BD8964FVM

Single-chip Type with Built-in FET Switching Regulator Series Low Noise High Efficiency Step-down Switching Regulator with Built-in Power MOSFET BD8964FVM No.09027EAT23 ●Description ROHM’s high efficiency step-down switching regulator BD8964FVM is a power supply designed to produce a low voltage including 1 volts from 5/3.3 volts power supply line. Offers high efficiency with synchronous rectifier. Employs a current mode control system to provide faster transient response to sudden change in load. ●Features 1) Offers fast transient response with current mode PWM control system. 2) Offers highly efficiency for all load range with synchronous rectifier (Nch/Pch FET) 3) Incorporates soft-start function. 4) Incorporates thermal protection and ULVO functions. 5) Incorporates short-current protection circuit with time delay function. 6) Incorporates shutdown function 7) Employs small surface mount package : MSOP8 ●Use Power supply for LSI including DSP, Micro computer and ASIC ●Line up Parameter VCC Voltage PVCC Voltage EN Voltage SW,ITH Voltage Power Dissipation 1 Power Dissipation 2 Operating temperature range Storage temperature range Maximum junction temperature ＊1 ＊2 ＊3 Symbol VCC PVCC VEN VSW,VITH Pd1 Pd2 Topr Tstg Tjmax Limits -0.3～+7 *1 Unit V V V V mW mW ℃ ℃ ℃ -0.3～+7 *1 -0.3～+7 -0.3～+7 387.5*2 587.4 *3 -25～+85 -55～+150 +150 Pd should not be exceeded. Derating in done 3.1mW/℃ for temperatures above Ta=25℃. Derating in done 4.7mW/℃ for temperatures above Ta=25℃, Mounted on 70mm×70mm×1.6mm Glass Epoxy PCB. ●Operating Conditions (Ta=25℃) Parameter VCC Voltage PVCC Voltage EN Voltage Output voltage Setting Range SW average output current ＊4 Symbol VCC *4 Limits Min. 4.0 4.0 0 1.0 Typ. 5.0 5.0 Max. 5.5 5.5 VCC 1.8 1.2 Unit V V V V A PVCC *4 VEN VOUT Isw *4 Pd should not be exceeded. www.rohm.com © 2009 ROHM Co., Ltd. All rights reserved. 1/13 2009.05 - Rev.A BD8964FVM ●Electrical Characteristics ◎ (Ta=25℃, VCC=5V, EN=VCC, R1=20kΩ, R2=10kΩ unless otherwise specified.) Parameter Symbol Min. Typ. Max. Standby current ISTB 0 10 Bias current ICC 250 450 EN Low voltage VENL GND 0.8 EN High voltage VENH 2.0 VCC EN input current IEN 1 10 Oscillation frequency FOSC 0.8 1 1.2 Pch FET ON resistance RONP 350 600 Nch FET ON resistance RONN 250 500 ADJ voltage VADJ 0.78 0.80 0.82 ITH SInk current ITHSI 10 20 ITH Source Current ITHSO 10 20 UVLO threshold voltage VUVLO1 3.6 3.8 4.0 UVLO release voltage VUVLO2 3.65 3.90 4.2 Soft start time TSS 0.5 1 2 Timer latch time TLATCH 1 2 3 ●Block Diagram, Application Circuit EN 3 VCC Technical Note Unit μA μA V V μA MHz mΩ mΩ V μA μA V V ms ms Conditions EN=GND Standby mode Active mode VEN=5V PVCC=5V PVCC=5V VADJ=H VADJ=L VCC=4→0V VCC=0→4V VADJ=H SCP/TSD operated 2.9±0.1 Max3.25(include.BURR) VREF 8 7 VCC Input PVCC 0.29±0.15 0.6±0.2 4 +6 -4 8 5 Current Comp. RQ Gm Amp. SLOPE VCC OSC S CLK 4.0±0.2 2.8±0.1 D89 6 4 Current Sense/ Protect + Driver Logic 5 4 6 SW Output 1 4 Lot No. 0.475 0.9Max. 0.75±0.05 0.08±0.05 1PIN MARK +0.05 0.145 -0.03 S +0.05 0.22 -0.04 Soft Start UVLO TSD PGND GND 0.65 0.08 S 1 ADJ 2 ITH Fig.1 BD8964FVM View ●Pin No. & function table Pin No. 1 2 3 4 5 6 7 8 Fig.2 BD8964FVM Block Diagram Pin name ADJ ITH EN GND PGND SW PVCC VCC Output voltage detect pin PIN function GmAmp output pin/Connected phase compensation capacitor Enable pin(Active High) Ground Nch FET source pin Pch/Nch FET drain output pin Pch FET source pin VCC power supply input pin www.rohm.com © 2009 ROHM Co., Ltd. All rights reserved. 