AAT4610 Datasheet, PDF (9/10 Pages) Advanced Analogic Technologies – Current Limited Load Switch in SOT-23 Package

AAT4610
Current Limited Load Switch
the value of R_SET may also be calculated using the
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 Table 1.
R(k_SΩET)
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
Limit
Typ (mA)
200
250
300
350
400
450
500
550
600
700
800
900
1000
1100
1200
1300
1400
Device Will
Not Current
Limit Below
(mA)
150
188
225
263
300
338
375
413
450
525
600
675
750
825
900
975
1050
Device Always
Current Limits
Below
(mA)
250
313
375
438
500
563
625
688
750
875
1000
1125
1250
1375
1500
1625
1750
Table 1: Current Limit R_SET Values.
Example: A USB port requires 0.5A. 0.5A multiplied
by 1.33 is 0.665A. From the chart "R_SET vs. I_LIM," R_SET
should be less than 11kΩ. 10.5 kΩ is a standard value
that is a little less than 11kΩ. The chart gives approx-
imately 0.700A as a typical I_LIM value for 10.5kΩ.
Multiplying 0.700A by 0.75 and 1.25 shows that the
AAT4610 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
AAT4610, the load current is limited to the value of
I_LIM determined by R_SET (see Figure 2). Since the
load is demanding more current than I_LIM, the volt-
age at the output drops. This causes the AAT4610 to
dissipate a larger than normal quantity of power, and
results in increased die temperature. When the die
temperature exceeds an over-temperature limit, the
AAT4610 will shut down until is has cooled suffi-
ciently, at which point it will start up again. The
AAT4610 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 (Pin 4).
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 (Pin 4)
of the AAT4610 has low and high threshold volt-
ages that accommodate this condition. The thresh-
old voltages are compatible with 5V TTL and 2.5V
to 5V CMOS.
Reverse Voltage
The AAT4610 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 damage the AAT4610.
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
Figure 2: Overload Operation.
1
0.75
0.5
0.25
0
0.3
4610.2006.09.1.3
Not recommended for new designs; pin-for-pin upgrade: AAT4610A.
9