Datasheet

CAT3649
http://onsemi.com
9
Table 5. PIN DESCRIPTION
Pin No Name Function
1 C1+ Bucket capacitor 1 Positive terminal
2 C1− Bucket capacitor 1 Negative terminal
3 C2+ Bucket capacitor 2 Positive terminal
4 C2− Bucket capacitor 2 Negative terminal
5 GND Ground Reference
6 LED1 LED1 cathode terminal.
7 LED2 LED2 cathode terminal.
8 LED3 LED3 cathode terminal.
9 LED4 LED4 cathode terminal.
10 LED5 LED5 cathode terminal.
11 LED6 LED6 cathode terminal.
12 ADIM Analog Dimming Control (Active high).
13 PWM Pulse width modulation ‘PWM’ (Active high).
14 CPWM Connect a capacitor for filtering the PWM signal.
15 VOUT Charge pump output connected to the LED anodes.
16 VIN Charge pump input, connect to battery or supply.
TAB 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 2.4 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.
ADIM is the 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 ADIM first transitions from low to high,
each LED channel current is set to 25 mA. Each subsequent
pulse will decrement the current by about 3% from the full
scale.
PWM is the pulse width modulation input pin. When in
logic high condition, the LED current in all six channels
equals the programmed level set via ADIM. When PWM is
low, the LED current is set to 0 mA. This allows the average
LED current to be programmed by the PWM duty cycle. To
place the device into “zero current” shutdown mode, the
ADIM or PWM pin must be held low for 20 ms typical.
VOUT is the charge pump output that is connected to the
LED anodes. A small 1 mF 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 to LED6 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.
CPWM is the pin for connecting an external capacitor used
to filter the PWM signal inside the CAT3649.