2/13 2009.05 - Rev.A BD8964FVM ●Characteristics data (Reference data) 2.0 OUTPUT VOLTAGE:VOUT[V] OUTPUT VOLTAGE:VOUT[V] Technical Note 2.0 1.5 1.5 OUTPUT VOLTAGE:VOUT[V] 【VOUT=1.5V】 Ta=25℃ Io=0A 【VOUT=1.5V】 2.0 【VOUT=1.5V】 VCC=5V Ta=25℃ 1.5 1.0 1.0 1.0 0.5 0.5 VCC=5V Ta=25℃ Io=0A 0 1 2 3 4 EN VOLTAGE:VEN[V] 5 0.5 0.0 0 1 2 3 4 INPUT VOLTAGE:VCC[V] 5 0.0 0.0 0 1 2 OUTPUT CURRENT:IOUT[A] 3 Fig.3 Vcc-Vout Fig.4 Ven-Vout Fig.5 Iout-Vout 1.55 1.54 OUTPUT VOLTAGE:VOUT[V] 100 FREQUENCY:FOSC[MHz] 1.53 1.52 1.51 1.50 1.49 1.48 1.47 1.46 1.45 【VOUT=1.5V】 VCC=5V Io=0A EFFICIENCY:η[%] 90 80 70 60 50 40 30 20 10 0 【VOUT=1.5V】 1.20 1.15 1.10 1.05 1.00 0.95 0.90 0.85 0.80 VCC=5V Ta=25℃ 1 10 100 1000 OUTPUT CURRENT:IOUT[mA] 10000 -25 -15 -5 5 15 25 35 45 55 65 75 85 -25 -15 -5 5 15 25 35 45 55 65 75 85 TEMPERATURE:Ta[℃] TEMPERATURE:Ta[℃] Fig.6 Ta-VOUT Fig.7 Efficiency Fig.8 Ta-FOSC 0.40 0.35 ON [Ω] 2.0 1.8 350 VCC=5V CIRCUIT CURRENT:I CC [μA] 300 250 200 150 100 50 0 -25 -15 -5 5 15 25 35 45 55 65 75 85 VCC=5V 0.30 0.25 0.20 0.15 0.10 0.05 0.00 -25 -15 PMOS EN VOLTAGE:VEN[V] 75 85 1.6 1.4 1.2 1.0 0.8 0.6 0.4 ON RESISTANCE:R NMOS VCC=5V -5 5 15 25 35 45 55 65 0.2 0.0 TEMPERATURE:Ta[℃] -25 -15 -5 5 15 25 35 45 55 65 75 85 TEMPERATURE:Ta[℃] TEMPERATURE:Ta[℃] Fig.9 Ta-RONN, RONP Fig.10 Ta-VEN Fig.11 Ta-ICC www.rohm.com © 2009 ROHM Co., Ltd. All rights reserved. 3/13 2009.05 - Rev.A BD8964FVM Technical Note 1.2 【VOUT=1.5V】 FREQUENCY:FOSC[MHz] 【SLLMTM SW VOUT=1.5V】 1.1 VCC=PVCC =EN 1 VOUT 0.9 VOUT VCC=5V Ta=25℃ Io=0A VCC=5V Ta=25℃ 0.8 4 4.5 5 INPUT VOLTAGE:VCC [V] 5.5 Fig.12 Vcc-Fosc Fig.13 Soft start waveform Fig.14 SW waveform 【VOUT=1.5V】 VOUT 58mV VOUT 【VOUT=1.5V】 62mV IOUT IOUT VCC=5V Ta=25℃ VCC=5V Ta=25℃ Fig. 15 Transient response Io=100→600mA(10μs) Fig.16 Transient response Io=600→100mA(10μs) www.rohm.com © 2009 ROHM Co., Ltd. All rights reserved. 4/13 2009.05 - Rev.A BD8964FVM ●Information on advantages Advantage 1：Offers fast transient response with current mode control system. Conventional product (Load response IO=0.1A→0.6A) Technical Note BD8964FVM (Load response IO=0.1A→0.6A) VOUT 110mV VOUT 58mV IOUT IOUT Voltage drop due to sudden change in load was reduced Fig.17 Comparison of transient response Advantage 2： Offers high efficiency with synchronous rectifier EFFICIENCY:η[%] 100 90 【VOUT=1.5V】 80 ・For heavier load: Utilizes the synchronous rectifying mode and the low on-resistance MOS FETs incorporated as power transistor. ON resistance of P-channel MOS FET : 350mΩ(Typ.) ON resistance of N-channel MOS FET : 250mΩ(Typ.) 70 60 50 40 30 20 10 0 1 10 100 1000 OUTPUT CURRENT:IOUT[mA] 10000 VCC=5V Ta=25℃ Advantage 3：・ Supplied in smaller package due to small-sized power MOS FET incorporated. Fig.18 Efficiency ・Output capacitor Co required for current mode control: 10μF ceramic capacitor ・Inductance L required for the operating frequency of 1 MHz: 4.7μH inductor Reduces a mounting area required. VCC 15mm Cin CIN DC/DC Convertor Controller RITH L VOUT Co 10mm CITH CO L RITH CITH Fig.19 Example application www.rohm.com © 2009 ROHM Co., Ltd. All rights reserved. 