Power Management ICs for Automotive Body Control LED Drivers for Automotive Light BD8381EFV-M No.11039EAT14 ●Description BD8381EFV-M is a white LED driver with the capability of withstanding high input voltage (50V MAX). A current-mode buck-boost DC/DC controller is also integrated to achieve stable operation against voltage input and also to remove the constraint of the number of LEDs in series connection. The brightness can be controlled by either PWM or DC. The PWM brightness signal generation circuit is built into, and the control without microcomputer is also possible. ●Features 1) Input voltage range 5.0 – 30 V 2) Integrated buck-boost current-mode DC/DC controller 3) Built-in CR timer for PWM brightness 4) PWM linear brightness 5) Built-in protection functions (UVLO, OVP, TSD, OCP, SCP) 6) LED error status detection function (OPEN/ SHORT) 7) HTSSOP-B28 package ●Applications Headlight and running (DRL) of night of daylight, etc. ●Absolute maximum ratings (Ta=25℃) Parameter Power supply voltage BOOT Voltage SW,CS,OUTH Voltage BOOT-SW Voltage VREG,OVP,OUTL,FAIL1,FAIL2,THM,SS, COMP,RT,SYNC,EN,DISC,VTH,FB,LEDR, LEDC,DRLIN, PWMOUT,CT Voltage Symbol Ratings Unit VCC 50 V VBOOT 55 V VSW, VCS, VOUTH 50 V VBOOT-SW 7 V VVREG,VOVP,VOUTL,VFAIL1,VFAIL2,VTHM,VSS, VCOMP,VRT,VSYNCVEN,VDISC,VVTH,VFB,VLEDR, VLEDC, ,VDRLIN,VPWMOUT VCT -0.3~7 < VCC V Pd 1.45※1 W Power Consumption Operating temperature range Topr -40~+125 ℃ Storage temperature range Tstg -55~+150 ℃ Tjmax 150 ℃ Junction temperature ※1 IC mounted on glass epoxy board measuring 70mm×70mm×1.6mm, power dissipated at a rate of 11.6mW/℃ at temperatures above 25℃. ※2 A radiation is not designed. ●Operating conditions (Ta=25℃) Parameter Power supply voltage Oscillating frequency range External synchronization frequency range ※3 ※4 External synchronization pulse duty range Symbol Ratings Unit VCC 5.0~30 V FOSC 200~600 kHz FSYNC fosc~600 kHz FSDUTY 40~60 % ※3 Connect SYNC to GND or OPEN when not using external frequency synchronization. ※4 Do not switch between internal and external synchronization when an external synchronization signal is input to the device. www.rohm.com © 2011 ROHM Co., Ltd. All rights reserved. 1/20 2011.04 - Rev.A Technical Note BD8381EFV-M ●Electrical characteristics (Unless otherwise specified, VCC=12V Ta=25℃) Limits Parameter Symbol Min Typ Max. Unit Conditions Circuit current ICC - 4.5 7.0 mA Standby current IST - 0 8 µA EN=Hi, SYNC=Hi, RT=OPEN, CIN=10µF EN=Low VREG 4.5 5.0 5.5 V IREG=-5mA,CREG=10µF OUTH high-side ON resistance RONHH 1.5 3.5 7.0 Ω ION=-10mA OUTH low-side ON resistance RONHL 1.0 2.5 5.0 Ω ION=10mA VOLIMIT VCC -0.68 VCC -0.60 VCC -0.52 V [VREG Block (VREG)] Reference voltage [OUTH Block] Over-current protection operating voltage [OUTL Block] OUTL high-side ON resistance RONLH 2.0 4.0 8.0 Ω ION=-10mA OUTL low –side ON resistance RONLL 1.0 2.5 5.0 Ω ION=10mA RONSW 2.0 4.5 9.0 Ω IONSW=10mA [SW Block] SW low -side ON resistance [PWMOUT Block] PWMOUT high-side ON resistance RONPWMH 2.0 4.0 8.0 Ω IONPWMH=-10mA PWMOUT low-side ON resistance RONPWML 1.0 2.5 5.0 Ω IONPWML=10mA Reference voltage VREF2 0.190 0.200 0.210 V FB-COMPShort, Ta=-40℃~125℃ COMP sink current ICOMPSINK 50 75 100 µA VFB>0.2V, Vcomp=1V ICOMPSOURCE -100 -75 -50 µA VFB <0.2V, Vcomp=1V FOSC 285 300 315 KHz Over-voltage detection reference voltage VOVP 1.9 2.0 2.1 V VOVP=Sweep up OVP hysteresis width VOHYS 0.45 0.55 0.65 V VOVP= Sweep down UVLO voltage VUVLO 4.0 4.3 4.6 V VCC : Sweep down UVLO hysteresis width VUHYS 50 150 250 mV VTH1 3 2/3VREG 3.7 V [Error Amplifier Block] COMP source current [Oscillator Block] Oscillating frequency RT=100kΩ [OVP Block] [UVLO Block ] VCC : Sweep up [PWM Generation circuit Block] VTH Threshold voltage VTH Threshold voltage VTH2 1 1/3VREG 2 V TPWMON 25 - - µs VOPEN 30 50 70 mV LED SHORT detection function VSHORT 100 200 400 mV VSHORT≧lVLEDR-VLEDCl LED GND short protection timer TSHORT 100 150 200 ms CT=0.1µF Input HIGH voltage VINH 3.0 - - V Input LOW voltage VINL GND - 1.0 V Input current 1 IIN 20 35 50 µA VIN=5V (SYNC/DRLIN) Input current 2 IEN 25 40 55 µA VEN=5V (EN) VOL - 0.1 0.2 V IOL=0.1mA PWM minimum ON width LED OPEN detection function [Logic Inputs] [FAIL Output (open drain) ] FAIL LOW voltage ◎ This product is not designed for use in radioactive environments. www.rohm.com © 2011 ROHM Co., Ltd. All rights reserved. 