S-8327 Seiko, S-8327 Datasheet - Page 15

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

SMALL PACKAGE PWM CONTROL STEP-UP SWITCHING REGULATOR
S-8323/8327 Series
14
1. Inductor
An inductance has strong influence on max. output current I
Figure 7 shows I
The peak current I
Further decreasing L decreases I
The loss of I
Further increasing L decreases efficiency due to the loss of DC resistance of the coil.
47 to 220 H inductor for S-8323 and 22 to 100 H inductor for S-8327 are recommended.
Choose a value for L by refering to the reference data because the maximum output current is due to the input voltage in an
actual case.
Choose an inductor so that the peak current I
Exceeding the allowable current of the inductor causes magnetic saturation, remarkable low efficiency and destruction of the
IC chip due to a large current.
The peak current I
For instance, when you choose 100 H at fosc=50 kHz for L using the S-8323A50MC at the following conditions, I
caluculated to 170 mA from the (17) formula.
The switching current limit circuit is not built into this IC chip.
I
PK
current must be 500 mA or less.






I
Input voltage V
Output voltage V
Load current I
OUT
S-8323
I
fosc: oscillation frequency
VD
PK
PK
=
by the switching transistor decreases by increasing L and the efficiency becomes max. at L value.
OUT
0.4V
PK
PK
OUT
increases by decreasing L and I
in uncontinuous mode is caluculated from the following formula:
IN
characteristics for inductance of S-8323 and S-8327.
recommended range
2 I
=3 V
D75
47
OUT
=30 mA
OUT
V
I
OUT
OUT
=5 V
(V
=5.0V, V
f
OSC
OUT


OUT
+V
220
L
IN
D
=3.0V
due to the lack of the current driving capacity of the switching transistor.
-V
IN
)
(A)
PK
L ( H
does not exceed the allowable current.
Seiko Instruments Inc.
)
OUT
Figure 7
(17)
is at max. value at L value.
OUT
and efficiency .
I
OUT
S-8327
CD105
V
I
OUT
OUT
recommended range
22
=5.0V, V
IN
=3.0V
100
L ( H
)
PK
is