5/13 2009.05 - Rev.A BD8964FVM Technical Note ●Operation BD8964FVM is a synchronous rectifying step-down switching regulator that achieves faster transient response by employing current mode PWM control system. ○Synchronous rectifier It does not require the power to be dissipated by a rectifier externally connected to a conventional DC/DC converter IC, and its P.N junction shoot-through protection circuit limits the shoot-through current during operation, by which the power dissipation of the set is reduced. ○Current mode PWM control Synthesizes a PWM control signal with a inductor current feedback loop added to the voltage feedback. ・PWM (Pulse Width Modulation) control The oscillation frequency for PWM is 1 MHz. SET signal form OSC turns ON a P-channel MOS FET (while a N-channel MOS FET is turned OFF), and an inductor current IL increases. The current comparator (Current Comp) receives two signals, a current feedback control signal (SENSE: Voltage converted from IL) and a voltage feedback control signal (FB), and issues a RESET signal if both input signals are identical to each other, and turns OFF the P-channel MOS FET (while a N-channel MOS FET is turned ON) for the rest of the fixed period. The PWM control repeat this operation. SENSE Current Comp RESET Level Shift Gm Amp. ITH OSC RQ FB SET S Driver Logic SW Load IL VOUT VOUT Fig.20 Diagram of current mode PWM control Current Comp SET PVCC SENSE FB GND GND RESET SW GND IL(AVE) IL VOUT VOUT(AVE) Fig.21 PWM switching timing chart www.rohm.com © 2009 ROHM Co., Ltd. All rights reserved. 6/13 2009.05 - Rev.A BD8964FVM Technical Note ●Description of operations ・Soft-start function EN terminal shifted to “High” activates a soft-starter to gradually establish the output voltage with the current limited during startup, by which it is possible to prevent an overshoot of output voltage and an inrush current. ・Shutdown function With EN terminal shifted to “Low”, the device turns to Standby Mode, and all the function blocks including reference voltage circuit, internal oscillator and drivers are turned to OFF. Circuit current during standby is 0μF (Typ.). ・UVLO function Detects whether the input voltage sufficient to secure the output voltage of this IC is supplied. And the hysteresis width of 300mV (Typ.) is provided to prevent output chattering. Hysteresis 100mV VCC EN VOUT Tss Soft start Standby mode Operating mode Standby mode UVLO Tss Tss Operating mode Standby mode EN Operating mode Standby mode UVLO UVLO Fig.22 Soft start, Shutdown, UVLO timing chart ・Short-current protection circuit with time delay function Turns OFF the output to protect the IC from breakdown when the incorporated current limiter is activated continuously for at least 1 ms. The output thus held tuned OFF may be recovered by restarting EN or by re-unlocking UVLO. EN Output OFF latch VOUT Limit IL 1msec Standby mode EN Standby mode Timer latch EN Operating mode Operating mode Fig.23 Short-current protection circuit with time delay timing chart www.rohm.com © 2009 ROHM Co., Ltd. All rights reserved. 7/13 2009.05 - Rev.A BD8964FVM ●Switching regulator efficiency Efficiency ŋ may be expressed by the equation shown below: η= VOUT×IOUT Vin×Iin ×100[%]= POUT Pin ×100[%]= POUT POUT+PDα ×100[%] Technical Note Efficiency may be improved by reducing the switching regulator power dissipation factors PDα as follows: Dissipation factors: 2 1) ON resistance dissipation of inductor and FET：PD(I R) 2) Gate charge/discharge dissipation：PD(Gate) 3) Switching dissipation：PD(SW) 4) ESR dissipation of capacitor：PD(ESR) 5) Operating current dissipation of IC：PD(IC) 2 2 1)PD(I R)=IOUT ×(RCOIL+RON) (RCOIL[Ω]：DC resistance of inductor, RON[Ω]：ON resistance of FET, IOUT[A]：Output current.) 2)PD(Gate)=Cgs×f×V (Cgs[F]：Gate capacitance of FET, f[Hz]：Switching frequency, V[V]：Gate driving voltage of FET) 3)PD(SW)= Vin2×CRSS×IOUT×f IDRIVE (CRSS[F]：Reverse transfer capacitance of FET, IDRIVE[A]：Peak current of gate.) 2 4)PD(ESR)=IRMS ×ESR (IRMS[A]：Ripple current of capacitor, ESR[Ω]：Equivalent series resistance.) 