LED Drivers for LCD Backlights White Backlight LED Driver for Medium to Large LCD Panels (Switching Regulator Type) BD6142AMUV No.11040EAT11 ●Description This IC is white LED driver IC with PWM step-up DC/DC converter that can boost max 41V and current driver that can drive max 30mA. The wide and precision brightness can be controlled by external PWM pulse. This IC has very accurate current drivers, and it has few current errors between each strings. So, it will be helpful to reduce brightness spots on the LCD panel. Small package is suited for saving space. ●Features 1) High efficiency PWM step-up DC/DC converter (fsw=typ 1.25MHz, 0.60MHz ~ 1.6MHz) 2) High accuracy & good matching current drivers 8ch (MAX30mA/ch) 3) Integrated 50V power Nch MOSFET 4) Soft Start function 5) Drive up to 11 LEDs in series, 8 strings in parallel 6) Wide input voltage range (4.2V ~ 27V) 7) Rich safety functions ・Over-voltage protection ・External SBD open detect / Output Short protection ・Over current limit ・CH Terminal open / GND short protect ・CH over voltage protect / LED short protect ・hermal shutdown ・UVLO 8) Analog Brightness Control 9) Small & thin package (VQFN024V4040) 4.0 × 4.0 × 1.0mm ●Applications All medium sized LCD equipments, Backlight of Notebook PC, net book, monitor, light, Portable DVD player, light source etc. www.rohm.com © 2011 ROHM Co., Ltd. All rights reserved. 1/27 2011.07 - Rev.A Technical Note BD6142AMUV ●Absolute maximum ratings (Ta=25℃) Parameter Symbol Ratings Unit Condition Maximum applied voltage 1 VMAX1 7 V VDC, ISET, ABC, COMP, FSET, TEST, FAULT Maximum applied voltage 2 VMAX2 45 V CH1 ~ CH8, LX, OVP Maximum applied voltage 3 VMAX3 30.5 V VIN, Enable Maximum applied voltage 4 VMAX4 15 V PWM Power dissipation 1 Pd1 500 *1 mW Power dissipation 2 Pd2 780 *2 mW Power dissipation 3 Pd3 1510 *3 mW Operating temperature range Topr -40 ~ +85 ℃ Storage temperature range Tstg -55 ~ +150 ℃ *1 Reduced 4.0mW/ ℃ With Ta>25℃ when not mounted on a heat radiation Board. *2 1 layer (ROHM Standard board) has been mounted. Copper foil area 0mm2, When it’s used by more than Ta=25 ℃, it’s reduced by 6.2mW/ ℃. *3 4 layer (JEDEC Compliant board) has been mounted. Copper foil area 1layer 6.28mm2, Copper foil area 2~4layers 5655.04mm2, When it’s used by more than Ta=25 ℃, it’s reduced by 12.1mW/℃. ●Operating conditions (Ta=-40℃ ~ +85℃) Parameter Power supply voltage www.rohm.com © 2011 ROHM Co., Ltd. All rights reserved. Symbol VIN Limits Min. Typ. Max. 4.2 12.0 27.0 2/27 Unit Conditions V 2011.07 - Rev.A Technical Note BD6142AMUV ●Electrical characteristics (Unless otherwise specified, VIN=12V, Ta = +25℃) Limits Parameter Symbol Min. Typ. Max. Unit Conditions [General] Quiescent Current Iq - 1.6 4.4 µA Enable=0V Current Consumption Idd - 3.6 5.4 mA OVP=0V,ISET=36kΩ Max. Output Voltage MOV - - 41 V Under Voltage Lock Out UVLO 3.1 3.7 4.1 V Low Input Voltage range EnL 0.0 - 0.8 V High Input Voltage range1 EnH 2.0 - VIN V Pull down resistor EnR 100 300 500 kΩ Enable=3V ENIout - 0 2 µA Enable=0V Low Input Voltage range PWML 0.0 - 0.8 V High Input Voltage range2 PWMH 1.3 - 12.0 V Pull down resistor PWMR 100 300 500 kΩ PWM=3V PWMIout - 0 2 µA PWM=0V FFCR - - 3 kΩ Enable=PWM=3V, OVP=2V VREG 4.2 5.0 6.0 V No load, VIN > 6V VLED 0.64 0.80 0.96 V Switching frequency accuracy Fsw 1.00 1.25 1.50 MHz Duty cycle limit Duty 91.0 95.0 99.0 % CH1-8=0.3V, FSET=56kΩ LX Nch FET RON RON - 0.48 0.58 Ω ILX=80mA Over Current Limit Ocp 1.5 2.5 - A *1 Over voltage limit Input OVP 1.16 1.20 1.24 V Detect voltage of OVP pin OVPfault 0.02 0.05 0.08 V Detect voltage of OVP pin OVIL - 0.1 1.0 µA VSC -15 0 +15 % LED maximum current ILMAX - - 30 mA LED current accuracy ILACCU - - ±2.5 % VIN falling edge [Enable Terminal] Output Current [PWM Terminal] Output Current [FAULT] Nch RON [Regulator] VDC Voltage [Switching Regulator] LED Control voltage FSET=56kΩ [Protection] Output Short Protect OVP leak current CH Terminal Over Voltage Protect accuracy [Current driver] LED current matching ILMAT - - 2.5 % LED current matching2 ILMAT2 - - 1.5 % LED current limiter ILOCP - 0 0.1 mA Iset - 0.733 - V ILACCU2 - ±3.0 - % ISET voltage LED current accuracy2 *1 VSC=5V ILED=20mA (36kΩ) (Max LED current – Min LED current)/ Ideal current (20mA) ILED=20mA ▪Each LED current/Average (CH1- 8) ▪ILED=20mA Current limit value at ISET Resistance 1kΩ setting ILED=20mA, ABC=0.733V This parameter is tested with DC measurement. www.rohm.com © 2011 ROHM Co., Ltd. All rights reserved. 3/27 2011.07 - Rev.A Technical Note BD6142AMUV ●Reference data LED Current vs PWM duty LED current vs PWM Duty 100 100.000 LED Current [mA] LED current[mA] 10 VIN=6V VIN=12V VIN=27V 1 0.1 10.000 VIN=6V VIN=12V VIN=27V 1.000 0.100 0.010 0.01 0.1 1 10 1 100 10 PWM Duty [%] duty[%] <Condition> ■10serial×8parallel ■Ta = 25℃ ■LED Current = 20mA ■PWM frequency = 200Hz ■Frequency = 1.25MHz(FSET=56kΩ) ■Coil = 10µH <Condition> ■10 serial×8parallel ■Ta = 25℃ ■LED Current = 20mA ■PWM frequency = 30kHz ■Frequency = 1.25MHz(FSET=56kΩ) ■Coil = 4.7µH Fig. 1 LED current characteristics PWM dimming Fig. 2 LED current characteristics PWM dimming LED current vs ISET current LED current vs ABC voltage 50 45 30.000 40 25.000 35 LED current [mA] LED current [mA] 35.000 20.000 15.000 VIN=4.2V VIN=12V VIN=27V 10.000 5.000 30 25℃ 85℃ -40℃ 25 20 15 10 5 0.000 0 0.2 0.4 0.6 0.8 ABC Voltage [V] 1 0 1.2 0 10 20 30 ISET current [uA] <Condition> ■Ta = 25℃ ■ISET = 36kΩ ■CH1 = 0.8V 40 50 <Condition> ■VIN = 12V ■CH1 = 0.8V Fig. 3 LED current characteristics Analog dimming Fig. 4 LED maximum current Efficiency vs VIN (10serials and 6strings) Efficiency vs VIN (10serials and 8strings) 100.0% 100.0% 98.0% 98.0% 96.0% 96.0% 94.0% 94.0% Efficiency[%] Efficiency[%] 100 92.0% 90.0% 88.0% 86.0% VIN=7V VIN=12V VIN=27V 84.0% 82.0% 92.0% 90.0% 88.0% 86.0% 84.0% VIN=7V VIN=12V VIN=27V 82.0% 80.0% 80.0% 0.5 0.7 0.9 1.1 1.3 1.5 Frequency [MHz] 1.7 0.5 1.9 0.9 1.1 1.3 1.5 Frequency [MHz] 1.7 1.9 <Condition> ■Ta = 25℃ ■10 serial×6parallel ■LED Current = 20mA ■Coil = TDK, LTF5022T-100M1R4-LC <Condition> ■Ta = 25℃ ■10 serial×8parallel ■LED Current = 20mA ■Coil = TDK, LTF5022T-100M1R4-LC Fig. 5 Efficiency www.rohm.com © 2011 ROHM Co., Ltd. All rights reserved. 0.7 Fig. 6 Efficiency 4/27 2011.07 - Rev.A Technical Note BD6142AMUV ●Block diagram and pin configuration VIN VDC FAULT Output short PROTECT REG UVLO Internal Reset OVP Output Over Voltage PROTECT TSD Enable Clamp FAULT DETECTOR Internal Power Supply Soft start Internal Power Control LX LED TERMINAL OPEN/SHORT DETECTOR ERRAMP PWM COMP CH1 - Control LX SENCE CH 2 CH 3 LED + CH 4 RETURN OSC Current SENCE CH 5 SELECT + CH 6 CH 7 Over Current Protect CH 8 8ch PGND Clamp + - PGND ISET Resistor driver TEST FSET COMP PWM ABC Current Driver ISET GND Fig. 7 Block diagram ●Pin assignment table Pin Pin IO No. Name 1 Enable In Function PWM input pin for power ON/OFF or Power control Terminal diagram E 2 TEST In TEST signal (Pull down 100kΩ within IC) E 3 FSET In Resister connection for frequency setting A 4 ABC In Analog Brightness Control C 5 GND - GND for Switching Regulator B 6 PWM In PWM input pin for power ON/OFF only driver E 7 CH8 In Current sink for CH8 C 8 CH7 In Current sink for CH7 C 9 CH6 In Current sink for CH6 C 10 CH5 In Current sink for CH5 C 11 ISET In Resister connection for LED current setting A 12 CH4 In Current sink for CH4 C 13 CH3 In Current sink for CH3 C 14 CH2 In Current sink for CH2 C 15 CH1 In Current sink for CH1 C 16 OVP In Detect input for SBD open and OVP C PGND - PGND for switching Tr D Out Switching Tr drive terminal F Out Switching Tr drive terminal F 17 18 19 20 VDC VIN PIN PIN GND PGND A B VIN PIN PIN GND GND C D PIN PIN 5.5V Clump PGND GND E F PIN LX 21 FAULT Out Fault signal C 22 COMP Out ERRAMP output A Battery input G Regulator output / Internal power-supply C 23 VIN In 24 VDC Out www.rohm.com © 2011 ROHM Co., Ltd. All rights reserved. 5/27 GND PGND G 2011.07 - Rev.A Technical Note BD6142AMUV ●Application example Fig. 8, Fig. 9 and Fig. 10 are Application examples (15.4inch and 12inch and 10.1inch model). Recommended schematics and Layout are shown in Page. 21. 7V to 27V 10µF 10 serial x 8 parallel (80pcs) 10µH VOUT 2.2µ F/50V 2.2µF LX LX FAULT VIN VDC 2.1V to VIN 2.2MΩ RESET OVP Enable 68kΩ PW M PW M fPWM =100Hz~25kHz B D6142AMUV CO MP CH1 1kΩ CH2 22nF CH3 CH4 CH5 CH6 CH7 PGND PGND GND TEST FSET ABC ISET CH8 20m A 56kΩ 1nF 36kΩ GND PG ND Fig. 8 BD6142A Application example (8 parallel) 7V to 27V 10µF 10µH VOUT 9 serial x 6 parallel (54pcs) 2.2µF/50V 2.2µF LX LX FAULT VIN VDC 2.1V to VIN RESET 2.2MΩ Enable OVP 73.2kΩ PW M PWM fPWM=100Hz~25kHz COMP BD6142AMUV CH1 1kΩ CH2 22nF CH3 CH4 CH5 CH6 CH7 PGND PGND GND TESTFSET ABC ISET CH8 20mA 56kΩ 1nF GND 36kΩ PGND Fig. 9 BD6142A Application example (6 parallel) www.rohm.com © 2011 ROHM Co., Ltd. All rights reserved. 6/27 2011.07 - Rev.A Technical Note BD6142AMUV 4.2V to 27V 10µF 10µH VOUT 10 serial x 3 parallel (30pcs) 2.2µF/50V 2.2µF LX LX FAULT VIN VDC 2.1V to VIN RESET 2.2MΩ Enable OVP 68kΩ PWM PWM fPWM=100Hz~25kHz COMP 1kΩ BD6142AMUV CH1 CH2 22nF CH3 CH4 CH5 20mA CH6 CH7 PGND PGND GND TEST FSET 110kΩ GND ABC 1nF ISET CH8 36kΩ PGND Fig. 10 BD6142A Application example (3 parallel) www.rohm.com © 2011 ROHM Co., Ltd. All rights reserved. 7/27 2011.07 - Rev.A Technical Note BD6142AMUV ●Functional descriptions 1) PWM current mode DC/DC converter While this IC is power ON, the lowest voltage of CH1, 2, 3, 4, 5, 6,7, 8 is detected, PWM duty is decided to be 0.8V and output voltage is kept invariably. As for the inputs of the PWM comparator as the feature of the PWM current mode, one is overlapped with error components from the error amplifier, and the other is overlapped with a current sense signal that controls the inductor current into Slope waveform to prevent sub harmonic oscillation. This output controls internal Nch Tr via the RS latch. In the period where internal Nch Tr gate is ON, energy is accumulated in the external inductor, and in the period where internal Nch Tr gate is OFF, energy is transferred to the output capacitor via external SBD. This IC has many safety functions, and their detection signals stop switching operation at once. 2) Pulse skip control This IC regulates the output voltage using an improved pulse-skip. In “pulse-skip” mode the error amplifier disables “switching” of the power stages when it detects low output voltage and high input voltage. The oscillator halts and the controller skip switching cycles. The error amplifier reactivates the oscillator and starts switching of the power stages again when this IC detects low input voltage. At light loads a conventional “pulse-skip” regulation mode is used. The “pulse-skip” regulation minimizes the operating current because this IC does not switch continuously and hence the losses of the switching are reduced. When the error amplifier disables “switching”, the load is also isolated from the input. This improved “pulse-skip” control is also referred to as active-cycle control. PWM VOUT duty 20% @1.25MHz(typ) Pulse skip LX LED current 20mA Fig. 11 Pulse-skip 3) Soft start This IC has soft start function. The soft start function prevents large coil current. Rush current at turning on is prevented by the soft start function. After Enable, PWM is changed ‘L’ ‘H’, and UVLO is detected, soft start becomes effective for within typ 4.3ms and soft start doesn't become effective even if Enable is changed ‘L’ ‘H’ after that. Enable Max 1ms Enable Typ 4.3ms PWM PWM UVLO UVLO VDC VDC Soft start Max 1ms Soft Start Time=T1+T2=4.3ms typ OFF ON OFF Soft start ON T1 OFF T2 ON OFF ON OFF Fig. 12 Soft start 4) FAULT When the error condition occurs, boost operating is stopped by the protection function, and the error condition is outputted from FAULT. After power ON, when the protection function is operating under about 4.3ms(typ.) have passed. Once enable change to ‘L’, FAULT status is reset Object of protect function is as shown below. - Over-voltage protection (OVP) - Thermal shut down (OTP) - Over current limit (OCP) - Output short protect - LED Short (Latch) - LED Open (Latch) Enable PWM VDC FAULT Typ4.3 ms ‘X’ ‘H’ Protection un-detection function(OVP, TSD, OCP) Protection Mask ‘L’ ‘H’ ‘L’ Latch detect off normal ‘X’ ‘H’ un-detect un-detect un-detect function(LED open, LED short) Boost operating Typ100us detect boost stop normal off normal Fig. 13 FAULT operating description www.rohm.com © 2011 ROHM Co., Ltd. All rights reserved. 