2/20 2011.04 - Rev.A Technical Note BD8381EFV-M ●Electrical characteristic curves (Reference data) (Unless otherwise specified, Ta=25℃) 4 2 0 0 5 600 0.215 500 400 300 200 100 0 -50 -25 0 25 50 75 100 TEMPERATURE:Ta [℃] 2.0 0.0 0 5 0.195 0.19 0.185 0.18 -50 0.60 0.58 VCC=12V 0.54 50 0 6 -25 0 25 50 75 100 125 TEMPERATURE:Ta [ ℃] Fig.7 THM Gain www.rohm.com © 2011 ROHM Co., Ltd. All rights reserved. 9 12 15 VCC VOLTAGE [V] 18 Fig.6 Efficiency (Input voltage dependence) Fig.5 Overcurrent detection voltage temperature characteristic 10 8 6 4 2 0 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 THM VOLTAGE:THM[V] Iout=600mA 70 50 -50 OUTPUT VOLTAGE:VREG [V] 100 80 60 0.56 PWMOUT OUTPUT VOLTAGE [V] 150 125 90 10 200 0 25 50 75 100 TEMPERATURE:Ta [℃] 100 0.62 250 -25 Fig.3 Standard voltage temperature characteristic 0.64 10 15 20 25 30 35 40 45 50 SUPPLY VOLTAGE:Vcc [V] Fig.4 Circuit current (Switching OFF) 0.2 EFFICIENCY [%] OUTPUT VOLTAGE:Vcc-Vcs [V] 4.0 0.205 125 0.66 6.0 0.21 Fig.2 OSC Temperature characteristic 8.0 OUTPUT CARRENT:Icc [mA] 0.22 10 15 20 25 30 35 40 45 50 VCC VOLTAGE [V] Fig.1 VREG Temperature characteristic REFERENCEVOLTAGE :VREF [mV] 700 FB REFERENCE VOLTAGE [V] SWITCHING FREQUENCY:FOSC [kHz] OUTPUT VOLTAGE:VREG [V] 6 8 6 4 2 0 0 1 2 3 4 VTH VOLTAGE:VVTH [V] 5 Fig.8 VTH Threshold voltage 3/20 0 1 2 3 4 EN VOLTAGE:VEN [V] 5 Fig.9 EN Threshold voltage 2011.04 - Rev.A Technical Note BD8381EFV-M ●Block diagram and pin configuration VREG Vin FAIL1 OVP UVLO VCC TSD COUT OVP OCP CS VREG Timer Latch EN PWM BOOT Control Logic OUTH DRV CTL SYNC OSC SW PWM SLOPE DGND RT VREG OUTL ERR AMP GND - COMP + SS VREG LEDR + OCP OVP SHORT Det SS LEDC PWMOUT THM FB VREG DRLIN OPEN/ SHORT/ SCP Detect DISC CR TIMER Open Det VTH Timer Latch CT PGND Fig.10 ●Pin layout BD8381EFV-M(HTSSOP-B28) Buck-boost application composition ●Pin function table 1 28 2 27 3 26 4 25 5 24 6 23 7 22 8 21 9 20 10 19 11 18 12 17 13 16 14 15 Pin 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 Fig.11 www.rohm.com © 2011 ROHM Co., Ltd. All rights reserved. FAIL2 SCP Det 4/20 Symbol COMP SS VCC EN RT SYNC GND THM FB DISC VTH DRLIN FAIL1 FAIL2 OVP LEDC LEDR N.C. PGND PWMOUT CT OUTL DGND SW OUTH CS BOOT VREG Function Error amplifier output Soft start Input power supply Enable input Oscillation frequency-setting resistance input External synchronization signal input Small-signal GND Thermally sensitive resistor connection pin ERRAMP FB signal input pin CR Timer discharge pin CR Timer threshold pin DRL switch terminal (Pulse output setting terminal) Failure signal output LED open/short detection signal output Over-voltage detection input LED short detection pin (LED detection side) LED short detection pin (Resistor detection side) PWM brightness source pin PWM brightness signal output pin GND short protection timer setting pin Low-side external FET Gate Drive out put Low-side FET driver source pin High-side FET Source pin High-side external FET Gate Drive out put DC/DC output current detection pin High-side FET driver source pin Internal reference voltage output 2011.04 - Rev.A Technical Note BD8381EFV-M ●5V voltage reference (VREG) 5V (Typ.) is generated from the VCC input voltage when the enable pin is set high. This voltage is used to power internal circuitry, as well as the voltage source for device pins that need to be fixed to a logical HIGH. UVLO protection is integrated into the VREG pin. The voltage regulation circuitry operates uninterrupted for output voltages higher than 4.5 V (Typ.), but if output voltage drops to 4.3 V (Typ.) or lower, UVLO engages and turns the IC off. Connect a capacitor (Creg = 10µF Typ.) to the VREG terminal for phase compensation. Operation may become unstable if Creg is not connected. ●About the method of setting the output current ILED=min[THM / 5 V , 0.2V] / RISET [A] As for min[THM / 5 V, 0.2V], small one is selected from among THM and VFB=0.2V. Please input within the range of 0.25-5.0V when controlling the output current with THM. Please connect with VREG when not using THM. There is a possibility that the LED GND short detection malfunctions when THM≦0.25V. As for PWM brightness, the control by the PWM signal from the outside and brightness with the CR timer are possible. (GND short protection detection timer (SCP) works at the same time as turning on EN when PWM brightness from the outside is used. Therefore, there is a possibility of mis-detecting SCP for the time from the EN turning on to the PWM turning on > GND short protection detection timer.) Rcr1 Rcr2 Ccr VTH 20 10 100000 OUTL FPWM= ILED kΩ kΩ pF 1.44 (RCR1+2RCR2)CCR TON_PWM= RCR2 (RCR1+2RCR2) ×100 Fig. 12 ●About time from EN turning on to PWM turning on and the start from PWM low Duty ※The GND short protection