BD6142AMUV

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 BD6142AMUV ●Absolute maximum ratings (Ta=25℃) Parameter Maximum applied voltage 1 Maximum applied voltage 2 Maximum applied voltage 3 Maximum applied voltage 4 Power dissipation 1 Power dissipation 2 Power dissipation 3 Operating temperature range Storage temperature range Symbol VMAX1 VMAX2 VMAX3 VMAX4 Pd1 Pd2 Pd3 Topr Tstg Ratings 7 45 30.5 15 500 *1 780 *2 1510 *3 -40 ~ +85 -55 ~ +150 Unit V V V V mW mW mW ℃ ℃ Technical Note Condition VDC, ISET, ABC, COMP, FSET, TEST, FAULT CH1 ~ CH8, LX, OVP VIN, Enable PWM *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 Symbol VIN Limits Min. 4.2 Typ. 12.0 Max. 27.0 Unit V Conditions www.rohm.com © 2011 ROHM Co., Ltd. All rights reserved. 2/27 2011.07 - Rev.A BD6142AMUV ●Electrical characteristics (Unless otherwise specified, VIN=12V, Ta = +25℃) Limits Parameter Symbol Min. Typ. Max. [General] Quiescent Current Current Consumption Max. Output Voltage Under Voltage Lock Out [Enable Terminal] Low Input Voltage range High Input Voltage range1 Pull down resistor Output Current [PWM Terminal] Low Input Voltage range High Input Voltage range2 Pull down resistor Output Current [FAULT] Nch RON [Regulator] VDC Voltage [Switching Regulator] LED Control voltage Switching frequency accuracy Duty cycle limit LX Nch FET RON [Protection] Over Current Limit Over voltage limit Input Output Short Protect OVP leak current CH Terminal Over Voltage Protect accuracy [Current driver] LED maximum current LED current accuracy LED current matching LED current matching2 LED current limiter ISET voltage LED current accuracy2 *1 Technical Note Unit Conditions Iq Idd MOV UVLO EnL EnH EnR ENIout PWML PWMH PWMR PWMIout FFCR VREG VLED Fsw Duty RON Ocp OVP OVPfault OVIL VSC 3.1 0.0 2.0 100 0.0 1.3 100 4.2 0.64 1.00 91.0 1.5 1.16 0.02 -15 1.6 3.6 3.7 300 0 300 0 5.0 0.80 1.25 95.0 0.48 2.5 1.20 0.05 0.1 0 4.4 5.4 41 4.1 0.8 VIN 500 2 0.8 12.0 500 2 3 6.0 0.96 1.50 99.0 0.58 1.24 0.08 1.0 +15 µA mA V V V V kΩ µA V V kΩ µA kΩ V V MHz % Ω A V V µA % Enable=0V OVP=0V,ISET=36kΩ VIN falling edge Enable=3V Enable=0V PWM=3V PWM=0V Enable=PWM=3V, OVP=2V No load, VIN > 6V FSET=56kΩ CH1-8=0.3V, FSET=56kΩ ILX=80mA *1 Detect voltage of OVP pin Detect voltage of OVP pin VSC=5V ILMAX ILACCU ILMAT ILMAT2 ILOCP Iset ILACCU2 - 0 0.733 ±3.0 30 ±2.5 2.5 1.5 0.1 - mA % % % mA V % ILED=20mA, ABC=0.733V 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 This parameter is tested with DC measurement. www.rohm.com © 2011 ROHM Co., Ltd. All rights reserved. 3/27 2011.07 - Rev.A BD6142AMUV ●Reference data 100 Technical Note LED current vs PWM Duty LED Current vs PWM duty 100.000 10 1 VIN=6V VIN=12V VIN=27V LED Current [mA] LED current[mA] 10.000 VIN=6V VIN=12V VIN=27V 1.000 0.1 0.100 0.01 0.1 1 duty[%] 10 100 0.010 1 10 PWM Duty [%] 100 ■10serial×8parallel ■Ta = 25℃ ■LED Current = 20mA ■PWM frequency = 200Hz ■Frequency = 1.25MHz(FSET=56kΩ) ■Coil = 10µH ■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 ABC voltage 35.000 30.000 LED current [mA] LED current [mA] 50 45 40 35 30 25 20 15 10 5 LED current vs ISET current 25.000 20.000 15.000 10.000 5.000 0.000 0 0.2 0.4 0.6 0.8 ABC Voltage [V] 1 1.2 VIN=4.2V VIN=12V VIN=27V 25℃ 85℃ -40℃ 0 0 10 20 30 ISET current [uA] 40 50 ■Ta = 25℃ ■ISET = 36kΩ ■CH1 = 0.8V ■VIN = 12V ■CH1 = 0.8V Fig. 3 LED current characteristics Analog dimming Fig. 4 LED maximum current Efficiency vs VIN (10serials and 8strings) 100.0% 98.0% 96.0% 92.0% 90.0% 88.0% 86.0% 84.0% 82.0% 80.0% 0.5 0.7 0.9 1.1 1.3 1.5 Frequency [MHz] 1.7 1.9 VIN=7V VIN=12V VIN=27V 94.0% Efficiency vs VIN (10serials and 6strings) 100.0% 98.0% 96.0% Efficiency[%] 94.0% 92.0% 90.0% 88.0% 86.0% 84.0% 82.0% 80.0% 0.5 0.7 0.9 1.1 1.3 1.5 Frequency [MHz] 1.7 1.9 VIN=7V VIN=12V VIN=27V Efficiency[%] ■Ta = 25℃ ■10 serial×8parallel ■LED Current = 20mA ■Coil = TDK, LTF5022T-100M1R4-LC ■Ta = 25℃ ■10 serial×6parallel ■LED Current = 20mA ■Coil = TDK, LTF5022T-100M1R4-LC Fig. 5 Efficiency Fig. 6 Efficiency www.rohm.com © 2011 ROHM Co., Ltd. All rights reserved. 