LED Drivers for LCD Backlights White Backlight LED Driver for Medium to Large LCD Panels (Switching Regulator Type) BD8113EFV No.11040EAT04 ●Description BD8113EFV is a white LED driver with the capability of withstanding high input voltage (36V MAX). This driver has 2ch constant-current drivers integrated in 1-chip, which each channel can draw up to 150mA max, so that high brightness LED driving can be realized. Furthermore, 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 VDAC techniques. ●Features 1) Input voltage range 5.0 – 30 V 2) Integrated buck-boost current-mode DC/DC controller 3) Two integrated LED current driver channels (150 mA max. each channel) 4) PWM Light Modulation(Minimum Pulse Width 25µs) 5) Oscillation frequency accuracy ±5% 6) Built-in protection functions (UVLO, OVP, TSD, OCP, SCP) 7) LED abnormal status detection function (OPEN/ SHORT) 8) HTSSOP-B24 package ●Applications Backlight for display audio, small type panels, etc. ●Absolute maximum ratings (Ta=25℃) Parameter Symbol Ratings Unit Power supply voltage VCC 36 V BOOT ,OUTH Voltage VBOOT, VOUTH 41 V SW,CS Voltage VSW, VCS 36 V BOOT-SW Voltage VBOOT-SW 7 V VLED1,2 VVREG, VOVP, VOUTL, VFAIL1, VFAIL2, VLEDEN, VISET, VVDAC, VPWM, VSS, VCOMP, VRT, VSYNC, VEN Pd 36 V -0.3~7 < VCC V LED output voltage VREG, OVP, OUTL, FAIL1, FAIL2, LEDEN, ISET, VDAC, PWM, SS, COMP, RT, SYNC, EN voltage Power Consumption 1.10 ※1 W Operating temperature range Topr -40~+105 ℃ Storage temperature range Tstg -55~+150 ℃ ILED ※2 ※3 LED maximum output current Junction temperature Tjmax 150 150 mA ℃ *1 IC mounted on glass epoxy board measuring 70mm×70mm×1.6mm, power dissipated at a rate of 8.8mw/℃ at temperatures above 25℃. *2 Dispersion figures for LED maximum output current and VF are correlated. Please refer to data on separate sheet. *3 Amount of current per channel. ●Operating conditions (Ta=25℃) Parameter Power supply voltage Oscillating frequency range External synchronization frequency range ※4 ※5 External synchronization pulse duty range *4 *5 Symbol Ratings Unit VCC 5.0~30 V FOSC 250~600 kHz FSYNC fosc~600 kHz FSDUTY 40~60 % Connect SYNC to GND or OPEN when not using external frequency synchronization. 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. 1/19 2011.07 - Rev.A Technical Note BD8113EFV ●Electrical characteristics (Unless otherwise specified, VCC=12V Ta=25℃) Limits Parameter Symbol Min Typ Max. Unit Conditions Circuit current ICC - 7 14 mA Standby current IST - 4 8 µA EN=Hi, SYNC=Hi, RT=OPEN PWM=Low, ISET=OPEN, CIN=10µF EN=Low VREG 4.5 5 5.5 V IREG=-5mA, CREG=2.2µF [VREG Block (VREG)] Reference voltage [OUTH Block] OUTH high-side ON resistance RONHH 1.5 3.5 7.0 Ω ION=-10mA OUTH low-side ON resistance Over-current protection operating voltage [OUTL Block] RONHL 2.5 VCC -0.6 5.0 VCC -0.54 Ω ION=10mA VOLIMIT 1.0 VCC -0.66 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 RON_SW 2.0 4.5 9.0 Ω ION_SW=10mA VLED 0.9 1.0 1.1 V V [SW Block] SW low -side ON resistance [Error Amplifie Block] LED voltage COMP sink current ICOMPSINK 15 25 35 µA VLED=2V, Vcomp=1V ICOMPSOURCE -35 -25 -15 µA VLED=0V, Vcomp=1V Oscillating frequency FOSC 285 300 315 KHz [OVP Block] Over-voltage detection reference voltage OVP hysteresis width VOVP 1.9 2.0 2.1 V VOVP=Sweep up VOHYS 0.45 0.55 0.65 V VOVP=Sweep down TSCP 70 100 130 ms UVLO voltage VUVLO 3.7 4.0 4.3 V UVLO hysteresis width VUHYS 400 500 600 mV △ILED1 -3 - +3 % △ILED2 -5 - +5 % COMP source current [Oscillator Block] SCP Latch OFF Delay Time RT=100kΩ RT=100kΩ [UVLO Block ] VCC : Sweep down VCC : Sweep up [LED Output Block] VISET 1.96 2.0 2.04 V ILED=50mA, ΔILED1=(ILED/ILED_AVG-1)×100 ILED=50mA, ΔILED2=(ILED/50mA-1)×100 RISET=120kΩ PWM minimum pulse width Tmin 25 - - µs FPWM=150Hz, ILED=50mA PWM maximum duty Dmax - - 100 % FPWM=150Hz, ILED=50mA PWM frequency FPWM - - 20 KHz VDAC gain GVDAC - 25 - mA/V Open detection voltage VOPEN 0.2 0.3 0.4 V Duty=50%, ILED=50mA VDAC=0~2V, RISET=120kΩ ILED=VDAC÷RISET×Gain VLED= Sweep down LED Short detection Voltage VSHORT 4.2 4.5 4.8 V VOVP= Sweep up LED Short Latch OFF Delay Time TSHORT 70 100 130 ms RT=100kΩ TPWM 70 100 130 ms RT=100kΩ LED current relative dispersion width LED current absolute dispersion width ISET voltage PWM Latch OFF Delay Time [Logic Inputs (EN, SYNC, PWM, LEDEN)] Input HIGH voltage VINH 2.1 - 5.5 V Input LOW voltage VINL GND - 0.8 V Input current 1 IIN 20 35 50 µA Input current 2 IEN 15 25 35 µA VIN=5V (SYNC, PWM, LEDEN) VEN=5V (EN) VOL - 0.1 0.2 V IOL=0.1mA [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. 2/19 2011.07 - Rev.A Technical Note BD8113EFV ●Electrical characteristic curves (Unless otherwise specified, Ta=25℃) 5.5 5.1 4.9 4.7 360 320 280 240 200 -40 -15 10 35 60 85 TEMPERATURE:Ta [℃] Fig.1 VREG temperature characteristic 51 49 47 47 45 -15 10 35 60 85 TEMPERATURE:Ta [℃] 0.5 40 30 20 10 85 Fig.4 ILED temperature characteristic 85 85 0.5 1 1.5 VDAC VOLTAGE:VDAC[V] EFFICIENCY [%] 55 40 25 70 55 25 100 150 200 Total_Io [mA] 250 Vcc=12V 2.0 0 0.60 0.58 VCC=12V 0.56 0.54 Fig.10 Overcurrent detecting voltage temperature characteristic www.rohm.com © 2011 ROHM Co., Ltd. All rights reserved. 36 10 8 6 4 2 0 85 6 12 18 24 30 SUPPLY VOLTAGE:Vcc [V] Fig.9 Circuit Current (Switching OFF) OUTPUTCURRENT :ILED [mA] OUTPUT VOLTAGE:VREG [V] 0.62 0.1 4.0 100 150 200 250 OUTPUT CURRENT [mA] 10 0.64 0.02 0.04 0.06 0.08 VDAC VOLTAGE:VDAC[V] 6.0 Fig.8 Efficiency (LED2 Parallel 7 step) 0.66 -15 10 35 60 TEMPERATURE:Ta [℃] 0 0.0 50 Fig.7 Efficiency (LED2 Parallel 5 step) -40 1 Fig.3 VDAC Gain② 40 50 2 2 VCC=12V VCC=12V 3 Fig.5 VDAC Gain① 100 70 4 0 0 100 4.5 5 OUTPUT CARRENT:Icc [mA] -15 10 35 60 TEMPERATURE:Ta [℃] 1.5 2.5 3.5 LED VOLTAGE:VLED[V] Fig.3 ILED depend on VLED 0 -40 EFFICIENCY [%] 49 OUTPUTCURRENT :ILED [mA] OUTPUTCURRENT :ILED [mA] Vcc= 12V 53 Vcc= 12V 51 50 45 OUTPUT VOLTAGE:Vcc-Vcs [V] 53 Fig.2 OSC temperature characteristic 55 OUTPUTCURRENT :ILED [mA] OUTPUTCURRENT :ILED [mA] VCC=12V SWITCHING FREQUENCY:FOSC [kHz] OUTPUT VOLTAGE:VREG [V] VCC=12V 5.3 4.5 -40 55 400 8 6 4 2 0 0 1 2 3 4 EN VOLTAGE:VEN [V] Fig.11 EN threshold voltage 3/19 5 0 1 2 3 4 PWM VOLTAGE:VEN [V] 5 Fig.12 PWM threshold voltage 2011.07 - Rev.A Technical Note BD8113EFV ●Block diagram and pin configuration COUT VREG Vin CIN UVLO VCC EN OVP TSD OVP VREG OCP + - Timer Latch PWM CS FAIL1 BOOT Control Lo gic OUTH DRV SYNC RT SLOPE SW CTL - PW M + DGND OSC VREG CRT RT OUTL ERR AMP GND - COMP Ccomp RPC - + OC P O VP LED1 CPC SS LED2 SS CSS Current drive r PWM VDAC ISET PGND Open Short De tect ISET Open Det RISET Timer Latch Short Det FAIL2 LEDEN Fig.13 ●Pin layout BD8113EFV(HTSSOP-B24) ●Pin function table COMP 1 24 VREG SS 2 23 BOOT VCC 3 22 CS EN 4 21 OUTH RT 5 20 SW SYNC 6 19 DGND GND 7 18 OUTL PWM 8 17 PGND FAIL1 9 16 ISET FAIL2 10 15 VDAC LEDEN 11 14 OVP LED1 12 13 LED2 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 Symbol COMP SS VCC EN RT SYNC GND PWM FAIL1 FAIL2 LEDEN LED1 LED2 OVP VDAC ISET PGND OUTL DGND SW OUTH CS BOOT VREG Function Error amplifier output Soft start time-setting capacitance input Input power supply Enable input Oscillation frequency-setting resistance input External synchronization signal input Small-signal GND PWM light modulation input Failure signal output LED open/short detection signal output LED output enable pin LED output 1 LED output 2 Over-voltage detection input DC variable light modulation input LED output current-setting resistance input LED output GND Low-side external MOSFET Gate Drive out put Low-side internal MOSFET Source out put High-side external MOSFET Source pin High-side external MOSFET Gate Drive out pin DC/DC Current Sense Pin High-side MOSFET Power Supply pin Internal reference voltage output Fig.14 www.rohm.com © 2011 ROHM Co., Ltd. All rights reserved. 