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1/15 www.rohm.com 2011.02 - rev. a ? 2011 rohm co., ltd. all rights reserved. single-chip type with built- in fet switching regulators simple step-down switching regulator with built-in power mosfet BD9328EFJ description the BD9328EFJ is a synchronous step-down switching regulato r that integrates 2 low re sistance n-channel mosfets. it achieves 2a continuous output curr ent over a wide input supply range. current mode operation provides fast transie nt response and easy phase compensation. features 1) wide operating input range 4.2v 18.0v 2) 2a output current 3) hi-side / lo-side fet on-resistance; 0.15 / 0.13 ? power switch 4) low esr output ceramic capacitors are available 5) low standby current during shutdown mode 6) 380 khz fixed operating frequency 7) feedback voltage 0.9v 1.5% accuracy at room temp. (2.0% guaranteed for -25 to 85 temperature range) 8) protection circuits under voltage lockout protection thermal shutdown over current protection 9) htsop-j8 package with exposed thermal pad. applications distributed power system pre-regulator for linear regulator absolute maximum ratings (ta = 25 ) parameter symbol ratings unit supply voltage v in 20 v switch voltage v sw 20 v power dissipation for htsop-j8 pd 3760 *1 mw package thermal resistance ja *2 ja 29.27 /w package thermal resistance jc *2 jc 3.75 /w 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 20 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 mount on 4-layer 50mm x 30mm x 1.6mm application board no.11027eat55
technical note 2/15 www.rohm.com 2011.02 - rev. a ? 2011 rohm co., ltd. all rights reserved. BD9328EFJ ? ?
technical note 3/15 www.rohm.com 2011.02 - rev. a ? 2011 rohm co., ltd. all rights reserved. BD9328EFJ
technical note 4/15 www.rohm.com 2011.02 - rev. a ? 2011 rohm co., ltd. all rights reserved. BD9328EFJ ? ? ? ? ? ? ? ? ?
technical note 5/15 www.rohm.com 2011.02 - rev. a ? 2011 rohm co., ltd. all rights reserved. BD9328EFJ outward form 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 fig.3 htsop-j8 package (unit:mm) +0.05 -0.03 4.90.1 (max5.25 include.burr) (3.2) (2.4) 6.00.2 3.90.1 0.545 1pin mark 8 7 6 5 4 3 2 1 1.050.2 0.17 1.27 0.42 -0.04 +0.05 0.850.05 1.0max -4 +6 s 0.08 0.08 s +0.05 -0.03 0.650.15 0.080.08 m
technical note 6/15 www.rohm.com 2011.02 - rev. a ? 2011 rohm co., ltd. all rights reserved. BD9328EFJ typical performance characteristics (unless otherwise specified, vin= 12v ta = 25 ) 1 10 100 1000 0.01 0.1 1 css [ uf] soft start time[ms] fig.12 soft start time 50 55 60 65 70 75 80 85 90 95 0 500 1000 1500 2000 2500 3000 io[ma] efficiency[%] fig.10 step down efficiency (vin= 12v v out = 3.3v l=10h) fig.9 operating frequency 340 345 350 355 360 365 370 -40-200 20406080 temp (c) fosc (khz) fig.6 input bias current -0.01 -0.005 0 0.005 0.01 00.40.81.21.6 22.4 vfb ( v) ifb (ua) 0 4 8 12 16 20 24 28 32 4 6 8 10 12 14 16 18 vin ( v) icc (ua) fig.5 stand by current (ic not active) 0.4 0.6 0.8 1 1.2 1.4 1.6 369121518 vin ( v) icc (ma) fig.4 circuit current (no switching) 0.88 0.89 0.90 0.91 0.92 -40 -20 0 20 40 60 80 temp[ ] feedback voltage[v] fig.7 feedback voltage 0.1 0.14 0.18 0.22 0.26 -40-200 20406080 temp [c] ron [ ] fig.8 hi,low-side on-resistance ss iout sw vout fig.11 overcurrent protection
technical note 7/15 www.rohm.com 2011.02 - rev. a ? 2011 rohm co., ltd. all rights reserved. BD9328EFJ fig.13 transient response (vin= 12v v out = 3.3v l= 10h cout =20f iout= 0.2-1.0a ) fig.17 start up waveform (vin= 12v v out = 3.3v l= 10h c ss = 0.1f) fig.15 transient response (vin= 12v v out = 3.3v l= 10h cout =20f iout= 0.2-2.0a) fig.16 output ripple voltage (vin= 12v v out = 3.3v l= 10h cout =20f i out= 2.0a ) v out i out v out v out v out v out i out i out i out en v out : 50 mv / div v out : 100 mv / div i out : 1.0 a / div i out : 1.0 a / div v out : 20.0 mv / div i out : 1.0 a / div i out :25.6 mv : 25.2 mv v out - max : +100mv v out - min : -100mv v out - max : +48mv v out - min : -50m v v out : 1.0v / div en: 10v / div v out : 20.0 mv / div i out : 1.0 a / div fig.14 output ripple voltage (vin= 12v v out = 3.3v l= 10h cout =20f i out= 1.0a ) tss 22ms
