BD9394FP Datasheet, PDF (11/31 Pages) Rohm – White LED Driver for large LCD Panels (DCDC Converter type)

BD9394FP, BD9394EFV
Datasheet
○SS (HSOP20:16pin / HTSSOP-B24：20pin)
The SS pin is used to make setting of soft start time and duty for soft start. It performs constant current charge of 2.0 uA
to the external capacitor connected with SS terminal, which enables soft-start of DC/DC converter.
Since the LED protection function (OPEN/SHORT detection) works when the SS terminal voltage reaches 3.7 V (typ.) or
higher, it must be set to bring stability to conditions such as DC/DC output voltage and LED constant current drive
operation, etc. before the voltage of 3.7 V is detected.
○FB (HSOP20:17pin / HTSSOP-B24：21pin)
The FB pin is an output pin used for DC/DC current mode control error amplifier. In other words, the FB 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 0.37V (NADIM=(2.62)V, ILED=100mA). As a result, the pin voltages of other LEDs become higher
by Vf variation. After completion of soft start, the FB pin is put into the high-impedance state with the PWM signal being in
the low state, thus maintaining the FB voltage.
○RT (HSOP20:18pin / HTSSOP-B24：22pin)
The RT pin is used to connect a DC/DC frequency setting resistor. DC/DC drive frequency is determined by connecting
the RT resistor.
cDrive frequency vs. RT resistance (Ideal)
R _RT
=
15000
f _SW [kHz ]
[kΩ]
When RT is 100kΩ, Fsw is 150kHz(typ.). However, drive frequency setting should be made in the range of 100 kHz to
800 kHz.
○NADIM (HSOP20:19pin / HTSSOP-B24：23pin)
NADIM pin is for analog dimming. Output current is proportionality with input voltage (negative). Basically, NADIM pin
assumes the voltage inputted externally using high accuracy of resistive divider and etc., IC internally is in OPEN (High
impedance) condition.
Please be sure to apply externally for Resistive divider and etc. from REG58 output. Cannot use in an OPEN condition.
○VCC (HSOP20:20pin / HTSSOP-B24：24pin)
The VCC pin is used to supply power for the IC in the range of 9 to 35V.
If the VCC pin voltage reaches 7.5V (Typ.) or more, the IC will initiate operation. If it reaches 7.2V (Typ.) or less, the IC
will be shut down.
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TSZ22111・15・001
11/28
TSZ02201-0F1F0C100180-1-2
09.Nov.2012 Rev.002