AAT4610A_07 Datasheet, PDF (9/11 Pages) Advanced Analogic Technologies – Current Limited Load Switch

AAT4610A
Current Limited Load Switch
I_LIM R_SET product found in the chart "R_SET
Coefficient vs. I_LIM." The maximum current is
derived by multiplying the typical current for the
chosen R_SET in the chart by 1.25. A few standard
resistor values are listed in the table "Current Limit
R_SET Values."
Current Limit R_SET Values
R_SET
(kΩ)
40.2
30.9
24.9
22.1
19.6
17.8
16.2
14.7
13.0
10.5
8.87
7.50
6.81
6.04
5.49
4.99
4.64
Current Device Will Device Always
Limit Not Current Current Limits
Typ Limit Below
Below
(mA)
(mA)
(mA)
200
150
250
250
188
313
300
225
375
350
263
438
400
300
500
450
338
563
500
375
625
550
413
688
600
450
750
700
525
875
800
600
1000
900
675
1125
1000
750
1250
1100
825
1375
1200
900
1500
1300
1400
975
1050
1625
1750
Example: A USB port requires 0.5A. 0.5A multiplied
by 1.33 is 0.665A. From the chart named "R_SET vs.
I_LIM," R_SET should be less than 11kΩ. 10.5kΩ is a
standard value that is a little less than 11kΩ but
very close. The chart reads approximately 0.700A
as a typical I_LIM value for 10.5kΩ. Multiplying
0.700A by 0.75 and 1.25 shows that the AAT4610A
will limit the load current to greater than 0.525A but
less than 0.875A.
Operation in Current Limit
When a heavy load is applied to the output of the
AAT4610A, the load current is limited to the value of
I_LIM determined by R_SET. See Figure 2, "Overload
Operation." Since the load is demanding more cur-
rent than I_LIM, the voltage at the output drops. This
causes the AAT4610A to dissipate a larger than nor-
mal quantity of power, and its die temperature to
increase. When the die temperature exceeds an
over-temperature limit, the AAT4610A will shut down
until is has cooled sufficiently, at which point it will
startup again. The AAT4610A will continue to cycle on
and off until the load is removed, power is removed,
or until a logic high level is applied to ON.
Enable Input
In many systems, power planes are controlled by
integrated circuits which run at lower voltages than
the power plane itself. The enable input ON of the
AAT4610A has low and high threshold voltages
that accommodate this condition. The threshold
voltages are compatible with 5V TTL and 2.5V to
5V CMOS.
Reverse Voltage
The AAT4610A is designed to control current flowing
from IN to OUT. If a voltage is applied to OUT which
is greater than the voltage on IN, large currents may
flow. This could cause damage to the AAT4610A.
5
4
3
2
1
0
- 0 .0 5
1Ω load is turned on at time = 0
Output Current
Output Voltage
0
0.05
0.1
0 .15
0 .2
0.25
1
0.75
0.5
0.25
0
0.3
Figure 2: Overload Operation.
4610A.2007.06.1.4
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