technical note 8/15 www.rohm.com 2011.02 - rev. a ? 2011 rohm co., ltd. all rights reserved. BD9328EFJ selecting application components (1) output lc filter constant selection (buck converter) the output lc filter is required to supp ly constant current to the output load. a larger value inductance at this filter results in less inductor ripple current( ? i l ) and less output ripple voltage. however, the larger value inductors tend to have less fast load transient-response, a larger physical size, a lower saturation current and higher series resistance. a smaller value inductance has almost opposite characte ristics above. so choosing the inductor ripple current( ? i l ) between 20 to 40% of the averaged inductor current (equivalent to the output load current) is a good compromise. fig.18 fig.19 setting ? i l = 30% x averaged inductor current (2a) = 0.6 [a] l = v out ? (v in - v out ) x 1 = 10 [h] v in x f osc x ? i l where v in = 12v, v out = 3.3v, f osc = 380 khz, ; f osc is a switching frequency also the inductor should have the higher saturation current than i outmax + ? i l / 2. the output capacitor c out affects the output ripple-voltage. choose the large capacitor to achieve the small ripple-voltage enough to meet the application requirement. output ripple voltage ? v rpl is calculated by the following equation. where r esr is a parasitic series resistance in output capacitor. setting c out = 20f, r esr = 10m ? v rpl = 0.6 x (10m + 1 / (8 x 20 x 380k)) = 15.8mv ? v rpl = ? i l ? ( r esr + 1 ) [v] 8x c out x f osc v out l v in c out i l t i outmax + ? i l /2 should not reach the rated value level i lr inductor averaged current
technical note 9/15 www.rohm.com 2011.02 - rev. a ? 2011 rohm co., ltd. all rights reserved. BD9328EFJ phase margin 180 90 180 90 0 0 a (a) gbw(b) f f gain [db] phase f crs (2) loop compensation choosing compensation capacitor c cmp and resistor r cmp the current-mode buck converter has 2-poles and 1-zero system. choosing the compensation resistor and capacitor is important for a good load-transient response and good stability. the example of dc/dc converter application bode plot is shown below. the compensation resistor r cmp will decides the cross over frequency f crs (the frequency that the total dc-dc loop-gain falls to 0db). setting the higher cross over frequency achieves good res ponse speed, however less stability. while setting the lower cross over frequency shows good stability but worse response speed. the 1/10 of switching frequency for the cross over fr equency shows a good performance at most applications. ( i ) choosing phase co mpensation resistor r cmp the compensation resistor r cmp can be on following formula. r cmp = 2 x v out x f crs x c out [ ] v fb x g mp x g ma where v out ; output voltage, f crs ; cross over frequency, c out ; output capacitor, v fb ; internal feedback voltage ( 0.9v (typ) ), g mp ; current sense gain ( 7.8a/v (typ) ) , g ma ; error amplifier trans-conductance ( 300a/v (typ) ) setting v out = 3.3v, f crs = 38khz, c out = 20f; r cmp = 2 x 3.3 x 38k x 20u = 7.48k ~= 7.5k [ ] 0.9 x 7.8 x 300u ( ii ) choosing phase comp ensation capa citor ccmp for the stability of dc/dc converter, canceling the phase delay that derives from output capacitor c out and resistive load r out by inserting the phase advance. the phase advance can be added by the zero on compensation resistor r cmp and capacitor c cmp . making fz= f crs / 6 gives a first-order estimate of c cmp . compensation capacitor c cmp = 1 [f] 2 x r cmp x fz setting fz= f crs /6 = 6.3khz; compensation capacitor c cmp = 1 = 3.54n ~= 3.3n [f] 2 x 7.5k x 6.3k ( iii ) the condition of the loop compensation stability the stability of dc/dc converter is important. to secure the operating stability, please check the loop compensation has the enough phase-margin. for the condition of loop compensation stability, the phase-delay must be less than 150 degree where gain is 0 db. feed forward capacitor c rup boosts phase margin over a limited frequency range and is sometimes used to improve loop response. c rup will be more effective if r up >> r up ||r dw fig.20 fig.21 v out r up c cmp comp r cmp fb r dw 0.9v c rup
