AL8807MP-7 Diodes Inc., AL8807MP-7 Datasheet - Page 13

• Manufacturer Part Number: AL8807MP-7
• Description: LED Lighting Drivers 36V High EFF Low EMI 1A Buck LED Driver
• Manufacturer: Diodes Inc.

Specifications of AL8807MP-7

• Product Category: LED Lighting Drivers
• Rohs: yes

Applications Information
The following equations can be used as a guide, with reference to Figure 1 - Operating waveforms.
Where:
Thermal Considerations
For continuous conduction mode of operation, the absolute maximum junction temperature must not be exceeded. The
maximum power dissipation depends on several factors: the thermal resistance of the IC package θ
surrounding the IC, and difference between junction and ambient temperature.
The maximum power dissipation can be calculated using the following formula:
where
The recommended maximum operating junction temperature, T
determined by the AL8807’s junction to ambient thermal resistance, θ
θ
standing in still air is approximately 250°C/W (160°C/W on a four-layer PCB).
The maximum power dissipation at T
Figure 35, shows the power derating of the AL8807W5 on two (one single-layer and four-layer) different 25x25mm PCB with
1oz copper standing in still air and the AL8807MP on an FR4 51x51mm PCB with 2oz copper standing in still air.
AL8807
Document number: DS35281 Rev. 4 - 2
t
ON
JA
, is layout dependent and package dependent; the AL8807W5’s θ
=
T
T
θ
V
JA
J(MAX)
A
IN
L is the coil inductance (H)
r
I
ΔI is the coil peak-peak ripple current (A) {Internally set to 0.3 x Iavg}
V
V
R
V
P
P
P
L
avg
is the ambient temperature, and
IN
LED
D
D(MAX)
D(MAX)
−
SW
D(MAX)
is the junction to ambient thermal resistance.
is the coil resistance (Ω)R
is the diode forward voltage at the required load current (V)
V
is the supply voltage (V)
is the required LED current (A)
LED
is the switch resistance (Ω) {=0.5Ω nominal}
is the maximum operating junction temperature,
is the total LED forward voltage (V)
Switch ‘On’ time
= (T
= (125°C − 25°C) / (250°C/W) = 0.4W for single-layer PCB
= (125°C − 25°C) / (160°C/W) = 0.625W for standard four-layer PCB
−
I
AVG
J(MAX)
L
Δ
x
I
(
R
− T
S
+
A
r
) / θ
L
+
R
(cont.)
JA
A
S
SW
= 25°C can be calculated by the following formulas:
is the current sense resistance (Ω)
)
1600
1400
1200
1000
800
600
400
200
0
-40 -25 -10 5
HIGH EFFICIENCY LOW EMI 36V 1A BUCK LED DRIVER
Fig. 35 Derating Curve for Different PCB
SOT25_4 Layer
SOT25_1 Layer
MSOP-8EP
AMBIENT TEMPERATURE (°C)
www.diodes.com
13 of 21
20 35 50 65 80 90 110 125
t
OFF
=
J
, is 125°C and so maximum ambient temperature is
V
JA
LED
JA
and device power dissipation.
Switch ‘Off’ time
on a 25x25mm single layer PCB with 1oz copper
+
V
D
+
L
I
Δ
AVG
I
x
(
R
S
+
r
L
)
JA
, PCB layout, airflow
AL8807
© Diodes Incorporated
June 2012