AAT4608
Current Limited Load Switch in SOT23 Package
Functional Block Diagram
IN
OUT
Under-
voltage
Lockout
Over-Temp
Protection
1.2V
Reference
Current
Limit
SET
R
SET
GND
Applications Information
Setting Current Limit
In most applications, the variation in I
LIM
must be
taken into account when determining R
SET.
The I
LIM
variation is due to processing variations from part
to part, as well as variations in the voltages at IN
(Pin 5) and OUT (Pin 1), plus the operating tem-
perature. See charts "Current Limit vs.
Temperature," and "Output Current vs. V
OUT
."
Together these three factors add up to a ±25% tol-
erance (see I
LIM
specification in Electrical
Characteristics section). In the figure below, a cold
device with a statistically higher current limit, and a
hot device with a statistically lower current limit,
both with R
SET
equal to 10.5kΩ, are shown. While
the chart, "R
SET
vs. I
LIM
" indicates an I
LIM
of 0.7A
with an R
SET
of 10.5kΩ, this figure shows that the
actual current limit will be at least 0.525A, and no
greater than 0.880A.
1.2
1
Current Limit Using 10.5kΩ
0.88 A
Device with high current limit at -40°C
0.8
I
LIM
(A)
0.6
0.4
0.525 A
Device with low current limit at 85°C
0.2
0
0
1
2
3
4
5
V
OUT
(V)
To determine R
SET,
start with the maximum current
drawn by the load and multiply it by 1.33.
(Typical_I
LIM
= minimum_I
LIM
/ 0.75.) This is the
typical current limit value. Next, refer to "R
SET
vs.
I
LIM
" and find the R
SET
that corresponds to the typ-
6
4608.2006.03.1.3
AAT [ ADVANCED ANALOG TECHNOLOGY, INC. ]
