BD9415FS Datasheet, PDF (9/34 Pages) Rohm – White LED Driver for 4Ch Large LCD Panels (DC/DC converter type)

BD9415FS
○PIN29：DUTYP
This is the ODP setting pin. The ODP (Over Duty Protection) is the function to limit DUTY of LED PWM frequency fPWM
by ODP detection Duty (ODPduty) set by resistance (RDUTY) connected to DUTYP pin.
○Relationship between LED PWM frequency fPWM, ODP Detection Duty and DUTYP resistance (ideal)
R_DUTYP

1172 ODP_duty[%]
f _PWM [Hz]
[k]　
The RDUTYP setting ranges from 15kΩ to 600kΩ.
The setting example is separately described in section ”3.2.6 ODP Setting”.
○PIN30：RT
This is the DC/DC switching frequency setting pin. DCDC frequency is decided by connected resistor.
○The relationship between the frequency and RT resistance value (ideal)
R_RT

15000
f _SW [kHz]
[k]　
○PIN31：SSFB
The SSFB pin is used to make setting of soft start time and duty for soft start, and DC/DC current mode control error
amplifier. It performs constant current charge of 10uA to the external capacitor connected to SSFB terminal, which
enables soft-start of DC/DC converter.
The SSFB pin detects the voltages of LED pins (1 to 4) and controls inductor current so that the pin voltage of the LED
located in the row with the highest Vf will come to 0.8V(Typ) (VREF=1.5V). As a result, the pin voltages of other LEDs
become higher by Vf variation. After completion of soft start, the SSFB pin is put into high-impedance state with the PWM
signal being in the low state, thus maintaining the SSFB voltage.
Since the LED protection function (OPEN/SHORT detection) works when it turns to the LED feedback mode.
○PIN32：AGND
This is the GND pin of the IC.
www.rohm.com
© 2015 ROHM Co., Ltd. All rights reserved.
TSZ22111・15・001
9/30
TSZ02201-0F2F0C100140-1-2
23.May.2016 Rev.001