4/27 2011.07 - Rev.A BD6142AMUV ●Block diagram and pin configuration VIN VDC FAULT Technical Note Output short PROTECT OVP REG TSD Enable UVLO Internal Reset Output Over Voltage PROTECT Clamp Internal Power Supply FAULT DETECTOR LED TERMINAL OPEN/SHORT DETECTOR ERRAMP PWM COMP + CH1 CH 2 LX LX Internal Power Control Soft start Control SENCE LED RETURN CH 3 CH 4 CH 5 CH 6 CH 7 CH 8 8ch OSC Current SENCE Over Current Protect + SELECT PGND PGND Clamp + - ISET Resistor driver Current Driver TEST FSET COMP PWM ABC ISET GND Fig. 7 Block diagram ●Pin assignment table Pin Pin IO No. Name 1 Enable In 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 TEST FSET ABC GND PWM CH8 CH7 CH6 CH5 ISET CH4 CH3 CH2 CH1 OVP PGND LX FAULT COMP VIN VDC In In In In In In In In In In In In In In Out Out Out Out In Out Function PWM input pin for power ON/OFF or Power control TEST signal (Pull down 100kΩ within IC) Resister connection for frequency setting Analog Brightness Control GND for Switching Regulator PWM input pin for power ON/OFF only driver Current sink for CH8 Current sink for CH7 Current sink for CH6 Current sink for CH5 Resister connection for LED current setting Current sink for CH4 Current sink for CH3 Current sink for CH2 Current sink for CH1 Detect input for SBD open and OVP PGND for switching Tr Switching Tr drive terminal Switching Tr drive terminal Fault signal ERRAMP output Battery input Regulator output / Internal power-supply Terminal diagram E E A C B E C C C C A C C C C C D VDC VIN PIN PIN GND PGND A VIN B PIN PIN GND GND C D PIN 5.5V Clump GND PIN PGND E F PIN F F C A G C GND PGND G www.rohm.com © 2011 ROHM Co., Ltd. All rights reserved. 5/27 2011.07 - Rev.A BD6142AMUV Technical Note ●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 10µH VOUT 2.2µ F/50V 2.2µF 10 serial x 8 parallel (80pcs) LX LX FAULT V IN V DC 2.2MΩ 2.1V to VIN RESET E nable PW M OVP PW M 68k Ω fPWM =100Hz~25kHz CO MP 1kΩ 22nF B D6142AMUV C H1 CH2 CH3 CH4 CH5 CH6 CH7 CH8 20m A 36k Ω P GND PGND GND TEST F SET ABC ISET 56kΩ 1nF GND P G ND Fig. 8 BD6142A Application example (8 parallel) 7V to 27V 10µF 10µH VOUT 2.2µF/50V 2.2µF 9 serial x 6 parallel (54pcs) LX LX FAULT VIN VDC 2.2MΩ 2.1V to VIN RESET Enable PWM OVP PW M 73.2kΩ fPWM=100Hz~25kHz COMP 1kΩ 22nF BD6142AMUV CH1 CH2 CH3 CH4 CH5 CH6 CH7 CH8 20mA 56kΩ 1nF 36kΩ PGND PGND GND TESTFSET ABC ISET GND PGND Fig. 9 BD6142A Application example (6 parallel) www.rohm.com © 2011 ROHM Co., Ltd. All rights reserved. 6/27 2011.07 - Rev.A BD6142AMUV Technical Note 4.2V to 27V 10µF 10µH VOUT 2.2µF/50V 2.2µF 10 serial x 3 parallel (30pcs) LX LX FAULT VIN VDC 2.2MΩ 2.1V to VIN RESET Enable PWM OVP PWM 68kΩ fPWM=100Hz~25kHz COMP 1kΩ 22nF BD6142AMUV CH1 CH2 CH3 CH4 CH5 CH6 CH7 CH8 20mA PGND PGND GND TEST FSET 110kΩ ABC 1nF ISET 36kΩ GND PGND Fig. 10 BD6142A Application example (3 parallel) www.rohm.com © 2011 ROHM Co., Ltd. All rights reserved. 