of the protection circuits. at the time of thermal designing, keep in mind that the current capacity has negative characteristics to temperatures. (pin a) gnd n p n n p+ p+ resistor parasitic elements p parasitic elements ( pin b ) gnd c b e parasitic elements gnd ( pin a ) gnd n p n n p+ p+ parasitic elements p substrate ( pin b ) c b e transistor (npn) n gnd technical note BD9325FJ, bd9326efj, bd9327efj 12/14 www.rohm.com 2010.08 - rev.c ? 2010 rohm co., ltd. all rights reserved. 10) thermal shutdown circuit (tsd) this ic incorporates a built-in tsd circuit for the protecti on from thermal destruction. t he ic should be used within the specified power dissipation range. however, in the event that the ic continues to be oper ated in excess of its power dissipation limits, the attendant rise in the chip's junction temperature tj will trig ger the tsd circuit to turn off all outpu t power elements. operation of the tsd circuit presumes that the ic's absolute maximum ratings have been exceeded. applicat ion designs should never make use of the tsd circuit. 11) testing on application boards at the time of inspection of t he installation boards, when the capacitor is c onnected to the pin with low impedance, be sure to discharge electricity per process because it may load stresse s to the ic. always turn the ic's power supply off before connecting it to or removing it from a jig or fixture during the inspection proce ss. ground the ic during assembly steps as an antistatic measure, and use similar cautio n when transporting or storing the ic. i/o equivalent circuit diagram 1.bst 3.sw 5.fb 6.comp 7.en 8.ss vin vin sw reg vin ef vin vin vin vin technical note BD9325FJ, bd9326efj, bd9327efj 13/14 www.rohm.com 2010.08 - rev.c ? 2010 rohm co., ltd. all rights reserved. power dissipation htsop-j8 package on 70 ? 70 ? 1.6 mm glass epoxy pcb (1) 1-layer board (backside copper foil area 0 mm ? 0 mm) (2) 2-layer board (backside copper foil area 15 mm ? 15 mm) (3) 2-layer board (backside copper foil area 70 mm ? 70 mm) (4) 4-layer board (backside copper foil area 70 mm ? 70 mm) sop-j8 package on 70 ? 70 ? 1.6 mm glass epoxy pcb (1) 1-layer board (backside copper foil area 0 mm ? 0 mm) 150 0 50 75 100 125 2000 4000 1000 3000 25 power dissipation: pd [mw] ambient temperature: ta [c] (1)820mw (2)1100mw (3)2110mw (4)3760mw 0 150 0 50 75 100 125 2000 4000 1000 3000 25 power dissipation: pd [mw] ambient temperature: ta [c] (1)675mw 0 technical note BD9325FJ, bd9326efj, bd9327efj 14/14 www.rohm.com 2010.08 - rev.c ? 2010 rohm co., ltd. all rights reserved. ordering part number b d 9 3 2 5 f j - e 2 part no. part no. 9325 9326 9327 package fj : sop-j8 efj : htsop-j8 packaging and forming specification e2: embossed tape and reel ? order quantity needs to be multiple of the minimum quantity. r1010 a www.rohm.com ? 2010 rohm co., ltd. all rights reserved. notice rohm customer support system http://www.rohm.com/contact/ thank you for your accessing to rohm product informations. more detail product informations and catalogs are available, please contact us. notes no copying or reproduction of this document, in part or in whole, is permitted without the consent of rohm co.,ltd. the content specied herein is subject to change for improvement without notice. the content specied herein is for the purpose of introducing rohm's products (hereinafter "products"). if you wish to use any such product, please be sure to refer to the specications, which can be obtained from rohm upon request. examples of application circuits, circuit constants and any other information contained herein illustrate the standard usage and operations of the products. the peripheral conditions must be taken into account when designing circuits for mass production. great care was taken in ensuring the accuracy of the information specied in this document. however, should you incur any damage arising from any inaccuracy or misprint of such information, rohm shall bear no responsibility for such damage. the technical information specied herein is intended only to show the typical functions of and examples of application circuits for the products. rohm does not grant you, explicitly or implicitly, any license to use or exercise intellectual property or other rights held by rohm and other parties. rohm shall bear no responsibility whatsoever for any dispute arising from the use of such technical information. the products specied in this document are intended to be used with general-use electronic equipment or devices (such as audio visual equipment, ofce-automation equipment, commu- nication devices, electronic appliances and amusement devices). the products specied in this document are not designed to be radiation tolerant. while rohm always makes efforts to enhance the quality and reliability of its products, a product may fail or malfunction for a variety of reasons. please be sure to implement in your equipment using the products safety measures to guard against the possibility of physical injury, re or any other damage caused in the event of the failure of any product, such as derating, redunda ncy, re control and fail-safe designs. rohm shall bear no responsibility whatsoever for your use of any product outside of the prescribed scope or not in accordance with the instruction manual. the products are not designed or manufactured to be used with any equipment, device or system which requires an extremely high level of reliability the failure or malfunction of which may result in a direct threat to human life or create a risk of human injury (such as a medical instrument, transportation equipment, aerospac e machinery, nuclear-reactor controller, fuel- controller or other safety device). rohm shall bear no responsibility in any way for use of any of the products for the above special purposes. if a product is intended to be used for any such special purpose, please contact a rohm sales representative before purchasing. if you intend to export or ship overseas any product or technology specied herein that may be controlled under the foreign exchange and the foreign trade law, you will be required to obtain a license or permit under the law. |
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