cat4004 Catalyst Semiconductor, cat4004 Datasheet - Page 8

• Manufacturer Part Number: cat4004
• Description: 4-channel Constant Current Led Driver With Ezdim?
• Manufacturer: Catalyst Semiconductor

CAT4004
BLOCK DIAGRAM
BASIC OPERATION
The CAT4004 uses four tightly matched current
sinks to accurately regulate LED current in each
channel proportional to the current sourced from the
RSET pin.
There are six different gain settings for LED
brightness that can be set through the EN/DIM pin.
The default gain on power-up is 132. Tight current
regulation for all channels is possible over a wide
range of input and LED voltages due to independent
current sensing circuitry on each channel.
Doc. No. MD-5024 Rev. B
I
LED
V
IN
=
GAIN
EN/DIM
RSET
VIN
×
R
0
6 .
SET
Figure 2. CAT4004 Functional Block Diagram
V
100kΩ
Reference
Voltage
Interface
Serial
Undervoltage
Lockout
Setting DAC
Register
Current
8
Each LED channel needs a minimum of 150mV
headroom to sink constant regulated current. If the
input supply falls below 1.8V, the under-voltage
lockout circuit disables all LED channels and resets
the circuit to default values. Any unused LED
channels should be left open.
4 Current Sink
Regulators
GND
Characteristics subject to change without notice
© Catalyst Semiconductor, Inc.