detecting function (hereafter, ①SCP timer detection starts SCP) starts with EN=Low→Hi, and after the time of the timer set with the external capacitor connected with CT, it EN becomes latch off. (Above figure ① and ②) ②Time of SCP timer The charge with SS begins synchronizing with turning on EN. The PWM latch off function is built into when there is ③Time until turning on PWM not PWM turning on, and when the PWM latch off is PWM detected, (② of SS and the SCP counter) is reset. (The time of the timer at latch OFF is calculated by oscillatory frequency ×32770 counts of DC/DC. ) Therefore, the ④Time of PWM latch timer ⑤Time until switching starts after inputting PWM following relations exist at time until PWM is turned on, time of PWM latch timer and SCP detection time after EN COUP is turned on at external brightness. (However, after ③ is turned on, ③ <④ is deleted from the sequence because ④ doesn't operate. ) OUTL Each sequence ②<④<③⇒SCP is detected and No LED light. SS ④<②<③⇒LED lighting ④<③<②⇒LED lighting ●About Dirating of the LED current that uses THM It is an ability to set the Dirating curve of the LED current to the temperature as one of the functions to use THM. As for LED, because deterioration at the high temperature is fast, the maximum allowance LED currents and the curve of temperatures is given to the data sheet of LED. The voltage with a negative temperature characteristic in THM the Thermistor resistance is used is input, and the LED current is controlled when the LED current is controlled according to the temperature characteristic. Moreover, external Tr is used, and two input composition is also possible. www.rohm.com © 2011 ROHM Co., Ltd. All rights reserved. 5/20 2011.04 - Rev.A Technical Note BD8381EFV-M ●Buck-Boost DC/DC controller ・Over-voltage protection circuit (OVP) The output of the DCDC converter should be connected to the OVP pin via a voltage divider. In determining an appropriate trigger voltage of for OVP function, consider the total number of LEDs in series and the maximum variation in VF. Also, bear in mind that over-current protection (OCP) is triggered at 0.85 x OVP trigger voltage. If the OVP function engages, it will not release unless the DCDC voltage drops to 72.5% of the OVP trigger voltage. For example, if ROVP1 (out put voltage side), ROVP2 (GND side), and DCDC voltage VOUT are conditions for OVP, then: VOUT ≥ (ROVP1 + ROVP2) / ROVP2 x 2.0 V. OVP will engage when VOUT ≧ 32 V if ROVP1 = 330 kΩ and ROVP2 = 22 kΩ. ・Buck-boost DC/DC converter oscillation frequency (FOSC) The regulator’s internal triangular wave oscillation frequency can be set via a resistor connected to the RT pin (pin 5). This resistor determines the charge/discharge current to the internal capacitor, thereby changing the oscillating frequency. Refer to the following theoretical formula when setting RT: fosc = 60 × 106 RT [Ω] x α [kHz] 6 60 x 10 (V/A/S) is a constant (±5%) determined by the internal circuitry, and α is a correction factor that varies in relation to RT: { RT: α = 50kΩ: 0.98, 60kΩ: 0.985, 70kΩ: 0.99, 80kΩ: 0.994, 90kΩ: 0.996, 100kΩ: 1.0, 150kΩ: 1.01, 200kΩ: 1.02, 300kΩ: 1.03, 400kΩ: 1.04, 500kΩ: 1.045 } DC/DC Frequency [kHz] A resistor in the range of 62.6kΩ~523kΩ is recommended. Settings that deviate from the frequency range shown below may cause switching to stop, and proper operation cannot be guaranteed. SYNC frequency[kHz] Fig.13 RT versus switching frequency Fig.14 RT versus SYNC frequency ・External DC/DC converter oscillating frequency synchronization (FSYNC) Do not switch from external to internal oscillation of the DC/DC converter if an external synchronization signal is present on the SYNC pin. When the signal on the SYNC terminal is switched from high to low, a delay of about 30 µs (typ.) occurs before the internal oscillation circuitry starts to operate (only the rising edge of the input clock signal on the SYNC terminal is recognized). Moreover, the external synchronizing signal is given to priority when an external input frequency is used. And in the case of using external input frequency, follow the Fig.14. ・Soft Start Function The soft-start (SS) limits the current and slows the rise-time of the output voltage during the start-up, and hence leads to prevention of the overshoot of the output voltage and the inrush current. The SS voltage is made Low when OVP of the overcurrent and the excess voltage is detected, and the switching is stopped. Resume operation is begun. www.rohm.com © 2011 ROHM Co., Ltd. All rights reserved. 