A8521 Datasheet, PDF (1/35 Pages) Allegro MicroSystems – The A8521 is a multi-output white LED driver for small-size LCD backlighting.

A8521
Wide Input Voltage Range, High Efficiency
Fault Tolerant LED Driver
Features and Benefits
• AEC-Q100 Qualified
• Wide input voltage range of 5 to 40 V for start/stop, cold
crank and load dump requirements
• Fully integrated LED current sinks and boost converter
with 60 V DMOS
• Sync function to synchronize boost converter switching
frequency up to 2.3 MHz, allowing operation above the
AM band
• Excellent input voltage transient response
• Single resistor primary OVP minimizes V_OUT leakage
• Internal secondary OVP for redundant protection
• LED current of 80 mA per channel
• Drives up to 12 series LEDs in 4 parallel strings
• 0.7% to 0.8% LED to LED matching accuracy
• PWM and analog dimming inputs
• 5000:1 PWM dimming at 200 Hz
• Provides driver for external PMOS input disconnect switch
• Extensive protection against:
▫ Shorted boost switch or inductor
▫ Shorted FSET or ISET resistor
▫ Shorted output
▫ Open or shorted LED pin
▫ Open boost Schottky
▫ Overtemperature (OTP)
Package: 20-pin TSSOP with exposed
thermal pad (suffix LP)
Not to scale
Description
The A8521 is a multi-output white LED driver for small-size
LCD backlighting. It integrates a current-mode boost converter
with internal power switch and four current sinks. The boost
converter can drive up to 48 LEDs, 12 LEDs per string, at
80 mA. The LED sinks can be paralleled together to achieve
even higher LED currents, up to 320 mA. The A8521 can
operate with a single power supply, from 5 to 40 V, which
allows the part to withstand load dump conditions encountered
in automotive systems.
The A8521 can drive an external P-FET to disconnect the input
supply from the system in the event of a fault. The A8521
provides protection against output short and overvoltage,
open or shorted diode, open or shorted LED pin, shorted
boost switch or inductor, shorted FSET or ISET resistor, and
IC overtemperature. A dual level cycle-by-cycle current limit
function provides soft start and protects the internal current
switch against high current overloads.
The A8521 has a synchronization pin that allows PWM
switching frequencies to be synchronized in the range of
580 kHz to 2.3 MHz. The high switching frequency allows
the A8521 to operate above the AM radio band.
Continued on the next page…
Applications:
LCD backlighting or LED lighting for:
▫ Automotive infotainment
▫ Automotive cluster
▫ Automotive center stack
Typical Application Circuit
V_IN
8 to 16 V
R_SC
0.033 Ω
L1
D1
Q1
10 μH
2 A / 60 V
C_IN
4.7 μF
50 V
R_ADJ
249 Ω
R_C
20 Ω
C_C
22 nF
V_C
100 kΩ
C_VDD
0.1 μF
R_ISET
8.25 kΩ
R_FSET
10 kΩ
GATE
SW
VSENSE
VIN _A8521
VDD
PAD
FAULT
PWM/EN
APWM
ISET
FSET/SYNC
OVP
LED1
LED2
LED3
LED4
COMP
AGND PGND
R_OVP
137 kΩ
C_P
120 pF
V_OUT
C_OUT
4.7 μF
50 V
R_Z
150 Ω
C_Z
0.47 μF
A8521-DS
Figure 1. Application with VIN to ground short protection, using P-MOSFET sensing