SI9140DQ VISHAY [Vishay Siliconix], SI9140DQ Datasheet - Page 13

• Manufacturer Part Number: SI9140DQ
• Description: MP Controller For High Performance Process Power Supplies
• Manufacturer: VISHAY [Vishay Siliconix]

For these reasons, synchronous rectification is a must in
today’s microprocessors power supply design.
skipping modes are undesirable in high-performance
microprocessor power supplies, especially when the minimum
load current is as high as 500 mA. This pulse-skipping mode
disables the synchronous rectification during light load and
generates a random noise spectrum which may produce EMI
problems.
Siliconix’ TrenchFETt technology has resulted in 20-mW
n-channel (Si4410DY) and 35-mW p-channel (Si4435DY)
MOSFETs in the SO-8 surface-mount package. These LITTLE
FOOTr products totally eliminate the need for an external
heatsink.
Document Number: 70026
S-40699—Rev. H, 19-Apr-04
Maxi-
I
mum
14.5 A
O
8.5 A
10 A
5 A
(A)
FIGURE 8. Non-Synchronous Converter BW
Quantity High-Side P-Channel
Frequency (Hz)
Si4435DY
CONVERTER REQUIREMENTS (FIGURES 1, 2, AND 3)
1
2
2
3
Phase
Gain
Quantity Low-Side N-Channel
Pulse-
TABLE 2.
Si4410DY
Worst case current of 10 A can be handled with two paralleled
Si4435DY and two paralleled Si4410DY MOSFETs, which
results in the efficiency levels shown in Figure 9.
Good electrical designs must provide an adequate margin for
the specification, but they should not be grossly overdesigned
to lower costs. LITTLE FOOT power MOSFETs allow
designers to balance cost and performance considerations
without sacrificing either. If the design requires only an 8.5-A
continuous current, for example, one Si4410DY can be
eliminated. Table 2 shows the number of MOSFETs required
to handle the various output current levels of today’s high-
performance microprocessors. For other output power levels,
the equations below should be used to calculate the power
handling capability of the MOSFET.
1
1
2
2
100
95
90
85
80
0
2
FIGURE 9. Efficiency
4
I
Capacitor Os-con 220 mF
OUT
Quantity Input (C1-C3)
(A)
Vishay Siliconix
6
1
2
2
3
V
OUT
8
V
IN
= 2.9 V
= 5 V
www.vishay.com
Si9140
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