4/19 2011.07 - Rev.A Technical Note BD8113EFV ●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 4.0 V (Typ.) or lower, UVLO engages and turns the IC off. Connect a capacitor (Creg = 2.2uF Typ.) to the VREG terminal for phase compensation. Operation may become unstable if Creg is not connected. ●Constant-current LED drivers If less than four constant-current drivers are used, unused channels should be switched off via the LEDEN pin configuration. The truth table for these pins is shown below. If a driver output is enabled but not used (i.e. left open), the IC’s open circuit-detection circuitry will operate. Please keep the unused pins open. The LEDEN terminals are pulled down internally in the IC, so if left open, the IC will recognize them as logic LO. However, they should be connected directly to VREG or fixed to a logic HI when in use. LED LED EN 1 2 L ON ON H ON OFF ・Output current setting LED current is computed via the following equation: ILED = min[VDAC , VISET(=2.0V)] / RSET x GAIN [A] (min[VDAC , 2.0V] = the smaller value of either VDAC or VISET; GAIN = set by internal circuitry.) In applications where an external signal is used for output current control, a control voltage in the range of 0.0 to 2.0 V can be connected on the VDAC pin to control according to the above equation. If an external control signal is not used, connect the VDAC pin to VREG (do not leave the pin open as this may cause the IC to malfunction). Also, do not switch individual channels on or off via the LEDEN pin while operating in PWM mode. The following diagram illustrates the relation between ILED and GAIN. ILED vs GAIN 3150 3100 GAIN 3050 3000 2950 2900 2850 0 20 40 60 80 100 120 140 160 ILED[mA] In PWM intensity control mode, the ON/OFF state of each current driver is controlled directly by the input signal on the PWM pin; thus, the duty ratio of the input signal on the PWM pin equals the duty ratio of the LED current. When not controlling intensity via PWM, fix the PWM terminal to a high voltage (100%). Output light intensity is greatest at 100% input. PWM PWM ILED(50mA/div) PWM=150Hz Duty=0.38% www.rohm.com © 2011 ROHM Co., Ltd. All rights reserved. ILED PWM=150Hz 5/19 Duty=50% 2011.07 - Rev.A Technical Note BD8113EFV ●Buck-Boost DC/DC controller ・Number of LEDs in series connection Output voltage of the DCDC converter is controlled such that the forward voltage over each of the LEDs on the output is set to 1.0V (Typ.). DCDC operation is performed only when the LED output is operating. When two or more LED outputs are operating simultaneously, the LED voltage output is held at 1.0V (Typ.) per LED over the column of LEDs with the highest VF value. The voltages of other LED outputs are increased only in relation to the fluctuation of voltage over this column. Consideration should be given to the change in power dissipation due to variations in VF of the LEDs. Please determine the allowable maximum VF variance of the total LEDs in series by using the description as shown below: VF variation allowable voltage 3.7V(Typ.) = short detecting voltage 4.5V(Typ.)