CAT3644_0710 Datasheet, PDF (8/14 Pages) Catalyst Semiconductor – 4-Channel Ultra High Efficiency Quad-Mode™ LED Driver

CAT3644
PIN DESCRIPTION
Pin #
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
TAB
Name
LED2
LED3
LED4
RSET
EN/DIM
VOUT
NC
VIN
C1+
C1-
C2+
C2-
NC
NC
GND
LED1
GND
Function
LED2 cathode terminal.
LED3 cathode terminal.
LED4 cathode terminal.
Connect resistor RSET to set the LED current.
Device enable (active high) and Dimming Control.
Charge pump output connected to the LED anodes.
Not connected inside the package.
Charge pump input, connect to battery or supply.
Bucket capacitor 1 Positive terminal
Bucket capacitor 1 Negative terminal
Bucket capacitor 2 Positive terminal
Bucket capacitor 2 Negative terminal
Not connected inside the package.
Not connected inside the package.
Ground Reference
LED1 cathode terminal.
Connect to GND on the PCB.
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.
VOUT is the charge pump output that is connected to
the LED anodes. A small 1μF ceramic bypass
capacitor is required between the V_OUT pin and ground
near the device.
GND is the ground reference for the charge pump. The
pin must be connected to the ground plane on the PCB.
C1+, C1- are connected to each side of the ceramic
bucket capacitor C₁.
C2+, C2- are connected to each side of the ceramic
bucket capacitor C₂.
LED1 to LED4 provide the internal regulated current
source for each of the LED cathodes. These pins
enter high-impedance zero current state whenever the
device is placed in shutdown mode.
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.
RSET is connected to the resistor (R_SET) to set the full
scale current for the LEDs. The voltage at this pin
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.
Doc. No. MD-5023, Rev. E
8
© Catalyst Semiconductor, Inc.
Characteristics subject to change without notice