5)PD(IC)=Vin×ICC (ICC[A]：Circuit current.) ●Consideration on permissible dissipation and heat generation As this IC functions with high efficiency without significant heat generation in most applications, no special consideration is needed on permissible dissipation or heat generation. In case of extreme conditions, however, including lower input voltage, higher output voltage, heavier load, and/or higher temperature, the permissible dissipation and/or heat generation must be carefully considered. For dissipation, only conduction losses due to DC resistance of inductor and ON resistance of FET are considered. Because the conduction losses are considered to play the leading role among other dissipation mentioned above including gate charge/discharge dissipation and switching dissipation. 2 P=IOUT ×(RCOIL+RON) RON=D×RONP+(1-D)RONN 1000 ①using an IC alone Power dissipation:Pd [mW] D：ON duty (=VOUT/VCC) RCOIL：DC resistance of coil RONP：ON resistance of P-channel MOS FET RONN：ON resistance of N-channel MOS FET IOUT：Output current If VCC=5V, VOUT=1.5V, RCOIL=0.15Ω, RONP=0.35Ω, RONN=0.25Ω IOUT=0.8A, for example, D=VOUT/VCC=1.5/5=0.3 RON=0.3×0.35+(1-0.3)×0.25 =0.105+0.175 =0.28[Ω] P =0.8 ×(0.15+0.28) ≒275.2[mW] 2 800 ①587.4mW θj-a=322.6℃/W ②mounted on glass epoxy PCB θj-a=212.8℃/W 600 400 ②387.5mW 200 0 0 25 50 75 85 100 125 150 Fig. 24 As RONP is greater than RONN in this IC, the dissipation increases as the ON duty becomes greater. With the consideration on the dissipation as above, thermal design must be carried out with sufficient margin allowed. www.rohm.com © 2009 ROHM Co., Ltd. All rights reserved. 8/13 2009.05 - Rev.A BD8964FVM ●Selection of components externally connected 1. Selection of inductor (L) IL ΔIL VCC Technical Note IL VOUT L Co The inductance significantly depends on output ripple current. As seen in the equation (1), the ripple current decreases as the inductor and/or switching frequency increases. (VCC-VOUT)×VOUT ΔIL= [A]・・・(1) L×VCC×f Appropriate ripple current at output should be 30% more or less of the maximum output current. ΔIL=0.3×IOUTmax. [A]・・・(2) L= (VCC-VOUT)×VOUT ΔIL×VCC×f [H]・・・(3) Fig.25 Output ripple current (ΔIL: Output ripple current, and f: Switching frequency) * Current exceeding the current rating of the inductor results in magnetic saturation of the inductor, which decreases efficiency. The inductor must be selected allowing sufficient margin with which the peak current may not exceed its current rating. If VCC=5V, VOUT=1.5V, f=1MHz, ΔIL=0.3×0.8A=0.24A, for example, L= (5-1.5)×1.5 0.24×5×1M =4.375μ → 4.7[μH] *Select the inductor of low resistance component (such as DCR and ACR) to minimize dissipation in the inductor for better efficiency. 2. Selection of output capacitor (CO) VCC Output capacitor should be selected with the consideration on the stability region and the equivalent series resistance required to smooth ripple voltage. Output ripple voltage is determined by the equation (4)： VOUT L ESR Co ΔVOUT=ΔIL×ESR [V]・・・(4) (ΔIL: Output ripple current, ESR: Equivalent series resistance of output capacitor) *Rating of the capacitor should be determined allowing sufficient margin against output voltage. Less ESR allows reduction in output ripple voltage. Fig.26 Output capacitor As the output rise time must be designed to fall within the soft-start time, the capacitance of output capacitor should be determined with consideration on the requirements of equation (5): Co≦ TSS×(Ilimit-IOUT) VOUT ・・・(5) Tss: Soft-start time Ilimit: Over current detection level, 2A(Typ) In case of BD8964FVM, for instance, and if VOUT=1.5V, IOUT=0.8A, and TSS=1ms, ≒800[μF] 1.5 Inappropriate capacitance may cause problem in startup. A 10 μF to 100 μF ceramic capacitor is recommended. 