CAT4137
2005 Catalyst Semiconductor, Inc.
1 of 14
Doc. 5012 , Rev. A
Characteristics subject to change without notice
CMOS Boost Converter - White LED Driver
Features
Drives up to 5 White LEDs from 3V
Power Efficiency up to 87%
Low Quiescent Ground Current 0.1mA
Adjustable Output Current (up to 30mA)
High Frequency 1MHz Operation
"Zero" current shutdown mode
Operates down to 2V (from two AA batteries)
Soft start power-up
Open LED low power mode
Automatic shutdown at 1.9V (UVLO)
Thermal shutdown protection
Thin SOT23 5-Lead (1mm max height)
Product Description
The CAT4137 is a DC/DC step-up converter that
delivers a regulated output current. Operation at
a constant switching frequency of 1MHz allows
the device to be used with small value external
ceramic capacitors and inductor.
The device drives a string of white LEDs
connected in series and provides the regulated
current to control the LEDs with inherent uniform
brightness and matching. An external resistor R1
sets the output current and allows up to 30mA
current to be supported over a wide range of
input supply voltages from 2.2V to 5.5V, making
the device ideal for battery-powered applications.
Applications
LCD Backlighting
Cellular Phones
Handheld Devices
Digital Cameras
Ordering Information
Part Number
Package
Quantity
per Reel
Package
Marking
CAT4137TS
TSOT23-5
3000
LW
CAT4137TD TSOT23-5
Lead Free
1
3000
LX
Note 1: NiPdAu Lead Plating
LED dimming can be done by using a DC
voltage, a logic signal, or a pulse width
modulation (PWM) signal. The shutdown control
pin allows the device to be placed in power-down
mode with "zero" quiescent current.
In addition to thermal protection and overload
current limiting, the device also enters a very low
power operating mode during "Open LED" fault
conditions. The device is housed in a low profile
(1mm max height) 5-lead thin SOT23 package for
space critical applications.
Pin Configuration
Top View
5-Lead Thin SOT23
1mm max height
Typical Application Circuit
L: Murata LQH32CN220
D: Central CMDSH2-3 (rated 30V)
CAT4137
2005 Catalyst Semiconductor, Inc.
2 of 14
Doc. 5012 , Rev. A
Characteristics subject to change without notice
ABSOLUTE MAXIMUM RATINGS
Parameter
Rating
Unit
VIN, FB voltage
-0.3 to +7
V
SHDN* voltage
-0.3 to +7
V
SW voltage
-0.3 to 40
V
Storage Temperature Range
-65 to +160
C
Junction Temperature Range
-40 to +125
C
Lead Temperature
300
C
RECOMMENDED OPERATING CONDITIONS
Parameter
Range
Unit
VIN
2.2 to 5.5
V
SW pin voltage
0 to 24
V
Ambient Temperature Range
-40 to +85
C
LED Bias Current
1 to 30
mA
ELECTRICAL OPERATING CHARACTERISTICS
VIN = 3.6V, ambient temperature of 25C (over recommended operating conditions unless specified otherwise)
Symbol Parameter
Conditions
Min
Typ
Max
Unit
I
Q
Operating Current
V
FB
= 0.3V
V
FB
= 0.4V (not switching)
0.4
0.1
1.5
0.3
mA
I
SD
Shutdown Current
V
SHDN*
= 0V
0.1
1
A
V
FB
FB Pin Voltage
3 LEDs with I
LED
=20mA
285
300
315
mV
I
FB
FB pin input leakage
0.1
1
A
I
LED
Programmed LED Current
R1 = 10
R1 = 15
R1 = 20
28.5
19
14.25
30
20
15
31.5
21
15.75
mA
V
IH
V
IL
SHDN* Logic High
SHDN* Logic Low
Enable Threshold Level
Shutdown Threshold Level
0.4
0.8
0.7
1.5
V
V
F
SW
Switching Frequency
0.7
1
1.3
MHz
I
LIM
Switch Current Limit
250
300
400
mA
R
SW
Switch "On" Resistance
I
SW
= 100mA
1.0
2.0
I
LEAK
Switch Leakage Current
Switch Off, V
SW
= 5V
1
5
A
T
SD
Thermal Shutdown
150
C
T
HYS
Thermal Hysteresis
20
C
Efficiency
Typical Application Circuit
86
%
V
UVLO
Under-voltage lock out
(UVLO) threshold
1.9
V
V
OV-SW
Output Clamp Voltage
"Open LED" fault
29
V
CAT4137
2005 Catalyst Semiconductor, Inc.
3 of 14
Doc. 5012 , Rev. A
Characteristics subject to change without notice
Typical Characteristics
V
IN
= 3.6V, C
IN
= 1.0uF, C
OUT
= 0.22F, L = 22H with 3 LEDs at 20mA, T
AMB
=25C, unless otherwise specified.