8/27 2011.07 - Rev.A Technical Note BD6142AMUV ●Protection PROTECTION TABLE FAILURE CASE MODE LED Short 1 connected CH1 2 3 4 5 DETECTION FAIL GOOD MODE CHANNEL CHANNEL CH1 > VSC(5V) LED current stop and CH2 to CH8 Normal DC/DC feedback doesn’t return LED current stop and CH2 to CH8 LED OPEN CH1 < 0.2V Normal DC/DC feedback connected CH1 and VOUT > VOVP doesn’t return VOUT/LX GND OVP < 50mV FAULT change from L to H, and SHORT switching is stopped. When OVP>50mV, FAULT return L Output LED VOUT > VOVP FAULT change from L to H, and stack voltage too switching is stopped. Even if OVP<1.2V, FAULT don’t return L high LX current too OCP > 2.5A FAULT change from L to H, and high or switching is stopped. OTP > 130C Even if IC return normal status, FAULT don’t return L VOUT FAULT REGULATED BY Terminal Highest VF ‘H’ ‘L’ of CH2 to CH8 (Latch) Highest VF of CH2 to CH8 - ‘H’ ‘L’ (Latch) ‘H’ ‘L’ ‘H’ ‘L’ ‘H’ ‘L’ - ・Over voltage protection (OVP) At such an error of output open as the output DC/DC and the LED is not connected to IC, the DC/DC will boost too much and the OVP terminal exceed the absolute maximum ratings, and may destruct the IC. Therefore, when OVP terminal becomes sensing voltage or higher, the over voltage limit protection works, and turns off the switching Tr, and DC/DC will be stopped. At this moment, the IC changes from activation into non-activation, and the output voltage goes down slowly. And, when the Feedback of CH1 isn’t returned, so that VOUT will return normal voltage. Enable, PWM Hysteresis(typ 2.5%) VOUT OVP Signal CH1 voltage CH1 connection normal open CH2 connection normal Feedback CH1 CH2 CH1 current 20mA CH1 0mA CH2 current 20mA 0mA Fig. 14 OVP operating description www.rohm.com © 2011 ROHM Co., Ltd. All rights reserved. 9/27 2011.07 - Rev.A Technical Note BD6142AMUV This section is especially mentioned here because the spec shown electrical characteristic is necessary to explain this section. Over voltage limit LED control voltage LED terminal over voltage protect min 1.16V typ 1.20V max 1.24V min 0.64V typ 0.80V max 0.96V min 4.25V typ 5.00 V max 5.75V 1. Calculate the conditions that the total value of LED VF is MAX. Example) In the case of serial 8 LEDs with VF=2.9V(min), 3.2V(typ), 3.5V(max) => 3.5V x 8=28V 2. Then calculate the biggest value of output with the following formula. The biggest value of output = the biggest value calculated for 1 + the biggest value of LED terminal voltage. (0.96V) Example) The biggest value of output = 28V + 0.96V =28.96V 3. Set the smallest value of over voltage larger than the biggest value of output. If over voltage is closer to the total value of VF, it could be occurred to detect over voltage by ripple, noise, and so on. It is recommended that some margins should be left on the difference between over voltage and the total value of VF. This time around 6% margin is placed. Example) Against the biggest value of output = 28.96V, the smallest value of over voltage = 28.96V x 1.06 = 30.70V Ic over voltage limit min=1.16V, typ=1.20V, max=1.24V typ = 30.70V×(1.20V/1.16V) = 31.76V max = 31.76V×(1.26V/1.20V) = 33.35V 4. The below shows how to control resistor setting over voltage Please fix resistor high between OVP terminal and output and then set over voltage after changing resistor between OVP terminal and GND. While PWM is off, output voltage decreases by minimizing this resistor. Due to the decrease of output voltage, ripple of output voltage increases, and singing of output condenser also becomes bigger. Example) Selecting OVP resistor. ・OVP resistor selection (Example. 1) VF=3.5V max, serial = 7 LED OVP = 1.2V, R1 = 2.2MΩ, R2 = 95.3kΩ VOUT = 1.2 × (2.2MΩ + 95.3kΩ)/ 95.3kΩ = 28.90V (Example. 2) VF=3.5V max, serial = 8 LED OVP = 1.2V, R1 = 2.2MΩ, R2 = 82kΩ VOUT = 1.2 × (2.2MΩ + 82kΩ)/ 82kΩ = 33.40V (Example. 3) VF=3.5V max, serial = 9 LED OVP = 1.2V, R1 = 2.2MΩ, R2 = 73.2kΩ VOUT = 1.2 × (2.2MΩ + 73.2kΩ)/ 73.2kΩ = 37.27V (Example. 4) VF=3.5V max, serial = 10 LED OVP = 1.2V, R1 = 2.2MΩ, R2 = 68kΩ VOUT = 1.2 × (2.2MΩ + 68kΩ)/ 68kΩ = 40.02V VOUT R1 OVP terminal R2 ・External SBD open detect / Output Short protection In the case of external SBD is not connected to IC, or VOUT is shorted to GND, the coil or internal Tr may be destructed. Therefore, at such an error as OVP becoming 50mV(typ.) or below, turns off the output Tr, and prevents the coil and the IC from being destructed. And the IC changes from activation into non-activation, and current does not flow to the coil (0mA). ・Thermal shut down This IC has thermal shut down function. The thermal shut down works at 130C (typ.) or higher, and the IC changes from activation into non-activation. www.rohm.com © 2011 ROHM Co., Ltd. All rights reserved. 