LTC3832EGN Linear Technology, LTC3832EGN Datasheet - Page 17

• Manufacturer Part Number: LTC3832EGN
• Description: IC DC/DC CTRLR SYNC STPDN 16SSOP
• Manufacturer: Linear Technology
• Type: Step-Down (Buck)r

Specifications of LTC3832EGN

• Internal Switch(s): No
• Synchronous Rectifier: Yes
• Number Of Outputs: 1
• Voltage - Output: 2.5V
• Current - Output: 20A
• Frequency - Switching: 300kHz
• Voltage - Input: 3 ~ 8 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 16-SSOP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Power - Output: -

APPLICATIO S I FOR ATIO
between the top of the resistor divider network and the V
pin to create a pole-zero pair in the loop compensation.
The zero location is prior to the pole location and thus,
phase lead can be added to boost the phase margin at the
loop crossover frequency. The pole and zero locations are
located at:
where R1||R2 is the parallel combination resistance of R1
and R2. For low R2/R1 ratios there is not much separa-
tion between f
capacitors with a high ESR • capacitance product to bring
f
a lower frequency compared to f
is high enough that the closed loop has enough phase
margin for stability. Figure 10c shows the Bode plot using
phase lead compensation around the LTC3832 resistor
divider network.
Although a mathematical approach to frequency compen-
sation can be used, the added complication of input and/or
output filters, unknown capacitor ESR, and gross operat-
ing point changes with input voltage, load current varia-
tions, all suggest a more practical empirical method. This
can be done by injecting a transient current at the load and
using an RC network box to iterate toward the final values,
or by obtaining the optimum loop response using a
network analyzer to find the actual loop poles and zeros.
Table 2 shows the suggested compensation component
value for 3.3V to 2.5V applications based on Sanyo OS-CON
4SP820M low ESR output capacitors.
Table 2. Recommended Compensation Network for 3.3V to 2.5V
Applications Using Multiple Paralleled 820 F Sanyo OS-CON
4SP820M Output Capacitors
ESR
L1 ( H)
f
f
ZC2
PC2
1.2
1.2
1.2
2.4
2.4
2.4
4.7
4.7
4.7
close to f
= 1/[2 (R2)(C2)] and
= 1/[2 (R1||R2)(C2)]
C
OUT
1640
2460
4100
1640
2460
4100
1640
2460
4100
CO
CZ2
( F)
. Choose C2 so that the zero is located at
and f
U
R
C
9.1
15
24
22
33
43
33
56
91
(k )
PC2
U
. In this case, use multiple
C
C
4.7
4.7
3.3
4.7
3.3
2.2
3.3
2.2
2.2
CO
(nF)
W
and the pole location
C1 (pF)
560
330
270
330
220
180
120
100
100
U
C2 (pF)
1500
1500
1500
1500
1500
1500
1500
1500
1500
FB
Table 3 shows the suggested compensation component
values for 3.3V to 2.5V applications based on 470 F Sanyo
POSCAP 4TPB470M output capacitors.
Table 3. Recommended Compensation Network for 3.3V to 2.5V
Applications Using Multiple Paralleled 470 F Sanyo POSCAP
4TPB470M Output Capacitors
Table 4 shows the suggested compensation component
values for 3.3V to 2.5V applications based on 1500 F
Sanyo MV-WX output capacitors.
Table 4. Recommended Compensation Network for 3.3V to 2.5V
Applications Using Multiple Paralleled 1500 F Sanyo MV-WX
Output Capacitors
LAYOUT CONSIDERATIONS
When laying out the printed circuit board, use the follow-
ing checklist to ensure proper operation of the LTC3832.
These items are also illustrated graphically in the layout
diagram of Figure 11. The thicker lines show the high
current paths. Note that at 10A current levels or above,
current density in the PC board itself is a serious concern.
Traces carrying high current should be as wide as pos-
sible. For example, a PCB fabricated with 2oz copper
requires a minimum trace width of 0.15" to carry 10A.
L1 ( H)
L1 ( H)
1.2
1.2
1.2
2.4
2.4
2.4
4.7
4.7
4.7
1.2
1.2
1.2
2.4
2.4
2.4
4.7
4.7
4.7
C
C
OUT
OUT
1410
2820
4700
1410
2820
4700
1410
2820
4700
4500
6000
9000
4500
6000
9000
4500
6000
9000
( F)
( F)
LTC3832/LTC3832-1
R
R
C
C
150
220
100
150
120
220
220
13
27
51
33
62
82
62
39
56
82
82
(k )
(k )
C
C
0.0047
0.0018
0.0015
0.0033
0.0022
0.0022
0.0015
0.0015
0.0042
0.0033
0.0033
0.0033
0.0022
0.0022
0.0022
0.0022
0.0015
0.001
C
C
( F)
( F)
sn3832 3832fs
C1 (pF)
C1 (pF)
17
100
180
120
100
56
47
56
15
39
15
10
82
56
68
39
27
33
2