Single-chip Type with Built-in FET Switching Regulator Series Output 1.5A or Less High-efficiency Step-down Switching Regulator with Built-in Power MOSFET No.10027ECT05 BD8313HFN Description BD8313HFN produces step-down output including 1.2, 1.8, 3.3, or 5 V from 4 batteries, batteries such as Li2cell or Li3cell, etc. or a 5V/12V fixed power supply line. BD8313HFN allows easy production of small power supply by a wide range of external constants, and is equipped with an external coil/capacitor downsized by high frequency operation of 1.0 MHz, built-in synchronous rectification SW capable of withstanding 15 V, and flexible phase compensation system on board. ●Features 1) Incorporates Pch/Nch synchronous rectification SW capable of withstanding 1.2 A/15V. 2) Incorporates phase compensation device between input and output of Error AMP. 3) Small coils and capacitors to be used by high frequency operation of 1.0MHz 4) Input voltage 3.5 V – 14 V Output current 1.2A(7.4V input, 3.3V output) 0.8A(4.5V input, 3.3V output) 5) Incorporates soft-start function. 6) Incorporates timer latch system short protecting function. 7) As small as 2.9mm×3 mm, SON 8-pin package HSON8 Application For portable equipment like DSC/DVC powered by 4 dry batteries or Li2cell and Li3cell, or general consumer-equipment with 5 V/12 V lines Operating Conditions (Ta = 25°C) Parameter Power supply voltage Output voltage Absolute Maximum Ratings Parameter Maximum applied power voltage Maximum input current Power dissipation Symbol Voltage circuit Unit VCC 3.5 - 14 V VOUT 1.2 - 12 V Symbol Rating Unit VCC, PVCC 15 V Iinmax 1.2 A Pd 630 mW Operating temperature range Topr -25～+85 °C Storage temperature range Tstg -55～+150 °C Tjmax +150 °C Junction temperature *1 When used at Ta = 25℃ or more installed on a 70×70×1.6tmm board, the rating is reduced by 5.04mW/℃. * These specifications are subject to change without advance notice for modifications and other reasons. www.rohm.com © 2010 ROHM Co., Ltd. All rights reserved. 1/17 2010.06- Rev.C Technical Note BD8313HFN Electrical Characteristics (Unless otherwise specified, Ta = 25 °C, VCC = 7.4 V) Parameter Symbol Target Value Min Typ Max Unit Conditions [Low voltage input malfunction preventing circuit] Detection threshold voltage VUV - 2.9 3.2 V ΔVUVhy 100 200 300 mV Fosc 0.9 1.0 1.1 MHz VREG 4.65 5.0 5.35 V INV threshold voltage VINV 0.99 1.00 1.01 V Input bias current IINV -50 0 50 nA Soft-start time Tss 4.8 8.0 11.1 msec Dmax - - (※)100 % PMOS ON resistance RONP - 450 600 mΩ NMOS ON resistance RONN - 300 420 mΩ Leak current Ileak -1 0 1 uA Operation VSTBH 2.5 - 14 V No-operation VSTBL -0.3 - 0.3 V RSTB 250 400 700 kΩ VCC pin ISTB1 - - 1 uA PVCC pin ISTB2 - - 1 uA Circuit current at operation VCC ICC1 - 600 900 uA VINV = 1.2 V Circuit current at operation ICC2 - 30 50 uA VINV = 1.2 V Hysteresis range VREG monitor [Oscillator] Oscillation frequency [Regulator] Output voltage [Error AMP] VCC = 12.0 V , VINV = 6.0 V [PWM comparator] LX Max Duty [Output] [STB] STB pin control voltage STB pin pull-down resistance [Circuit current] Standby current PVCC (※1)100% is MAX Duty as behavior of a PWM conparetor. Using in region where High side PMOS is 100% on state as application circuit causes detection of SCP then DC/DC converter stops. Not designed to be resistant to radiation www.rohm.com © 2010 ROHM Co., Ltd. All rights reserved. 