10/27 2011.07 - Rev.A Technical Note BD6142AMUV ●Operating of the application deficiency 1)When 1 LED or 1string OPEN during the operating The LED string which became OPEN isn't lighting, but other LED strings are lighting. Then LED terminal is 0V , output boosts up to the over voltage protection voltage. When over voltage is detected, the feedback of open string isn’t returned, so that VOUT will return normal voltage. Enable, PWM VOUT OVP CH1 connection normal open CH2 connection CH 1 CH 2 normal CH1 voltage CH1 enable 100µs Feedback CH2 CH1 CH1 current 20mA CH2 current OFF CH1 0mA 20mA 0mA Fig. 15 LED open protect 2)When LED short-circuited in the plural All LED strings is turned on unless CH1~8 terminal voltage is more than 5V(typ.). When it was more than 5V only the strings which short-circuited is turned off normally and LED current of other lines continue to turn on. Short line(CH1) current is changed from 20mA to 0.05mA(typ), so CH1 terminal don’t heat. LED short CH1terminal CH2 terminal 0.8V Typ 5V CH1>CH2 0.8V Vout FeedBack CH 1 CH 2 CH1 current CH2 current CH1 20mA CH2 100us(typ) 0.05mA(typ) 20mA Fig. 16 LED short protect 3)When Schottky diode remove All LED strings aren’t turned on. Also, IC and a switching transistor aren't destroyed because boost operating stops by the Schottky diode open protected function. www.rohm.com © 2011 ROHM Co., Ltd. All rights reserved. 11/27 2011.07 - Rev.A Technical Note BD6142AMUV ●Control Signal input timing Timing sequence1 Referring to Fig.17, the recommended turn “on” sequence is VIN followed by ENABLE and PWM. The recommended turn ”off” sequence is ENABLE and PWM followed by VIN. This sequence is recommendation. LED IC Timing Sequence for PWM Control Turn-on 4.2 ~ 27V VIN VIN 0V Min 0µs ENABLE 0 ~ 0.8V ENABLE, PWM PWM 2 ~ 5V Min 0µs 2 ~ 5V 0 ~ 0.8V *other signal is input after a signal turned on. Power ON Power OFF Fig. 17 Timing sequence1 LED IC Timing Sequence for PWM Control Turn-off 4.2 ~ 27V VIN Min 0µs 2 ~ 5V ENABLE 2 ~ 5V 0V 0 ~ 0.8V Min 0µs PWM 0 ~ 0.8V *other signal is input after a signal turned off. Timing sequence2 Referring to Fig.18, the recommended turn “on” sequence is VIN, ENABLE followed by PWM. The recommended turn “off” sequence is PWM followed by ENABLE and VIN. LED IC Timing Sequence for PWM Control Turn-on VIN, ENABLE 2 ~ 5V ENABLE 0 ~ 0.8V PWM VIN 0V PWM Power ON Min 0µs 4.2 ~ 27V Min 0µs 2 ~ 5V 0 ~ 0.8V Power OFF *other signal is input after a signal turned on. Fig. 18 Timing sequence2 LED IC Timing Sequence for PWM Control Turn-off 2 ~ 5V ENABLE Min 0µs 0 ~ 0.8V 4.2 ~ 27V VIN 2 ~ 5V PWM Min 0µs 0V 0 ~ 0.8V *Other signal is input after a signal turned off. www.rohm.com © 2011 ROHM Co., Ltd. All rights reserved. 12/27 2011.07 - Rev.A Technical Note BD6142AMUV Timing sequence3 Referring to Fig.19, the recommended turn “on” sequence is VIN, PWM followed by ENABLE. The recommended turn “off” sequence is ENABLE followed by PWM and VIN. LED IC Timing Sequence for PWM Control Turn-on 2 ~ 5V VIN, PWM PWM ENABLE 0 ~ 0.8V VIN 0V ENABLE Power ON Power OFF Min 0µs 4.2 ~ 27V Min 0µs 2 ~ 5V 0 ~ 0.8V *other signal is input after a signal turned on. Fig. 19 Timing sequence3 LED IC Timing Sequence for PWM Control Turn-off 2 ~ 5V PWM Min 0µs 0 ~ 0.8V 4.2 ~ 27V VIN Min 0µs 2 ~ 5V ENABLE VIN wake up speed 0V 0 ~ 0.8V *other signal is input after a signal turned off. Min. 100µs 4.1 V VIN 1 2 Fig. 20 control Signal timing In case, there is PWM OFF status (min: 10ms) during operation as Fig. 21, ENABLE should turn from ‘H’ to ‘L’ as Fig.21. If PWM stops and VOUT voltage is dropped, this IC will be condition of current limiter when PWM starts (no soft start). If soft start isn’t needed, reset is no need. VIN reset ENABLE Min 10ms PWM PWM OFF PWM Fig. 21 PWM stop and ENABLE turn “off” www.rohm.com © 2011 ROHM Co., Ltd. All rights reserved. 13/27 2011.07 - Rev.A Technical Note BD6142AMUV ●How to activate Please be careful about the following when being activated. - Regulator (VDC) operates after ENABLE=H. Inside circuit operates after releasing UVLO. When IC boosts after releasing UVLO, soft start function operates. (Refer to Fig.12, 7th page). Soft start circuit needs t15 (more than 15µs) as Fig. 22 shows. Soft start operates for Tsoft time. Please make H width of PWM more than 15µs until soft start finishes. - Please input PWM signal according to Fig. 23 after soft start finishes. VIN ENABLE VDC UVLO PWM tsoft t１５ tsoft tsoft SOFT START Over current value increases.. Fig. 22 Soft start Example) Time until soft start finishes at PWM frequency 25kHz and PWM=H time16µs According to soft start time typ4.3ms tsoft = 16µs – 15µs = 1µs Soft start time/ tsoft /PWM frequency = 4300µs / 1µs /25kHz = 4300 / 25kHz = 172ms At light dimming of PWM terminal (after soft start finishes) t1 VIN L[V] H[V] H[V] t2 t4 t5 t3 t3 ENABLE t6 VDC t7 t8 t9 t14 t14 PWM t10 t11 Fig. 23 Input timing (after soft start) Name t1 t2 t3 t4 t5 t6 t7 t8 t9 t10 t11 t12 t13 t14 t15 H L Power supply rising time Power supply-ENABLE time ENABLE rising time ENABLE falling time ENABLE low width Power supply-PWM time PWM rising time PWM high width PWM falling time PWM low width PWM frequency ENABLE (H)->PWM (H) time ENABLE (L)->PWM (L) time PWM (L)->ENABLE (L) time PWM high width (while soft start) Operating voltage Non operating voltage www.rohm.com © 2011 ROHM Co., Ltd. All rights reserved. Unit Min. Typ. Max. µs µs µs µs µs µs µs µs µs µs µs µs µs µs µs V V 100 0 0 0 50 0 0 5 0 5 40 0 0 0 15 4.2 - 5000 12 - 100 100 100 100 10000 27 4.2 14/27 2011.07 - Rev.A Technical Note BD6142AMUV ●How to select the number of LED strings of the current driver When the number of LED strings of the current driver is reduced, the un-select can be set the matter that the unnecessary CH1 ~ 8 terminal is opened. When it uses with 6 lines and so on, it can correspond to it by becoming 2 unnecessary lines to open. When VOUT wake up, VOUT boost up until OVP voltage. Once IC detect OVP, VOUT don’t boost up until OVP from next start up. To set PWM and Enable to L, IC reset CH7, 8 status as Fig. 24. When VOUT wake up, CH8 (open terminal) and CH1 are selected as Fig. 25. PWM Reset Enable CH 1 CH 2 CH 3 CH 4 CH 5 CH 6 CH 7 CH 8 OVP Normal voltage VOUT 0.8V(typ) 0V CH1~6 CH7~8 0V Fig. 24 Select the number of CH lines 1 ENABLE PWM Soft start: typ 4.3ms 100µs(typ) Vout Over Voltage Protect Over voltage protect signal Terminal select (LED open protect) Normal condition Mask “Unmask CH1 Terminal Typ 0.8V CH8 Terminal open Feedback terminal Stable CH8 CH1 20mA CH1 Current 0mA CH8 Current 0mA Fig. 25 Select the number of CH lines 2 (wake up) www.rohm.com © 2011 ROHM Co., Ltd. All rights reserved. 