BD9394FP Datasheet, PDF (10/31 Pages) Rohm – White LED Driver for large LCD Panels (DCDC Converter type)

BD9394FP, BD9394EFV
Datasheet
○OVP (HSOP20:7pin / HTSSOP-B24：7pin)
The OVP pin is an input pin for over-voltage protection and short circuit protection of DC/DC output voltage. If
over-voltage is detected, the OVP pin will stop the DC/DC converter conducting step-up operation. When the short circuit
protection (SCP) function is activated, the DC/DC converter will stop operation, and then the timer will start counting.
When the timer completes counting the preset period of time, the LED drivers are stopped.
The OVP pin is of the high impedance type and involves no pull-down resistor, resulting in unstable potential in the
open-circuited state. To avoid this problem, be sure to make input voltage setting with the use of a resistive divider or
otherwise.
○LED1 – LED4 (HSOP20:8,9,12,13pin / HTSSOP-B24：8,9,14,16pin)
The LED1 to 4 pins are used to output constant current to LED drivers. Current value setting can be made by connecting
a resistor to the ISET pin.
For the current value setting procedure, refer to the description of “ISET pin”.
If any of the LED pins is put in an erroneous state (e.g. short circuit mode, open circuit mode, or ground short circuit
mode), the relevant protection function will be activated.
○LED_GND (HSOP20:10pin / HTSSOP-B24：11pin)
The LED_GND pin is a power ground pin used for the LED driver block.
○STB (HSOP20:11pin / HTSSOP-B24：13pin)
The STB pin is used to make setting of turning ON and OFF the IC and allowed for use to reset the IC from shutdown.
Note: 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).
○PWM (HSOP20:14pin / HTSSOP-B24：17pin)
The PWM pin is used to turn ON and OFF LED drivers. Light can be modulated by changing the duty cycle through the
direct input of a PWM light modulation signal
The high and low voltage levels of PWM pin is as listed in the table below:
State
LED ON 状態
LED OFF 状態
PWM Voltage
PWM= 2.0V~35V
PWM= －0.3V～0.8V
○ISET (HSOP20:15pin / HTSSOP-B24：18pin)
The ISET pin is an output current setting resistor. Output current ILED varies in inverse proportion to resistance.
The relation between output current ILED and the resistance of ISET pin connection resistor RISET is given by the
following equation:
I _LED [mA]
=
5000 _×
R_ISET [kΩ]
7.12 − V_NADIM [V ]
3
(NADIM=0~5V)
I _LED [mA]
=
7500
R_ISET [kΩ]
(NADIM>7V~35V)
Output current setting should be made in the range of 30 to 150mA.
It prepares automatically to suitable LED feedback voltage that can output LED current set by ISET pin.
In short LED feedback voltage is dropped when the LED current is small and the IC heating is held automatically.
In case of a large current is needed, raise the LED pin feedback voltage. And it adjusts automatically to LED pin voltage
that can be flow large LED current.
The calculation is as below.
VLED = 3.7 × I _LED [ A] [V ] 　
The LED feedback voltage (VLED) is clamped to 0.3V (typ.) when the LED current (ILED) is less than 81.1mA.
NADIM input range is from 0V to 5V. And the range which the LED currents change with linearity is from 1.5V to 5.0V.
When it reaches under VISET×0.90V(typ), the LED current is off to prevent from passing a large current to the LED pin
when the RISET is shorted and the ISET pin is shorted to the GND. And as the ISET pin returns to a normal state, the
LED current returns.
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TSZ22111・15・001
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TSZ02201-0F1F0C100180-1-2
09.Nov.2012 Rev.002