Quiescent Current vs. VIN (Not Switching)
0
20
40
60
80
100
120
2.5
3.0
3.5
4.0
4.5
5.0
INPUT VOLTAGE [V]
SUPPLY CURRENT [uA]
VFB = 0.4V
Quiescent Current vs. VIN (Switching)
0.00
0.25
0.50
0.75
1.00
2.5
3.0
3.5
4.0
4.5
5.0
INPUT VOLTAGE [V]
SUPPLY CURRENT [mA]
FB Pin Voltage vs. Supply Voltage
290
295
300
305
310
2.5
3.0
3.5
4.0
4.5
5.0
INPUT VOLTAGE [V]
FB PIN VOLTAGE [mV]
3 LEDs
FB Pin Voltage vs. Output Current
290
295
300
305
310
0
5
10
15
20
25
30
OUTPUT CURRENT [mA]
FB PIN VOLTAGE [mV]
3 LEDs
Switching Frequency vs. Supply Voltage
0.90
0.95
1.00
1.05
1.10
2.5
3.0
3.5
4.0
4.5
INPUT VOLTAGE [V]
CLOCK FREQUENCY [MHz].
3 LEDs at 20mA
Switch ON Resistance vs. Input Voltage
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
INPUT VOLTAGE [V]
SWITCH RESISTANCE [ohm]
CAT4137
2005 Catalyst Semiconductor, Inc.
4 of 14
Doc. 5012 , Rev. A
Characteristics subject to change without notice
Typical Characteristics
V
IN
= 3.6V, C
IN
= 1.0uF, C
OUT
= 0.22F, L = 22H, with 3 LEDs at 20mA, T
AMB
=25C, unless otherwise specified.
LED Current vs. Input Voltage (3 LEDs)
0
5
10
15
20
25
30
35
2.0
2.5
3.0
3.5
4.0
4.5
5.0
INPUT VOLTAGE [V]
LED CURRENT [mA]
Rfb = 10O
Rfb = 15O
Rfb = 20O
LED Current Regulation
-0.4
-0.2
0.0
0.2
0.4
2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
INPUT VOLTAGE [V]
LED CURR
ENT VARIATION [%]
Efficiency across Supply Voltage (3 LEDs)
60
70
80
90
100
2.0
2.5
3.0
3.5
4.0
4.5
5.0
INPUT VOLTAGE [V]
EFFICIENCY [%]
20mA
15mA
Efficiency across Load Current (3 LEDs)
60
70
80
90
100
0
5
10
15
20
25
30
LED CURRENT [mA]
EFFICIENCY [%]
VIN = 3.6V
VIN = 4.2V
Efficiency across Supply Voltage (4 LEDs)
60
70
80
90
100
2.0
2.5
3.0
3.5
4.0
4.5
5.0
INPUT VOLTAGE [V]
EFFICIE
NCY [%]
20mA
15mA
Efficiency across Load Current (4 LEDs)
60
70
80
90
100
0
5
10
15
20
25
30
LED CURRENT [mA]
EFFICIENCY [%]
VIN = 3.6V
VIN = 4.2V
CAT4137
2005 Catalyst Semiconductor, Inc.
5 of 14
Doc. 5012 , Rev. A
Characteristics subject to change without notice
Typical Characteristics
V
IN
= 3.6V, C
IN
= 1.0uF, C
OUT
= 0.22F, L = 22H, with 3 LEDs at 20mA, T
AMB
=25C, unless otherwise specified.
FB Pin Voltage vs. Temperature
294
296
298
300
302
304
-50
-25
0
25
50
75
100
TEMPERATURE [C]
FB PIN VOLTAGE [mV]
3 LEDs at 20mA
Shutdown Voltage vs. Input Voltage
0.2
0.4
0.6
0.8
1.0
3.0
3.5
4.0
4.5
5.0
INPUT VOLTAGE [V]
SHUTDOWN VOLTAGE [V]
25C
85C
-40C
Under Voltage Lock Out vs. Temperature
1.6
1.7
1.8
1.9
2.0
2.1
2.2
-50
-25
0
25
50
75
100
TEMPERATURE [C]
UVLO [V]
Switching Frequency vs. Temperature
0.90
0.95
1.00
1.05
1.10
-50
-25
0
25
50
75
100
TEMPERATURE [C]
CLOCK
FREQUENCY[MHz].
20mA per LED
Switching Waveforms (3 LEDs in Series)
Switching Waveforms (2 LEDs in Series)
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