Step-up Converter. A8431 Datasheet

A8431 Converter. Datasheet pdf. Equivalent

Part A8431
Description White LED Driver Constant Current Step-up Converter
Feature www.DataSheet4U.com Preliminary Data Sheet Subject to Change without Notice April 5, 2005 A8431 Th.
Manufacture Allegro MicroSystems
Total Page 10 Pages
Datasheet
Download A8431 Datasheet



A8431
www.DataSheet4U.com
Preliminary Data Sheet
Subject to Change without Notice
A8431April 5, 2005
White LED Driver Constant Current Step-up Converter
A8431 MLPD
Approximate actual size
SW
GND
FB
1
2
3
6 VIN
5 OVP
4 EN
RθJA = 50 °C/W, see note 1, page 2
ABSOLUTE MAXIMUM RATINGS
SW Pin ................................................–0.3 V to 36 V
OVP Pin ..............................................–0.3 V to 36 V
Remaining Pins .................................. –0.3 V to 10 V
Ambient Operating Temperature, TA....... –40°C to 85°C
Junction Temperature, TJ(max)............................... 150°C
Storage Temperature, TS .................... –55°C to 150°C
The A8431 is a noninverting boost dc-dc converter that provides a
programmable constant current output up to 32 V for driving white
LEDs in series.The A8431 also offers an OVP (overvoltage protection)
pin. Driving the LEDs in series ensures identical currents and uniform
brightness. Up to four white LEDs can be driven at 20 mA from a single
cell Li-ion or a multicell NiMH power source. Up to two parallel strings
of eight white LEDs can be driven at 20 mA by increasing the supply
voltage up to 10 V.
The A8431 incorporates a power switch and a feedback sense amplifier
to provide a solution with minimum external components. The output
current can be set by adjusting a single external sense resistor and can
be varied with a voltage or a filtered PWM signal when dimming con-
trol is required. The high switching frequency of 1.2 MHz allows the
use of small inductor and capacitor values.
The A8431 is provided in a 0.75 mm high, 6-pin, 2 x 3 mm MLP pack-
age. It is lead (Pb) free, with 100% matte tin leadframe plating.
FEATURES
Output voltage up to 32 V (OVP level)
2.5 V to 10 V input
Drives up to 4 LEDs at 20 mA from a 2.5 V supply
Drives up to 5 LEDs at 20 mA from a 3 V supply
1.2 MHz switching frequency
300 mA switch current limit
1 µA shutdown current
OVP pin eliminates the need for an external Zener diode on the output
APPLICATIONS
LED backlights
Portable battery-powered equipment
Cellular phones
PDAs (Personal Digital Assistant)
Camcorders, personal stereos, MP3 players, cameras
Mobile GPS systems
Use the following complete part numbers when ordering:
Part Number
A8431EEH-T
Package
6-pin, MLPD
Description
Pb-Free, Surface Mount
26185.301



A8431
Preliminary Data Sheet
Subject to Change Without Notice
April 5, 2005
A8431
White LED Driver Constant Current Step-up Converter
Functional Block Diagram
FB
SW
VIN VREF
1.25 V
95 mV
A1
OVP
OVP
EN
Enable
A2
RC
CC
Σ
Ramp
Generator
1.2 MHz
Oscillator
RQ
S
Driver
GND
ELECTRICAL CHARACTERISTICS at TA = 25°C, VIN = 3 V (unless otherwise noted)
Characteristics
Symbol
Test Conditions
Min.
Input Voltage Range
Supply Current
VIN
Active
ISUP Shutdown (EN = 0 V)
2.5
Feedback Reference Voltage
Feedback Input Current
Switch Current Limit
Switch Frequency
Switch Maximum Duty Cycle
VFB
IFB
ISWLIM
FSW
D
86
0.8
85
Switch Saturation Voltage
Switch Leakage Current
Enable Input
VCE(SAT)
ISL
VSW = 5 V
Input Threshold Low
Input Threshold High
Input Leakage
Overvoltage Protection
VIL
VIH
Leakage
IIL
1.5
Output Overvoltage Rising Limit
Output Overvoltage Falling Limit
Output Overvoltage Hysteresis
OVP Pin Resistance
VOVPR
VOVPF
VOVPHYS
ROVP
28
27.5
Typ.
2.5
0.1
95
20
300
1.2
90
350
32
31.5
0.5
1.0
Max.
10
3.5
1
104
75
1.6
5
0.4
1
35
34.5
Units
V
mA
µA
mV
nA
mA
MHz
%
mV
µA
V
V
µA
V
V
V
M
Note 1. Measured with 4-layer PCB. Please refer to application note “Package Thermal Characteristics,“ for thermal perfor-
mance measurement for 2 x 3 mm MLP package for additional information.
26185.301
Allegro MicroSystems, Inc.
2
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com





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