6/20 2011.04 - Rev.A Technical Note BD8381EFV-M ・Self-diagnostic functions The operating status of the built-in protection circuitry is propagated to FAIL1 and FAIL2 pins (open-drain outputs). FAIL1 becomes low when UVLO, TSD, OVP, or SCP protection is engaged, whereas FAIL2 becomes low when open or short LED is detected. FAIL2 FAIL1 OPEN UVLO TSD OVP OCP SCP Counter EN=Low S SHORT S MASK R Q EN=Low UVLO/TSD Q R UVLO/TSD ・Operation of the Protection Circuitry ・Under-Voltage Lock Out (UVLO) The UVLO shuts down all the circuits other than REG when VREG ≦ 4.3V (TYP). ・Thermal Shut Down (TSD) The TSD shuts down all the circuits other than REG when the Tj reaches 175℃ (TYP), and releases when the Tj becomes below 150℃ (TYP). ・Over Current Protection (OCP) The OCP detects the current through the power-FET by monitoring the voltage of the high-side resistor, and activates when the CS voltage becomes less than VCC-0.6V (TYP). When the OCP is activated, the external capacitor of the SS pin becomes discharged and the switching operation of the DCDC turns off. ・Over Voltage Protection (OVP) The output voltage of the DCDC is detected with the OVP-pin voltage, and the protection activates when the OVP-pin voltage becomes greater than 2.0V (TYP). When the OVP is activated, the external capacitor of the SS pin becomes discharged and the switching operation of the DCDC turns off. ・Short Circuit Protection (SCP) When the FB-pin voltage becomes less than 0.05V (TYP), the internal counter starts operating and latches off the circuit approximately after 150ms (when CT = 0.1µF). If the FB-pin voltage becomes over 0.05V before 150ms, then the counter resets. When the LED anode (i.e. DCDC output voltage) is shorted to ground, then the LED current becomes off and the FB-pin voltage becomes low. Furthermore, the LED current also becomes off when the LED cathode is shorted to ground. Hence in summary, the SCP works with both cases of the LED anode and the cathode being shorted. ・LED Open Detection When the LED-pin voltage 0.05V (TYP) as well as OVP-pin voltage 1.7V (TYP) simultaneously, the device detects as LED open and latches off that particular channel. www.rohm.com © 2011 ROHM Co., Ltd. All rights reserved. 7/20 2011.04 - Rev.A Technical Note BD8381EFV-M ・LED Short Detection When the voltage between LEDR-pin and LEDC-pin 0.2 (TYP), the internal counter starts operating, and approximately after 100ms (when FOSC = 300kHz) the operation latches off. With the PWM brightness control, the detecting operation is processed only when PWMOUT-pin = High. If the condition of the detection operation is released before 100ms (when FOSC = 300kHz), then the internal counter resets. There is a possibility that the LED short detection malfunctions when the difference of Vf is large. Therefore, please adjust external resistance for connected Vf. It is recommended 2V-3V to the input range of LEDR and LEDC. ※The counter frequency is the DCDC switching frequency determined by the RT. The latch proceeds at the count of 32770. ○High luminance LED (multichip) with built-in LED of X piece in 1chip when using Y piece VOUT(DC/DC output) R3 LEDR Y piece R4 X piece Setting method R1:R2 = X:1 R3:R4 = ( X + 1 ) Y – 1:1 R1 LEDC R2 PWMOUT FB Fig. 15 ○When using the single chip VOUT(DC/DC output) R3 LEDR Y piece R4 R1 LEDC R2 Setting method R1:R2 = 1:1 R3:R4 = 2Y – 1:1 PWMOUT FB Fig. 16 www.rohm.com © 2011 ROHM Co., Ltd. All rights reserved. 8/20 2011.04 - Rev.A Technical Note BD8381EFV-M ●Error all condition Detecting Condition Protection Operation after detect [Detect] [Release] UVLO VREG<4.3V VREG>4.45V TSD Tj>175℃ Tj<150℃ OVP VOVP>2.0V VOVP<1.45V SS discharged OCP VCS≦VCC-0.6V VCS>VCC-0.6V SS discharged SCP VFB<0.05V (150ms delay when CT=0.1µF) EN or UVLO LED open VFB<0.05V & VOVP>1.7V EN or UVLO LED short lVLEDR-VLEDCl>0.2V (100ms delay when FOSC=300kHz) EN or UVLO All blocks (but except REG) shut down All blocks (but except REG) shut down Counter starts and then latches off all blocks (but except REG) Counter starts and then latches off all blocks (but except REG) Counter starts and then latches off all blocks (but except REG) ●Protection sequence Vcc EN ① 4.5V VREG Release UVLO THM (Input by the resistance division of VREG. ) ② ② SYNC ② DRLIN SS OUTL VOUT Fig.17 Power supply turning on sequence ① Please turn on EN with Vcc≧4.5V or more after impressing Vcc. ② Please fix the potential of DRLIN and THM before turning on EN. ③ A soft start operates at the same time as turning on EN, and the switching is output. ④ After turning on VCC, the order is not related to other input when inputting external PWM from VTH.) ※It leads to the destruction of IC and external parts because it doesn't error output according to an external constant of adjacent pin 24pin SW terminal, 25pin OUTH terminal, 26pin CS terminal and 27pin BOOT terminal. www.rohm.com © 2011 ROHM Co., Ltd. All rights reserved. 