al8807 Diodes, Inc., al8807 Datasheet - Page 12

• Manufacturer Part Number: al8807
• Description: High Efficiency Low Emi 30v 1a Buck Led Driver
• Manufacturer: Diodes, Inc.

Applicatio
Diode Selec
For maximum
leakage at the
PN diodes, du
It is important
than the maxim
than the opera
average diode
Schottky diode
AL8807 applic
Thermal con
For continuou
maximum pow
surrounding th
The maximum
where
The recomme
determined by
θ
standing in stil
The maximum
Figure 34, sho
1oz copper sta
AL8807
Document Numbe
JA
, is layout
T
T
θ
JA
J(MAX)
A
P
P
P
is the
D(MA
D(MA
D(MA
is th
ons Informa
e maximum ope
cations.
wer dissipation
he IC, and diffe
y the AL8807’s
nsiderations
ended maximu
ows the power
he junction to a
anding in still a
ating voltage to
es, e.g. B240 o
AX)
AX)
AX)
mum output lo
e to a combina
e ambient temp
r: DS35281 Rev. 3
tion
s conduction
dependent and
l air is approxim
efficiency and
is the maximum
to select parts
current. The p
power dissipa
power dissipa
= (T
= (125°C −
= (125°C −
J(MAX)
ation can be cal
ation at T
−
− T
ambient therma
um operating j
ation of lower fo
3 - 2
ation
erating voltage
s with a peak
o ensure safe
mately 250°C/W
power rating is
or B140, with t
mode of opera
rence between
m operating jun
perature, and
d package dep
ir and the AL88
ad current. In
junction to amb
derating of the
performance,
25°C) / (250°C
25°C) / (160°C
depends on s
A
) / θ
(cont.
JA
A
= 25
Fig
g. 34 Derating
e and temperat
5°C can be calc
several factors:
n junction and a
al resistance.
C/W) = 0.4W fo
C/W) = 0.625W
e AL8807W5 o
orward voltage
pendent; the A
W (160°C/W on
807MP on an F
ation, the abso
nction tempera
their low forwa
lculated using t
junction tempe
bient thermal r
)
the rectifier (D
current rating
operation duri
verified by cal
particular, it is
HIGH E
ww
W for standard fo
AL8807W5’s θ
or single-layer P
ard voltage dro
ature,
culated by the f
FR4 51x51mm
ww.diodes.com
ture. The Scho
ambient tempe
g Curve for D
s recommende
lculating the po
: the thermal re
erature, T
n a four-layer P
FFICIENCY
olute maximum
1) should be a
above the pea
the following fo
esistance, θ
n two (one sin
ng the switchin
and reduced r
12 of 20
J
, is
JA
op and fast rev
ak coil current
ed to have a d
ower loss throu
s 125°C and
PCB).
Different PCB
Y LOW EM
recovery time.
m junction tem
ormula:
ottky diode als
J
JA
PCB
following formu
ng and a curre
esistance of th
our-layer PCB
rature.
gle-layer and f
and device pow
PCB with 2oz
fast low capac
on a 25x25
MI 30V 1A B
mperature mus
ugh the diode.
verse recovery
he IC package
ulas:
ent rating at le
four-layer) diffe
B
citance Schottk
o provides bet
iode voltage ra
so maximum
wer dissipation
mm single lay
and a continuo
copper standin
BUCK LED
east 10% highe
yer PCB with 1
erent 25x25mm
n.
ating at least 1
ky diode with lo
ng in still air.
ous current rat
, are the ideal
ter efficiency th
t not be exce
ambient temp
θ
JA
, PCB layo
AL
© Diodes
Nove
L8807
m PCB with
perature is
er than the
out, airflow
ow reverse
han silicon
ting higher
mber 2011
s Incorporated
eded. The
DRIVER
5% higher
oz copper
choice for