BD9420F Datasheet, PDF (9/31 Pages) Rohm – White LED Driver for large LCD Panels (DCDC Converter Type)

BD9420F
Datasheet
 Pin 21-23: PWMC, PWMB, PWMA
ON/OFF terminal of LED driver pin. It inputs PWM dimming signal directly to adjust output DUTY dimming.
For details of PWM control state, refer to the description of the ＜SEL pin＞.
High/Low level of PWM terminal is shown as follows:
State
LED ON state
LED OFF state
PWM Voltage
PWM= 1.5V~18.0V
PWM= -0.3V～0.8V
 Pin 24: OVP
The OVP pin is an input pin for overvoltage protection and short circuit protection of DC/DC output voltage. When voltage
of it over 3.0V or higher, CP counting start.
When OVP pin voltage<0.1V (typ.) or lower, short circuit protection (SCP) function is activated, and output of Gate driver
will become low immediately.
 Pin 25: RT
RT sets charge/discharge current determining frequency inside IC.
Only a resistor connected to RT determines saw-tooth wave frequency inside IC.
When RT=100kΩ,Frequency=150kHz(typ.).
For calculation example, please refer to section in “P15 – DC/DC drive frequency setting”.
When it reaches under VRT×0.90V(typ), DCDC operation will be stopped in order to prevent from high speed oscillation
when the RT resistance is shorted to GND. And when RT pin returns to normal state, DCDC also returns to operation.
 Pin 26: AGND
GND pin for analog system inside IC.
 Pin 27: STB
ON/OFF setting pin and allowed for use to reset the IC from shutdown.
※The IC state is switched (i.e., The IC is switched between ON and OFF state) according to voltages input in the STB
pin. Avoid using the STB pin between two states (0.8 to 2.0V).
 Pin 28: VCC
Power source pin of IC, which should be input in the range of 9 – 35 V.
Operation starts when VCC is 7.5V (TYP.) or higher and shuts down when VCC is 7.2 V (TYP.).
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31.Jan.2014 Rev.002