S-8327 Seiko, S-8327 Datasheet - Page 49

• Manufacturer Part Number: S-8327
• Description: (S-8323 / S-8327) SMALL PACKAGE PWM CONTROL STEP-UP SWITCHING REGULATOR
• Manufacturer: Seiko

<Remarks>
The minimum value (VEEmin.) and maximum value (VEEmax.) of the output-voltage adjustment range
are defined as follows:
1. Disregard Tr2 and RE, and set RA, RB, and CC such that the output voltage will be less than
2. Then, set an RE that will allow the output voltage to exceed VEEmax. when Tr2 comes on. Such a
FAQ No.: 11S8323012
VEEmin. The procedure for this should comply with FAQ No. 11S8323007. (In particular, use of the
software is recommended.)
value can be found using the following equation, where OUTmin. is the minimum deviation value
(OUTmin. resulting from software calculation) of the voltage VEE computed in 1. above, VDACmax.
is the maximum value of the DAC output, and VBE is the base-emitter voltage of Tr2. (However,
deviations in the resistance values of RA and RB must be taken into consideration.)
Tr2 is a transistor designed for small signals. Select one that features a withstand voltage that is
higher than the output voltage VEE to be set. Moreover, select an output voltage VOUT of the S-
8327/8E that will allow the following condition to be met and will not allow saturated operation of
Tr2.
VOUT
RE
(
VEEmax
(
VDACmax
VDACmax+VBE
-
OUTmin
-
VBE
)
)
×
RA
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