2/17 2010.06- Rev.C Technical Note BD8313HFN Description of Pins GND INV VCC STB VREG PVCC PGND Lx Pin No. Pin Name 1 GND Function Ground terminal 2 VCC 3 VREG 5 V output terminal of regulator for internal circuit Control part power input terminal 4 PGND Power transistor ground terminal 5 Lx 6 PVCC Coil connecting terminal 7 STB ON/OFF terminal 8 INV Error AMP input terminal DC/DC converter input terminal Fig.1 Terminal layout Block Diagram ON/OFF STB Reference 5V REG STBY_IO OSC 1.0MHz PRE DRIVER SCP 450mΩ OSC×4000 ｃount PWM CONTROL Step down TIMMING CONTROL LX VREG PRE DRIVER + + - GND UVLO VREF DC/DC converter 100% High Duty STOP VREF PVCC VREG VCC 300mΩ ERROR_AMP Soft Start PGND OSC×8000 ｃount INV Fig.2 Block diagram www.rohm.com © 2010 ROHM Co., Ltd. All rights reserved. 3/17 2010.06- Rev.C Technical Note BD8313HFN Description of Blocks 1. Reference This block produces ERROR AMP standard voltage. The standard voltage is 1.0 V. 2. 5 V Reg 5 V low saturation regulator for internal analog circuit BD8313HFN is equipped with this regulator for the purpose of protecting the internal circuit from high voltage. Therefore, this output is reduced when VCC is less than 5 V, then PMOS ON resistance increases and Power efficiency and Maximum output current of DC/DC converter decreases in this region. Please see attached data (fig14,15,16,17) about increasing of PMOS ON resistance in this region. 3 UVLO Circuit for preventing low voltage malfunction Prevents malfunction of the internal circuit at activation of the power supply voltage or at low power supply voltage. Monitors VCC pin voltage to turn off all output FET and DC/DC converter output when VCC voltage is lower than 2.9 V, and reset the timer latch of the internal SCP circuit and soft-start circuit. This threshold contains 200 mV hysteresis. 4 SCP Timer latch system short-circuit protection circuit When DC/DC converter is 100% High Duty , the internal SCP circuit starts counting. The internal counter is in synch with OSC, the latch circuit is activated about 4 msec after the counter counts about 4000 oscillations to turn off DC/DC converter output. To reset the latch circuit, turn off the STB pin once. Then, turn it on again or turn on the power supply voltage again. 5 OSC Circuit for oscillating sawtooth waves with an operation frequency fixed at 1.0 MHz 6 ERROR AMP Error amplifier for detecting output signals and output PWM control signals The internal standard voltage is set at 1.0 V. A primary phase compensation device of 200 pF, 62 kΩ is built in-between the inverting input terminal and the output terminal of this ERROR AMP. 7 PWM COMP Voltage-pulse width converter for controlling output voltage corresponding to input voltage Comparing the internal SLOPE waveform with the ERROR AMP output voltage, PWM COMP controls the pulse width to the output to the driver. 8 SOFT START Circuit for preventing in-rush current at startup by bringing the output voltage of the DC/DC converter into a soft-start Soft-start time is in synch with the internal OSC, and the output voltage of the DC/DC converter reaches the set voltage after about 8000 oscillations. 