CAT3606 Datasheet, PDF (5/11 Pages) Catalyst Semiconductor – 6-Channel Low Noise Charge Pump White LED Driver

CAT3606
Basic Operation
At power-up, the CAT3606 starts operation in 1x mode. If
it is able to drive the programmed LED current, it continues
in 1x mode. If the battery voltage drops to a level where the
LED current cannot be met, the driver automatically
switches into 1.5x mode, to boost the output voltage high
enough to achieve the nominal LED current.
The above sequence is reinitialized each and every time
the chip is powered up or is taken out of shutdown mode (via
EN pin). The use of the Main and Sub display enable pins
(ENM or ENS) does not affect the mode of operation.
LED Current Setting
The LED current is set by the external resistor R_SET
connected between the RSET pin and ground. Table 5 lists
various LED currents and the associated R_SET resistor value
for standard 1% precision surface mount resistors.
Table 5. RSET Resistor Selection
LED Current (mA)
1
2
5
10
15
20
30
R_SET (kW)
649
287
102
49.9
32.4
23.7
15.4
The enable lines ENM and ENS allow to turn On or Off
a group of LEDs as shown in Table 6.
Table 6. LED Selection
Control Lines
EN
ENM ENS
0
X
X
1
1
1
1
0
1
1
1
0
1
0
0
LED Outputs
Main
Sub
LED1 − LED4 LED5 − LED6
–
–
–
–
ON
−
−
ON
ON
ON
NOTES: 1 = logic high (or VIN)
0 = logic low (or GND)
– = LED output OFF
X = don’t care
The unused LED channels can also be turned off by
connecting the respective LED pins to VOUT. In which
case, the corresponding LED driver is disabled and the
typical LED sink current is only about 0.2 mA. When the
following equation is true on any channel, the driver turns
off the LED channel:
VOUT * V_LED v 1 V (LED channel OFF)
Note: The CAT3606 is designed to drive LEDs with forward
voltage greater than 1 V and is not compatible with resistive
loads.
http://onsemi.com
5