CAT3604 Datasheet, PDF (5/11 Pages) Catalyst Semiconductor – 4-Channel Regulated Charge Pump White LED Driver

CAT3604
Basic Operation
At power-up, the CAT3604 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. The 1.5x charge pump will boost
the output voltage accordingly to achieve the nominal LED
current.
The operating mode 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 control pins (CTR0, CTR1, CTR2)
does not reconfigure 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.
The digital control lines CTR0, CTR1 and CTR2 allow to
turn On or Off a combition of LEDs as shown in Table 6.
Short Circuit Detect/Disables
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 20 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 CAT3604 is designed to drive LEDs with forward
voltage greater than 1 V and is not compatible with resistive
loads.
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
Table 6. LED Selection
Control Lines
CTR2 CTR1 CTR0 LED4
0
0
0
–
0
0
1
–
0
1
0
–
0
1
1
ON
1
0
0
–
1
0
1
–
1
1
0
ON
1
1
1
–
NOTE: 1 = logic high (or VIN)
0 = logic low (or GND)
– = LED output OFF
LED Outputs
LED3 LED2
–
–
–
ON
ON
–
−
–
–
ON
ON
ON
ON
ON
–
–
LED1
ON
–
–
–
ON
ON
ON
–
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