CAT4004_08 Datasheet, PDF (8/11 Pages) Catalyst Semiconductor – 4-Channel Constant Current LED Driver with EZDim™

CAT4004
BLOCK DIAGRAM
V_IN
VIN
RSET
Undervoltage
Lockout
Reference
Voltage
Current
Setting DAC
EN/DIM
Serial
Interface
100kΩ
Register
4 Current Sink
Regulators
GND
Figure 2. CAT4004 Functional 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.
I_LED
=
GAIN ×
0.6V
R_SET
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.
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.
Doc. No. MD-5024 Rev. B
8
© Catalyst Semiconductor, Inc.
Characteristics subject to change without notice