7/27 2011.07 - Rev.A BD6142AMUV Technical Note ●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 d uty 20% @1.25MHz(typ) Pulse skip LX LED current 2 0mA 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 Typ 4.3ms Enable PWM Max 1ms Soft Start Time=T1+T2=4.3ms typ PWM UVLO UVLO VDC Soft start OFF ON OFF ON VDC Soft start OFF T1 ON OFF T2 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 Protection ‘X’ Typ4.3 ms ‘H’ Mask ‘L’ detect Typ100us ‘H’ ‘L’ Latch ‘X’ un-detect un-detect detect ‘H’ un-detection function(OVP, TSD, OCP) Protection Boost operating un-detect function(LED open, LED short) off normal 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 BD6142AMUV ●Protection PROTECTION TABLE FAILURE CASE MODE LED Short 1 connected CH1 2 3 4 Technical Note 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 2.5A FAULT change from L to H, and high or switching is stopped. OTP > 130C 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 VOUT OVP Signal CH1 voltage CH1 connection normal CH2 connection Feedback CH1 open normal CH2 0mA 0mA CH1 Hysteresis(typ 2.5%) CH1 current 20mA CH2 current 20mA Fig. 14 OVP operating description www.rohm.com © 2011 ROHM Co., Ltd. All rights reserved. 9/27 2011.07 - Rev.A BD6142AMUV Technical Note 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 1. 2. 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 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 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 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 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 3. 4. 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 130C (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 BD6142AMUV Technical Note ●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 CH2 connection open normal CH 1 CH 2 CH1 voltage CH1 enable Feedback CH1 current 20mA CH2 current 20mA CH1 100µs CH2 0mA 0mA OFF CH1 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 Typ 5V CH1terminal CH2 terminal Vout FeedBack 0.8V CH1>CH2 0.8V CH1 20mA 20mA CH 1 CH 2 C H2 100us(typ) 0.05mA(typ) CH1 current C H2 current 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 BD6142AMUV ●Control Signal input timing Technical Note 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 ENABLE, PWM VIN 0V Min 0µs Min 0µs 2 ~ 5V 2 ~ 5V ENABLE 0 ~ 0.8V PWM 0 ~ 0.8V *other signal is input after a signal turned on. Power ON Power OFF LED IC Timing Sequence for PWM Control Turn-off 4.2 ~ 27V Fig. 17 Timing sequence1 VIN 2 ~ 5V Min 0µs Min 0µs 0V 0 ~ 0.8V 0 ~ 0.8V ENABLE 2 ~ 5V PWM *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 ENABLE 0 ~ 0.8V Min 0µs Min 0µs 2 ~ 5V 4.2 ~ 27V 2 ~ 5V PWM VIN PWM 0V 0 ~ 0.8V Power ON 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 4.2 ~ 27V Min 0µs 0 ~ 0.8V Min 0µs 0V 0 ~ 0.8V VIN 2 ~ 5V PWM *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 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. Technical Note LED IC Timing Sequence for PWM Control Turn-on VIN, PWM PWM 0 ~ 0.8V 0V 0 ~ 0.8V 2 ~ 5V Min 0µs Min 0µs 4.2 ~ 27V 2 ~ 5V ENABLE VIN ENABLE Power ON Power OFF *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 4.2 ~ 27V Min 0µs 0 ~ 0.8V Min 0µs 0V 0 ~ 0.8V VIN 2 ~ 5V ENABLE VIN wake up speed *other signal is input after a signal turned off. 4.1 V VIN 1 2 Min. 100µs 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 ENABLE Min 10ms PWM PWM reset 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 BD6142AMUV Technical Note ●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 t１５ SOFT START Over current value increases.. tsoft tsoft tsoft 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 H[V] t4 t5 t3 VIN L[V] H[V] t2 t3 ENABLE t6 VDC t7 t14 t8 t9 t14 t10 t11 PWM 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 Unit µs µs µs µs µs µs µs µs µs µs µs µs µs µs µs V V Min. 100 0 0 0 50 0 0 5 0 5 40 0 0 0 15 4.2 - Typ. 5000 12 - Max. 100 100 100 100 10000 27 4.2 www.rohm.com © 2011 ROHM Co., Ltd. All rights reserved. 