CAT32
CMOS White LED Driver
Description
The CAT32 is a DC/DC step up converter that delivers a regulated
output current. Operation at a constant switching frequency of
1.2 MHz allows the device to be used with very small value external
inductor and ceramic capacitors.
The CAT32 is targeted to drive multiple white light−emitting diodes
(LEDs) connected in series and provides the necessary regulated current
to control the brightness and the color purity. An external resistor R
SET
controls the output current level. LED currents of up to 40 mA can be
supported over a wide range of input supply voltages from 2 V to 7 V,
making the device ideal for battery−powered applications.
A high voltage output stage allows up to 4 White LEDs to be driven
in series. Series drive provides inherent current matching.
LED dimming can be done by using a DC voltage, a logic signal, or
a pulse width modulation (PWM) signal. The shutdown input pin
allows the device to be placed in power−down mode with “near zero”
quiescent current.
In addition to overcurrent limiting protection, the device also
includes detection circuitry to ensure protection against open−circuit
load fault conditions.
The device is available in a low profile (1 mm max height) 6−lead
TSOT−23 package.
Features
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1
TSOT−23
TD SUFFIX
CASE 419AF
PIN CONNECTIONS
1
SW
GND
LED
VIN
SHDN
RSET
TSOT−23
1 mm Maximum Height
q
JA
= 250°C/W (free air)
(Top View)
•
•
•
•
•
•
•
•
•
•
•
•
•
Low Quiescent Ground Current (0.5 mA Typical)
Power Efficiency Over 80%
Compatible Pinout with LT1932
Adjustable Output Current (up to 40 mA)
High Frequency 1.2 MHz Operation
Input Voltage Operation down to 2.0 V
Low Resistance (0.5
W)
High Voltage Power Switch
Drives up to 4 White LEDs in Series
Shutdown Current Less than 1
mA
Load Fault Protection Against Open−circuits
Low Value External Components
Low Profile (1 mm) TSOT−23 6−lead Package
These Devices are Pb−Free, Halogen Free/BFR Free and are RoHS
Compliant
MARKING DIAGRAMS
VFYM
VF = CAT32TDI−GT3
Y = Production Year (Last Digit)
M = Production Month (1−9, A, B, C)
ORDERING INFORMATION
Device
CAT32TDI−GT3
Package
TSOT−23
(Pb−Free)
Shipping
3,000/
Tape & Reel
Applications
•
•
•
•
•
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Color LCD and Keypad Backlighting
Cellular Phones
Handheld Terminals
Digital Cameras
PDAs/Games
Portable MP3 Players
©
Semiconductor Components Industries, LLC, 2014
1
April, 2014 − Rev. 5
Publication Order Number:
CAT32/D
CAT32
Typical Application Circuit
L
1
6.8
mH
VIN
2.7 V
to
4.2 V
D1
C1: Taiyo Yuden JMK212BJ475
C2: Taiyo Yuden EMK212BJ105
D1: Zetez ZHCS400
L1: Sumida CLQ4D106R8
(Panasonic ELJEA6R8)
C1
4.7
mF
6
VIN
CAT32
1
SW
PWM
DIMMING
CONTROL
5
SHDN
RSET
4
R
SET
1.50 kW
LED
GND
2
3
15 mA
C2
1
mF
TSOT−23 Pin Numbers
Figure 1. Li−Ion Driver for Four High−Brightness White LEDs
Table 1. PIN DESCRIPTION
Pin Number
SOT23
1
2
3
4
5
6
−
Pin Number
TDFN
8
5
6
4
3
2
1
Name
SW
GND
LED
RSET
SHDN
VIN
Power
Ground
Function
Switch pin. This is the drain of the internal power switch. For minimum EMI, min-
imize the trace area connected to this pin.
Ground pin. Connect pin 2 to ground.
LED (cathode) connection pin.
RESET pin. A resistor connected from pin 4 to ground sets the LED current. This
pin is also used to dim the LEDs.
Shutdown pin.
Input supply pin. This pin should be bypassed with a capacitor to ground. A
4.7
mF
capacitor mounted close to the pin is recommended.
Power Ground
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CAT32
Table 2. ABSOLUTE MAXIMUM RATINGS
Parameter
V
IN
, LED, SHDN voltage
SW voltage
RSET voltage
Storage Temperature Range
Junction Temperature
Lead Soldering Temperature (10 secs)
ESD Rating – Human Body Model
Rating
8
20
1
−65 to +150
125
300
2000
Unit
V
V
V
°C
°C
°C
V
Stresses exceeding those listed in the Maximum Ratings table may damage the device. If any of these limits are exceeded, device functionality
should not be assumed, damage may occur and reliability may be affected.
Table 3. RECOMMENDED OPERATING CONDITIONS
Parameter
V
IN
Ambient Temperature Range
Inductor L1
Input Capacitor C1
Output Capacitor C2
I
LED
with 1 to 4 LEDs in series
Range
2 to 7
−40 to +85
6.8
±20%
typical
4.7
±20%
typical
1.0
±20%
typical
0 to 20
Unit
V
°C
mH
mF
mF
mA
Functional operation above the stresses listed in the Recommended Operating Ranges is not implied. Extended exposure to stresses beyond
the Recommended Operating Ranges limits may affect device reliability.