9 PRE DRIVER/TIMING CONTROL CMOS inverter circuit for driving the built-in synchronous rectification SW The synchronous rectification OFF time for preventing feedthrough is about 25 nsec. 10 STBY_IO Voltage applied on STB pin (7 pin) to control ON/OFF of IC Turned ON when a voltage of 2.5 V or higher is applied and turned OFF when the terminal is open or 0 V is applied. Incorporates approximately 400 kΩ pull-down resistance. 11 Pch/Nch FET SW Built-in synchronous rectification SW for switching the coil current of the DC/DC converter Incorporates a 450 mΩ PchFET SW capable of withstanding 15 V.and 300 mΩ SW capable of withstanding 15 V. Since the current rating of this FET is 1.2 A, it should be used within 1.2 A including the DC current and ripple current of the coil. www.rohm.com © 2010 ROHM Co., Ltd. All rights reserved. 4/17 2010.06- Rev.C Technical Note BD8313HFN Reference data (Unless otherwise specified, Ta = 25°C, VCC = 7.4 V) 1.02 1.02 1.01 1.01 5.3 1.00 0.99 VREG VOLTAGE [V] INV THRESHOLD [V] INV THRESHOLD [V] 5.2 1.00 5.1 5.0 4.9 0.99 4.8 0.98 4.7 0.98 -40 -20 0 20 40 60 80 100 120 0 2 4 6 TEMPERATURE [℃] 8 10 12 -40 14 0 VCC [V] Fig.3. INV threshold temperature property 80 120 Fig.5. VREG output temperature property Fig.4. INV threshold power supply property 8 40 TEMPERATURE [℃] 1.2 1.2 1.1 1.1 FREQUENCY [MHz] VREG[V] 6 5 4 3 2 FREQUENCY [ MHz ] 7 1.0 1.0 0.9 0.9 1 0 0.8 0.8 0 2 4 6 8 10 12 14 -40 0 80 Fig.6. VREG output power supply property 0.25 500 600 UVLO detection voltage 0.05 40 80 0.00 120 Environmental temperature Ta [℃] Ta [°C] 環境温度 Fig.9. UVLO threshold temperature property www.rohm.com © 2010 ROHM Co., Ltd. All rights reserved. ID=500mA 500 ON RESISTANCE [ mΩ] 0.10 ON RESISTANCE [ mΩ ] Hysteresis VoltageVhys Vhys[V] ヒステリシス電圧 [V] 2.90 2.50 15 400 0.15 2.70 12 Fig.8. fosc voltage property 0.20 3.10 0 9 VCC [V] ID=500mA UVLO release voltage -40 6 Fig.7. fosc temperature property Hysteresis width 3.30 3 120 TEMPERATURE [℃] VCC [V] 3.50 40 400 300 300 200 200 100 100 0 -40 0 40 80 120 TEMPARATURE [℃] Fig.10. Nch FET ON resistance temperature property 5/17 3 6 9 12 VCC [V] Fig.11. Nch FET ON resistance power supply property 2010.06- Rev.C 15 Technical Note BD8313HFN 800 1000 200 PMOS ON Resistance (Ω) 400 600 400 200 0 0 40 80 120 1.5 1.0 Ta=-25℃ 6 9 12 0.0 15 Fig.13. Pch FET ON resistance power supply property Fig.14.PchFET ON resistance Io property [VCC=3.5V] 2.5 2.5 2.5 Ta=25℃ 1.5 1.0 Ta=85℃ 2.0 Ta=25℃ 1.5 1.0 0.5 Ta=-25℃ PMOS ON Resistance (Ω) 3.0 PMOS ON Resistance (Ω) 3.0 Ta=85℃ 0.0 1.0 Ta=85℃ 1.0 1.0 Ta=-25℃ 0.0 2.0 1.0 2.5 Fig.17.PchFET ON resistance Io property [VCC=5.0V] Fig.16.PchFET ON resistance Io property [VCC=4.5V] 1000 1000 800 800 600 600 ON 2.0 Io [A] Io [A] Io [A] Fig.15.PchFET ON resistance Io property [VCC=4.0V] Ta=25℃ 1.5 0.0 0.0 2.0 2.0 0.5 Ta=-25℃ 0.0 0.0 2.0 Io [A] 3.0 0.5 1.0 VCC [V] Fig.12. Pch FET ON resistance temperature property PMOS ON Resistance (Ω) 2.0 0.0 3 TEMPARATURE [℃] 2.0 Ta=25℃ 0.5 0 -40 Ta=85℃ 2.5 ID=500mA 800 600 SWOUT ON Resistance [Ω ] SWOUT ON Resistance [Ω ] ID=500mA 3.0 1.5 ICC [uA] ICC [uA] STB Voltage [V] 2.0 400 400 200 200 OFF 1.0 -50 0 50 100 150 Ta [℃] Fig.18. STB threshold temperature property www.rohm.com © 2010 ROHM Co., Ltd. All rights reserved. 