15/27 2011.07 - Rev.A Technical Note BD6142AMUV ●Start control (Enable) and select LED current driver (PWM) This IC can control the IC system by Enable, and IC can power off compulsory by setting 0.8V or below. Also, It powers on Enable is at more than 2.0V. After it’s selected to Enable=H, When it is selected at PWM=H, LED current decided with ISET resistance flow. Next, When it is selected at PWM=L, LED current stop to flow. Enable 0 1 0 1 PWM 0 0 1 1 IC Off On Off On LED current OFF OFF OFF Current decided with ISET ●LED current setting range LED current can set up Normal current by resistance value (RISET) connecting to ISET voltage. Setting of each LED current is given as shown below. RISET = 720/ILEDmax Also, Normal current setting range is 10mA~30mA. LED current becomes a leak current MAX 2µA at OFF setting. ISET Normal current setting example RISET LED current 24kΩ (E24) 30.0mA 30kΩ (E24) 24.0mA 36kΩ (E24) 20.0mA 43kΩ (E24) 16.7mA 68kΩ (E12) 10.6mA ●Frequency setting range Switching frequency can be set up by resistance value (RFSET) connecting to FSET port. Setting of frequency is given as shown below. Frequency Also, Frequency setting range is 0.60MHz~1.60MHz. [MHz] FSET frequency setting example RFSET frequency 130kΩ (E96) 0.57MHz 56kΩ (E24) 1.25MHz 43kΩ (E24) 1.59MHz Max Duty example Max Duty[%] Frequency Min Typ Max 0.57MHz 96.0 1.25MHz 91.0 95.0 99.0 1.59MHz 92.0 - 1.59 1.25 0.57 43 kΩ 56kΩ 130 kΩ FSET[kΩ] Min Duty example Min Duty[%] Frequency Min Typ Max 1.25MHz 20 - www.rohm.com © 2011 ROHM Co., Ltd. All rights reserved. 16/27 2011.07 - Rev.A Technical Note BD6142AMUV ●PWM dimming Current driver PWM control is controlled by providing PWM signal to PWM port, as it is show in Fig. 26. The current set up with ISET is chosen as the H section of PWM and the current is off as the L section. Therefore, the average LED current is increasing in proportion to duty cycle of PWM signal. This method that it lets internal circuit and DC/DC to work, because it becomes to switch the driver, the current tolerance is a few when the PWM brightness is adjusted, it makes it possible to brightness control until 5µs (Min 0.1% at 200Hz). And, don't use for the brightness control, because effect of ISET changeover is big under 1µs ON time and under 1µs OFF time. Typical PWM frequency is 100Hz~25kHz. PWM PWM ON OFF LED current ON OFF Coil current ON OFF IC’s active current VOUT LED current 400ns/div 10mA/div ON PWM Fig. 26 PWM sequence Conditions： 8serial 6parallel, LED current=20mA/ch, VIN=7V, Ta=25℃, Output capacitor=2.2μF(50V/B3) VOUT 40ns/div 10mA/div LED current ●Analog dimming BD6142 control LED current according analog input (ABC terminal). For ABC voltage = typ 0.733V, LED current can set up Normal current by resistance value (RISET) connecting to ISET voltage. To decrease ABC voltage, LED current decrease, and to increase ABC voltage, LED current increase. ABC DC Input 120.9kΩ 0.733V 180kΩ Please set max LED current to check LED current setting range of P.12 Please care that ABC voltage of max LED current is 0.733V ABC input range is 0.05V～0.9V(Target). This dimming is effected by ISET tolerance as follows. When you don’t use analog dimming, please set condenser to ABC terminal. Until the condenser of ABC terminal is finished to charge, LED current increase with that speed. The resister between 1.2V and ABC terminal is 120.9kΩ. Please select the capacitor to care charge time. ISET Resistor driver 1.2V + - ISET 36kΩ Fig. 27 Analog dimming application ISET Resistor driver 1.2V ABC 120.9kΩ 0.733V 180kΩ + - ISET 36kΩ Fig. 28 PWM dimming application ILED [mA] 20mA 0.733V 0.9V ABC[V] Fig. 29 ILED vs ABC voltage www.rohm.com © 2011 ROHM Co., Ltd. All rights reserved. 17/27 2011.07 - Rev.A Technical Note BD6142AMUV ●Coil selection The DC/DC is designed by more than 4.7µH. When L value sets to a lower value, it is possibility that the specific sub-harmonic oscillation of current mode DC / DC will be happened. Please do not let L value to 3.3µH or below. And, L value increases, the phase margin of DC / DC becomes to zero. Please enlarge the output capacitor value when you increase L value. Please select lower DC resistance (DCR) type, efficiency still relies on the DCR of Inductor. Please estimate Peak Current of Coil. Peak current can be calculated as following. Peak Current calculation <The estimate of the current value which need for the normal operation> As over current detector of this IC is detected the peak current, it have to estimate peak current to flow to the coil by operating condition. In case of, - Supply voltage of coil = VIn - Inductance value of coil = L - Switching frequency = fsw (Min=1.0MHz, Typ = 1.25MHz, Max = 1.5MHz) - Output voltage = VOUT - Total LED current = ILED - Average current of coil = Iave - Peak current of coil = Ipeak - Cycle of Switching = T - Efficiency = eff (Please set up having margin) - ON time of switching transistor = Ton - ON Duty = D CCM: Ipeak = (VIn / L) × (1 / fsw) × (1-( VIn / VOUT)), DCM: Ipeak = (VIn / L) × Ton Iave=( VOUT × IOUT / VIn) / eff 1/2 Ton=(Iave × (1- VIn / VOUT) × (1/fsw) × (L/ VIn) × 2) Each current is calculated. As peak current varies according to whether there is the direct current superposed, the next is decided. CCM: (1- VIn / VOUT) × (1/fsw) < Ton peak current = Ipeak /2 + Iave DCM: (1- VIn / VOUT) × (1/fsw) > Ton peak current = VIn / L × Ton (Example 1) In case of, VIn = 7.0V, L = 10µH, fsw = 1.2MHz, VOUT = 32V, ILED = 120mA, Efficiency = 88% Iave = (32 × 120m / 7) / 88% = 0.62A 1/2 Ton = (0.62 × (1 - 7 / 32) × (1 / 1.2M) × (10µ / 7) × 2) = 1.07µs (1- VIn / VOUT) × (1 / fsw) = 0.65µs < Ton(1.07µs) CCM Ipeak = (7 / 10µ) × (1 / 1.2M) × (1 - (7 / 32)) = 0.46A