-LED control voltage 1.0V(Typ.) The number of LEDs that can be connected in series is limited due to the open-circuit protection circuit, which engages at 85% of the set OVP voltage. Therefore, the maximum output voltage of the under normal operation becomes 30.6 V (= 36 V x 0.85, where (30.6 V – 1.0 V) / VF > N [maximum number of LEDs in series]). ・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 voltages 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: 30 × 106 RT [Ω] fosc = x α [kHz] 30 x 106 (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: 0.94, 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 } A resistor in the range of 47kΩ~523kΩ is recommended. Settings that deviate from the frequency range shown below may cause switching to stop, and proper operation cannot be guaranteed. 550K Frequency 周波数 [kHz] 450K 350K 250K 150K 50K 0 100 200 300 400 RT [kΩ] 500 600 700 800 Fig.15 RT versus switching 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, if external input frequency is less than the internal oscillation frequency, the internal oscillator will engage after the above-mentioned 30 µs (typ.) delay; thus, do not input a synchronization signal with a frequency less than the internal oscillation frequency. ・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. www.rohm.com © 2011 ROHM Co., Ltd. All rights reserved. 6/19 2011.07 - Rev.A Technical Note BD8113EFV ・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 ≦ 4.0V (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 LED-pin voltage becomes less than 0.3V (TYP), the internal counter starts operating and latches off the circuit approximately after 100ms (when FOSC = 300kHz). If the LED-pin voltage becomes over 0.3V before 100ms, 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 LED-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 0.3V (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. 7/19 2011.07 - Rev.A Technical Note BD8113EFV ・LED Short Detection When the LED-pin voltage 4.5V (TYP) as well as OVP-pin voltage 1.6V (TYP) simultaneously the internal counter starts operating, and approximately after 100ms (when FOSC = 300kHz) the only detected channel (as LED short) latches off. With the PWM brightness control, the detecting operation is processed only when PWM-pin = High. If the condition of the detection operation is released before 100ms (when FOSC = 300kHz), then the internal counter resets. ※ The counter frequency is the DCDC switching frequency determined by the RT. The latch proceeds at the count of 32770. Detecting Condition Protection Operation after detect [Detect] [Release] UVLO VREG<4.0V VREG>4.5V All blocks (but except REG) shut down TSD Tj>175℃ Tj<150℃ All blocks (but except REG) shut down OVP VOVP>2.0V VOVP<1.45V SS discharged OCP VCS≦VCC-0.6V VCS>VCC-0.6V SS discharged SCP VLED<0.3V (100ms delay when FOSC=300kHz) EN or UVLO Counter starts and then latches off all blocks (but except REG) LED open VLED<0.3V & VOVP>1.7V EN or UVLO The only detected channel latches off LED short VLED>4.5V & VOVP<1.6V (100ms delay when FOSC=300kHz) EN or UVLO The only detected channel latches off (after the counter sets) www.rohm.com © 2011 ROHM Co., Ltd. All rights reserved. 8/19 2011.07 - Rev.A Technical Note BD8113EFV ●Protection Sequence VCC EN *1 4.45V VREG UVLO VDAC *1 SYNC PWM *2 *2 ④ SS ILED1 ① ILED2 ② ILED1' ILED2' VLED1 1.0V VLED2 <0.3V VLED1' >4.7V VLED2' >4.5 100ms *3 100ms *3 0.3V 2.0V 1.7V VOVP FAIL1 ③ *4 FAIL2 Case for LED2 in open-mode When VLED2<0.3V and VOVP>1.7V simultaneously, then LED2 becomes off and FAIL2 becomes low ② Case for LED1’ in short-mode When VLED1’>4.5V and VOVP < 1.6V simultaneously, then LED1’ becomes off after 100ms approx ③ Case for LED2’ in short to GND ③-1 DCDC output voltage increases, and then SS dichages and FAIL1 becomes low ③-2 Detects VLED2’<0.3V and shuts down after 100ms approx ① www.rohm.com © 2011 ROHM Co., Ltd. All rights reserved. 