DataSheet39.com

What is A8431?

This electronic component, produced by the manufacturer "Allegro MicroSystems", performs the same function as "White LED Driver Constant Current Step-up Converter".


A8431 Datasheet PDF - Allegro MicroSystems

Part Number A8431
Description White LED Driver Constant Current Step-up Converter
Manufacturers Allegro MicroSystems 
Logo Allegro MicroSystems Logo 


There is a preview and A8431 download ( pdf file ) link at the bottom of this page.





Total 10 Pages



Preview 1 page

No Preview Available ! A8431 datasheet, circuit

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

line_dark_gray
A8431 equivalent
Preliminary Data Sheet
Subject to Change Without Notice
April 5, 2005
A8431
White LED Driver Constant Current Step-up Converter
Device Operation
The A8431 uses a constant-frequency, current-mode control
scheme to regulate the current through the load. The load
current produces a voltage across the external sense resistor
(R1 in schematic 1) and the input at the FB pin. This voltage
is then compared to the internal 95 mV reference to produce
an error signal. The switch current is sensed by the internal
sense resistor and compared to the load current error signal.
As the load current increases, the error signal diminishes,
reducing the maximum switch current and thus the current
delivered to the load. As the load current decreases, the
error signal rises, increasing the maximum switch current
and thus increasing the current delivered to the load.
To set the load current, ensure that the required internal
reference value of 95 mV is produced at the desired load. To
do so, select a resistance value for the sense resistor, R1 (),
such that:
R1 = 95 mV ILOAD
where ILOAD is the target load current (mA).
The table below shows typical values for R1. Note that the
resistance value is from the standard E96 series.
As load current is reduced, the energy required in the
inductor, L1, diminishes, resulting in the inductor current
dropping to 0 A for low load-current levels. This is known
as Discontinuous mode operation, and results in some low-
frequency ripple. The average load current, however, remains
regulated down to 0 A.
In Discontinuous mode, when the inductor current drops to
0 A, the voltage at the SW pin rings, due to the capacitance
in the resonant LC circuit formed by the inductor and the
capacitance of the switch and the diode. This ringing is
low-frequency and is not harmful. It can be damped with a
resistor across the inductor, but this reduces efficiency and is
not recommended.
Overvoltage Protection
An overvoltage event can occur when the LEDs become
disconnected or fail in an open state. In these cases, the
current flow through the sense resistor, R1, becomes 0 A and
thus the feedback voltage, VFB becomes 0 V. The A8431
compensates by increasing the on time of the switch, which
increases the output voltage.
The A8431 has built-in protection to guard against excessive
voltage on the SW pin. If the output voltage exceeds the
typical level of the Output Overvoltage Rising Limit, VOVPR,
then the overvoltage protection circuitry shuts off the internal
switch until the output voltage falls below the Output
Overvoltage Falling Limit, VOVPF . At this point, the A8431
operates normally. There is no need for an external Zener
diode for the A8431.
120
110
100
90
80
70
60
50
40
30
20
10
0
5
Power Dissipation versus IOUT
10
Vin = 3V, 3 LED
15
IOUT (mA)
20
Vin = 5V, 3 LED
Vin = 3V, 4 LED
25
Vin = 5V, 4 LED
26185.301
Target Load Current
(ILOAD)
(mA)
5
10
12
15
20
Sense Resistor (R1)
()
19.1
9.53
7.87
6.34
4.75
Allegro MicroSystems, Inc.
5
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com


line_dark_gray

Preview 5 Page


Part Details

On this page, you can learn information such as the schematic, equivalent, pinout, replacement, circuit, and manual for A8431 electronic component.


Information Total 10 Pages
Link URL [ Copy URL to Clipboard ]
Download [ A8431.PDF Datasheet ]

Share Link :

Electronic Components Distributor


An electronic components distributor is a company that sources, stocks, and sells electronic components to manufacturers, engineers, and hobbyists.


SparkFun Electronics Allied Electronics DigiKey Electronics Arrow Electronics
Mouser Electronics Adafruit Newark Chip One Stop


Featured Datasheets

Part NumberDescriptionMFRS
A8430The function is White LED Driver Constant Current Step-up Converter. Allegro MicroSystemsAllegro MicroSystems
A8431The function is White LED Driver Constant Current Step-up Converter. Allegro MicroSystemsAllegro MicroSystems
A8434The function is 6-Channel High Efficiency Charge Pump White LED Driver. Allegro MicroSystemsAllegro MicroSystems

Semiconductors commonly used in industry:

1N4148   |   BAW56   |   1N5400   |   NE555   |  

LM324   |   BC327   |   IRF840  |   2N3904   |  



Quick jump to:

A843     1N4     2N2     2SA     2SC     74H     BC     HCF     IRF     KA    

LA     LM     MC     NE     ST     STK     TDA     TL     UA    



Privacy Policy   |    Contact Us     |    New    |    Search