LTC3831 Datasheet, PDF (17/20 Pages) Linear Technology – High Power Synchronous Switching Regulator Controller for DDR Memory Termination

LTC3831
APPLICATIO S I FOR ATIO
Table 2 shows the suggested compensation component
value for 2.5V to 1.25V applications based on the 470µF
Sanyo POSCAP 4TPB470M output capacitors.
Table 3 shows the suggested compensation component
values for 2.5V to 1.25V applications based on 1500µF
Sanyo MV-WX output capacitors.
LAYOUT CONSIDERATIONS
When laying out the printed circuit board, the following
checklist should be used to ensure proper operation of the
LTC3831. These items are also illustrated graphically in
the layout diagram of Figure 10. The thicker lines show the
high current paths. Note that at 5A current levels or above,
Table 2. Recommended Compensation Network for 2.5V to
1.25V Applications Using Multiple Paralleled 470µF Sanyo
POSCAP 4TPB470M Output Capacitors
L1 (µH)
1.2
C_OUT (µF)
1410
R_C (kΩ)
6.8
C_C (nF)
3.3
C1 (pF)
33
1.2
2820
15
3.3
33
1.2
4700
22
1.5
33
2.4
1410
15
10
33
2.4
2820
36
3.3
10
2.4
4700
47
4.7
10
4.7
1410
33
10
10
4.7
2820
68
22
10
4.7
4700
120
10
10
Table 3. Recommended Compensation Network for 2.5V to
1.25V Applications Using Multiple Paralleled 1500µF Sanyo
MV-WX Output Capacitors
L1 (µH)
1.2
C_OUT (µF)
4500
R_C (kΩ)
20
C_C (nF)
1.5
C1 (pF)
120
1.2
6000
27
1
82
1.2
9000
43
0.47
56
2.4
4500
51
1
56
2.4
6000
62
1
33
2.4
9000
82
0.47
27
4.7
4500
82
3.3
33
4.7
6000
100
1
15
4.7
9000
150
1
15
PV_CC
+
4.7µF
C1
R_C
C_C
100Ω
1µF
GND
NC
V_CC
PV_CC2
PV_CC1
TG
LTC3831
I_MAX
FREQSET
I_FB
SHDN
R⁺
COMP
BG
SS
FB
R^–
GND PGND
C_SS
GND
1µF 10k
PGND
0.1µF
1k
V_IN
+
C_IN
OPTIONAL
Q1
MBRS340T3
L_O
MBRS340T3
Q2
V_OUT
+
C_OUT
PGND
3830 F11
Figure 10. Typical Schematic Showing Layout Considerations
3831f
17