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BD1754HFN-TR Datasheet(PDF) 9 Page - Rohm

Part No. BD1754HFN-TR
Description  Constant Current LED Driver with 64 Dimming Steps for up to 4 LEDs
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Maker  ROHM [Rohm]
Homepage  http://www.rohm.com
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BD1754HFN-TR Datasheet(HTML) 9 Page - Rohm

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BD1754HFN
Datasheet
TSZ02201-0G3G0C200060-1-2
9.NOV.2012 Rev.001
www.rohm.com
© 2012 ROHM Co., Ltd. All rights reserved.
TSZ22111・15・001
●Application Circuit Examples
(1) Circuit example when the power supply is separated
VIN
ISET
GND
Current
DAC
UPIC
6
EN
L4
L3
L2
L1
On the assumption that Vf is 3 V
Power Supply2=5V
0.1µF
120k
The voltage value of L* pin must
be VIN-1.4 V at the maximum
when the LED is powered ON.
Power Supply1
(When ILED -max =32mA)
(Maximum rating = 7.0 V)
Cin
RISET
(Ex.)
Figure 16. Circuit example when the power supply is separated
This figure shows a circuit example when the power supply for VIN and for LEDs is separated. Apply a voltage of Vf
(threshold voltage value of a white LED) or higher to the LED. In this case, please note that when the LED is powered
ON, the voltage value of L* pin (each pin of L1 to L4) must be VIN-1.4 V at the maximum. If a voltage of higher than
VIN-1.4 V is applied to L* pin, a desired current value cannot be obtained. Also, please pay attention to the voltage
application procedure at start-up. Be sure to power the current driver ON using the UPIC after applying power supply
voltages to the VIN and the LED-anode pins. If the current driver is powered ON prior to applying power supply
voltages to the LED, a rush current occurs in the LED. Determine the resistance value with which the LED current
value is maximized and then connect such resistor between the ISET and the GND pins. The power ON/OFF and the
brightness of the LEDs are controlled through the EN pin in accordance with the UPIC format.
(2) Circuit example when using only two LEDs
120k
VIN
ISET
GND
Current
DAC
UPIC
6
EN
L2
L1
0.1µF
Connect to the GND pin.
(When ILED-max =32mA)
Cin
RISET
L4
L3
Figure 17. Circuit Example when using only two LEDs
This figure shows a circuit example when none of L3 and L4 LEDs are used. Connect both of the unused L3 and L4
pins to the GND pin. Likewise, it is possible to make the L1 and/or the L2 pins unused, which allows the back lights to
be used with the one or three LED(s) turned on. In all cases, connect the unused L* pin to the GND pin. Determine the
resistance value with which the LED current value is maximized and then connect such resistor between the ISET and
the GND pins. The power ON/OFF and the brightness of the LEDs are controlled through the EN pin in accordance
with the UPIC format.


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