A8518 Datasheet, PDF (1/30 Pages) Allegro MicroSystems – Fully integrated 42 V MOSFET for boost converter

A8518 and A8518-1
Wide Input Voltage Range, High-Efficiency,
Fault-Tolerant LED Driver
FEATURES AND BENEFITS
• Automotive AEC-100 qualified
• Fully integrated 42 V MOSFET for boost converter
• Fully integrated LED current sinks
• Withstands surge input to 40 V_IN for load dump
• Operates down to 3.9 V_IN (max) for idle stop
• Drives two strings of LEDs
• Maximum output voltage 40 V
□□Up to 11 white LEDs in series
• Drive current for each string is 200 mA
• Fixed 2.15 MHz boost switching frequency
• Dithering of boost switching frequency to reduce EMI
(A8518 only)
• Extremely high LED contrast ratio
□□10,000:1 using PWM dimming alone
□□100,000:1 when combining PWM and analog dimming
• Excellent input voltage transient response at lowest
PWM duty cycle
• Gate driver for optional P-channel MOSFET input
disconnect switch
• LED current accuracy 0.7%
Continued on the next page…
Package: 16-Pin TSSOP with Exposed Thermal
Pad (suffix LP)
DESCRIPTION
The A8518 is a multi-output LED driver for small-size LCD
backlighting. It integrates a current-mode boost converter
with internal power switch and two current sinks. The boost
converter can drive up to 22 white LEDs, 11 LEDs per string, at
200 mA. The LED sinks can be paralleled together to achieve
higher LED currents up to 400 mA. The A8518 operates from
a single power supply from 4.5 to 40 V, which allows the part
to withstand load dump conditions encountered in automotive
systems.
The A8518 can control LED brightness through a digital
(PWM) signal. An LED brightness contrast ratio of 10,000:1
can be achieved using PWM dimming at 100 Hz; a higher ratio
of 100,000:1 is possible when using a combination of PWM
and analog dimming.
If required, theA8518 can drive an external P-channel MOSFET
to disconnect input supply from the system in the event of a
fault. The A8518 provides protection against output short,
overvoltage, open or shorted diode, open or shorted LED pin,
and overtemperature. A cycle-by-cycle current limit protects
the internal boost switch against high-current overloads.
Continued on the next page…
Not to scale
APPLICATIONS:
• Automotive infotainment backlighting
• Automotive cluster
• Automotive center stack
V_IN
C_IN
V_C
R_PU
*optional
L1
D1
R_SC
Q1
R_ADJ
R_OVP
GATE
VSENSE
VIN
VDD
SW
VOUT
OVP
C_VDD
A8518
LED1
FAULT
PWM
APWM
ISET
R_ISET
LED2
COMP
AGND PGND
C_P
GND
V_OUT > V_IN
C_OUT1
C_OUT2
R_Z
C_Z
Typical Application Circuit Showing VOUT-to-Ground Short Protection Using Optional P-Channel MOSFET
A8518-DS, Rev. 4
October 24, 2016