0 0 -40 0 40 80 TEMPARATURE [℃] Fig.19. Circuit current temperature property 6/17 120 0 2 4 6 8 10 12 VCC [V] Fig.20. Circuit current voltage property 2010.06- Rev.C 14 Technical Note BD8313HFN Example of Application1 Input: 4.5 to 10 V, output: 3.3 V / 500mA VBAT=4.5～10V 10μF GRM31CBE106KA75L （Murata） GND INV VCC STB ON/OFF 10pF 1μF GRM188B11A105KA61 （Murata） PVCC VREG 68k 3.3V/500mA Lx PGND 1μF GRM188B11A105KA61 （Murata） 4.7μH 1127AS4R7M（TOKO） 200k 51k 10μF GRM31CB11A106KA01 （Murata） 22k Fig.21 Reference application diagram1 Reference application data 1 (Example of application1) 3.50 100 3.45 3.40 80 60 OUTPUT VOLTAGE [V] EFFICIENCY [%] VCC=4.5V VCC=7.5V VCC=5.5V 40 VCC=4.5V 3.35 3.30 3.25 VCC=5.5V 3.20 VCC=7.5V 3.15 3.10 20 3.05 0 3.00 1 10 100 1 1000 OUTPUT CURRENT [mA] www.rohm.com 100 1000 Fig.23 Load regulation (VOUT = 3.3 V) Fig.22 Power conversion efficiency (VOUT = 3.3 V) © 2010 ROHM Co., Ltd. All rights reserved. 10 OUTPUT CURRENT [mA] 7/17 2010.06- Rev.C Technical Note BD8313HFN Reference application data 2 (Input 4.5 V, 6.0 V, 8.4 V, 10 V, output 3.3 V ) (Example of application1) 120 40 20 60 20 0 0 Gain[dB] Gain cccc -20 -60 -40 -120 -60 100 1000 10000 -180 100000 1000000 Phase 0 60 120 40 60 20 0 Gain 180 Phase 60 0 0 Gain -20 -60 -20 -60 -40 -120 -40 -120 -180 100000 1000000 -60 -60 100 Frequency[Hz] 1000 10000 100 -180 100000 1000000 10000 Fig.26 Frequency response 3 (VCC=8.4V, Io=250mA) Fig.25 Frequency response 2 (VCC=6.0V, Io=250mA) 60 180 1000 Frequency[Hz] Frequency[Hz] Fig.24 Frequency response 1 (VCC=4.5V, Io=250mA) 60 120 Phase[deg] 40 180 Phase[deg] Gain[dB] 60 Phase Phase[deg] Gain[dB] 180 60 180 60 180 Phase 120 40 20 60 20 60 20 60 0 0 0 0 Gain[dB] Gain 0 0 Gain Phase[deg] Gain[dB] 40 Phase[deg] Gain[dB] 120 -20 -60 -20 -60 -20 -40 -120 -40 -120 -40 -180 100000 1000000 -60 -180 100000 1000000 -60 100 1000 10000 100 Frequency[Hz] 40 20 60 20 0 0 Gain[dB] Gain Gain[dB] 120 Phase Phase[deg] 60 Phase Fig.29 Frequency response 6 0 0 Gain -40 -120 -40 -120 -180 100000 1000000 -60 Frequency[Hz] Fig.30 Frequency response 7 (VCC=8.4V, Io=500mA) www.rohm.com © 2010 ROHM Co., Ltd. All rights reserved. (VCC=6.0V, Io=500mA) 60 -60 10000 -180 100000 1000000 120 -20 1000 10000 180 -60 100 1000 Frequency[Hz] -20 -60 -60 -120 100 Fig.28 Frequency response 5 (VCC=4.5V, Io=500mA) 180 40 10000 Frequency[Hz] Fig.27 Frequency response 4 (VCC=10V, Io=250mA) 60 1000 Gain 120 100 1000 10000 Phase[deg] -60 Phase -180 100000 1000000 Frequency[Hz] Fig.31 Frequency response 8 (VCC=10V, Io=500mA) 8/17 2010.06- Rev.C Phase[deg] Phase 40 Technical Note BD8313HFN Example of application2 input4.5 to 12V, output1.2V / 500mA VBAT=4.5~ 12V 10µF GRM31CB31E106KA75L (Murata) GND INV VCC STB 100O ON/OFF 10pF 1µF GRM188B11A105KA61 ( Murata) PVCC VREG 68kO 3.3V/500mA PGND 1µF GRM188B11A105KA61 ( Murata) Lx 4.7µH NR4012-4R7M (Taiyo yuden) 560kO 20kO 10µF 2para 100kO GRM31CB11A106KA01 ( Murata) Fig.32 Reference application diagram2 Reference application data 1 (Example of application2) 100 1.36 VCC=7.4V 80 60 EFFICIENCY [%] EFFICIENCY [%] 1.30 VCC=5.0V 40 20 VCC=12V VCC=5.0V VCC=7.4V 1.24 1.18 1.12 VCC=12V 1.06 0 1.00 1 10 100 1000 1 OUTPUT CURRENT [mA] Fig.33 Power conversion efficiency (VOUT = 1.2 V) www.rohm.com © 2010 ROHM Co., Ltd. All rights reserved. 