9/20 2011.04 - Rev.A Technical Note BD8381EFV-M ●Operation in error circumstances of LED ① LED open detection VCC LED OPEN FB 50m 0V V Switching Duty extends. OUTH OUTH/OUTL VOUT SW Switching stop 1.7V VOUT/OVP OUTL OPEN FAIL2 LED open detection when VOVP≧1.7 and VFB≦50mV (When it achieves the detection condition, the FP latch is done. ) Q1 PWMOUT FB RSENSE Fig.18 ②LED short detection VCC VOUT It gets down by LED1 step. OUTH VOUT SW LEDR-LEDC N 0V N LEDR OUTL fosc OUTH/OUTL Switching stop 1 1 1 △T=32770× fosc FAIL2 Short Q1 PWMOUT 0.2V It detects short, and after the timer of △T, error is detected with FAIL2. RSENSE Fig.19 ③ LED anode/cathode land GND short detection VCC VOUT LED anode GND short OUTH 0V Short to GND VOUT SW FB 200mV 50mV 0V Capacity dependence connected with CT OUTH/OUTL OUTL Switching stop FAIL2 PWMOUT 1 Timer operation of CT after GND short detection. FAIL1 becomes Hi? Low. Q1 It detects short, and after the timer of △T, error is detected with FAIL2. RSENSE Fig.20 www.rohm.com © 2011 ROHM Co., Ltd. All rights reserved. 10/20 2011.04 - Rev.A Technical Note BD8381EFV-M ●Procedure for external components selection Follow the steps as shown below for selecting the external components 1. Work out IL_MAX from the operating conditions. 2. Select the value of RSC such that IOCP > IL_MAX 3. Select the value of L such that 0.05[V/µs] < 4. Select coil, schottky diodes, MOSFET and RCS which meet with the ratings 5. Select the output capacitor which meets with the ripple voltage requirements 6. Select the input capacitor 7. Work on with the compensation circuit 8. Work on with the Over-Voltage Protection (OVP) setting 9. Work on with the soft-start setting 10. Feedback the value of L Vout *RCS < 0.3[V/ µs] L Verify experimentally www.rohm.com © 2011 ROHM Co., Ltd. All rights reserved. 11/20 2011.04 - Rev.A Technical Note BD8381EFV-M 1. Computation of the Input Peak Current and IL_MAX ①Calculation of the maximum output voltage (Vout_max) To calculate the Vout_max, it is necessary to take into account of the VF variation and the number of LED connection in series. ΔVF: VF Variation N: Number of LED connection in series Vout_max = (VF + ΔVF) × N + 0.2+ RPWMON×Iout RPWMON: PWMOUT FET Ron ②Calculation of the output current Iout D: FB standard voltage variation 0.2V Iout= M: Output current resistance variation RISET ③Calculation of the input peak current IL_MAX IL_MAX = IL_AVG + 1/2ΔIL IL_AVG = (VIN + Vout) × Iout / (n × VIN) ΔIL= VIN × L 1 Fosc × Vout n: efficiency VIN+Vout Fosc: switching frequency ・The worst case scenario for VIN is when it is at the minimum, and thus the minimum value should be applied in the equation. ・ The L value of 10µH 47µH is recommended. The current-mode type of DC/DC conversion is adopted for BD8381EFV-M, which is optimized with the use of the recommended L value in the design stage. This recommendation is based upon the efficiency as well as the stability. The L values outside this recommended range may cause irregular switching waveform and hence deteriorate stable operation. ・n (efficiency) is approximately 80% VIN IL Rcs CS M1 D2 L Vout M2 Co D1 Fig.21 External Application Circuit 2. The setting of over-current protection Choose Rcs with the use of the equation Vocp_min (=0.54V) / Rcs > IL_MAX When investigating the margin, it is worth noting that the L value may vary by approximately ±30%. 3. The selection of the L In order to achieve stable operation of the current-mode DC/DC converter, we recommend selecting the L value in the range indicated below: Vout×Rcs < 0.3 [V/µs] L Vout×Rcs allows stability improvement but slows down the response time. L 0.05 [V/µs] < The smaller 4. Selection of coil L, diode D1 and D2, MOSFET M1 and M2, and Rcs ※ ※ Current rating Voltage rating Coil L > IL_MAX ― Diode D1 > Iocp > VIN_MAX Diode D2 > Iocp > Vout MOSFET M1 > Iocp > VIN_MAX MOSFET M2 > Iocp > Vout Rcs ― ― Heat loss > Iocp2 × Rcs Allow some margin, such as the tolerance of the external components, when selecting. In order to achieve fast switching, choose the MOSFETs with the smaller gate-capacitance. www.rohm.com © 2011 ROHM Co., Ltd. All rights reserved. 