2005 by Catalyst Semiconductor, Inc.
Characteristics subject to change without notice
1
CAT3604
4-Channel Regulated Charge Pump White LED Driver
Doc. No. 5008, Rev. I
I
Automatic short circuit detect/disable
I
High-frequency Operation at 1MHz
I
Low value ceramic capacitors
I
"604" compatible pinout
I
Soft start and current limiting
I
Thin QFN 16-lead package, 4x4mm, 0.8mm
max height
DESCRIPTION
The CAT3604 is a charge pump operating in either
1x (LDO) mode or 1.5x fractional mode regulating
current through each of the 4 LED pins. Operation
at a fixed high frequency of 1MHz typical allows the
use of very small value ceramic capacitors.
The CAT3604 drives white light-emitting diodes
(LEDs) connected in parallel and provides tightly
matched regulated current to achieve uniformity of
brightness in LCD backlighting applications. An
external resistor R
SET
controls the output current
level. LED currents of up to 30mA are supported
over a range of input supply voltages from 3V to
FEATURES
I
Drives individually up to 4 LEDs
I
Output current up to 30mA per LED
I
Digital control On/Off of each LED
I
Compatible with supply voltage of 3V to 5.5V
I
Power efficiency up to 93%
I
2 modes of operation 1x and 1.5x
APPLICATIONS
I
Color LCD and keypad Backlighting
I
Cellular Phones
I
Handheld Devices
5.5V, making the device ideal for battery-powered
applications.
LED dimming can be accomplished by several
methods including using a DC voltage to set the
R
SET
pin current, applying a PWM signal on the
Control signals, or adding a switched resistor in
parallel with R
SET
. The Enable input pin allows the
device to be placed in power-down mode with
"zero" quiescent current.
The CAT3604 features short circuit and overcurrent
limiting protection. The device is available in a 16-
lead thin QFN package with a max height of 0.8mm.
I
Digital Cameras
I
PDAs
I
Portable MP3 players
TYPICAL APPLICATION
CAT3604
+
-
C1+
C2+
C1-
C2-
VIN
EN
CTR0
CTR1
CTR2
RSET
VOUT
LED1
LED2
LED3
LED4
COUT
20mA
RSET
VIN
3V to 4.2V
Battery
EN
Control 0
Control 1
Control 2
CIN
GND
CAT3604
2
Doc. No. 5008, Rev. I
2005 by Catalyst Semiconductor, Inc.
Characteristics subject to change without notice
PIN CONFIGURATION
Top View
16-lead Thin QFN (4mm x 4mm)
ORDERING INFORMATION
PIN DESCRIPTIONS
16
15
14
13
12
11
10
9
1
2
3
4
5
6
7
8
EN
CTR0
CTR1
CTR2
GND
C2+
C2-
C1-
LED1
LED2 LED3
LED4
RSET VOUT
VIN
C1+
GND
Note: The package exposed pad is electrically connected inside the package to GND and to pin 12.
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CAT3604
3
Doc. No. 5008, Rev. I
2005 by Catalyst Semiconductor, Inc.
Characteristics subject to change without notice
ELECTRICAL OPERATING CHARACTERISTICS
Limits over recommended operating conditions unless specified otherwise. Typical values at T
A
= 25C, VIN = 3.5V,
I
RSET
= 5
A
ABSOLUTE MAXIMUM RATINGS
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RECOMMENDED OPERATING CONDITIONS
Note 1:
Machine model is with 200pF capacitor discharged directly into each pin.
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CAT3604
4
Doc. No. 5008, Rev. I
2005 by Catalyst Semiconductor, Inc.
Characteristics subject to change without notice
Current
Setting
1.2V Ref
1MHz
Oscillator
Mode Control
1x mode (LDO)
1.5x Charge Pump
VIN
CIN
+
-
3<VIN<4.2V
Battery
EN
RSET
CTR0
CTR1
CTR2
LED1
LED2
LED3
LED4
LED
Output
Select
4 Current
Sink Regulators
COUT
20mA
VOUT
C1-
C2-
C1+
C2+
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.
Figure 1: CAT3604 Functional Block Diagram
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.
CAT3604
5
Doc. No. 5008, Rev. I
2005 by Catalyst Semiconductor, Inc.
Characteristics subject to change without notice
s
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4
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3
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2
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0
0
0
-
-
-
N
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-
0
1
0
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N
O
-
-
0
1
1
N
O
-
-
-
1
0
0
-
-
N
O
N
O
1
0
1
-
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1
0
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1
1
-
-
-
-
Table 2: LED Selection
Notes: 1 = logic high (or VIN)
0 = logic low (or GND)
- = LED output OFF
SHORT CIRCUIT DETECT/DISABLE
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
A.
When the following equation is true on any channel,
the driver turns off the LED channel:
VOUT - V
LED
1V (LED channel OFF)
Note: The CAT3604 is designed to drive LEDs with
forward voltage greater than 1V and is not compatible
with resistive loads.
LED CURRENT SETTING
The LED current is set by the external resistor R
SET
connected between the RSET pin and ground.
Table 1 lists various LED currents and the associ-
ated R
SET
resistor value for standard 1% precision
surface mount resistors.
)
A
m
(
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(
)
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2
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2
0
1
0
1
9
.
9
4
5
1
4
.
2
3
0
2
7
.
3
2
0
3
4
.
5
1
Table 1. RSET Resistor Selection
The digital control lines CTR0, CTR1 adn CTR2
allow to turn On or Off a combition of LEDs as
shown in Table 2.
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