technical note 10/15 www.rohm.com 2011.02 - rev. a ? 2011 rohm co., ltd. all rights reserved. BD9328EFJ (3) design of feedback resistance constant set the feedback resistance as shown below. v out = r1 + r2 ? 0.9 [v] r2 fig.22 soft start function an adjustable soft-start function to prevent high inrush current during start-up is available. the soft-start time is set by th e external capacitor connected to ss pin. the soft start time is given by; t ss [s] = 2.2 x css / i ss setting c ss = 0.1f; t ss = 2.2 x 0.1 / 10 = 22 [ms] please confirm the overshoot of the output voltage and inrush current when deciding the ss capacitor value. fig.23 en function the en terminal control ic?s shut down. leaving en terminal open makes ic shutdown. to start the ic, en terminal should be connected to vin or the other power source output. when the en voltage exceed 1.2v (typ.), the ic start operating. (attention) chattering happens if standing lowering speed is slow when standing of en pin is lowered. the reverse current in which the input side and the pressure operation are done from the output side is generated when chattering operates with the output voltage remained, and there is a case to destruction. please set to stand within 100us when you control on/off by the en signal. this necessity doesn't exist when en pin is connected with vin and en is not controlled. the control by open drain mosfet shown in a left chart is recommended. fig.24 vin en 66 k ? (typ.) 91 k ? (typ.) + v out r1 r2 err 0.9v fb ren on/off signal en c ss ss + + - comp i ss 10a erramp
technical note 11/15 www.rohm.com 2011.02 - rev. a ? 2011 rohm co., ltd. all rights reserved. BD9328EFJ c in fet c out l v out vin layout pattern consideration two high pulsing current flowing loops exist in the buck regulato r system. the first loop, when fet is on, starts from the input capacitors, to the vin terminal, to the sw terminal, to the inductor, to t he output capacitors, and then returns to the input capacitor through gnd. the second loop, when fet is off, starts from the low fet, to the inductor, to the output capacitor, and then returns to the low fet through gnd. to reduce the noise and improve the efficiency, please minimize these two loop area. especially input capacitor, output capacitor and low fet 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 and the output capacitors should be placed close to sw pin as much as possible. comp bst vin sw fb ss en gnd c out l v out c in fig.25 current loop in buck regulator system fig.26 the example of pcb layout pattern
technical note 12/15 www.rohm.com 2011.02 - rev. a ? 2011 rohm co., ltd. all rights reserved. BD9328EFJ i/o equivalent circuit diagram 1.bst 3.sw 5.fb 6.comp 7.en 8.ss 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) 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 vin vin sw reg vin vin ef vin vin vin
technical note 13/15 www.rohm.com 2011.02 - rev. a ? 2011 rohm co., ltd. all rights reserved. BD9328EFJ (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 notes for use 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 power 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 board, connecting a capaci tor 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 patterns, 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.27 , 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.27 example of a simple monolithic ic architecture
technical note 14/15 www.rohm.com 2011.02 - rev. a ? 2011 rohm co., ltd. all rights reserved. BD9328EFJ 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. 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 stresses 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. 12) en control speed chattering happens if standing lowering speed is slow when st anding of en pin is lowered. the reverse current in which the input side and the pressure operation are done from th e output side is generated when chattering operates with the output voltage remained, and there is a case to destruction. please set to stand within 100us when you control on/off by the en signal.
technical note 15/15 www.rohm.com 2011.02 - rev. a ? 2011 rohm co., ltd. all rights reserved. BD9328EFJ ordering part number b d 9 3 2 8 e f j - e 2 part no. part no. package efj: htsop-j8 packaging and forming specification e2: embossed tape and reel (unit : mm) htsop-j8 0.08 s 0.08 m s 1.0max 0.850.05 1.27 0.080.08 0.42 +0.05 - 0.04 1.050.2 0.650.15 4 + 6 ? 4 0.17 +0.05 - 0.03 234 568 (max 5.25 include burr) 7 1 0.545 (3.2) 4.90.1 6.00.2 (2.4) 3.90.1 1pin mark ? order quantity needs to be multiple of the minimum quantity. embossed carrier tape tape quantity direction of feed the direction is the 1pin of product is at the upper left when you hold reel on the left hand and you pull out the tape on the right hand 2500pcs e2 () direction of feed reel 1pin
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