12/20 2011.04 - Rev.A Technical Note BD8381EFV-M 5. Selection of the output capacitor Select the output capacitor Cout based on the requirement of the ripple voltage Vpp. Vpp = Iout × Cout Vout × Vout+VIN 1 Fosc + IL_MIN × RESR Choose Cout that allows the Vpp to settle within the requirement. Allow some margin also, such as the tolerance of the external components. 6.Selection of the input capacitor A capacitor at the input is also required as the peak current flows between the input and the output in DC/DC conversion. We recommend an input capacitor greater than 10µF with the ESR smaller than 100m. The input capacitor outside of our recommendation may cause large ripple voltage at the input and hence lead to malfunction. 7. Phase Compensation Guidelines In general, the negative feedback loop is stable when the following condition is met: Overall gain of 1 (0dB) with a phase lag of less than 150º (i.e., a phase margin of 30º or more) However, as the DC/DC converter constantly samples the switching frequency, the gain-bandwidth (GBW) product of the entire series should be set to 1/10 the switching frequency of the system. Therefore, the overall stability characteristics of the application are as follows: Overall gain of 1 (0dB) with a phase lag of less than 150º (i.e., a phase margin of 30º or more) GBW (frequency at gain 0dB) of 1/10 the switching frequency Thus, to improve response within the GBW product limits, the switching frequency must be increased. The key for achieving stability is to place fz near to the GBW. GBW is decided by phase delay fp1 by COUT and output impedance RL. Of each becomes like the next expression. Vout 1 Phase-lead fz = [Hz] 2πCpcRpc 1 Phase-lag fp1 = [Hz] 2πRLCout LED FB A COMP Rpc Cpc Good stability would be obtained when the fz is set between 1kHz~10kHz. Please substitute the value at the maximum load for RL. In buck-boost applications, Right-Hand-Plane (RHP) Zero exists. This Zero has no gain but a pole characteristic in terms of phase. As this Zero would cause instability when it is in the control loop, so it is necessary to bring this zero before the GBW. fRHP= Vout+VIN/(Vout+VIN) 2πILOADL [Hz] ILOAD: MAXIMUM LOAD CURRENT It is important to keep in mind that these are very loose guidelines, and adjustments may have to be made to ensure stability in the actual circuitry. It is also important to note that stability characteristics can change greatly depending on factors such as substrate layout and load conditions. Therefore, when designing for mass-production, stability should be thoroughly investigated and confirmed in the actual physical design. www.rohm.com © 2011 ROHM Co., Ltd. All rights reserved. 13/20 2011.04 - Rev.A Technical Note BD8381EFV-M 8. Setting of the soft-start The soft-start allows minimization of the coil current as well as the overshoot of the output voltage at the start-up. For the capacitance we recommend in the range of 0.001 0.1µF. For the capacitance less than 0.001µF may cause overshoot of the output voltage. For the capacitance greater than 0.1µF may cause massive reverse current through the parasitic elements of the IC and damage the whole device. In case it is necessary to use the capacitance greater than 0.1µF, ensure to have a reverse current protection diode at the Vcc or a bypass diode placed between the SS-pin and the Vcc. Soft-start time TSS TSS = CSSX0.7V / 5uA [s] CSS: The capacitance at the SS-pin 9. Verification of the operation by taking measurements The overall characteristic may change by load current, input voltage, output voltage, inductance, load capacitance, switching frequency, and the PCB layout. We strongly recommend verifying your design by taking the actual measurements. www.rohm.com © 2011 ROHM Co., Ltd. All rights reserved. 14/20 2011.04 - Rev.A Technical Note BD8381EFV-M ●Power consumption calculation Pc(N) = ICC*VCC + 1 2 *Ciss*VREG*Fsw*VREG×2×2+ 1 2 ×Ciss×VREG×FPWM×VREG×2 ICC : Current of the maximum circuit VCC :Power-supply voltage Ciss : External FET capacity Vsw : SW gate voltage Fsw : SW frequency FPWM : PWM frequency <Calculation example> When assuming Pc(4) = 10mA × 30V + 500pF × 5V × 300kHz × 5V×2×2+ 1 2 ×1500pF×5×200×5×2, it becomes Pc = about 300mW. 4 Power Consumption Pd[W] (1) θja=66.5℃/W (Density of board copper foil3%) 3 2 (3) 3.12W (2) θja=45℃/W (Density of board copper foil34%) (2) 2.77W (3) θja=40℃/W (Density of board copper foil60%) (1) 1.88W 1 0 25 50 75 95 100 125 150 Ambient temperature Ta[℃] Fig.22 Note1: The value of Power consumption : on glass epoxy board measuring 70mm×70mm×1.6mm (1 layer board/Copper foil thickness 18µm) Note2: The value changes depending on the density of the board copper foil. However, this value is an actual measurement value and no guarantee value. Pd=2200mW (968mW) : Density of the board copper foil 3% Pd=3200mW (1408mW): Density of the board copper foil 34% Pd=3500mW (1540mW): Density of the board copper foil 60% The value in () is a Power consumption of the Ta=125℃. www.rohm.com © 2011 ROHM Co., Ltd. All rights reserved. 