A8508 View Datasheet(PDF) - Allegro MicroSystems
Part Name
Description
MFG CO.
A8508
Allegro MicroSystems
'A8508' PDF : 28 Pages View PDF
A8508
Wide Input Voltage Range, High Efficiency
8-Channel Fault Tolerant LED Driver
ELECTRICAL CHARACTERISTICS1 (continued) Valid at VIN = 12 V, TA = 25°C, indicates specifications guaranteed by design
and characterization over the full operating temperature range with TA = TJ = –40°C to 105°C; unless otherwise noted
Characteristics
Symbol
Test Conditions
Min.
Typ.
Max.
Unit
Boost Switch Gate Driver (continued)
Soft Start Boost Current Limit
Reference Voltage
VSWSS(LIM)
Reference voltage for boost switch current
limit during soft start.
−
39
−
mV
Minimum Switch On-Time
Minimum Switch Off-Time
Oscillator Frequency
tSWONTIME
tSWOFFTIME
−
−
110
ns
−
−
85
ns
Oscillator Frequency
FSET/SYNC Pin Voltage
Synchronization
fSW
VFSET
RFSET = 7.5 kΩ
RFSET = 10 kΩ
RFSET = 20 kΩ
RFSET = 8.25 kΩ
725
800
875
kHz
540
600
660
kHz
−
300
−
kHz
−
1.00
−
V
Synchronized PWM Frequency
Synchronization Input
Minimum Off-Time
fSWSYNC
tPWSYNCOFF
300
−
800
kHz
150
−
−
ns
Synchronization Input
Minimum On-Time
tPWSYNCON
150
−
−
ns
LED Current Sinks
LEDx Accuracy
LEDx Matching
LEDx Regulation Voltage
ISET to ILEDx Current Gain
ISET Pin Voltage
Allowable ISET Current
LEDx Pin Short Detect
ErrLED
ΔLEDx
VLED
AISET
VISET
ISET
VLEDSC
ISET = 100 μA
ISET = 100 μA
VLED1 through VLED8 all equal, ISET = 100 μA
ISET = 100 μA
While LED sinks are in regulation, sensed
from LEDx pin to GND
–
0.7
–
%
–
0.8
2.5
%
−
650
−
mV
–
1160
–
A/A
−
1.000
−
V
34
−
130
μA
4.6
−
−
V
Soft Start LEDx Current Gain
PWM High to LED-On Delay
ILEDSS
tdPWM(on)
Current through each enabled LEDx pin
during soft start, RISET = 12.4 kΩ
Time between PWM enable and LEDx
current reaching 90% of maximum
−
44
−
A/A
−
0.5
1.1
μs
PWM Low to LED-Off Delay
tdPWM(off)
Time between PWM enable going low and
LEDx current reaching 10% of maximum
−
−
500
ns
Continued on the next page…
Allegro MicroSystems, Inc.
6
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
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