al8400 Diodes, Inc., al8400 Datasheet - Page 5

• Manufacturer Part Number: al8400
• Description: Linear Led Driver-controller With 200mv Current Sense Voltage
• Manufacturer: Diodes, Inc.

Typical Characteristics
Application Information
Description
The AL8400 Linear LED driver controller uses an external pass element to drive the LEDs and uses its FB pin to sense the
LED current through an external resistor R
allows the pass element to be either an NPN transistor or N-channel MOSFET. An external resistor, R
connected from the OUT pin to V
which the pass element requires.
Bipolar transistor as the pass element
For driving at currents in the region of about 50mA to about 400mA, the recommended NPN is DNLS320E in the SOT223
package. The high DC current gain of the DNLS320E is useful in this application, in order to minimize the current in R
design procedure is as follows, referring to Figure 2.
AL8400
Document number: DS35115 Rev. 2 - 2
210
208
206
204
202
200
198
196
194
192
190
4
T
One LED
MOSFET = DMN6068SE
A
= 25°C
6
MOSFET driving
8
Supply Voltage (V)
10
Figure 2. Application Circuit Using Bipolar Transistor
(Continued)
CC
I
I
LED
LED
. This resistor supplies the output bias current of the AL8400 together with any current
= 350mA
= 150mA
12
SET
14
. The pass element is driven by the AL8400’s open collector OUT pin which
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LINEAR LED DRIVER-CONTROLLER with
210
208
206
204
202
200
198
196
194
192
190
4
T
One LED
Transistor = FZT690B
(Min HFE ~500)
200mV CURRENT SENSE VOLTAGE
A
= 25°C
6
Bipolar transistor driving
8
Supply Voltage (V)
10
I
LED
= 350mA
12
I
LED
= 150mA
B
, is required to be
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AL8400
© Diodes Incorporated
March 2011
16
B
. The
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