Technical Note

9/11

BD1754HFN

www.rohm.com

2011.06 - Rev.B

© 2011 ROHM Co., Ltd. All rights reserved.

(7) Circuit example when connecting the two LEDs to each of the channels in series

VIN

ISET

GND

Current

DAC

UPIC

6

EN

L4

L3

L2

L1

Power Supply2=6.2~7V

0.1µF

120kΩ

The voltage value of L* pin must

be VIN-1.4 V at the maximum

when the LED is powered ON.

Power Supply1

(Maximum rating = 7.0 V)

On the assumption that Vf is 3 V

(Ex.)

Fig.20

Circuit example when connecting the two LEDs to each of the channels in series

This figure shows a circuit example when making 8 (2 x 4) LEDs available by connecting two LEDs to each of the

channels in series. In this example, when Vf is set to approx. 3 V in order to ensure the voltage to L1 through L4 pins,

it is necessary to apply a voltage of 6.2 V (3 V x 2 LEDs in series + 0.2 V of the minimum voltage value of the driver

pin) or higher to the LED anode pin as its power supply voltage. Pay attention that the voltage should not exceed the

7.0-V maximum rating of the L1 through L4 pins. 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.

●

Application Component Selection

<Capacitor>

Symbol

Recommended value

Recommended component

Manufacturer

Cin

0.1µF

GRM188B31H104KA92B

MURATA

<Resistor>

Symbol

Recommended value

Recommended component

Manufacturer

120kΩ

MCR10PZHZF1203

ROHM

●

Recommended PCB Layout

Design PCB pattern to provide low impedance for the wiring to the power supply line.

Also, provide a bypass capacitor if needed.

Fig.21

Layout image of the application components (Top View)

Fig.22

Surface (Top View)

L4

L2

L1

L3

EN

ISET

VIN

GND

EN

GND

Cin

LED_PWR

VIN

LED_PWR

EN

GND

VIN

Connect

Cin

input-bypass

capacitor in close proximity

between the VIN and GND pins.

close proximity to the ISET pin.