LTC1753CSW#TRPBF Linear Technology, LTC1753CSW#TRPBF Datasheet - Page 18

• Manufacturer Part Number: LTC1753CSW#TRPBF
• Description: IC SW REG CNTRLR PENT III 20SOIC
• Manufacturer: Linear Technology

Specifications of LTC1753CSW#TRPBF

• Applications: Controller, Intel Pentium® III
• Voltage - Input: 5V
• Number Of Outputs: 1
• Voltage - Output: 1.3 ~ 3.5 V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 20-SOIC (7.5mm Width)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

APPLICATIO S I FOR ATIO
LTC1753
response using a network analyzer to find the actual loop
poles and zeros.
Table 5 shows the suggested compensation components
for 5V input applications based on the inductor and output
capacitor values. The values were calculated using mul-
tiple paralleled 330 F AVX TPS series surface mount
tantalum capacitors as the output capacitor. The optimum
component values might deviate from the suggested
values slightly because of board layout and operating
condition differences.
Table 5. Suggested Compensation Network for 5V Input
Application Using Multiple Paralleled 330 F AVX TPS Output
Capacitors
An alternate output capacitor is the Sanyo MV-GX series.
Using multiple parallel 1500 F Sanyo MV-GX capacitors
for the output capacitor, Table 6 shows the suggested
compensation component value for a 5V input application
based on the inductor and output capacitor values.
Table 6. Suggested Compensation Network for 5V Input
Application Using Multiple Paralleled 1500 F Sanyo MV-GX
Output Capacitors
18
L
L
O
O
2.7
2.7
2.7
5.6
5.6
5.6
2.7
2.7
2.7
5.6
5.6
5.6
( H)
1
1
1
( H)
1
1
1
C
C
1980
4950
1980
4950
1980
4950
4500
6000
9000
4500
6000
9000
4500
6000
9000
O
O
990
990
990
( F)
( F)
U
R
R
U
C
C
1.8
3.6
9.1
5.1
4.3
5.6
8.2
10
24
10
20
51
11
15
22
24
30
47
(k )
(k )
W
C
0.0047
0.0047
0.0033
C
0.0047
0.0047
0.022
0.022
0.015
C
0.01
0.01
0.01
0.01
0.01
C
0.01
0.01
0.01
0.01
0.01
( F)
( F)
U
C1 (pF)
C1 (pF)
680
330
120
220
120
120
270
220
150
100
47
56
22
82
56
56
39
27
Table 7 shows the suggested compensation component
value for a 5V application based on the Sanyo OS-CON
4SP820M low ESR output capacitors
Table 7. Suggested Compensation Network for 5V Input
Application Using Multiple Paralleled 820 F Sanyo OS-CON
4SP820M Output Capacitors
Remote Sense Considerations
In some installations such as Intel Slot 2 designs, the
regulator is by necessity a relatively long distance from the
load. It is desirable in these instances to connect the
regulator sense connection at the load rather than directly
at the regulator output. This forces the supply voltage to
be regulated at the load which, after all, is the desired point
to control. In most cases no problems will be encountered
as a result of doing this. However, care must be exercised
if the power path is long or the capacitance at the load is
very large.
The power distribution path has some finite amount of
inductance. There will also be a significant amount of
capacitance at the load as the local bypass. These two
circuit elements constitute a second order, lowpass filter
and the SENSE lead connects to the output of this filter. As
is true for any LC filter, there is 180 of phase shift at a
frequency beyond the double pole. If the resonant fre-
quency of the filter falls below the regulator’s feedback
loop crossover frequency, the loop will likely oscillate.
There are a couple of measures that may be taken to
alleviate this problem. The first is to minimize the induc-
tance of the power path. Therefore, it is desirable to make
the power trace as wide as possible and as short as
L
O
2.7
2.7
2.7
5.6
5.6
5.6
( H)
1
1
1
C
1640
2460
4100
1640
2460
4100
1640
2460
4100
O
( F)
R
C
5.6
9.1
15
16
24
39
33
47
82
(k )
C
0.0047
0.0047
0.0047
0.0033
0.0022
0.0033
0.0022
0.0022
C
0.01
( F)
C1 (pF)
220
150
82
82
56
33
39
27
15
C2 (pF)
270
270
270
270
270
270
270
270
270
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