15/20 2011.04 - Rev.A Technical Note BD8381EFV-M ●Application circuit 1 VREG Vin FAIL1 OVP UVLO VCC TSD COUT OVP OCP CS VREG Timer Latch EN PWM BOOT Control Logic OUTH DRV CTL SYNC SW PWM SLOPE OSC DGND RT VREG OUTL ERR AMP GND - COMP + SS LEDR + OCP OVP SHORT Det LEDC SS VREG PWMOUT THM INP1 FB INP2 VREG DRLIN OPEN/ SHORT/ SCP Detect CR TIMER DISC Open Det VTH Timer Latch FAIL2 SCP Det PGND CT Fig. 23 Buck application composition (It is INP1, INP2, and two input selector function. ) ●Application circuit 2 VREG Vin FAIL1 OVP UVLO VCC TSD COUT OVP OCP CS VREG Timer Latch EN PWM BOOT Control Logic OUTH DRV CTL SYNC OSC SLOPE SW PWM DGND RT VREG OUTL ERR AMP GND - COMP + SS VREG LEDR + OCP OVP SHORT Det SS LEDC PWMOUT THM FB VREG DRLIN OPEN/ SHORT/ SCP Detect DISC CR TIMER Open Det VTH Timer Latch SCP Det FAIL2 CT PGND Fig. 24 Boost application composition (When invalidating short detection. ) www.rohm.com © 2011 ROHM Co., Ltd. All rights reserved. 16/20 2011.04 - Rev.A Technical Note BD8381EFV-M ●Input/output Equivalent Circuits 1. COMP VREG 2. SS VREG 4. EN VREG VCC EN SS COMP 5. RT 6. SYNC 8. THM VCC VREG VREG VREG RT 9. FB SYNC 10. DISC 11. VTH VREG VREG VCC DISC FB 12. DRLIN 13,14. FAIL1,FAIL2 VTH 15. OVP VCC VCC DRLIN FAIL1 FAIL2 OVP ※The values are all Typ. value. www.rohm.com © 2011 ROHM Co., Ltd. All rights reserved. 17/20 2011.04 - Rev.A Technical Note BD8381EFV-M ●Input/output Equivalent Circuits(Continuation) 16,17. LEDC, LEDR 19,22. PWMOUT, OUTL 20. CT VREG VREG VREG LEDC LEDR 24. SW CT 25. OUTH BOOT 26. CS BOOT VCC SW OUTH CS SW SW SW 28. VREG 27. BOOT VREG VCC VREG BOOT VREG ※The values are all Typ. value. www.rohm.com © 2011 ROHM Co., Ltd. All rights reserved. 18/20 2011.04 - Rev.A Technical Note BD8381EFV-M ●Notes for use 1. Absolute maximum ratings We are careful enough for quality control about this IC. So, there is no problem under normal operation, excluding that it exceeds the absolute maximum ratings. However, this IC might be destroyed when the absolute maximum ratings, such as impressed voltages or the operating temperature range(Topr), is exceeded, and whether the destruction is short circuit mode or open circuit mode cannot be specified. Please take into consideration the physical countermeasures for safety, such as fusing, if a particular mode that exceeds the absolute maximum rating is assumed. 2. Reverse polarity connection Connecting the power line to the IC in reverse polarity (from that recommended) will damage the part. Please utilize the direction protection device as a diode in the supply line. 3. Power supply line Due to return of regenerative current by reverse electromotive force, using electrolytic and ceramic suppress filter capacitors (0.1µF) close to the IC power input terminals (Vcc and GND) are recommended. Please note the electrolytic capacitor value decreases at lower temperatures and examine to dispense physical measures for safety. And, for ICs with more than one power supply, it is possible that rush current may flow instantaneously due to the internal powering sequence and delays. Therefore, give special consideration to power coupling capacitance, width of power wiring, GND wiring, and routing of wiring. Please make the power supply lines (where large current flow) wide enough to reduce the resistance of the power supply patterns, because the resistance of power supply pattern might influence the usual operation. 4. GND line The ground line is where the lowest potential and transient voltages are connected to the IC. 5. Thermal design Do not exceed the power dissipation (Pd) of the package specification rating under actual operation, and please design enough temperature margins. 6. Short circuit mode between terminals and wrong mounting Do not mount the IC in the wrong direction and be careful about the reverse-connection of the power connector. Moreover, this IC might be destroyed when the dust short the terminals between them or power supply, GND. 7. Radiation Strong electromagnetic radiation can cause operation failures. 8. ASO(Area of Safety Operation.) Do not exceed the maximum ASO and the absolute maximum ratings of the output driver. 