Peak current = 0.46A / 2 + 0.62A = 0.85A (Example 2) In case of, VIn = 16.0V, L = 10µH, fsw = 1.2MHz, VOUT = 32V, ILED = 120mA, Efficiency = 88% Iave = (32 × 120m / 16.0) / 88% = 0.27A 1/2 Ton = (0.27 × (1-16 / 32) × (1 / 1.2M) × (10µ / 16) × 2) = 0.37µs (1- VIn / VOUT) × (1 / fsw)=0.41µs > Ton(0.37µs) DCM Ipeak = VIn / L x Ton = 16 / 10µ x 0.37µs = 0.59A Peak current = 0.59A *When too large current is set, output overshoot is caused, be careful enough because it is led to break down of the IC in case of the worst. DCM/CCM calculation Discontinuous Condition Mode (DCM) and Continuous Condition Mode (CCM) are calculated as following. CCM: L > VOUT × D × (1 - D)2 × T / (2 × ILED) 2 DCM: L < VOUT × D × (1 - D) × T / (2 × ILED) *D = 1- VIn / VOUT (Example 1) In case of, VIn = 7.0V, L = 10µH, fsw = 1.2MHz, VOUT = 32V, ILED = 120mA VOUT × D × (1 - D)2 × T / (2 × ILED) = 32 × (1 – 7 / 32) × (7 / 32)2 × 1/(1.2 × 106) / (2 × 0.12) = 4.15µ < L(10µH) CCM (Example 2) In case of, VIn = 12.0V, L = 10µH, fsw = 1.2MHz, VOUT = 32V, ILED = 60mA VOUT × D × (1 - D)2 × T / (2 × ILED) = 32 × (1 – 12 / 32) × (12 / 32)2 × 1/(1.2 × 106) / (2 × 0.06) = 19.5µ > L(10µH) DCM www.rohm.com © 2011 ROHM Co., Ltd. All rights reserved. 18/27 2011.07 - Rev.A Technical Note BD6142AMUV ●OUTPUT Capacitor selection Output Capacitor smoothly keeps output voltage and supplies LED current. Output Voltage consists of Charge (FET ON) and Discharge (LED current). So Output voltage has Output ripple Voltage every FET switching. Output ripple voltage is calculated as following. Output ripple Voltage - Switching cycle = T - Total LED current = ILED - Switching ON duty = D - Output ripple Voltage = Vripple - Output Capacitor (real value) = Creal - Output Capacitor = COUT - Decreasing ratio of Capacitor = Cerror (Capacitor value is decreased by Bias, so) Creal = COUT × Cerror Creal = ILED × (1-D) × T / Vripple COUT = ILED × (1-D) × T / Vripple / Cerror (Example 1) In case of, VIN=12.0V, fsw = 1.2MHz, VOUT =32V, ILED =120mA, COUT = 8.8µF, Cerror = 50% T = 1 / 1.2MHz D = 1 – VIN / VOUT = 1 – 12/32 Vripple = ILED × (1-D) × T / (COUT×Cerror) = 120mA × (12/32) / 1.2MHz / (8.8µF×0.5) = 8.5mV C out Capa [ µF] Creal 0V 35V 50V Output voltage Fig. 30 Bias Characteristics of Capacitor www.rohm.com © 2011 ROHM Co., Ltd. All rights reserved. 19/27 2011.07 - Rev.A Technical Note BD6142AMUV ●The separations of the IC Power supply and coil Power supply This IC can work in separating the power source in both IC power supply and coil power supply. With this application, it can obtain that decrease of IC power consumption, and the applied voltage exceeds IC rating 27V. That application is shown in below Fig.31. The higher voltage source is applied to the power source of coil that is connected from an adapter etc. Next, the IC power supply is connected with a different coil power supply. Under the conditions for inputting from 4.2V to 5.5V into IC VIN, please follow the recommend design in Fig.31. It connects VIN terminal and VDC terminal together at IC outside. When the coil power supply is applied, it is no any problem even though IC power supply is the state of 0V. Although IC power supply is set to 0V, pull-down resistance is arranged for the power off which cuts off the leak route from coil power supply in IC inside, the leak route is cut off. And, there is no power on-off sequence of coil power supply and IC power supply. Separate VIN and Coil power supply 4.2V to 30V 10µF 7V to 27V 10µH 10 serial x 6 parallel (60pcs) VOUT 2.2µF/50V 2.2µF LX LX FAULT VIN VDC 2.1V to VIN RESET 2.2MΩ Enable OVP 68kΩ PWM PWM fPWM=100Hz~25kHz BD6142AMUV COMP CH1 1kΩ CH2 22nF CH3 CH4 CH5 CH6 CH7 PGND PGND GND TEST FSET ABC 56 kΩ GND CH8 ISET 1nF 20mA 36kΩ PGND Connect VIN and VDC terminals 4.2V to 30V 10µF 4.2V to 5.5V 10µH VOUT 10 serial x 6 parallel (60pcs) 2.2µF/50V 2.2µF LX LX FAULT VIN VDC 2.1V to VIN RESET 2.2MΩ Enable OVP 68kΩ PWM PWM fPWM=100Hz~25kHz COMP BD6142AMUV CH1 1kΩ CH2 22nF CH3 CH4 CH5 CH6 CH7 PGND PGND GND TEST FSET 56kΩ GND ABC ISET CH8 20mA 36kΩ PGND Fig. 31 Application at the time of power supply isolation www.rohm.com © 2011 ROHM Co., Ltd. All rights reserved. 20/27 2011.07 - Rev.A Technical Note BD6142AMUV ●Layout In order to make the most of the performance of this IC, its PCB layout is very important. Characteristics such as efficiency and ripple and the likes change greatly with layout patterns, which please note carefully. 7V to 27V CIN(10µF) L1(10µH) VOUT 10 serial x 8 parallel (80pcs) SBD CVDC1 (2.2µF) COUT1(2.2µF/50V) LX LX FAULT VIN VDC ROVP1 (2.2MΩ) 2.1V to VIN RESET PWM Enable OVP ROVP2 (68kΩ) PWM fPWM=100Hz~25kHz COMP BD6142AMUV CH1 RCMP(1kΩ) CH2 CCMP(22nF) CH3 CH4 CH5 CH6 CH7 PGND PGND GND TESTFSET ABC ISET CH8 20mA RISET(36kΩ) GND PGND RFSET(56kΩ) CABC(1nF) Fig. 32 Schematic <Input bypath capacitor CIN (10μF)> Put input bypath capacitor CIN (10μF) as close as possible between coilL1 and PGND pin. <Smoothing capacitor CVDC1(2.2µF) of the regulator> Connect smoothing capacitor CVDC1(2.2μF) as close as possible between VDC pin and GND. <Schottky barrier diode SBD> Connect schottky barrier diode SBD as close as possible between coil1and SW pin. <Output capacitor COUT1> Connect output capacitor COUT1 between cathode of SBD and PGND. Make both PGND sides of CVIN and COUT1 as close as possible. <LED current setting resistor RISET(36kΩ)>> Connect LED current setting resistor RISET(36kΩ) as close as possible between ISET pin and GND. There is possibility to oscillate when capacity is added to ISET terminal, so pay attention that capacity isn’t added. <Analog dimming pin smoothing capacitor CABC (1nF)> Put analog dimming pin smoothing capacitor CABC (1nF) close to ABC pin and do not extend the wiring to prevent noise increasing and also LED current waving. <Frequency setting resistor(56KΩ)> Put frequency setting resistor(56KΩ) as close as possible between FSET pin and GND. <Over