CAT3604
4-Channel Regulated Charge Pump White LED Driver
FEATURES
s
s
s
s
s
Drives individually up to 4 LEDs
Output current up to 30mA per LED
Digital control On/Off of each LED
Compatible with supply voltage of 3V to 5.5V
Shutdown current less than 50nA typical
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High-frequency Operation at 1MHz
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Power efficiency up to 93%
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2 modes of operation 1x and 1.5x
Low value ceramic capacitors
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Compatible pinout with the SC604
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Soft start and current limiting
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Thin QFN 16-lead package, 4x4mm, 0.8mm
max height
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APPLICATIONS
Color LCD and keypad Backlighting
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Cellular Phones
s
Handheld Devices
s
Digital Cameras
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PDAs
s
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Portable MP3 players
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
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.
TYPICAL APPLICATION
C1+
VIN
Battery
+
-
VIN
3V to 4.2V
EN
CIN
Control 0
Control 1
Control 2
EN
CTR0
CTR1
CTR2
RSET
GND
RSET
C1- C2+
C2-
VOUT
COUT
CAT3604
LED1
LED2
LED3
LED4
20mA
© 2004 by Catalyst Semiconductor, Inc.
Characteristics subject to change without notice
Doc. No. 5008, Rev. B
1
CAT3604
ORDERING INFORMATION
Part Number
CAT3604HS4
Package
Thin QFN-16 4x4mm
Top View
LED1 LED2 LED3 LED4
16
EN
1
15
14
13
12 GND
11 C2+
GND
CTR1
3
10 C2-
9 C1
5
6
7
VIN
8
C1+
Quantity per Reel
3500
Package Marking
C364
PIN CONFIGURATION
CTR0
2
CTR2
4
RSET VOUT
Thin QFN
4mm x 4mm
16-lead
Note: The package exposed pad is electrically connected inside the package to GND and to pin 12.
PIN DESCRIPTIONS
Pin Number
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
Pad
Name
EN
CTR0
CTR1
CTR2
RSET
VOUT
VIN
C1+
C1-
C2-
C2+
GND
LED4
LED3
LED2
LED1
GND Pad
Function
Enable input, active HIGH
Digital control input 0
Digital control input 1
Digital control input 2
The LED output current is set by the current sourced out of the RSET pin
Charge pump output connected to the LED anodes
Supply voltage
Bucket capacitor 1 terminal
Bucket capacitor 1 terminal
Bucket capacitor 2 terminal
Bucket capacitor 2 terminal
Ground reference
LED 4 cathode terminal
LED 3 cathode terminal
LED 2 cathode terminal
LED 1 cathode terminal
Ground reference
Doc. No. 5008, Rev. B
2
CAT3604
ABSOLUTE MAXIMUM RATINGS
Parameter
VIN, VOUT, LEDx voltage
EN, CTRx voltage
RSET voltage
RSET current
Ambient Temperature Range
Storage Temperature Range
Lead Temperature
ESD Ratings
Human Body Model (HBM)
Machine Model (MM) (note 1)
Note 1:
Rating
-0.3 to 7.0
-0.3 to VIN
-0.3 to VIN
+1
-40 to +85
-65 to +160
300
2000
200
Unit
V
V
V
mA
o
C
C
C
o
o
V
V
Machine model is with 200pF capacitor discharged directly into each pin.
RECOMMENDED OPERATING CONDITIONS
Parameter
VIN
Ambient Temperature Range
Input/Output/Bucket Capacitors
I
LED
per LED pin
Rating
3.0 to 5.5
-40 to +85
1 +20% typical
0 to 30
Unit
V
o
C
µF
mA
ELECTRICAL OPERATING CHARACTERISTICS
Limits over recommended operating conditions unless specified otherwise. Typical values at T
A
= 25˚C, VIN = 3.5V,
I
RSET
= 5µA
Symbol
I
Q
V
RSET
I
LED
I
LED-ACC
I
LED-DEV
R
OUT
f
OSC
T
DROPOUT
I
EN-CTR
V
EN-CTR
I
SC
I
LIM
Parameter
Quiescent Current
RSET Regulated Voltage
Programmed LED Current
LED Current Accuracy
LED Channel Matching
Output Resistance
(Open Loop)
Charge Pump Frequency
1x to 1.5x Mode Transition
Dropout Delay
Input Leakage Current
High Detect Threshold
Low Detect Threshold
Input Current Limit
Maximum Input Current
On Inputs EN, CTR0, 1 & 2
On Inputs EN, CTR0, 1 & 2
VOUT = GND
VOUT > 1V
3
Conditions
V
EN
= 0V Shutdown Mode
1x Mode, No Load
1.5x Mode, No Load
Min
Typ
0.05
0.3
2.6
Max
1
1
5
1.23
Unit
µA
mA
mA
V
mA
mA
mA
%
%
1.17
I
RSET
= 5µA
I
RSET
= 37µA
I
RSET
= 78µA
0.5mA < I
LED
< 3mA
3mA < I
LED
< 30mA
(I
LED -
I
LEDAVG
) / I
LEDAVG
1x Mode
1.5x Mode, I
OUT
= 100mA
0.8
0.4
1.2
2.4
15.0
30.0
+15
+5
+3
1.4
6.5
1.0
0.6
0.001
2.5
10
1.3
0.9
1
1.3
60
600
%
Ω
Ω
MHz
ms
µA
V
V
mA
mA
0.4
30
200
0.8
0.7
45
400
Doc. No. 5008, Rev. B
CAT3604
BLOCK DIAGRAM
C1-
C1+ C2-
C2+
3<VIN<4.2V
Battery
+
-
VIN
CIN
1x mode (LDO)
1.5x Charge Pump
VOUT
COUT
1MHz
Oscillator
EN
Mode Control
LED1
LED2
1.2V Ref
RSET
Current
Setting
LED
Output
Select
LED3
LED4
20mA
CTR0
CTR1
CTR2
4 Current
Sink Regulators
Figure 1: CAT3604 Functional Block Diagram
BASIC OPERATION
The device provides an output voltage to support
the desired LED current in all 4 LEDs. The output
voltage depends on the forward voltage (Vf) char-
acteristics of the LEDs. Typically, when the input
voltage VIN is higher that the output voltage VOUT,
the driver operates in 1x mode or LDO mode. When
the input voltage VIN is lower than the LED forward
voltage plus the current source dropout, the driver
operates in 1.5x mode or fractional charge pump
mode where the device boosts the voltage to 1.5
times the input.
At power-up, the CAT3604 starts operation in 1x
mode. If it is able to drive the requested LED
current, it stays in 1x mode. If the current source
drops out of regulation, in other words the LED
current cannot be met, the driver goes into 1.5x
mode and boost the output voltage high enough so
that the LED current can be reached.
Doc. No. 5008, Rev. B
4
CAT3604
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.
LED Current (mA)
1
2
5
10
15
20
30
R
SET
(k
Ω
)
649
287
102
49.9
32.4
23.7
15.4
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 20µA.
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.
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.
Control Lines
CTR2
0
0
0
0
1
1
1
1
CTR1
0
0
1
1
0
0
1
1
CTR0
0
1
0
1
0
1
0
1
LED4
-
-
-
ON
-
-
ON
-
-
-
ON
-
-
ON
ON
-
LED Outputs
LED3
LED2
-
ON
-
-
ON
ON
ON
-
LED1
ON
-
-
-
ON
ON
ON
-
Table 2: LED Selection
Notes: 1 = logic high (or VIN)
0 = logic low (or GND)
- = LED output OFF
5
Doc. No. 5008, Rev. B
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