AAT4601A
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
(k ) Typ (mA)
Below (mA)
Below (mA)
A simple three-step procedure can be used to
adjust the AAT4601A's current limit. First, the max-
imum 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.
7.5
8.2
9.1
10
2476
2277
2065
1895
1748
1633
1528
1353
1280
1158
1055
972
1857
1708
1549
1421
1311
1224
1146
1015
960
869
791
729
673
608
552
507
469
436
400
368
341
314
285
262
240
221
200
183
167
155
144
125
118
3095
2847
2581
2369
2185
2041
1910
1691
1600
1448
1318
1215
1122
1014
919
11
12
13
15
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.
16
18
20
22
Step 2: The most convenient method for deter-
mining a current limit resistor value is to look it up
in Table 1, "Current Limit RSET Values." Find the
lowest current value that is greater than the maxi-
mum load current in the given application as listed
in the column, "Device Will Not Current Limit
Below." The resistor value needed is listed in the
corresponding row in the column, "RSET." For
example, a USB port requires 500mA. The lowest
level where the device will current limit above
500mA is 507mA. The corresponding resistor
value for RSET would be 33kΩ.
24
897
27
811
30
736
33
676
845
36
625
781
39
582
727
43
533
666
47
491
613
51
455
568
56
418
523
62
380
476
68
350
437
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,
"Device Always Current Limits Below." If the power
supply connected to the AAT4601A's input can pro-
vide 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
AAT4601A with a 33kΩ resistor connected between
the SET pin and GND. If the power supply con-
nected to the AAT4601A's IN pin can provide more
than 845mA, this supply will remain in regulation
even if a short circuit is applied to the USB port.
75
320
400
82
295
369
91
267
334
100
110
120
130
150
160
245
306
223
279
206
258
192
239
167
209
157
197
Figure 1: Current Limit RSET Values.
4601A.2006.05.1.5
9
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