9. TSD(Thermal shut-down) The TSD is activated when the junction temperature (Tj) reaches 175℃(with 25℃ hysteresis), and the output terminal is switched to Hi-z. The TSD circuit aims to intercept IC from high temperature. The guarantee and protection of IC are not purpose. Therefore, please do not use this IC after TSD circuit operates, nor use it for assumption that operates the TSD circuit. 10. Inspection by the set circuit board The stress might hang to IC by connecting the capacitor to the terminal with low impedance. Then, please discharge electricity in each and all process. Moreover, in the inspection process, please turn off the power before mounting the IC, and turn on after mounting the IC. In addition, please take into consideration the countermeasures for electrostatic damage, such as giving the earth in assembly process, transportation or preservation. 11. IC terminal input + This IC is a monolithic IC, and has P isolation and P substrate for the element separation. Therefore, a parasitic PN junction is firmed in this P-layer and N-layer of each element. For instance, the resistor or the transistor is connected to the terminal as shown in the figure below. When the GND voltage potential is greater than the voltage potential at Terminals A or B, the PN junction operates as a parasitic diode. In addition, the parasitic NPN transistor is formed in said parasitic diode and the N layer of surrounding elements close to said parasitic diode. These parasitic elements are formed in the IC because of the voltage relation. The parasitic element operating causes the wrong operation and destruction. Therefore, please be careful so as not to operate the parasitic elements by impressing to input terminals lower voltage than GND(P substrate). Please do not apply the voltage to the input terminal when the power-supply voltage is not impressed. Moreover, please impress each input terminal lower than the power-supply voltage or equal to the specified range in the guaranteed voltage when the power-supply voltage is impressing. Resistor Transistor(NPN) Terminal-A Terminal-B C Terminal-B B E Terminal-A B P+ P+ P Parasitic element C E P+ P-Substrate P P+ P-Substrate Surrounding elements Parasitic element GND Parasitic element GND Parasitic element GND GND structure of IC 12. Earth wiring pattern Use separate ground lines for control signals and high current power driver outputs. Because these high current outputs that flows to the wire impedance changes the GND voltage for control signal. Therefore, each ground terminal of IC must be connected at the one point on the set circuit board. As for GND of external parts, it is similar to the above-mentioned www.rohm.com © 2011 ROHM Co., Ltd. All rights reserved. 19/20 2011.04 - Rev.A Technical Note BD8381EFV-M ●Ordering part number B D 8 Part No. 3 8 1 Part No. E F V Package EFV: HTSSOP-B28 - M E 2 for Packaging and forming specification Automotive E2: Embossed tape and reel HTSSOP-B28 <Tape and Reel information> 9.7±0.1 (MAX 10.05 include BURR) (5.5) 1 Tape Embossed carrier tape (with dry pack) Quantity 2500pcs Direction of feed E2 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 ) 14 +0.05 0.17 -0.03 1PIN MARK 1.0MAX 0.625 1.0±0.2 (2.9) 0.5±0.15 15 4.4±0.1 6.4±0.2 28 +6° 4° −4° 0.08±0.05 0.85±0.05 S 0.08 S 0.65 +0.05 0.24 -0.04 0.08 1pin M Reel (Unit : mm) www.rohm.com © 2011 ROHM Co., Ltd. All rights reserved. 20/20 Direction of feed ∗ Order quantity needs to be multiple of the minimum quantity. 2011.04 - 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. The content specified herein is subject to change for improvement without notice. The content specified 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 specifications, 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 specified 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 specified 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 specified in this document are intended to be used with general-use electronic equipment or devices (such as audio visual equipment, office-automation equipment, communication devices, electronic appliances and amusement devices). The Products specified 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, fire or any other damage caused in the event of the failure of any Product, such as derating, redundancy, fire 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, aerospace machinery, nuclear-reactor controller, fuelcontroller 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 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 © 2011 ROHM Co., Ltd. All rights reserved. R1120A