A8501 Datasheet, PDF (1/24 Pages) Allegro MicroSystems – 2 MHz, 4 Channel100 mA WLED/RGB Driver

A8501
2 MHz, 4 Channel×100 mA WLED/RGB Driver
with Output Disconnect
Features and Benefits
▪ 600 kHz to 2.2 MHz switching frequency—ability to
operate above the AM band
▪ Internal bias supply for single-supply operation (V_IN = 8 to 21 V)
▪ Boost converter with integrated 40 V DMOS switch and
OVP–load-dump protection
▪ 3.5 μA shutdown current—limits battery drain
▪ Active current sharing between LED strings for
0.8% current matching and 0.7% accuracy
▪ Drive up to 9 series LEDs in 4 parallel strings, 36 LEDs
maximum (V_f = 3.5 V, I_f = 100 mA)
▪ LED sinks rated for 100 mA each (400 mA total)
▪ PWM dimming with LED PWM duty cycle control
▪ 4000:1 dimming range
▪ Extensive fault mode protection schemes:
▫ Shorted LED protection against misconnected loads—
with true output disconnect
▫ Open LED disconnect protects against LED failures
▫ External thermistor sensing to limit LED temperature
▫ Output overvoltage protection (OVP): 19.5 V default can
be adjusted as high as 38 V
▫ Open Schottky and open OVP resistor protection against
external component failure
▫ Input under- and overvoltage protection (UVLO and
OVLO) against V_IN variation
▫ Boost current limit, output short circuit limit,
overtemperature protection (OTP), and soft start
Package:
Not to scale
28-pin TSSOP with
exposed thermal pad
(package LP)
Description
TheA8501 is a multioutputWLED/RGB driver for backlighting
medium-size displays. The A8501 integrates a boost converter
and four 100 mA current sinks. LED channels can be tied
together for up to 400 mA sink capability. It can work from
a single power supply of 8 to 21 V and withstand up to 40 V.
The boost converter is a constant frequency, current-mode
converter.
Operating frequency can be set to 2 MHz in order to avoid
interference with the AM radio band. The integrated boost
DMOS switch is rated for 40 V at 3.6 A. PWM dimming allows
LED currents to be controlled at up to a 1000:1 ratio.Additional
4:1 dimming can be achieved by using the DIM pin.
TheA8501 provides protection against output connector shorts
through an integrated output disconnect switch. An optional
external thermistor can be used to limit LED current based on
panel temperature.
The device is supplied in a surface mount, 28-pin TSSOP
package (suffix LP), with exposed thermal pad for enhanced
thermal dissipation. It is lead (Pb) free, with a leadframe
plating choice of 100% matte-tin (suffix T) or tin-bismuth
(suffix B).
Applications include:
▪ GPS navigation systems
▪ Automotive infotainment
▪ Back-up camera displays
▪ Cluster backlighting
▪ Portable DVD players
▪ Industrial LCD displays
Typical Application
Figure 1. LCD monitor backlight driving
V_BAT
8 to 21 V _CBAT
4.7 μF
35 V
4 LED strings. On/off and dimming
control using ENABLE pin.
CCOMP
• Current = 50 mA per string
1 μF
• OVP = 35 V nominal
10 V
• Switching frequency = 2 MHz
CBIAS
A8501
0.1 μF
10 V
RVC
NTC
VTO
VTI
–t°
Optional Configuration
for Thermal Derating
RISET
24.3 kΩ
D1
CIN
L1
10 μH
ROVP
78.7 kΩ
COUT
4.7 μF
50 V
VIN
SW SW SW OVP CAP
EN
OUT
COMP
DIM
A8501
RFSET
25.5 kΩ
FSET
BIAS
NC
PAD
SEL2
SEL1
VTO
LED1
LED2
VTI
LED3
ISET
LED4
AGND PGND PGND PGND LGND DGND
8501-DS, Rev.3