NOTE: Typical application circuit with external components is shown on page 2.
Table 4. ELECTRICAL OPERATING CHARACTERISTICS
(Over recommended operating conditions unless otherwise specified. T
A
= 25°C, V
IN
= 2 V and V
SHDN
= 1.2 V.)
Symbol
I
Q
I
GND
V
LED
I
LED
I
LED
Parameter
Quiescent Current
Ground Current in Shutdown
LED Pin Voltage
LED Current Adjust Range
Programmed LED Current
R
SET
= 562
W
R
SET
= 750
W
R
SET
= 1.5 kW
R
SET
= 4.53 kW
I
LED
V
RSET
LED Pin Current Temperature Coefficient
RSET Pin Voltage
Shutdown Pin Logic High Level
Shutdown Pin Logic Low Level
f
SW
I
SWL
R
SW
Boost Converter Frequency
Switch Current Limit
Switch Resistance
V
IN
= 2 V, I
SW
= 100 mA
V
IN
= 3 V, I
SW
= 100 mA
Switch Leakage Current
Efficiency
Switch Off, V
SW
= 5 V
Components shown on Figure 1
0.8
400
1.2
550
0.7
0.5
0.01
83
I
LED
= 15 mA
R
SET
= 1.5 kW
0.85
0.25
1.6
780
1.2
0.9
5
mA
%
Conditions
V
RSET
= 0.2 V
V
SHDN
= 0 V
V
IN
< V
OUT
, I
LED
= 15 mA
5
33
25
12.5
38
30
15
5
−0.01
100
mA/°C
mV
V
V
MHz
mA
W
Min
Typ
0.5
0.05
120
Max
0.7
1
180
40
45
36
17.5
Unit
mA
mA
mV
mA
mA
Product parametric performance is indicated in the Electrical Characteristics for the listed test conditions, unless otherwise noted. Product
performance may not be indicated by the Electrical Characteristics if operated under different conditions.
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CAT32
TYPICAL CHARACTERISTICS
(V
IN
= 3.6 V, T
AMB
= 25°C, C
IN
= 4.7
mF,
C
OUT
= 1
mF,
L = 6.8
mH,
unless otherwise specified.)
600
QUIESCENT CURRENT (mA)
QUIESCENT CURRENT (mA)
600
VIN = 7 V
500
VIN = 2 V
400
500
400
300
300
200
2
3
4
5
6
7
INPUT VOLTAGE (V)
200
−50
−25
0
25
50
75
100
125
TEMPERATURE (°C)
Figure 2. Quiescent Current vs. Input Voltage
2.0
SWITCH FREQUENCY (MHz)
SWITCH FREQUENCY (MHz)
2.0
Figure 3. Quiescent Current vs. Temperature
1.6
1.6
1.2
1.2
0.8
0.8
0.4
0
2
3
4
5
6
7
INPUT VOLTAGE (V)
0.4
0
−50
−25
0
25
50
75
100
125
TEMPERATURE (°C)
Figure 4. Switching Frequency vs. Input
Voltage
35
R
SET
= 750
W
30
LED CURRENT (mA)
25
20
15
10
5
0
2
3
4
5
6
7
INPUT VOLTAGE (V)
0
−50
R
SET
= 1.13 kW
R
SET
= 1.50 kW
R
SET
= 2.26 kW
LED CURRENT (mA)
15
20
Figure 5. Switching Frequency vs.
Temperature
10
5
−25
0
25
50
75
100
125
TEMPERATURE (°C)
Figure 6. LED Current vs. Input Voltage
Figure 7. LED Current vs. Temperature
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CAT32
TYPICAL CHARACTERISTICS
(V
IN
= 3.6 V, T
AMB
= 25°C, C
IN
= 4.7
mF,
C
OUT
= 1
mF,
L = 6.8
mH,
unless otherwise specified.)
1.0
SWITCH RESISTANCE (W)
SWITCH RESISTANCE (W)
1.0
0.8
0.8
0.6
0.6
V
IN
= 3 V
0.4
0.4
0.2
0
2
3
4
INPUT VOLTAGE (V)
5
6
0.2
0
−50
−25
0
25
50
75
100
125
TEMPERATURE (°C)
Figure 8. Switch Resistance vs. Input Voltage
300
250
200
150
100
50
0
0
8
16
24
32
40
LED CURRENT (mA)
Figure 9. Switch Resistance vs. Temperature
LED PIN VOLTAGE (mV)
Figure 10. LED Pin Voltage vs. LED Current
85
Figure 11. V
SW
, I
L
, & V
OUT
Signal Waveforms
80
EFFICIENCY (%)
75
4 LEDs at 15 mA
V
OUT
= 13 V
70
65
60
2
3
4
INPUT VOLTAGE (V)
5
6
Figure 12. Efficiency vs. Input Voltage
Figure 13. PWM on SHDN Pin Waveform
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