CAT4004 Datasheet, PDF (7/11 Pages) Catalyst Semiconductor – 4-Channel Constant Current LED Driver with EZDi TM

PIN DESCRIPTIONS
Pin #
1
2
3
4
5
6
7
8
TAB
Name
EN/DIM
GND
LED1
LED2
LED3
LED4
RSET
VIN
TAB
Function
Device enable (active high) and dimming control
Ground reference
LED1 cathode terminal
LED2 cathode terminal
LED3 cathode terminal
LED4 cathode terminal
RSET external LED mirror gain 128
Device supply input, connect to battery or supply
Connect to GND on the PCB
CAT4004
PIN FUNCTION
VIN is the supply pin for the charge pump. A small
1μF ceramic bypass capacitor is required between the
VIN pin and ground near the device. The operating
input voltage range is from 2.5V to 5.5V. Whenever
the input supply falls below the under-voltage
threshold (1.8V), 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 1.3V and 0.4V respectively. When EN/DIM
is initially taken high, the device becomes enabled
and all LED currents are set to the full scale according
to the resistor R_SET. To place the device into “zero
current” shutdown mode, the EN/DIM pin must be
held low for at least 1.5ms.
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.
RSET is connected to the resistor (R_SET) to set the full
scale current for the LEDs. The voltage at this pin is
regulated to 0.6V. The ground side of the external
resistor should be star connected back to the GND of
the PCB. In shutdown mode, RSET beomes high
impedance.
GND is the ground reference for the device. The pin
must be connected to the ground plane on the PCB.
TAB 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.
© 2007 Catalyst Semiconductor, Inc.
7
Characteristics subject to change without notice
Doc. No. 5024 Rev. A