AL5812MP-13 Diodes Inc., AL5812MP-13 Datasheet - Page 8

• Manufacturer Part Number: AL5812MP-13
• Description: LED Lighting Drivers 60V 150mA ADJ Linear LED Driver
• Manufacturer: Diodes Inc.

Specifications of AL5812MP-13

• Rohs: yes
• Input Voltage: 3.5 V to 60 V
• Maximum Supply Current: 500 uA
• Maximum Operating Temperature: + 125 C
• Mounting Style: SMD/SMT
• Package / Case: MSOP-8EP
• Minimum Operating Temperature: - 40 C
• Power Dissipation: 366 mW

Application Information
PWM Dimming
The AL5812 can be used to provide LED current dimming driving the R
to ground (Figure 17). The R
shown in Figure 18.
Thermal Considerations
When designing linear LED drivers careful consideration must be given to:
A Linear LED driver has to be able to handle the large potential input voltage variations due to the supply voltage tolerance and also the variation
in LED forward voltage due to binning and temperature.
This can result in a large potential difference across the LED driver resulting in a larger than anticipated power dissipation.
For example in an 12V powered system with a 5% output voltage tolerance; the input voltage could typically vary from 12.6V down to 11.4V
driving 3 LEDs with a voltage varying from 3V to 3.5V at 100mA. This means that the LED driver has to cope with a voltage drop across varying
from approximately 3.6V to 0.9V. This means that the power dissipation of the AL5812 could be as much as 366mW.
Figure 19 below shows how the AL5812’s power dissipation capability varies with package; these values will vary with PCB size and area of
metal associated with the ground plane used for heat sinking. By increasing the area on the top layer the thermal impedance of both packages
could be improved.
AL5812
Document number: DS35616 Rev. 2 - 2
1.
2.
PWM-Dim
C
IN
the power dissipation within the LED driver
and
PCB layout/heat sinking.
0.1µF
V
IN
R
SET
Figure 17 PWM Dimming
SET
V
R
CC
SET
pin current is then effectively switched on and off causing the LED current to turn on and off. The linearity is
AL5812
(cont.)
GND
LED
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
-40 -25 -10
MSOP-8EP
U-DFN3030-6
Figure 19 Power Dissipation Derating
AMBIENT TEMPERATURE (C)
www.diodes.com
5
20 35 50 65 80 95 110 125
8 of 12
SET
pin via the current setting resistor (R
100
110
90
80
70
60
50
40
30
20
10
0
0
T = +25°C
2 LEDs
R
f
PWM
A
10
SET
= 500Hz
= 7.5k
Figure 18 PWM Dimming Linearity
20
Ω
30
DUTY CYCLE (%)
40
50
SET
60
) and a series MOSFET switch
70
80
90 100
© Diodes Incorporated
December 2012
AL5812