9/19 *1 After VCC voltage reached to operating conditions, set VDAC voltage, and turn on the EN. After VREG≧4.6V, turn on SYNC and PWM inputs. *2 Don’t care input sequence PWM and SYNC. *3 Aprox 100ms of delay when Fosc = 300kHz *4 When FAIL1 pull-up to outside power supply. 2011.07 - Rev.A Technical Note BD8113EFV ●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. 10/19 2011.07 - Rev.A Technical Note BD8113EFV 1. Computation of the Input Peak Current and IL_MAX ① Calculation 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. Vout_max = (VF + ΔVF) × N + 1.0V ΔVF: VF Variation N: Number of LED connection in series Calculation of the output current Iout Iout = ILED × 1.05 × M ② ③ M:Number of LED connection in parallel Calculation 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 VIN+Vout n: efficiency 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 10µF 47µF is recommended. The current-mode type of DC/DC conversion is adopted for BD8113EFV, 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 M2 D1 2. 3. Co External Application Circuit 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%. 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: 0.05 [V/µs] < The smaller 4. Vout Vout×Rcs L Vout×Rcs < 0.3 [V/µs] L allows stability improvement but slows down the response time. 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. 11/19 2011.07 - Rev.A Technical Note BD8113EFV 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. Vout 1 Phase-lead fz = [Hz] 2πCpcRpc Phase-lag fp1 = 1 2πRLCout [Hz] LED FB A COMP Rpc Cpc Good stability would be obtained when the fz is set between 1kHz~10kHz. 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. Vout+VIN/(Vout+VIN) fRHP= 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. 12/19 2011.07 - Rev.A Technical Note BD8113EFV 8. Vo Setting of the over-voltage protection We recommend setting the over-voltage protection Vovp 1.2V to 1.5V greater than Vout which is adjusted by the number of LEDs in series connection. Less than 1.2V may cause unexpected detection of the LED open and short during the PWM brightness control. For the Vovp greater than 1.5V, the LED short detection may become invalid. 9. - + ROVP2 2.0V/1.45V OVP ROVP1 - + 1.7V/1.6V 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 0.1uF. For the capacitance less than 0.001uF may cause overshoot of the output voltage. For the capacitance greater than 0.1uF 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 0.1uF, 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 10 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. 13/19 2011.07 - Rev.A Technical Note BD8113EFV ●Power Dissipation Calculation Power dissipation can be calculated as follows: Pc(N) = ICC*VCC + 2*Ciss*VREG*Fsw*Vcc+[VLED*N+△Vf*(N-1)]*ILED ICC VCC Ciss Vsw Fsw VLED N ΔVf ILED Maximum circuit current Supply power voltage External FET capacitance SW gate voltage SW frequency LED control voltage LED parallel numeral LED Vf fluctuation LED output current Sample Calculation: Pc(2) = 10mA × 30V + 500pF × 5V × 300kHz × 30V + [1.0V × 2 + △Vf × 1] × 100mA When △Vf = 3.0V, Pc (2) = 0.82W Power Dissipation Power Dissipation Pd [W] 2.0 1.5 1.1W 1.0 0.5 0 25 50 75 100 105 125 150 Ambient Temperature Ta[℃] Fig.26 Note 1: Power dissipation calculated when mounted on 70mm X 70mm X 1.6mm glass epoxy substrate (1-layer platform/copper thickness 18µm) Note 2: Power dissipation changes with the copper foil density of the board. This value represents only observed values, not guaranteed values. www.rohm.com © 2011 ROHM Co., Ltd. All rights reserved. 