10 100 1000 OUTPUT CURRENT [mA] Fig.34 Load regulation (VOUT = 1.2 V) 9/17 2010.06- Rev.C Technical Note BD8313HFN Reference application data 2(input5.0V, 7.4V, 10V output1.2V )Example of application(2) 60 20 60 20 60 20 60 Gain 0 -20 -60 -40 -60 -20 -60 -120 -40 -120 -40 -120 -180 100000 1000000 -60 -180 100000 1000000 -60 100 1000 Frequency [Hz] 20 60 0 0 Gain Gain [dB] 40 Phase [deg] 120 Phase 120 40 20 60 20 0 0 -20 -40 -120 -40 -180 100000 1000000 -60 10000 Phase Gain 100 1000 10000 60 100000 0 0 Gain Gain [dB] 60 Phase [deg] 20 -20 -60 -120 -40 -120 -180 1000000 -60 40 120 20 60 Gain 0 0 -60 -40 -120 -40 -120 -180 1000000 -60 10000 100000 Frequency [Hz] Fig.41 Frequency response 7 (VCC=10V, Io=100mA) www.rohm.com © 2010 ROHM Co., Ltd. All rights reserved. 100 1000 10000 100000 -180 1000000 Frequency [Hz] Fig.42 Frequency response 8 (VCC=10V, Io=300mA) 10/17 1000 10000 100000 -180 1000000 60 180 -20 1000 100 Fig.40 Frequency response 6 (VCC=7.4V, Io=900mA) -60 100 0 Gain -60 -20 -60 60 0 Phase 120 120 Frequency [Hz] 60 Phase 40 -180 1000000 Phase Fig.39 Frequency response 5 (VCC=7.4V, Io=300mA) 180 100000 180 Frequency [Hz] Frequency [Hz] Fig.38 Frequency response 4 (VCC=7.4V, Io=100mA) 10000 Frequency [Hz] 60 -60 1000 Fig.37 Frequency response 3 (VCC=5.0V, Io=900mA) 180 -20 1000 100 Frequency [Hz] 60 40 10000 Fig.36 Frequency response 2 (VCC=5.0V, Io=300mA) 180 60 100 0 Gain -20 Fig.35 Frequency response 1 (VCC=5.0V, Io=100mA) -60 0 180 40 120 Phase 20 Gain [dB] 10000 0 Gain Phase [deg] Gain [dB] 1000 0 Phase [deg] 0 Phase [deg] 120 Gain [dB] 40 Phase [deg] 120 Gain [dB] 40 Phase [deg] Gain [dB] 120 100 Gain [dB] 180 Phase 40 -60 Gain [dB] 60 180 Phase Phase [deg] 180 Phase 60 0 0 Gain -20 -60 -40 -120 -60 100 1000 10000 100000 -180 1000000 Frequency [Hz] Fig.43 Frequency response 9 (VCC=10V, Io=900mA) 2010.06- Rev.C Phase [deg] 60 Technical Note BD8313HFN 2 0usec/Div Vout(20 m/ Div) 出力リプル=2 4.4mVp- p 24.4mVpp Fig.44 Output ripple 1 (VCC=12V, Io=40mA) 20usec/ Div Vout(20m/Div) 出力リプル=1 0.4mVp- p 10.4mVpp Fig.47 Output ripple 4 (VCC=12V, Io=170mA) 20usec/ Div 20usec/ Div Vout(20m/Div) 出力リプル=38.4mVp-p 38.4mVpp Fig.45 Output ripple 2 (VCC=12V, Io=100mA) Vout(20m/Div) 出力リプル= 9.2mVp-p 9.2mVpp Fig.46 Output ripple 3 (VCC=12V, Io=140mA) 20usec/ Div Vout(20m/Div) 出力リプル=14 .8mVp- p 14.8mVpp Fig.48 Output ripple 5 (VCC=12V, Io=900mA) Output ripple voltage SLOPE 0.75 BD8313HFN is controlled by PWM(Pulse Width Modulation)mode. PWM output made by comparison SLOPE with FB(error amp FB output) controls switching of IC under the PWM mode. 0.25 When FB level is completely lower than SLOPE level, DC/DC converter switches as non- synchronous step-down switching mode not to make output voltage level drop quickly caused by full ON state of Low side Nch FET. PWMoutput Ripple voltage of output voltage in non-synchronous mode is larger than that in synchronous mode. When voltage difference between input and output voltage is large and output current is small, DCDC converter switches as this non-synchronous mode then ripple voltage of output voltage could be large. In the reference data above ( output ripple 1 to 4 ), ripple voltage at 12V input 1.2V output , output current is smaller than 100mA is larger than other region. www.rohm.com © 2010 ROHM Co., Ltd. All rights reserved. 