CAT3606
6-Channel Low Noise Charge Pump White LED Driver
FEATURES
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Drives up to 4 main LEDs and 2 sub LEDs
Separate control for main and sub LEDs
Compatible with supply voltage of 3V to 5.5V
Power efficiency up to 90%
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White LED detect circuitry on all channels
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Shutdown current less than 1µA
Small ceramic capacitors
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Soft start and current limiting
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Short circuit protection
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16-lead thin QFN package, 0.8mm
max height
Output current up to 30mA per LED
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High-frequency Operation at 1MHz
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2 modes of operation 1x and 1.5x
APPLICATIONS
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Cell phone main and sub-display backlight
Navigation
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PDAs
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Digital Cameras
DESCRIPTION
The CAT3606 controls up to four LEDs for the main
display and two LEDs for the sub-display in cellular
phones. The device is capable of operating in either
1x (LDO) mode or 1.5x charge pump mode. All LED
pin currents are regulated and tightly matched to
achieve uniformity of brightness across the LCD
backlight. An external resistor (R
SET
) sets the
nominal output current.
The device can deliver as much as 20mA per
channel during low voltage operation (3V), and
30mA per channel during nominal operation (3.3V).
A constant high-frequency switching scheme
(1MHz) provides low noise and allows the use of
very small value ceramic capacitors.
A “zero” quiescent current mode can be achieved
via the chip enable pin EN. The Main and Sub LEDs
each have their own dedicated ON/OFF control
pins (ENM,
ENS).
Dimming can be achieved using
either a DC voltage to control the R
SET
pin current,
or by applying a PWM signal on the
ENM
and
ENS
pins.
The device is available in a 16-lead thin QFN
package with a max height of 0.8mm.
TYPICAL APPLICATION CIRCUIT
C1+
VIN
Li-Ion
Battery
+
-
CIN
C1- C2+
C2-
VOUT
Main Display
Sub Display
COUT
CAT3606
ON/OFF
ENABLE
LED1-4
ENABLE
LED5-6
EN
ENM
ENS
RSET
RSET
GND
LED6
LED1
LED2
LED3
LED4
LED5
20mA
© 2005 by Catalyst Semiconductor, Inc.
Characteristics subject to change without notice
1
Doc. No. 5009, Rev. B
CAT3606
ORDERING INFORMATION
Part Number
CAT3606HS4
CAT3606HV4
Package
Thin QFN-16 4x4mm
Thin QFN-16 4x4mm
Lead Free
Quantity per Reel
2000
2000
Package Marking
C366
G366
PIN CONFIGURATION
Top View
LED5 LED4 LED3 LED2
16
LED6
1
15
14
13
12 LED1
11 C2+
GND PAD
ENM
3
10 C2-
9 C1-
5
6
7
VIN
8
C1+
EN
2
ENS
4
RSET VOUT
16-lead Thin QFN (4mm x 4mm)
Note: The "exposed pad" under the package must be connected to the ground plane on the PCB.
PIN DESCRIPTIONS
Pin Number
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
PAD
Name
LED6
EN
ENM
ENS
RSET
VOUT
VIN
C1+
C1-
C2-
C2+
LED1
LED2
LED3
LED4
LED5
GND
Function
LED6 cathode terminal
Enable/shutdown input, active high
Enable "main" input for LED1 to LED4, active low
Enable "sub" input for LED5 and LED6, active low
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
LED 1 cathode terminal
LED 2 cathode terminal
LED 3 cathode terminal
LED 4 cathode terminal
LED 5 cathode terminal
Ground reference
Doc. No. 5009, Rev. B
2
© 2005 by Catalyst Semiconductor, Inc.
Characteristics subject to change without notice
CAT3606
ABSOLUTE MAXIMUM RATINGS
Parameter
VIN, VOUT, LEDx voltage
EN, ENM, ENS 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
o
C
o
C
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
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LED
per LED pin
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OUT
Total Output Current
Rating
3.0 to 5.5
-40 to +85
1 +20% typical
0 to 30
0 to 150
Unit
V
o
C
µF
mA
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
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Q
V
RSET
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LED
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LED
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LED
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LED-ACC
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LED-DEV
R
OUT
f
OSC
T
DROPOUT
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EN-CTR
V
EN-CTR
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SC
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LIM
Parameter
Quiescent Current
RSET Regulated Voltage
Programmed LED Current
LED Current Range with 6 LEDs
LED Current Range with 4 LEDs
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
Conditions
V
EN
= 0V
1x Mode, No Load
1.5x Mode, No Load
Min
Typ
0.1
0.3
2.6
1.2
2.4
15.0
30.0
Max
1
1
5
1.23
Unit
µA
mA
mA
V
mA
mA
mA
mA
mA
mA
%
%
%
Ω
Ω
MHz
ms
µA
V
V
mA
mA
1.17
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RSET
= 5µA
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RSET
= 37µA
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RSET
= 78µA
3.3
≤
VIN
≤
4.5 V
3.0
≤
VIN
≤
4.5 V
3.0
≤
VIN
≤
4.5V
0.5mA
≤
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LED
≤
3mA
3mA
≤
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LED
≤
30mA
(I
LED
- I
LEDAVG
) / I
LEDAVG
1x Mode
1.5x Mode, I
OUT
= 100mA
0.8
0.4
On Inputs EN, ENM, ENS
On Inputs EN, ENM, ENS
VOUT = GND
VOUT > 1V
3
30
20
30
+15
+5
+3
1.4
6.5
1.0
0.6
2.5
10
1.3
0.9
1
0.4
30
200
0.8
0.7
45
400
1.3
60
600
© 2005 by Catalyst Semiconductor, Inc.
Characteristics subject to change without notice
Doc. No. 5009, Rev. B
CAT3606
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
LED3
LED4
20mA
1.2V
Reference
RSET
Current
Setting
Main
Sub
LED5
LED6
6 Current
Sink Regulators
ENM
ENS
LED Output
Selection
GND
Figure 1: CAT3606 Functional Block Diagram
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 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
Table 1. RSET Resistor Selection
Doc. No. 5009, Rev. B
4
© 2005 by Catalyst Semiconductor, Inc.
Characteristics subject to change without notice
CAT3606
The enable lines
ENM
and
ENS
allow to turn On or
Off a group of LEDs as shown in Table 2.
Control Lines
EN
0
1
1
1
1
ENM
X
1
0
1
0
ENS
X
1
1
0
0
LED Outputs
Sub
Main
LED1 - LED4
LED5 - LED6
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 0.2mA. 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 CAT3606 is designed to drive LEDs with
forward voltage greater than 1V and is not
compatible with resistive loads.
-
-
ON
-
ON
-
-
-
ON
ON
Table 2: LED Selection
Notes: 1 = logic high (or VIN)
0 = logic low (or GND)
- = LED output OFF
X = don't care
© 2005 by Catalyst Semiconductor, Inc.
Characteristics subject to change without notice
5
Doc. No. 5009, Rev. B
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