a8530 Allegro MicroSystems, Inc., a8530 Datasheet - Page 9

• Manufacturer Part Number: a8530
• Description: Ultracompact 6-channel Backlight And Flash/torch White Led Driver
• Manufacturer: Allegro MicroSystems, Inc.

Flash/Torch LED5 and LED6 Operation The flash/torch LEDs
(LED5 and LED6) brightness and on/off can be controlled using
digital input at ENF pin. ENF accepts one-wire serial pulse input
to enable the A8530 and to set up to 11 dimming levels, from
100 mA (the default 100% level) down to 5 mA.
When the ENF pin is initially pulled up from shutdown, after a
soft-start (if the IC is not yet soft-started using the ENM pin),
the current for LED5 and LED6 is, by default, programmed to
100 mA, corresponding to 100% of flash/torch brightness. Each
subsequent pulse reduces the LED current by 10 mA, and the
10th pulse reduces the current by 5 mA. The next pulse then
restores to 100 mA (full) output current per channel. Figure 6
shows the timing diagram for ENF.
Absolute Level Operation Some applications require dimming
to a specific level, regardless of the present level of dimming.
For example, if the IC should dim to 30%, this can be done with
7 steps, as shown in figure 6, irrespective of the dimming level
in effect. This can be achieved by pulling corresponding ENx
A8530
Symbol
C1
C2
C3
t
Figure 7. Absolute Dimming Level Setting. With ENM pulled low longer the t
pulsing the corresponding ENx pin sets an absolute target level.
Parameter
V
V
I
time
OUT
ENM
OUT
Units/Division
2.00 V
2.00 V
0.5 ms
50 mA
C2
C3
C1
100%
pin low for time greater than t
shown in figure 6 (7 for 30% dimming). If the pulses are applied
within 2 to 3 ms, the display flicker is not visible. The procedure
is shown in figure 7.
Shutdown
When the ENM pin is pulled low for 0.5 ms or longer, the display
backlight channels are shut off and dimming is reset to 100%
upon the next ENM going high edge. When the ENF pin is
pulled low for 0.5 ms or longer, the brightness of the flash/torch
channels is reset to 100 mA upon the next ENF going high edge.
When both ENM and ENF are pulled low for 0.5 ms or longer,
the A8530 enters the shutdown mode.
Short Circuit Protection
The A8530 is protected against short circuits on the output. When
V
mode. The A8530 resumes normal operation when the short
circuit is removed.
ENx pulled low
OUT
and Flash/Torch White LED Driver
Ultracompact 6-Channel Backlight
is externally pulled below 1.2 V, the IC enters Short Circuit
∆t > t
SHDN
I
SET
t
counter resets
115 Northeast Cutoff, Box 15036
Allegro MicroSystems, Inc.
Worcester, Massachusetts 01615-0036 [phone]
www.allegromicro.com
SHDN
SHDN
,
and then applying pulses as
Rapid pulse pattern
30%
V
V
I
ENM
OUT
OUT
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