11/17 2010.06- Rev.C Technical Note BD8313HFN Reference board pattern VOUT Lx VBAT GND The radiation plate on the rear should be a GND flat surface of low impedance in common with the PGND flat surface. It is recommended to install a GND pin in another system as shown in the drawing without connecting it directly to this PNGD. Produce as wide a pattern as possible for the VBAT, Lx and PGND lines in which large current flows. Selection of Part for Applications (1) Inductor A shielded inductor that satisfies the current rating (current value, Ipecac as shown in the drawing below) and has a low DCR (direct resistance component) is recommended. Inductor values affect inductor ripple current, which will cause output ripple. Ripple current can be reduced as the coil L value becomes larger and the switching frequency becomes higher. Ipeak =Iout ＋ ⊿IL/2 [A] ⊿IL= Vin-Vout L × ・・・(1) Vout Vin × 1 [A] Δ IL Fig.49 Inductor current ・・・(2) f (η: Efficiency, ⊿IL: Output ripple current, f: Switching frequency) As a guide, inductor ripple current should be set at about 20 to 50% of the maximum input current. *Current over the coil rating flowing in the coil brings the coil into magnetic saturation, which may lead to lower efficiency or output oscillation. Select an inductor with an adequate margin so that the peak current does not exceed the rated current of the coil. (2) Output capacitor A ceramic capacitor with low ESR is recommended for output in order to reduce output ripple. There must be an adequate margin between the maximum rating and output voltage of the capacitor, taking the DC bias property into consideration. Output ripple voltage is acquired by the following equation. 1 ・・・(3) Vpp=⊿IL× ＋ ⊿IL×RESR [V] 2π×f×Co Setting must be performed so that output ripple is within the allowable ripple voltage. www.rohm.com © 2010 ROHM Co., Ltd. All rights reserved. 12/17 2010.06- Rev.C Technical Note BD8313HFN (3) Output voltage setting The internal standard voltage of the ERROR AMP is 1.0 V. Output voltage is acquired by Equation (4). VOUT ERROR AMP R1 INV Vo= (R1+R2) R2 ×1.0 [V] ・・・ (4) R2 VREF 1.0V Fig.50 Setting of voltage feedback resistance (4) DC/DC converter frequency response adjustment system Condition for stable application The condition for feedback system stability under negative feedback is that the phase delay is 135 °or less when gain is 1 (0dB). Since DC/DC converter application is sampled according to the switching frequency, the bandwidth GBW of the whole system (frequency at which gain is 0 dB) must be controlled to be equal to or lower than 1/10 of the switching frequency. In summary, the conditions necessary for the DC/DC converter are: - Phase delay must be 135°or lower when gain is 1 (0 dB). - Bandwidth GBW (frequency when gain is 0 dB) must be equal to or lower than 1/10 of the switching frequency. To satisfy those two points, R1, R2, R3, DS and RS in Fig. 51 should be set as follows. VOUT [1] R1, R2, R3 BD8313HFN incorporates phase compensation devices of R4=62kΩ and C2=200pF. These C2 and R1, R2, and R3 values decide the primary pole that determines the bandwidth of DC/DC converter. Primary pole point frequency fp= Cs R1 Inside of IC R4 C2 Rs FB R3 R2 1 R1×R2 2π A×( +R3)×C2 R1+R2 ・・・・(1) Fig.51 Example of phase compensation setting DC/DC converter DC Gain DC Gain =A× 1 B × VIN VO A: Error AMP Gain 5 About 100dB = 10 B: Oscillator amplification = 0.5 Input voltage VIN: VOUT: Output voltage ・・・・(2) By Equations (1) and (2), the frequency fsw of point 0 dB under limitation of the bandwidth of the DC gain at the primary pole point is as shown below. 