CAT3643
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9
Table 6. PIN DESCRIPTION
Name Function
LED1 LED1 cathode terminal.
LED2 LED2 cathode terminal.
LED3 LED3 cathode terminal.
RSET Connect resistor RSET to set the LED current.
EN/DIM Device enable (active high) and Dimming Control.
VOUT Charge pump output connected to the LED anodes.
VIN Charge pump input, connect to battery or supply.
C1+ Bucket capacitor 1 Positive terminal
C1− Bucket capacitor 1 Negative terminal
C2+ Bucket capacitor 2 Positive terminal
C2− Bucket capacitor 2 Negative terminal
GND Ground Reference
NC Not connected inside package.
GND Connect to GND on the PCB.
Pin Function
VIN is the supply pin for the charge pump. A small 1 mF
ceramic bypass capacitor is required between the VIN pin
and ground near the device. The operating input voltage
range is from 2.5 V to 5.5 V. Whenever the input supply falls
below the under−voltage threshold (1.8 V), 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
1.3 V and 0.4 V 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 1.5 ms.
VOUT is the charge pump output that is connected to the
LED anodes. A small 1 m F 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 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
0.6 V. The ground side of the external resistor should be star
connected back to the GND of the PCB. In shutdown mode,
RSET becomes high impedance.
