AAT4611 Datasheet, PDF (8/10 Pages) Advanced Analogic Technologies – Current Limited Load Switch in SOT-23 Package

AAT4611
Current Limited Load Switch in SOT23 Package
Functional Block Diagram
IN
Under-
Voltage
Lockout
Over-Temperature
Protection
OUT
ON (ON)
1.2V
Reference
Current
Limit
GND
SET
R_SET
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) and the operating temper-
ature. See charts "Current Limit vs. Temperature"
and "Output Current vs. Output Voltage." Together,
these three factors add up to a ±25% tolerance
(see I_LIM specification in Electrical Characteristics
section). In Figure 1, a cold device with a statisti-
cally 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.
8
1.2
1
0.88A
Device With High Current Limit at -40°C
0.8
0.6
0.4
0.525 A
Device With Low Current Limit at 85°C
0.2
0
0
1
2
3
4
5
Output Voltage (V)
Figure 1: Current Limit Using 10.5kΩ.
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 typical current limit
value; choose the largest resistor available that is
less than or equal to it. For greater precision, the
value of R_SET may also be calculated using the I_LIM
R_SET product found in the chart "R_SET Coefficient vs.
4611.2006.09.1.4