1 fSW = fp×DC Gain = 2πC2×( (R1・R2) +R3 ) (R1+R2) × 1 B × VIN ・・・・(3) VO It is recommended that fsw should be approx.10 kHz. When load response is difficult, it may be set at approx. 20 kHz. By Equation (3), R1 and R2, which determine the voltage value, will be in the order of several hundred kΩ. If an appropriate resistance value is not available since the resistance is so high and routing may cause noise, the use of R3 enables easy setting. www.rohm.com © 2010 ROHM Co., Ltd. All rights reserved. 13/17 2010.06- Rev.C Technical Note BD8313HFN [2] Cs and Rs setting For DC/DC converter, the 2nd dimension pole point is caused by the coil and capacitor as expressed by the following equation. fLC= 1 ・・・・(4) 2π√(LC) This secondary pole causes a phase rotation of 180°. To secure the stability of the system, put a zero point in 2 places to perform compensation. Zero point by built-in CR fZ1= Zero point by Cs fZ1= 1 2πR4C2 1 2π(R1+R3)CS = 13kHz ・・・・(5) ・・・・(6) Setting fZ2 to be half to 2 times a frequency as large as fLC provides an appropriate phase margin. It is desirable to set Rs at about 1/20 of (R1+R3) to cancel any phase boosting at high frequencies. Those pole points are summarized in the figure below. The actual frequency property is different from the ideal calculation because of part constants. If possible, check the phase margin with a frequency analyzer or network analyzer. Otherwise, check for the presence or absence of ringing by load response waveform and also check for the presence or absence of oscillation under a load of an adequate margin. (5) (6) (3) (4) Fig.52 Example of DC/DC converter frequency property (Measured with FRA5097 by NF Corporation) www.rohm.com © 2010 ROHM Co., Ltd. All rights reserved. 14/17 2010.06- Rev.C Technical Note BD8313HFN I/O Equivalence Circuit STB INV VCC VCC STB VREG INV Lx, PGND, PVCC VREG VCC VCC PVCC VREG Lx PGND www.rohm.com © 2010 ROHM Co., Ltd. All rights reserved. 15/17 2010.06- Rev.C Technical Note BD8313HFN Ordering part number 1) Absolute Maximum Rating We dedicate much attention to the quality control of these products, however the possibility of deterioration or destruction exists if the impressed voltage, operating temperature range, etc., exceed the absolute maximum ratings. In addition, it is impossible to predict all destructive situations such as short-circuit modes, open circuit modes, etc. If a special mode exceeding the absolute maximum rating is expected, please review matters and provide physical safety means such as fuses, etc. 2) GND Potential Keep the potential of the GND pin below the minimum potential at all times. 3) Thermal Design Work out the thermal design with sufficient margin taking power dissipation (Pd) in the actual operation condition into account. 4) Short Circuit between Pins and Incorrect Mounting Attention to IC direction or displacement is required when installing the IC on a PCB. If the IC is installed in the wrong way, it may break. Also, the threat of destruction from short-circuits exists if foreign matter invades between outputs or the output and GND of the power supply. 