a6280ees-t Allegro MicroSystems, Inc., a6280ees-t Datasheet - Page 5

• Manufacturer Part Number: a6280ees-t
• Description: 3-channel Constant-current Led Driver With Programmable Pwm Control
• Manufacturer: Allegro MicroSystems, Inc.

A6280
(Output Enable Output)
Brightness Data = 1022
(Output Enable Input)
NOTE: At least one rising edge on the CI pin is needed while OE is high in order to reset the PWM counter and start
a new PWM cycle. Otherwise, when OE is brought low, the outputs will operate according to the current PWM data
and PWM count, and will finish the current cycle before resetting the count to 0. Therefore, if the counter is not reset
(as explained above) after new PWM data has been latched, the outputs will complete the current PWM cycle (up to
1024 clock pulses if no clock divider is selected, 2048 clock pulses if a divide-by count of 2 is selected, and so forth)
before starting a new PWM cycle with the new data.
Brightness Data= 0
Brightness Data= 1
(Serial Data Out)
(Serial Data In)
PWM Counter
(Latch Out)
(Latch In)
(Clock In)
(Clock In)
SDO
OEO
I
I
I
OUT0
OUT1
OUT2
t
SDI
OEI
SU (D )
t
SU (O E )
LO
CI
CI
LI
t
t
D30
P(OE)2
P(OE)
0
T
0
0
D29
t
t
1
w(C L K)
H( D)
D28 D27 D26 D24 D23 D22 D21
2
Figure 3. PWM Counter and Output Timing
T
1
3
1
Outputs Off
Outputs On
4
Figure 2. Shift Register Timing
T
2
2
t
P(OUT)
5
Timing Diagrams
3-Channel Constant-Current LED Driver
Don’t Care
6
t
P(OUT)
7
t
w (OE)
with
8
1023
Programmable
T
0
N
t
P(OUT)
D15 D14
15 16
1
2
t
SU (L I )
115 Northeast Cutoff
1.508.853.5000; www.allegromicro.com
Allegro MicroSystems, Inc.
Worcester, Massachusetts 01615-0036 U.S.A.
t
P(IO)
D0
31
D30
X
PWM Control
t
t
H (L I )
P(SD O)
0
5