SI786 Vishay, SI786 Datasheet - Page 14

• Manufacturer Part Number: SI786
• Description: Dual-output Power-supply Controller
• Manufacturer: Vishay

Si786
Vishay Siliconix
Both minimum capacitance and maximum ESR requirements
must be met. In order to get the low ESR, a capacitance value
of two to three times greater than the required minimum may
be necessary.
The equation for output ripple in continuous current mode is:
V
The equations for capacitive and resistive components of the
ripple in pulse-skipping mode are:
V
V
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14
The total ripple, V
as follows:
otherwise, V
OUT(RPL)
OUT(RPL)
OUT(RPL)
then V
(C) +
(R) +
+ I
if V
V
LPP(MAX)
OUT(RPL)
OUT(RPL)
OUT(RPL)
OUT(RPL)
(0.02) ESR
OUT(RPL)
(4) 10
R
R
CS
CS
(R) < 0.5 V
(R).
= V
= 0.5 V
2
–4
, can be approximated
ESR
C
CF
OUT(RPL)
(L)
F
OUT(RPL)
CF
)
OUT(RPL)
V
(C),
OUT
2
1
(C) +
)
P x f
(C),
V
1
IN
–V
1
C
OUT
F
Lower Voltage Input
The application circuit shown here can be easily modified to
work with 5.5-V to 12-V input voltages. Oscillation frequency
should be set at 200 kHz and increase the output capacitance
to 660 mF on the 5-V output to maintain stable performance up
to 2 A of load current. Operation on the 3.3-V supply will not be
affected by this reduced input voltage.
S-40807—Rev. J, 26-Apr-04
Document Number: 70189