CAT3643
PIN DESCRIPTION
Name
LED1
LED2
LED3
RSET
EN/DIM
VOUT
VIN
C1+
C1-
C2+
C2-
GND
NC
GND
Function
LED1 cathode terminal.
LED2 cathode terminal.
LED3 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.
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
Ground Reference
Not connected inside package.
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 VOUT 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 C
1
.
C2+, C2-
are connected to each side of the ceramic
bucket capacitor C
2
.
LED1, LED2, LED3
provide the internal regulated
current sources for each of the LED cathodes. These
pins enter high-impedance zero current state when-
ever 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.
© Catalyst Semiconductor, Inc.
Characteristics subject to change without notice
9
Doc. No. MD-5022 Rev. E
CATALYST [ CATALYST SEMICONDUCTOR ]
