A6278 ALLEGRO [Allegro MicroSystems], A6278 Datasheet - Page 8

• Manufacturer Part Number: A6278
• Description: Serial-Input Constant-Current Latched LED Drivers with Open LED Detection
• Manufacturer: ALLEGRO [Allegro MicroSystems]

A6278
A6279
Constant Current (R
The A6278 and A6279 allow the user to set the magnitude of
the constant current to the LEDs. Once set, the current remains
constant regardless of the LED voltage variation, the supply
voltage variation, or other circuit parameters that could otherwise
and
90
80
70
60
50
40
30
20
10
90
80
70
60
50
40
30
20
10
0
100
0
100
0
EXT
)
0.2
200
200
Figure 1. Output Current versus Current Control Resistance
0.4
Figure 2. Output Current versus Device Voltage Drop
300
300
0.6
Serial-Input, Constant-Current Latched
500
LED Drivers with Open LED Detection
500
T
0.8
A
= 25°C, V
700
700
R
EXT
T
V
A
CE
affect LED current. The output current is determined by the value
of an external current-control resistor (R
these parameters is shown in figure 1. Typical characteristics for
output current and V
of R
= 25°C
1.0
CE
1k
(Ω)
1K
(V)
= 0.7 V
EXT
.
1.2
2k
2K
1.4
CE
are shown in figure 2 for common values
R
3k
3K
R
R
EXT
115 Northeast Cutoff, Box 15036
Allegro MicroSystems, Inc.
Worcester, Massachusetts 01615-0036 [phone]
www.allegromicro.com
EXT
EXT
1.6
= 3900 Ω
= 225 Ω
= 470 Ω
5k
5K
1.8
EXT
). The relationship of
2.0
8