Multiple-Output Regulator for

Automotive LCD Displays

A8603

28

Allegro MicroSystems, LLC

115 Northeast Cutoff

Worcester, Massachusetts 01615-0036 U.S.A.

1.508.853.5000; www.allegromicro.com

AB

C

DE

F

G

VGH

FAULT

(pull-up to VIN)

BIAS (IC

internal supply)

EN (external

enable)

VIN

(power supply)

VGL

VCOM

AVDD

Internal

Enable

0

0

0

0

90%

90%

Startup Phase

(Regulator OCP not recorded)

Normal Operation Phase

(Regulator OCP recorded)

50 ms

FAULT = L if overcurrent

persists for 50 ms

VGH tripped current

limit in normal op phase

VGH operating

at current limit

t1

t2

t3

t4

t≥ 0

Sequence of events:

A: System controller brings EN = H to enable the A8603.

other faults detected).

D: After programming the A8603 registers, system controller sets the internal_enable bit to 1, to turn on all output regulators.

E: The last regulator (VGH in this example) starts charging.

F: When all regulators have reached 90% of regulation target, the A8603 declares Startup Phase over and enters into normal operation phase.

However, VGH is still operating at its current limit, to charge its output cap to 100% . Therefore A8603 records this overcurrent status in

Reg0x18, bit3. This is not considered a fault.

G: During normal operation phase, if any regulator shows overcurrent for 50 ms, then the A8603 will pull FAULT = L and shutdown all regula-

tors in sequence.

Figure 16: Timing Diagram Showing when a Regulator Overcurrent Condition is Reported