3. Selection of input capacitor (Cin) VCC Co≦ 1m×(2-0.8) Cin Input capacitor to select must be a low ESR capacitor of the capacitance sufficient to cope with high ripple current to prevent high transient voltage. The ripple current IRMS is given by the equation (5): IRMS=IOUT× √ OUT(VCC-VOUT) V VCC [A]・・・(5) VOUT L Co < Worst case > IRMS(max.) IOUT 2 If VCC=5.0V, VOUT=1.5V, and IOUTmax.=0.8A When Vcc is twice the VOUT, IRMS= √ (5-1.5) 5 IRMS=0.8× =0.67[ARMS] 5 A low ESR 10μF/10V ceramic capacitor is recommended to reduce ESR dissipation of input capacitor for better efficiency. Fig.27 Input capacitor www.rohm.com © 2009 ROHM Co., Ltd. All rights reserved. 9/13 2009.05 - Rev.A BD8964FVM Technical Note 4. Determination of RITH, CITH that works as a phase compensator As the Current Mode Control is designed to limit a inductor current, a pole (phase lag) appears in the low frequency area due to a CR filter consisting of a output capacitor and a load resistance, while a zero (phase lead) appears in the high frequency area due to the output capacitor and its ESR. So, the phases are easily compensated by adding a zero to the power amplifier output with C and R as described below to cancel a pole at the power amplifier. fp(Min.) A Gain [dB] fp(Max.) 0 IOUTMin. 0 IOUTMax. fz(ESR) 1 2π×RO×CO 1 fz(ESR)= 2π×ESR×CO fp= Pole at power amplifier When the output current decreases, the load resistance Ro increases and the pole frequency lowers. fp(Min.)= 1 2π×ROMax.×CO 1 2π×ROMin.×CO [Hz]←with lighter load Phase [deg] -90 Fig.28 Open loop gain characteristics fp(Max.)= A Gain [dB] 0 0 -90 fz(Amp.) [Hz] ←with heavier load Zero at power amplifier Increasing capacitance of the output capacitor lowers the pole frequency while the zero frequency does not change. (This is because when the capacitance is doubled, the capacitor ESR reduces to half.) fz(Amp.)= 1 2π×RITH×CITH Phase [deg] Fig.29 Error amp phase compensation characteristics VCC Cin EN VOUT VOUT ITH RITH CITH VCC,PVCC L SW ESR RO VOUT GND,PGND CO Fig.30 Typical application Stable feedback loop may be achieved by canceling the pole fp (Min.) produced by the output capacitor and the load resistance with CR zero correction by the error amplifier. fz(Amp.)= fp(Min.) 1 2π×RITH×CITH = 1 2π×ROMax.×CO 5. Determination of output voltage The output voltage VOUT is determined by the equation (7): VOUT=(R2/R1+1)×VADJ・・・(7) VADJ: Voltage at ADJ terminal (0.8V Typ.) With R1 and R2 adjusted, the output voltage may be determined as required. (Adjustable output voltage range： 1.0V～1.8V) Use 1 kΩ～100 kΩ resistor for R1. If a resistor of the resistance higher than 100 kΩ is used, check the assembled set carefully for ripple voltage etc. 4.7µH 6 SW 1 ADJ R1 10µF R2 Output Fig.31 Determination of output voltage www.rohm.com © 2009 ROHM Co., Ltd. All rights reserved. 