voltage limit setting resistor ROVP1(2.2MΩ) and ROVP2(68KΩ) Put over voltage limit setting resistor ROVP1(2.2MΩ) and ROVP2(68KΩ) as close as possible to OVP pin and do not extend the wiring to prevent noise increasing and also detecting over voltage protection in error. <GMAMP setting resistor RCMP(1kΩ) and CCMP(1nF) for phase compensation > Put GMAMP setting resistor RCMP(1KΩ) and CCMP(22nF) as close as possible to COMP pin and do not extend the wiring to prevent noise increasing and also oscillating. <Connect to GND and PGND> GND is analog ground, and PGND is power ground. PGND might cause a lot of noise due to the coil current of PGND. Try to connect with analog ground, after smoothing with input bypath capacitor CVIN and output capacitor COUT1. <Heat radiation of back side PAD> PAD is used for improving the efficiency of IC heat radiation. Solder PAD to GND pin (analog ground). Moreover, connect ground plane of board using via as shown in the patterns of next page. The efficiency of heat radiation improves according to the area of ground plane. <Others> When those pins are not connected directly near the chip, influence is give to the performance of BD6142AMUV, and may limit the current drive performance. As for the wire to the inductor, make its resistance component small so as to reduce electric power consumption and increase the entire efficiency. www.rohm.com © 2011 ROHM Co., Ltd. All rights reserved. 21/27 2011.07 - Rev.A Technical Note BD6142AMUV ●Recommended PCB layout L1 PGND CIN VOUT ROVP2 ROVP1 Input Voltage D6142 RISET CCMP RCMP GND CVDC1 RFSET CABC Fig. 33 Top Copper trace layer Fig. 34 Middle1 Copper trace layer Fig. 35 Middle2 Copper trace layer COUT1 SBD PGND GND Fig. 36 Bottom Copper trace layer www.rohm.com © 2011 ROHM Co., Ltd. All rights reserved. 22/27 2011.07 - Rev.A Technical Note BD6142AMUV ●Selection of external parts Recommended external parts are as shown below. When to use other parts than these, select the following equivalent parts. ・Coil Value Size (mm) L W H (MAX) DC current (mA) DCR (Ω) LTF5022T-4R7N2R0-LC 5.0 5.2 2.2 2000 0.073 A915AY-4R7M 5.2 5.2 3.0 1870 0.045 TOKO A915AY-100M 5.2 5.2 3.0 1400 0.140 TDK LTF5022T-100M1R4-LC 5.0 5.2 2.2 1400 0.140 TOKO B1047AS-100M 7.6 7.6 5.0 2700 0.053 Manufacturer Product number 4.7μH TDK 4.7μH TOKO 10µH 10µH 10µH ・Capacitor Value Pressure Manufacturer Product number 10µF 25V MURATA 4.7μF 25V 2.2μF 50V Size L W H GRM31CB31E106KA75 3.2 1.6 1.6 MURATA GRM319R61E475K 3.2 1.6 0.85±0.1 TDK C3225JB1H225K 3.2 2.5 2.0±0.2 2.2µF 50V MURATA GRM31CB31H225K 3.2 1.6 1.6 2.2µF 50V Panasonic ECJHVB1H225K 3.2 1.6 0.85 2.2µF 10V MURATA GRM188B31A225K 1.6 0.8 0.8 0.1µF 50V MURATA GRM188B31H104K 1.6 0.8 0.8 0.1µF 10V MURATA GRM188B31A104K 1.6 0.8 0.8 0.022µF 10V MURATA GRM155B31H223K 1.0 0.5 0.5 470pF 50V MURATA GRM155B11H471K 1.0 0.5 0.5 ・Resistor Value Tolerance Manufacturer Product number Size (mm) L W H 2.2MΩ ±1.0% ROHM MCR03PZPZFX2204 1.6 0.8 0.45 91kΩ ±0.5% ROHM MCR03PZPZD9102 1.6 0.8 0.45 75kΩ ±0.5% ROHM MCR03PZPZD7502 1.6 0.8 0.45 68kΩ ±0.5% ROHM MCR03PZPZD6802 1.6 0.8 0.45 56kΩ ±0.5% ROHM MCR03PZPZD5602 1.6 0.8 0.45 36kΩ ±0.5% ROHM MCR03PZPZD3602 1.6 0.8 0.45 10kΩ ±1.0% ROHM MCR03PZPZF103 1.6 0.8 0.45 1kΩ ±0.5% ROHM MCR03PZPZD1002 1.6 0.8 0.45 330Ω ±0.5% ROHM MCR03PZPZD3300 1.6 0.8 0.45 ・SBD Pressure Manufacturer Product number 60V ROHM RB160M-60 Size (mm) L W H 3.5 1.6 0.8 The coil is the part that is most influential to efficiency. Select the coil whose direct current resistor (DCR) and current inductance characteristic is excellent. BD6142A is designed for the inductance value of 10µH. Don’t use the inductance value less than 3.3µH. Select a capacitor of ceramic type with excellent frequency and temperature characteristics. Further, select Capacitor to be used with small direct current resistance. ●About heat loss In heat design, operate the DC/DC converter in the following condition. (The following temperature is a guarantee temperature, so consider the margin.) 1. Ambient temperature Ta must be less than 85℃. 2. The loss of IC must be less than dissipation Pd. www.rohm.com © 2011 ROHM Co., Ltd. All rights reserved. 23/27 2011.07 - Rev.A Technical Note BD6142AMUV ●Application example 1. ESD & Flicker (wakeup (duty 5%@200Hz)) LED current: 20mA (ISET = 36kΩ) LED: 10 LEDs in series, 3 strings in parallel 4.2V to 27V 10µF 10µH 10 serial x 3 parallel (30pcs) VOUT 2.2µF/50V 2.2µF LX LX FAULT 0.1uF VIN VDC 2.1V to VIN RESET 560kΩ Enable OVP 18kΩ PWM PWM fPWM=100Hz~25kHz BD6142AMUV COMP CH1 1kΩ For ESD protection CH2 22nF CH3 CH4 20mA CH5 470pF CH6 470pF CH7 PGND PGND GND TEST FSET ABC 56kΩ GND 1nF ISET 470pF CH8 1uF 36kΩ 20Ω PGND Fig. 37 Application example of 10inch panel Capa 470pF Resistor 20Ω D6 1 4 2 Capa 1µ F IC Fig. 38 Layout example for ESD protection www.rohm.com © 2011 ROHM Co., Ltd. All rights reserved. 24/27 2011.07 - Rev.A Technical Note BD6142AMUV 2. Analog Dimming and monitoring FAULT terminal LED current: 20mA (ISET = 36kΩ) LED: 10 LEDs in series, 8 strings in parallel 7V to 27V 10µF 3V to 5V 30kΩ 10µH monitor VOUT 10 serial x 8 parallel (80pcs) 2.2µF 2.2µF/50V LX LX FAULT VIN VDC 2.1V to VIN RESET 2.2MΩ Enable OVP 68kΩ PWM COMP BD6142AMUV CH1 1kΩ CH2 22nF CH3 CH4 CH5 CH6 CH7 PGND PGND GND TEST FSET ABC CH8 ISET 20mA 56kΩ GND PGND 1nF 36kΩ Max 0.9V D/A Fig. 39 Application example of Analog dimming www.rohm.com © 2011 ROHM Co., Ltd. All rights reserved. 