CAT32
CMOS White LED Driver
FEATURES
s
Low quiescent ground current (0.5mA typical)
s
Power efficiency over 80%
s
Compatible pinout with LT1932
s
Adjustable output current (up to 40mA)
s
High frequency 1.2MHz operation
s
Input voltage operation down to 2.0V
s
Low resistance (0.5Ω) high voltage
Ω
H
GEN
FR
ALO
EE
LE
s
Drives up to 4 White LEDs in series
s
Shutdown current less than 1µA
A
D
F
R
E
E
TM
s
Load fault protection against open-circuits
s
Low value external components
s
Low profile (1mm) 6-lead SOT23 and TDFN
(0.8mm) package
power switch
APPLICATIONS
s
Color LCD and keypad backlighting
s
Cellular phones
s
Handheld terminals
s
Digital cameras
s
PDAs/Games
s
Portable MP3 players
DESCRIPTION
The CAT32 is a DC/DC step up converter that delivers
a regulated output current. Operation at a constant
switching frequency of 1.2MHz 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 40mA
can be supported over a wide range of input supply
voltages from 2V to 7V, 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 (1mm max height)
6-lead thin SOT23 package and in a TDFN (0.8mm max
height) package.
D1
TYPICAL APPLICATION
VIN
2.7V to 4.2V
6
VIN
1
SW
PWM
DIMMING
CONTROL
CAT32
5
SHDN
RSET
4
LED
GND
2
3
15mA
SOT23 Pin Numbers
C1: Taiyo Yuden JMK212BJ475
C2: Taiyo Yuden EMK212BJ105
D1: Zetez ZHCS400
L1: Sumida CLQ4D106R8
(Panasonic ELJEA6R8)
Figure 1. Li-Ion Driver for Four High-Brightness White LEDs
© 2004 by Catalyst Semiconductor, Inc.
Characteristics subject to change without notice
1
Doc No. 5001, Rev. AC
CAT32
ORDERING INFORMATION
Part Number
CAT32EKT-TE7
CAT32RD4-TE7
CAT32RD4
CAT32TDI-TE7
Package
6-lead, thin SOT23
8-pad TDFN (3x3mm)
8-pad TDFN (3x3mm)
6-lead thin SOT23,
Lead Free
Tube
Quantity
—
Reel
Quantity
3000
3500
—
Package
Marking Code
BD
CCEM
CCEM
LL
—
120
—
3000
PIN CONFIGURATION
SW
GND
LED
1
2
3
CAT32
6
5
4
VIN
SHDN
RSET
Power 1
GROUND
VIN 2
SHDN
3
RSET 4
8 SW
7 NC
6 LED
5 GND
6-Lead SOT-23
1mm maximum height
θ
[Free Air]
(Top View)
TDFN Package: 3mm x 3mm
0.8mm maximum height
(RD4)
PIN DESCRIPTIONS
Pin Number
SOT23
1
Pin Number
TDFN
8
Name
SW
Function
Switch pin. This is the drain of the internal power
switch. For minimum EMI, minimize 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 4.7µF capacitor
mounted close to the pin is recommended.
Power Ground
2
3
4
5
6
4
GND
LED
RSET
5
6
3
2
SHDN
VIN
—
1
Power
Ground
Doc. No. 5001, Rev. AC
2
CAT32
ABSOLUTE MAXIMUM RATINGS
These are stress ratings only and functional operation is not implied. Exposure to absolute maximum ratings for
prolonged time periods may affect device reliability. All voltages are with respect to ground.
V
IN
, LED,
SHDN
Voltage ....................................... 8V
SW Voltage ........................................................... 20V
RSET Voltage ......................................................... 1V
Junction Temperature ....................................... 125°C
Lead Soldering Temperature (10 secs) ............ 300°C
Storage Temperature .......................... -65°C to 150°C
ESD Rating - Human Body Model .................... 2000V
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
µH
µF
µF
mA
ELECTRICAL SPECIFICATIONS
Over recommended operating conditions unless otherwise specified. T
A
= 25°C, V
IN
= 2V and V
SHDN
= 1.2V.