10/13 2009.05 - Rev.A BD8964FVM ●BD8964FVM Cautions on PC Board layout VCC 1 2 3 RITH ③ CITH 4 8 7 6 5 L CIN ② Co Technical Note ADJ VCC ITH GND EN PVCC SW PGND EN ① VOUT GND Fig.32 Layout diagram ① ② ③ For the sections drawn with heavy line, use thick conductor pattern as short as possible. Lay out the input ceramic capacitor CIN closer to the pins PVCC and PGND, and the output capacitor Co closer to the pin PGND. Lay out CITH and RITH between the pins ITH and GND as near as possible with least necessary wiring. ●Recommended components Lists on above application Symbol Part Value L CIN CO CITH RITH Coil Ceramic capacitor Ceramic capacitor Ceramic capacitor Resistance 4.7μH 10μF 10μF 1000pF VOUT=1.0V VOUT=1.2V VOUT=1.5V VOUT=1.8V 4.3kΩ 6.8kΩ 9.1kΩ 12kΩ Manufacturer Sumida TDK Kyocera Kyocera murata ROHM ROHM ROHM ROHM Series CMD6D11B VLF5014AT-4R7M1R1 CM316X5R106K10A CM316X5R106K10A GRM18series MCR10 4301 MCR10 6801 MCR10 9101 MCR10 1202 * The parts list presented above is an example of recommended parts. Although the parts are sound, actual circuit characteristics should be checked on your application carefully before use. Be sure to allow sufficient margins to accommodate variations between external devices and this IC when employing the depicted circuit with other circuit constants modified. Both static and transient characteristics should be considered in establishing these margins. When switching noise is substantial and may impact the system, a low pass filter should be inserted between the VCC and PVCC pins, and a schottky barrier diode established between the SW and PGND pins. ●I/O equivalence circuit ・EN pin ・SW pin PVCC PVCC PVCC EN SW ・ADJ pin VCC ・ITH pin VCC 10kΩ ADJ ITH Fig.33 I/O equivalence circuit www.rohm.com © 2009 ROHM Co., Ltd. All rights reserved. 11/13 2009.05 - Rev.A BD8964FVM Technical Note ●Notes for use 1. Absolute Maximum Ratings While utmost care is taken to quality control of this product, any application that may exceed some of the absolute maximum ratings including the voltage applied and the operating temperature range may result in breakage. If broken, short-mode or open-mode may not be identified. So if it is expected to encounter with special mode that may exceed the absolute maximum ratings, it is requested to take necessary safety measures physically including insertion of fuses. 2. Electrical potential at GND GND must be designed to have the lowest electrical potential In any operating conditions. 3. Short-circuiting between terminals, and mismounting When mounting to pc board, care must be taken to avoid mistake in its orientation and alignment. Failure to do so may result in IC breakdown. Short-circuiting due to foreign matters entered between output terminals, or between output and power supply or GND may also cause breakdown. 4.Operation in Strong electromagnetic field Be noted that using the IC in the strong electromagnetic radiation can cause operation failures. 5. Thermal shutdown protection circuit Thermal shutdown protection circuit is the circuit designed to isolate the IC from thermal runaway, and not intended to protect and guarantee the IC. So, the IC the thermal shutdown protection circuit of which is once activated should not be used thereafter for any operation originally intended. 6. Inspection with the IC set to a pc board If a capacitor must be connected to the pin of lower impedance during inspection with the IC set to a pc board, the capacitor must be discharged after each process to avoid stress to the IC. For electrostatic protection, provide proper grounding to assembling processes with special care taken in handling and storage. When connecting to jigs in the inspection process, be sure to turn OFF the power supply before it is connected and removed. 