A8511 Datasheet, PDF (1/24 Pages) Allegro MicroSystems – 2 MHz, 4 Channel × 150 mA WLED/RGB Driver

A8511
2 MHz, 4 Channel × 150 mA WLED/RGB Driver
with Output Disconnect
Features and Benefits
▪ Four LED sinks rated for 150 mA each (600 mA total)
▪ Boost converter with integrated 40 V DMOS switch and
OVP–load-dump protection
▪ 600 kHz to 2.2 MHz switching frequency—ability to
operate above the AM band
▪ Internal bias supply for single-supply operation (V_IN=6.8 to 21V)
▪ 3.5 μA shutdown current—limits battery drain
▪ Active current sharing between LED strings for
0.8% current matching and 0.7% accuracy
▪ 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
The A8511 is a multioutput WLED/RGB driver for backlight-
ing medium-size displays. It is a fully integrated high-brightness
(HB) LED driver solution that does not require external power
devices to complete the backlighting design criteria.TheA8511
integrates FETs for a boost converter as well as four 150 mA
current sinks, offering a complete integrated solution at HB
LED current levels. LED channels can be tied together for up to
600 mA sink capability. It can work from a single power supply
of 6.8 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 avoiding 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 up to a 1000:1 ratio. Additional 4:1 dimming
can be achieved by using the DIM pin.
The A8511 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 100% matte-tin
leadframe plating.
Applications include:
▪ GPS navigation systems
▪ Automotive infotainment
▪ Back-up camera displays
▪ Cluster backlighting
▪ Portable DVD players
▪ Industrial LCD displays
Figure 1. LCD monitor backlight driving
4 LED strings. On/off and dimming
control using ENABLE pin.
• Current = 50 mA per string
• OVP = 35 V nominal
• Switching frequency = 2 MHz
A8511
8511-DS
RVC
NTC
VTO
VTI
–t°
Optional Configuration
for Thermal Derating
Typical Application
V_BAT
CBAT
4.7 μF
35 V
CCOMP
1 μF
10 V
CBIAS
0.1 μF
10 V
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
A8511
RFSET
25.5 kΩ
FSET
BIAS
PAD
NC
SEL2
SEL1
VTO
VTI
LED1
LED2
LED3
ISET
LED4
AGND PGND PGND PGND LGND DGND