AAT4601
1.8A Current Limited P-Channel Switch
Applications Information
Current Device Will Not Device Always
RSET
Limit
Current Limit Current Limits
Setting Current Limit
Ω
( )
Typ (mA)
Below (mA)
Below (mA)
0
10
20
30
36
47
56
68
2510
2463
2423
2386
2361
2332
2297
2258
2214
2161
2107
2028
1918
1840
1737
1649
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
1807
1773
1745
1718
1700
1679
1654
1626
1594
1556
1517
1460
1381
1325
1251
1187
1141
1101
1055
1006
960
911
869
823
784
745
710
677
623
597
554
516
485
456
419
388
362
3213
3152
3102
3054
3022
2985
2940
2890
2834
2766
2697
2596
2455
2355
2223
2111
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
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.
82
100
120
150
200
240
300
360
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
Step 1: The maximum current required by a load
is usually defined in port specifications design
application references. For example, USB ports
may be specified to support loads of up to 500mA.
Step 2: The most convenient method for determin-
ing a current limit resistor value is to look it up in
Table 1, "Current Limit RSET Values.". Find the low-
est current value that is greater than the maximum
load current in the given application; refer to the
column, "Device Will Not Current Limit Below." The
resistor value needed is in the corresponding row
named "RSET." For example, a USB port requires
500mA. The lowest level where the device will cur-
rent limit above 500mA is 516mA. The correspon-
ding resistor value for RSET 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 referring to 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 volt-
age will not collapse when a short circuit is applied
to the load switch output. For example, a notebook
computer 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 917mA, this supply will remain in regulation
even if a short circuit is applied to the USB port.
339
318
295
275
258
239
220
204
306
283
268
193
Table 1: Current Limit RSET Values.
4601.2006.05.1.3
9
AAT [ ADVANCED ANALOG TECHNOLOGY, INC. ]