14/19 2011.07 - Rev.A Technical Note BD8113EFV VCC VCC CPC2 CIN1 CIN2 CPC1 RPC1 CCS 1. COMP 24. VREG 2. SS 23. BOOT RCS1 RCS2 RCS3 VREG CSS RCS5 3. VCC EN SW1 4. EN 5. RT SYNC CRT 22. CS 21. OUTH 20. SW 6. SYNC 19. DGND 7. GND 18. OUTL CREG D CBT G VOUT M1 S D1 D2 L1 D ROVP2 G RRT CIN3 FIN. FIN FIN. FIN 8. PWM 17. PGND 9. FAIL1 16. ISET M2 S COUT1 COUT2 ROVP1 VREG CISET PWM RFL2 RFL1 FAIL1 RDAC VREG RISET 10. FAIL2 FAIL2 SW2 VREG LED1 15. VDAC 11. LEDEN 14. OVP 12. LED1 13. LED2 VDAC LED2 The coupling capacitors CVCC and CREG should be mounted as close as possible to the IC’s pins. Large currents may pass through DGND and PGND, so each should have its own low-impedance routing to the system ground. Noise should be minimized as much as possible on pins VDAC, ISET,RT and COMP. PWM, SYNC and LED1,2 carry switching signals, so ensure during layout that surrounding traces are not affected by crosstalk. www.rohm.com © 2011 ROHM Co., Ltd. All rights reserved. 15/19 2011.07 - Rev.A Technical Note BD8113EFV ●How to select parts of application Serial No. component name component value product name Manufacturer 1 CIN1 10µF GRM31CB31E106KA75B murata 2 CIN2 - 3 CIN3 - 4 CPC1 0.1µF 5 CPC2 - 6 RPC1 510Ω 7 CSS 0.1µF GRM188B31H104KA92 murata 8 RRT 100kΩ MCR03 Series Rohm 9 CRT - 10 RFL1 100kΩ MCR03 Series Rohm 11 RFL2 100kΩ MCR03 Series Rohm murata 12 CCS - 13 RCS1 620mΩ MCR100JZHFLR620 Rohm 14 RCS2 620mΩ MCR100JZHFLR620 Rohm 15 RCS3 - 16 RCS5 0Ω 17 CREG 2.2µF GRM188B31A225KE33 murata 18 CBT 0.1µF GRM188B31H104KA92 murata 19 M1 - RSS070N05 Rohm 20 M2 - RSS070N05 Rohm 21 D1 - RB050L-40 Rohm 22 D2 - RF201L2S Rohm 23 L1 33µH CDRH105R330 Sumida 24 COUT1 10µF GRM31CB31E106KA75B murata 25 COUT2 10µF GRM31CB31E106KA75B murata 26 ROVP1 30kΩ MCR03 Series Rohm 27 ROVP2 360kΩ MCR03 Series Rohm 28 RISET 120kΩ MCR03 Series Rohm 29 CISET - 30 RDAC 0Ω When performing open/short tests of the external components, the open condition of D1 or D2 may cause permanent damage to the driver and/or the external components. In order to prevent this, we recommend having parallel connections for D1 and D2. www.rohm.com © 2011 ROHM Co., Ltd. All rights reserved. 16/19 2011.07 - Rev.A Technical Note BD8113EFV ●Interfaces Input/output Equivalent Circuits (terminal name follows pin number) 1. COMP 2. SS VREG VREG VREG Vcc Vcc 1K 2K 4. EN EN SS COMP 175k 10k 2K 135k 5. RT 6. SYNC, 8. PWM 9. FAIL1, 10. FAIL2 3.3V VREG FAIL1 10K 167 RT PWM 150K 11. LEDEN 12. LED1, 13. LED2 3.3V FAIL2 1K SYNC 14. OVP Vcc Vcc 5K LED1,2 10K 10K 10K LEDEN 15. VDAC 16. ISET VREG OVP 2.5K 150K 18. OUTL 500 500 12.5 VREG VREG Vcc VREG Vcc ISET VDAC OUTL 100K 20. SW 21. OUTH Vcc 22. CS BOOT BOOT Vcc 5K SW OUTH CS 100K SW 23. BOOT SW SW 24. VREG VREG Vcc VREG VREG BOOT 205K 100K SW ※All values typical. www.rohm.com © 2011 ROHM Co., Ltd. All rights reserved. 17/19 2011.07 - Rev.A Technical Note BD8113EFV ●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. Simplified 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. 18/19 2011.07 - Rev.A Technical Note BD8113EFV ●Ordering part number B D 8 Part No. 1 1 3 E Part No. F V Package EFV : HTSSOP-B24 - E 2 Packaging and forming specification E2: Embossed tape and reel HTSSOP-B24 <Tape and Reel information> 7.8±0.1 (MAX 8.15 include BURR) (5.0) 1.0±0.2 0.53±0.15 (3.4) 1 0.325 Tape Embossed carrier tape (with dry pack) Quantity 2000pcs 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 ) 12 1PIN MARK +0.05 0.17 -0.03 S 0.08±0.05 0.85±0.05 1.0MAX +6° 4° −4° 13 5.6±0.1 7.6±0.2 24 0.65 0.08 S +0.05 0.24 -0.04 0.08 1pin M Reel (Unit : mm) www.rohm.com © 2011 ROHM Co., Ltd. All rights reserved. 19/19 Direction of feed ∗ Order quantity needs to be multiple of the minimum quantity. 2011.07 - 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