al8400 Diodes, Inc., al8400 Datasheet - Page 9

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

Application Information
MOSFET Example
Finally, the maximum power dissipation of the external MOSFET is:
This determines the package choice (θ
Stability
In order to maintain the stability of the current control loop, a capacitor, C
Ground. The value is determined by the minimum time constant, C
0.1µF or greater. The capacitor type is recommended to be X7R ceramic.
For best stability a power supply decoupling capacitor, C
between V
OFFLINE LED LAMPS
The configuration of the AL8400 also makes it suitable for controlling the current of an offline (mains) isolated LED lamp by
way of an opto-coupler to drive the feedback pin of the primary-side switching controller.
The current sensing of the LED current is done via R
coupler. See Figure 4 below.
AL8400
Document number: DS35115 Rev. 2 - 2
P
T
TOT
J
CC
and Ground.
= I
= I
= T
= T
LED
LED
A
A
+ P
+ 0.27*62.5 = T
* (V
* V
(Continued)
TOT
DSMAX
CC
• θ
– V
JA
LEDMIN
Figure 4. Off-line LED Drive Application of AL8400
(Continued)
A
– V
+ 16.86˚C
JA
) in order to keep the junction temperature below the maximum value allowed.
REF
) = 0.27W
SET
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but the OUT pin now drives the cathode of the diode in the opto-
9 of 12
D
is recommended, 0.1µF minimum, X7R ceramic, connected
LINEAR LED DRIVER-CONTROLLER with
L
R
B
≥ 1ms. For example if R
200mV CURRENT SENSE VOLTAGE
L
, is required to be connected from the OUT pin to
B
= 10kΩ, then C
AL8400
© Diodes Incorporated
March 2011
L
must be