14/27 2011.07 - Rev.A BD6142AMUV Technical Note ●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 CH 1 CH 2 CH 3 CH 4 CH 5 CH 6 CH 7 CH 8 Enable OVP Normal voltage VOUT CH1~6 CH7~8 0V 0.8V(typ) 0V Reset Fig. 24 Select the number of CH lines 1 ENABLE PWM Soft start: typ 4.3ms 100µs(typ) Vout Over voltage protect signal Terminal select (LED open protect) CH1 Terminal CH8 Terminal Feedback terminal Mask Over Voltage Protect Normal condition “Unmask Typ 0.8V open Stable CH8 20mA 0mA CH1 CH1 Current 0mA CH8 Current 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 BD6142AMUV Technical Note ●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] 1.59 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 Min Duty example Min Duty[%] Frequency Min Typ Max 1.25MHz 20 - 1.25 0.57 43 kΩ 56kΩ 130 kΩ FSET[kΩ] www.rohm.com © 2011 ROHM Co., Ltd. All rights reserved. 16/27 2011.07 - Rev.A BD6142AMUV Technical Note ●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 LED current Coil current IC’s active current ON ON ON OFF OFF OFF ON VOUT LED current 400ns/div 10mA/div PWM Fig. 26 PWM sequence Conditions： 8serial 6parallel, LED current=20mA/ch, VIN=7V, Ta=25℃, Output capacitor=2.2μF(50V/B3) VOUT 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. 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. 40ns/div 10mA/div 1.2V DC Input ABC 120.9kΩ 0.733V 180kΩ ISET Resistor driver + - ISET 36kΩ Fig. 27 Analog dimming application 1.2V ABC 120.9kΩ 0.733V 180kΩ ISET Resistor driver + - 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 BD6142AMUV Technical Note ●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 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 BD6142AMUV Technical Note ●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 Creal Capa [ µF] 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 BD6142AMUV ●The separations of the IC Power supply and coil Power supply Technical Note 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 7V to 27V 10µF 10µH VOUT 2.2µF/50V 2.2µF 10 serial x 6 parallel (60pcs) LX LX FAULT VIN VDC 2.2MΩ 2.1V to VIN R ESET Enable PWM OVP PWM 68k Ω fPWM=100Hz~25kHz COMP 1kΩ 22nF BD6142AMUV CH1 CH2 CH3 CH4 CH5 CH6 CH7 CH8 20mA PGND PGND GND TEST FSET ABC ISET 56 k Ω GND PGND 1nF 36kΩ Connect VIN and VDC terminals 4.2V to 30V 4.2V to 5.5V 10µF 10µH VOUT 2.2µF/50V 2.2µF 10 serial x 6 parallel (60pcs) LX LX FAULT VIN V DC 2.2MΩ 2.1V to VIN RESET Enable PWM OVP PWM 68k Ω fPWM=100Hz~25kHz C OMP 1k Ω 22nF BD6142AMUV C H1 CH2 CH3 CH4 CH5 CH6 CH7 CH8 20mA PGND PGND GND TEST FSET ABC ISET 56kΩ GND PGND 36k Ω 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 BD6142AMUV Technical Note ●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 COUT1(2.2µF/50V) CVDC1 (2.2µF) LX LX FAULT VIN VDC ROVP1 (2.2MΩ) 2.1V to VIN RESET Enable PWM OVP PWM ROVP2 (68kΩ) fPWM=100Hz~25kHz COMP RCMP(1kΩ) CCMP(22nF) BD6142AMUV CH1 CH2 CH3 CH4 CH5 CH6 CH7 CH8 20mA RISET(36kΩ) PGND PGND GND TESTFSET ABC ISET GND PGND RFSET(56kΩ) CABC(1nF) Fig. 32 Schematic Put input bypath capacitor CIN (10μF) as close as possible between coilL1 and PGND pin. Connect smoothing capacitor CVDC1(2.2μF) as close as possible between VDC pin and GND. Connect schottky barrier diode SBD as close as possible between coil1and SW pin. Connect output capacitor COUT1 between cathode of SBD and PGND. Make both PGND sides of CVIN and COUT1 as close as possible. > 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. 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. Put frequency setting resistor(56KΩ) as close as possible between FSET pin and GND.