AL8808WT-7 Diodes Inc., AL8808WT-7 Datasheet - Page 9

• Manufacturer Part Number: AL8808WT-7
• Description: LED Lighting Drivers LED MV Int Switch TS Switch TSOT25 T&R 3K
• Manufacturer: Diodes Inc.

Specifications of AL8808WT-7

• Rohs: yes
• Input Voltage: 6 V to 30 V
• Operating Frequency: 1 MHz
• Maximum Supply Current: 450 uA
• Maximum Operating Temperature: + 125 C
• Mounting Style: SMD/SMT
• Package / Case: TSOT-25
• Minimum Operating Temperature: - 40 C

Applicatio
AL8808 Opera
In normal opera
inductor L1, and
voltage and the
This rising curre
voltage to the in
When this voltag
L1, the LEDs an
of the LEDs and
This decaying c
applied at the in
This switch-on-a
LED Current C
The LED curren
connected from
with CTRL left flo
If the CTRL pin i
For example for
When the CTRL
AL8808
Document number
on Informat
ent produces a vo
ation, when volta
d the schottky dio
nput of the intern
L voltage is broug
nd the schottky d
and-off cycle con
nt is controlled b
d the LEDs. The
r: DS35648 Rev. 2
ation
ge reaches an in
Control
put of the interna
urrent produces
oating. If the CT
is driven by an e
inductor L1.
the CTRL pin to
a desired LED c
age is applied at
by the resistor R
diode D1, and ba
ode.
o an internal 5V r
current of 660mA
e current ramps
oltage ramp acro
al comparator.
ght below 0.4V, t
tion
nternally set upp
RL pin is left floa
al comparator. W
tinues to provide
xternal voltage (
- 2
a falling voltage
per threshold, the
e at R1, which is
A and V
oss R1. The inter
ack to the supply
ating or driven ab
When this voltag
e the average LE
regulator. When
1
higher than 0.5V
he output switch
+V
up linearly, and
(in Figure 32)
IN
Figure 32.
, the AL880
CTRL
R
Where
Where
SET
=2.5V
=
=
ED current set by
V and lower than
I
h is turned off wh
y rail, but it decay
d the ramp rate
bove 2.5V the no
e V
rnal circuit of the
e internal switch
L
LED
w
www.diodes.co
08 internal switc
V or with the CTR
e falls to the inte
V
connected betw
Typical Applica
the CTRL pin is
sensed by the A
I
V
LED
TH
I
REF
TH
LED
=
is nominally
9 of 20
V
=
is nomina
V
=
CTRL
REF
. 0
0
V
R
66
1 .
TH
1
V
R
R
ween V
≈
ally 2.5V
y the sense resist
ominal average o
y 100mV.
ch is turned on.
s left floating it ge
T
TH
AL8808. A voltag
ys, with the rate
ernally set lower
ation Circuit
RL pin left open
m
1
ich allows PWM
is determined b
2.5V), the avera
150
AL8808 senses
is turned off. Th
m
IN
Ω
and SE
ET pins. The AL8
by the input volta
s the voltage acro
age LED current
r threshold, the in
he inductor curre
ge proportional to
tor R1.
ets pulled up to 5
Current starts to
utput current in t
the resulting res
of decay determ
dimming.
mined by the forw
o flow through se
oss R1 and appli
ent continues to
nternal switch is
8808 has an inte
the LED(s) is def
age (+V
5V - increasing i
o the sense volt
is:
istor is:
IN
) minu
us the LED chain
ward voltage drop
ernal 50k resisto
ense resistor R1
ies a proportiona
its noise rejectio
fined as:
age across R1 is
flow through R1
© Diodes Incorporate
turned on again
AL8808
January 201
n.
al
or
ed
n
p
s
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