Symbol
I
Q
I
GND
V
LED
I
LED
Parameter
Quiescent Current
Ground Current in Shutdown
LED Pin Voltage
LED Current Adjust Range
R
SET
= 562
Ω
I
LED
Programmed LED Current
R
SET
= 750
Ω
R
SET
= 1.5k
Ω
R
SET
= 4.53k
Ω
I
LED
V
RSET
LED Pin Current Temperature Coefficient
R
SET
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
Switch Leakage Current
Efficiency
V
IN
= 2V, I
SW
= 100mA
V
IN
= 3V, I
SW
= 100mA
Switch Off, V
SW
= 5V
Components shown
on Figure 1
0.8
400
1.2
550
0.7
0.5
0.01
83
I
LED
= 15mA
R
SET
= 1.5k
Ω
0.85
0.25
1.6
780
1.2
0.9
5
Conditions
V
RSET
= 0.2V
V
SHDN
= 0V
V
IN
< V
OUT
, I
LED
=15mA
5
33
25
12.5
38
30
15
5
-0.01
100
mA/° C
mV
V
V
MHz
mA
Ω
Ω
µA
%
Min
Typ
0.5
0.05
120
Max
0.7
1
180
40
45
36
17.5
mA
Units
mA
µA
mV
mA
3
Doc No. 5001, Rev. AC
CAT32
TYPICAL CHARACTERISTICS
V
IN
=3.6V, T
AMB
=25˚C, C
IN
=4.7µF, C
OUT
=1µF, L=6.8µH, unless otherwise specified.
Quiescent Current vs. Input Voltage
600
Quiescent Current vs. Temperature
600
.
VIN = 7V
500
500
400
400
VIN = 2V
300
300
200
2
3
4
5
6
7
INPUT VOLTAGE [V]
200
-50
-25
0
25
50
75
100
125
Switching Frequency vs. Input Voltage
2.00
1.60
1.20
0.80
0.40
0.00
2
3
4
5
6
7
INPUT VOLTAGE [V]
Switching Frequency vs. Temperature
2.0
SWITCH FREQUENCY [MHz]
SWITCH FREQUENCY [MHz]
1.6
1.2
0.8
0.4
0.0
-50
-25
0
25
50
75
100
125
LED Current vs. Input Voltage
35
Rset = 750
LED Current vs. Temperature
20
LED CURRENT [mA]
30
LED CURRENT [mA]
6
7
25
20
15
Rset = 1.13k
Rset = 1.5k
15
10
5
0
2
3
10
Rset = 2.26k
5
4
5
INPUT VOLTAGE [V]
0
-50
-25
0
25
50
75
100
125
Doc. No. 5001, Rev. AC
4
CAT32
TYPICAL CHARACTERISTICS
V
IN
=3.6V,T
AMB
=25˚C, C
IN
=4.7µF, C
OUT
=1µF, L=6.8µH, unless otherwise specified.
Switch Resistance vs. Input Voltage
SWITCH RESISTANCE [Ohm] .
1.0
0.8
0.6
0.4
0.2
0.0
2
3
4
5
6
INPUT VOLTAGE [V]
Switch Resistance vs. Temperature
SWITCH RESISTANCE [Ohm] .
1.0
0.8
0.6
0.4
0.2
0.0
-50
-25
0
25
50
75
100
125
VIN = 3V
LED Pin Voltage vs. LED current
300
250
200
150
100
50
0
0
8
16
24
32
LED CURRENT [mA]
40
Vsw, I
L
, & Vout Signal Waveforms
VIN = 3.7V with 15mA load through 4 LEDs
Efficiency vs. Input Voltage
85
EFFICIENCY (%) .
80
75
70
65
60
2
3
4
5
INPUT VOLTAGE [V]
6
4 LEDs at 15mA
Vout =13V
PWM on SHDN pin Waveform
5
Doc No. 5001, Rev. AC
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