AL8807AMP-13 Diodes Inc., AL8807AMP-13 Datasheet - Page 14

• Manufacturer Part Number: AL8807AMP-13
• Description: LED Lighting Drivers High EFF DIMM 36V 1A / 1.3A Buck LED
• Manufacturer: Diodes Inc.

Specifications of AL8807AMP-13

• Rohs: yes
• Input Voltage: 6 V to 36 V
• Operating Frequency: 1 MHz
• Maximum Supply Current: 1 A
• Mounting Style: SMD/SMT
• Package / Case: MSOP-8EP

Application Information
The inductor value should be chosen to maintain operating duty cycle and switch 'on'/'off' times over the supply voltage and load current range.
The following equations can be used as a guide, with reference to Figure 39 – typical switching waveform.
Switch ‘On’ time
Switch ‘Off’ time
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
between junction and ambient temperature.
The maximum power dissipation can be calculated using the following
formula:
where
The recommended maximum operating junction temperature, T
and so maximum ambient temperature is determined by the AL8807A’s
junction to ambient thermal resistance, θ
θ
25 x 25mm single layer PCB with 1oz copper standing in still air is
approximately +250°C/W and around 130°C/W on a 51mm x 51mm dual layer
board with maximum coverage top and bottom and 3 vias.
The maximum power dissipation at T
following formulas:
Figure 40, shows the power derating of the AL8807AW5 on two different PCBs and the AL8807AMP on one PCB.
Figure 40 shows that the MSOP-8EP version of the AL8807A can handle more power than its SOT25 version. So the AL8807AMP is the
preferred variant when operating at larger supply voltage rails (>24V) and/or driving larger LED currents. This is especially true in high power
density/space constraint applications such as high power 24VAC MR16 applications.
AL8807A
Document number: DS35990 Rev. 1 - 2
JA
L is the coil inductance (H)
r
R
I
ΔI is the coil peak-peak ripple current (A)
V
V
R
V
, is layout dependent and package dependent; the AL8807AW5’s θ
L
avg
IN
LED
D
S
SW
{Internally set to
is the coil resistance (Ω)
is the current sense resistance (Ω)
is the diode forward voltage at the required load current (V)
SOT25 – 25mm x 25mm: AL8807AW5’s θ
SOT25 – 25mm x 25mm: AL8807AW5’s θ
MSOP-8EP - 51mm x 51mm: AL8807AMP’s θ
is the supply voltage (V)
is the required LED current (A)
is the switch resistance (Ω) {= 0.25Ω nominal (SOT25)}
T
T
θ
is the total LED forward voltage (V)
P
P
P
t
t
JA
J(MAX)
A
ON
OFF
D(MAX)
D(MAX)
D(MAX)
is the ambient temperature,
is the junction to ambient thermal resistance.
=
=
V
is the maximum operating junction temperature,
= (T
= (+125°C − +25°C) / (250°C/W) = 0.4W for single-layer 25mm x25mm PCB
= (+125°C − +25°C) / (130°C/W) =0.77W for dual layer 51mm x 51mm PCB
V
IN
LED
−
J(MAX)
V
+
LED
V
0.3 x Iavg}
D
− T
−
+
L
I
AVG
I
A
Δ
AVG
) / θ
L
I
Δ
x
I
JA
x
(
R
(
R
S
S
(cont.)
A
+
JA
+
r
= +25°C can be calculated by the
r
L
and device power dissipation.
L
+
)
R
SW
JA
JA
on a 25 x 25mm single layer PCB with 1oz copper
on a 51mm x 51mm dual layer board with maximum coverage top and bottom and 3 vias
)
JA
on a 51mm x 51mm dual layer board with maximum coverage top and bottom and 4 vias
www.diodes.com
J
, is +125°C
14 of 20
JA
on a
Off
Figure 39 Typical Switching Waveform
JA
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
, PCB layout, airflow surrounding the IC, and difference
0
-40 -25 -10
SOT25
51mm x 51mm
SOT25
25mm x 25mm
MSOP-8EP
51mm x 51mm
V
T
2 LEDs
20ns/div
SW Pin: 2V/div
A
IN
Figure 40 Derating Curve for Different PCB
= 25°C
= 12V
On
AMBIENT TEMPERATURE (°C)
5
20 35 50 65 80 95 110 125
AL8807A
© Diodes Incorporated
September 2012