AAT4601 Datasheet, PDF (8/14 Pages) Advanced Analogic Technologies – 1.5A Current Limited P-Channel Switch

AAT4601
1.5A Current Limited P-Channel Switch
Applications Information
Setting Current Limit
A simple three-step procedure can be used to
adjust the AAT4601's current limit. First, the maxi-
mum current required by the load should be deter-
mined. Second, select a resistor that guarantees
adequate current is available to the load under nor-
mal conditions. Finally, the maximum current that
can pass through the switch can be calculated and
compared to the maximum current available.
Step 1: The maximum current required by a load
is usually defined in port specifications design
application references. For example, USB ports
are specified to support loads of up to 500 mA.
Step 2: The most convenient method for deter-
mining a current limit resistor value is to look it up
in the provided table named "Current Limit R_SET
Values". Find the lowest current value that is
greater than the maximum load current in the given
application. Refer to the column named "Device
will not current limit below". The resistor value
needed is in the corresponding row named "R_SET".
For example, a USB port requires 500 mA. The
lowest level where the device will current limit
above 500 mA is 516 mA. The corresponding
resistor value for R_SET would be 2kΩ .
Step 3: Now the required resistor value has been
determined. The maximum current that can be
drawn, even with a short circuit applied to the out-
put, can be determined by reading the column
labeled "Device always current limits below". If the
power supply connected to the AAT4601's input can
provide this current level, the power supply voltage
will not collapse when a short circuit is applied to the
load switch output. For example, a notebook com-
puter has a USB port which is powered by an
AAT4601 with a 2kΩ resistor connected between
the SET pin and GND. If the power supply con-
nected to the AAT4601's IN pin can provide more
than 917 mA, this supply will remain in regulation
even if a short circuit is applied to the USB port.
Current Limit R_SET Values
R_SET
(Ω)
470
510
560
620
680
750
820
910
1000
1100
1200
1300
1500
1600
1800
2000
2200
2400
2700
3000
3300
3600
3900
4300
4700
5100
5600
6200
6800
7500
Current
Limit typ
(mA)
1585
1529
1466
1397
1334
1266
1206
1144
1089
1034
986
941
865
829
769
716
673
633
582
539
502
470
442
410
382
358
332
306
283
268
Device will
not current
limit below:
(mA)
1141
1101
1055
1006
960
911
869
823
784
745
710
677
623
597
554
516
485
456
419
388
362
339
318
295
275
258
239
220
204
193
Device always
current limits
below:
(mA)
2029
1957
1876
1788
1707
1620
1544
1464
1394
1324
1262
1204
1107
1061
985
917
861
811
745
690
643
602
565
524
489
458
424
392
362
343
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