A6271 Datasheet, PDF (1/36 Pages) Allegro MicroSystems – Automotive, High-Current LED Controller

A6271
Automotive, High-Current LED Controller
FEATURES AND BENEFITS
• Automotive AEC-Q100 qualified
• Constant-current LED drive
• 4.2 to 50 V supply
• 53.3 V maximum LED string voltage
• Boost, buck-boost, and buck switching converters
• Programmable switching frequency 70 to 700 kHz
• PWM-controlled PMOS driver allows accurate LED
current control at low duty cycles
• Dimming via external PWM, internal PWM and/or
analog dimming
• Frequency dither scheme for effective spread spectrum to
reduce EMI
• Comprehensive fault protection and fault flag
PACKAGES:
16-Pin eTSSOP (LP)
with Exposed Thermal Pad
DESCRIPTION
The A6271 is a DC-DC converter controller, providing a
programmable constant-current output for driving high-power
LEDs in series. The controller is based on a programmable
fixed-frequency, peak current-mode control architecture. The
DC-DC converter can be configured in a myriad of different
switching configurations including boost, buck-boost, and
buck (ground-referenced switch).
The A6271 provides a cost-effective solution using an external
logic-level MOSFET and minimum additional external
components. The maximum LED current is set with a single
external sense resistor and can be accurately modulated using
a current reference input (analog control). External PWM
dimming is possible via the PWMIN input, which also provides
a shutdown mode.As an alternative, an internal PWM dimming
circuit can be used by programming the PWMIN and DR pins.
Either PWM scheme controls the PWMOUT output which
drives an external p-channel MOSFET connected in series
with the LED string. This MOSFET is also used to isolate the
load during certain fault conditions, including output shorts
to ground.
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Not to scale
APPLICATIONS
• Automotive high-power LED lighting systems
• Fog lights, reversing lights, daytime running lights,
position lights, headlights
VBAT
C1
4.7 µF
C2
4.7 µF
L1
56 µH
D2
C7
47 nF
R5
150 Ω
R6
1.35 Ω
A6271-DS, Rev. 5
C3
R1
2.7 kΩ
1 µF
PWM Control
C4
22 nF
VREG ^VIN
LP LN _PWMOUT
M2
GND
FAULTn
DR
A6271
OVUV
PWMIN
R8
12 Ω
M1
SG
IREF
OSC
DITH
SP
COMP
R9
1.3 kΩ
R7
4.3 kΩ
C8
4.4 µF
R11
240 kΩ
R2
73.2 kΩ
R3
110 kΩ
R4
39 Ω
C5
680 nF
C6
22 pF
R10
75 mΩ
GND
Boost Switcher Driving 14 LEDs at 150 mA
LED1
LED14
December 2, 2016