25/27 2011.07 - Rev.A Technical Note BD6142AMUV ●Notes for use (1) Absolute Maximum Ratings An excess in the absolute maximum ratings, such as supply voltage, temperature range of operating conditions, etc., can break down devices, thus making impossible to identify breaking mode such as a short circuit or an open circuit. If any special mode exceeding the absolute maximum ratings is assumed, consideration should be given to take physical safety measures including the use of fuses, etc. (2) Operating conditions These conditions represent a range within which characteristics can be provided approximately as expected. The electrical characteristics are guaranteed under the conditions of each parameter. (3) Reverse connection of power supply connector The reverse connection of power supply connector can break down ICs. Take protective measures against the breakdown due to the reverse connection, such as mounting an external diode between the power supply and the IC’s power supply terminal. (4) Power supply line Design PCB pattern to provide low impedance for the wiring between the power supply and the GND lines. In this regard, for the digital block power supply and the analog block power supply, even though these power supplies has the same level of potential, separate the power supply pattern for the digital block from that for the analog block, thus suppressing the diffraction of digital noises to the analog block power supply resulting from impedance common to the wiring patterns. For the GND line, give consideration to design the patterns in a similar manner. Furthermore, for all power supply terminals to ICs, mount a capacitor between the power supply and the GND terminal. At the same time, in order to use an electrolytic capacitor, thoroughly check to be sure the characteristics of the capacitor to be used present no problem including the occurrence of capacity dropout at a low temperature, thus determining the constant. (5) GND voltage Make setting of the potential of the GND terminal so that it will be maintained at the minimum in any operating state. Furthermore, check to be sure no terminals are at a potential lower than the GND voltage including an actual electric transient. (6) Short circuit between terminals and erroneous mounting In order to mount ICs on a set PCB, pay thorough attention to the direction and offset of the ICs. Erroneous mounting can break down the ICs. Furthermore, if a short circuit occurs due to foreign matters entering between terminals or between the terminal and the power supply or the GND terminal, the ICs can break down. (7) Operation in strong electromagnetic field Be noted that using ICs in the strong electromagnetic field can malfunction them. (8) Inspection with set PCB On the inspection with the set PCB, if a capacitor is connected to a low-impedance IC terminal, the IC can suffer stress. Therefore, be sure to discharge from the set PCB by each process. Furthermore, in order to mount or dismount the set PCB to/from the jig for the inspection process, be sure to turn OFF the power supply and then mount the set PCB to the jig. After the completion of the inspection, be sure to turn OFF the power supply and then dismount it from the jig. In addition, for protection against static electricity, establish a ground for the assembly process and pay thorough attention to the transportation and the storage of the set PCB. (9) Input terminals In terms of the construction of IC, parasitic elements are inevitably formed in relation to potential. The operation of the parasitic element can cause interference with circuit operation, thus resulting in a malfunction and then breakdown of the input terminal. Therefore, pay thorough attention not to handle the input terminals, such as to apply to the input terminals a voltage lower than the GND respectively, so that any parasitic element will operate. Furthermore, do not apply a voltage to the input terminals when no power supply voltage is applied to the IC. In addition, even if the power supply voltage is applied, apply to the input terminals a voltage lower than the power supply voltage or within the guaranteed value of electrical characteristics. (10) Ground wiring pattern If small-signal GND and large-current GND are provided, It will be recommended to separate the large-current GND pattern from the small-signal GND pattern and establish a single ground at the reference point of the set PCB so that resistance to the wiring pattern and voltage fluctuations due to a large current will cause no fluctuations in voltages of the small-signal GND. Pay attention not to cause fluctuations in the GND wiring pattern of external parts as well. (11) External capacitor In order to use a ceramic capacitor as the external capacitor, determine the constant with consideration given to a degradation in the nominal capacitance due to DC bias and changes in the capacitance due to temperature, etc. (12) Thermal shutdown circuit (TSD) When junction temperatures become 130℃ (typ) or higher, the thermal shutdown circuit operates and turns a switch OFF. The thermal shutdown circuit, which is aimed at isolating the LSI from thermal runaway as much as possible, is not aimed at the protection or guarantee of the LSI. Therefore, do not continuously use the LSI with this circuit operating or use the LSI assuming its operation. (13) Thermal design Perform thermal design in which there are adequate margins by taking into account the permissible dissipation (Pd) in actual states of use. (14) Selection of coil Select the low DCR inductors to decrease power loss for DC/DC converter. www.rohm.com © 2011 ROHM Co., Ltd. All rights reserved. 26/27 2011.07 - Rev.A Technical Note BD6142AMUV ●Ordering part number B D 6 Part No. 1 4 2 Part No. A M U - V Package MUV: VQFN024V4040 E 2 Packaging and forming specification E2: Embossed tape and reel VQFN024V4040 <Tape and Reel information> 4.0±0.1 4.0±0.1 1.0MAX 2.4±0.1 0.4±0.1 7 12 19 18 0.5 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 ) 6 24 0.75 E2 2.4±0.1 1 2500pcs (0.22) +0.03 0.02 -0.02 S C0.2 Embossed carrier tape Quantity Direction of feed 1PIN MARK 0.08 S Tape 13 +0.05 0.25 -0.04 1pin (Unit : mm) www.rohm.com © 2011 ROHM Co., Ltd. All rights reserved. Reel 27/27 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. 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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