Datasheet LED Drivers series for LCD Backlights PWM pulse Generator for LCD Panels BD9478F General Description Features BD9478F is PWM pulse generator for LCD panel. This The signal that the frequency synchronizes with the IC compares triangle waveform which is generated VSYNC signal is output to PWMOUT. inside IC and external DC signal, and generates a The PWM pulse is generated with the DC signal of a PWM pulse. This PWM pulse is provided to LED driver triangular wave and PDIM generated with the LCT and controls LED grayscale. PWM pulse frequency capacitor. can be synchronized to external signal frequency When the VSYNC frequency exceeds the stipulated inputted to SYNC terminal. Even if this frequency gets range, it fixes by a set frequency. out of range, it works in the setting frequency, is (fSYNC<fPLLtyp*0.35 -> fPLL=0.36*fPLLtyp , fSYNC> protected and it always provides stable PWM pulse to fPLLtyp*2.75 -> fPLL=2.75*fPLLtyp) LED driver. When VSYNC is a no signal input, the self-oscillation is operated by set frequency decided on the CT capacitance. Key Specification When the pulse signal is input to the terminal EXTPWM, Operating power supply voltage range: 4.5V to 5.5V it shifts automatically to external PWM mode. Free Run frequency: 150Hz (CT=0.01F) Operating Current: 2mA (typ.) Operating temperature range: -40 to +85 Package W(Typ.) D(Typ.) H(Max.) SOP-8: 5.00mm x 6.20mm x 1.71mm Pin Pitch: 1.27mm Applications LED backlight of monitor, TV, NOTE PC, etc. Typical Application Circuit CVCC VIN PWM sign al out 1 8 V CC PWMOUT (to LE D driv er) 2 7 EXT PWM GND CEXTP WM Figure 1. SOP-8 r CLP F1 CLPF2 o t PDIM c 3 6 e LPF PDIM n n CP DIM o RLPF2 C fVSYNC CCT 4 5 VSYNC CT CVSYN C Figure 2. Typical Application Circuit Product structureSilicon monolithic integrated circuit This product is not designed protection against radioactive rays .w ww.rohm.com TSZ02201-0F1F0C100010-1-2 2012 ROHM Co., Ltd. All rights reserved. 1/12 TSZ2211114001 24. Jul.2012 Rev.002Datasheet BD9478F Absolute maximum ratings (Ta=25) Parameter Symbol Ratings Unit Power supply voltage VCC 7 V Operating Temperature Range Ta(opr) -40 ~ +85 C Storage Temperature Range Tstg -55 ~ +150 C Junction Temperature Tjmax 150 C Power Dissipation Pd 6891 mW *1 Decreases 5.5mW/C at Ta=25C or higher (When mounting a one-layer 70.0mmx70.0mmx1.6mm board) Operating Ratings (Ta = 25) Parameter Symbol Range Unit Power supply voltage VCC 4.5 5.5 V 0.040 0.8 VSYNC input frequency range F VSYNC kHz FCT 30 EXTPWM input PWM signal frequency range F EXTPWM kHz The operating conditions written above are constants of the IC unit. Be careful enough when setting the constant in the actual set. FCT is dimming frequency that oscillates itself when VSYNC terminal is input no signal External Components Recommended Range Item Symbol Setting Range Unit VCC capacitance CVCC 0.1 ~ 10 F PLL Burst OSC oscillation frequency setting capacitance CT 0.040 0.8 F The operating conditions written above are constants of the IC unit. Be careful enough when setting the constant in the actual set. Pin Configuration Marking diagram and physical dimension 8 7 6 5 D9478 Lot No. 1 2 3 4 SOP-8 Figure 3. Pin Configuration Figure 4. Physical Dimension www.rohm.com TSZ02201-0F1F0C100010-1-2 2012 ROHM Co., Ltd. All rights reserved. 2/12 TSZ2211115001 24. Jul.2012 Rev.002 VCC PWMOUT EXTPWM GND PDIM LPF VSYNC CT