CAT4002A, CAT4004A

http://onsemi.com

6

Table 6. PIN DESCRIPTIONS

Name

Function

EN/DIM

Device enable (active high) and dimming control

GND

Ground reference

LED1

LED1 cathode terminal

LED2

LED2 cathode terminal

LED3

LED3 cathode terminal (CAT4004A only)

LED4

LED4 cathode terminal (CAT4004A only)

RSET

Connect external RSET resistor to set the LED current

VIN

Device supply input, connect to battery or supply

TAB

Connect to GND on the PCB (CAT4004A only)

Pin Function

VIN is the supply pin for the charge pump. A small 1

mF

ceramic bypass capacitor is required between the VIN pin

and ground near the device. The operating input voltage

range is from 2.5 V to 5.5 V. Whenever the input supply falls

below the under−voltage threshold (2.0 V), all the LED

channels are disabled and the device enters shutdown mode.

EN/DIM is the enable and one wire dimming input for all

LED channels. Levels of logic high and logic low are set at

1.3 V and 0.4 V respectively. When EN/DIM is initially

taken high, the CAT400XA becomes enabled and the LED

channel current is set to the full scale according to the

shutdown mode, the EN/DIM pin must be held low for 3 ms

typical.

LED1 to LED4 provide the internal regulated current for

each of the LED cathodes. There pins enter a high

impedance zero current state whenver the device is placed

in shutdown mode.

current for the LEDs. The voltage at this pin is regulated to

0.6 V. The ground side of the external resistor should be star

connected back to the GND of the PCB. In shutdown mode,

the RSET input becomes high impedance.

GND is the ground reference for the device. The pin must be

connected to the ground plane on the PCB.

TAB (CAT4004A only) is the exposed pad underneath the

package. For best thermal performance, the tab should be

soldered to the PCB and connected to the ground plane.

Block Diagram

4 Current Sink

Regulators

Current

Setting DAC

Undervoltage

Lockout

Register

Serial

Interface

RSET

100 kW

EN/DIM

GND

VIN

Reference

Voltage

Figure 15. CAT4004A Functional Block Diagram