5) Operation under Strong Electromagnetic Field Be careful of possible malfunctions under strong electromagnetic fields. 6) Common Impedance When providing a power supply and GND wirings, show sufficient consideration for lowering common impedance and reducing ripple (i.e., using thick short wiring, cutting ripple down by LC, etc.) as much as you can. 7) Thermal Protection Circuit (TSD Circuit) BD8313HFN contains a thermal protection circuit (TSD circuit). The TSD circuit serves to shut off the IC from thermal runaway and does not aim to protect or assure operation of the IC itself. Therefore, do not use the TSD circuit for continuous use or operation after the circuit has tripped. 8) Rush Current at the Time of Power Activation Be careful of the power supply coupling capacity and the width of the power supply and GND pattern wiring and routing since rush current flows instantaneously at the time of power activation in the case of CMOS IC or ICs with multiple power supplies. 9) IC Terminal Input This is a monolithic IC and has P+ isolation and a P substrate for element isolation between each element. P-N junctions are formed and various parasitic elements are configured using these P layers and N layers of the individual elements. For example, if a resistor and transistor are connected to a terminal as shown on Fig.53: ○ The P-N junction operates as a parasitic diode when GND > (Terminal A) in the case of a resistor or when GND > (Terminal B) in the case of a transistor (NPN) ○ Also, a parasitic NPN transistor operates using the N layer of another element adjacent to the previous diode in the case of a transistor (NPN) when GND > (Terminal B). The parasitic element consequently rises under the potential relationship because of the IC’s structure. The parasitic element pulls interference that could cause malfunctions or destruction out of the circuit. Therefore, use caution to avoid the operation of parasitic elements caused by applying voltage to an input terminal lower than the GND (P board), etc. B C N P＋ N P N P Substrate P＋ P＋ N Parasitic Element GND P N Ｎ E (Pin A) P＋ ～ ～ (Pin B) (Pin A) ～ ～ Transistor (NPN) Resistor N Parasitic Element P Substrate Parasitic Element GND GND Fig.53 Example of simple structure of Bipolar IC www.rohm.com © 2010 ROHM Co., Ltd. All rights reserved. 16/17 2010.06- Rev.C Technical Note BD8313HFN Ordering part number B D 8 Part No. 3 1 3 H Part No. F N Package HFN:HSON8 - T R Packaging and forming specification TR: Embossed tape and reel HSON8 <Tape and Reel information> (0.05) (0.3) (0.2) 1234 5678 (0.45) (0.2) (1.8) 8 765 2.8 ± 0.1 3.0 ± 0.2 0.475 (2.2) (0.15) 2.9±0.1 (MAX 3.1 include BURR) 4321 +0.1 0.13 –0.05 Tape Embossed carrier tape Quantity 3000pcs Direction of feed TR The direction is the 1pin of product is at the upper right when you hold ( reel on the left hand and you pull out the tape on the right hand 1pin 1PIN MARK S +0.03 0.02 –0.02 0.6MAX ) 0.1 S 0.65 0.32±0.1 0.08 Direction of feed M (Unit : mm) www.rohm.com © 2010 ROHM Co., Ltd. All rights reserved. Reel 17/17 ∗ Order quantity needs to be multiple of the minimum quantity. 2010.06- Rev.C 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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