7. Input to IC terminals + This is a monolithic IC with P isolation between P-substrate and each element as illustrated below. This P-layer and the N-layer of each element form a P-N junction, and various parasitic element are formed. If a resistor is joined to a transistor terminal as shown in Fig 34. ○P-N junction works as a parasitic diode if the following relationship is satisfied; GND>Terminal A (at resistor side), or GND>Terminal B (at transistor side); and ○if GND>Terminal B (at NPN transistor side), a parasitic NPN transistor is activated by N-layer of other element adjacent to the above-mentioned parasitic diode. The structure of the IC inevitably forms parasitic elements, the activation of which may cause interference among circuits, and/or malfunctions contributing to breakdown. It is therefore requested to take care not to use the device in such manner that the voltage lower than GND (at P-substrate) may be applied to the input terminal, which may result in activation of parasitic elements. Resistor Pin A Pin A P + Transistor (NPN) Pin B C B E B P P+ N C E Pin B N P N P+ N Parasitic element N P+ N P substrate Parasitic element GND P substrate Parasitic element GND GND GND Parasitic element Other adjacent elements Fig.34 Simplified structure of monorisic IC 8. Ground wiring pattern If small-signal GND and large-current GND are provided, It will be recommended to separate the large-current GND pattern from the small-signal GND pattern and establish a single ground at the reference point of the set PCB so that resistance to the wiring pattern and voltage fluctuations due to a large current will cause no fluctuations in voltages of the small-signal GND. Pay attention not to cause fluctuations in the GND wiring pattern of external parts as well. 9 . Selection of inductor It is recommended to use an inductor with a series resistance element (DCR) 0.1Ω or less. Note that use of a high DCR inductor will cause an inductor loss, resulting in decreased output voltage. Should this condition continue for a specified period (soft start time + timer latch time), output short circuit protection will be activated and output will be latched OFF. When using an inductor over 0.1Ω, be careful to ensure adequate margins for variation between external devices and this IC, including transient as well as static characteristics. Furthermore, in any case, it is recommended to start up the output with EN after supply voltage is within operation range. www.rohm.com © 2009 ROHM Co., Ltd. All rights reserved. 12/13 2009.05 - Rev.A BD8964FVM ●Ordering part number Technical Note B D 8 Part No. 9 6 4 F V M - T R Part No. Package FVM:MSOP8 Packaging and forming specification TR: Embossed tape and reel (MSOP8) MSOP8 2.9±0.1 (MAX 3.25 include BURR) 8765 Tape 0.29±0.15 0.6±0.2 +6° 4° −4° Embossed carrier tape 3000pcs TR The direction is the 1pin of product is at the upper right when you hold Quantity Direction of feed 4.0±0.2 2.8±0.1 ( reel on the left hand and you pull out the tape on the right hand 1pin ) 1 234 1PIN MARK 0.475 S +0.05 0.22 –0.04 0.08 S 0.65 +0.05 0.145 –0.03 0.9MAX 0.75±0.05 0.08±0.05 Direction of feed (Unit : mm) Reel ∗ Order quantity needs to be multiple of the minimum quantity. www.rohm.com © 2009 ROHM Co., Ltd. All rights reserved. 13/13 2009.05 - Rev.A Notice Notes No copying or reproduction of this document, in part or in whole, is permitted without the consent of ROHM Co.,Ltd. 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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 specified 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. Thank you for your accessing to ROHM product informations. More detail product informations and catalogs are available, please contact us. ROHM Customer Support System http://www.rohm.com/contact/ www.rohm.com © 2009 ROHM Co., Ltd. All rights reserved. R0039A