CAT3604
BLOCK DIAGRAM
C1-
C1+ C2-
C2+
1x mode (LDO)
1.5x Charge Pump
3<VIN<4.2V
Battery
VOUT
VIN
+
-
C
C
IN
OUT
Mode Control
1MHz
Oscillator
EN
LED1
LED2
LED3
LED4
20mA
1.2V Ref
RSET
Current
Setting
4 Current
Sink Regulators
CTR0
CTR1
CTR2
LED
Output
Select
Figure 1: CAT3604 Functional Block Diagram
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 nomi-
nal 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)doesnotreconfigurethe
mode of operation.
© 2005 by Catalyst Semiconductor, Inc.
Characteristics subject to change without notice
Doc. No. 5008, Rev. I
4
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