S-8353 Seiko Instruments, S-8353 Datasheet - Page 18

• Manufacturer Part Number: S-8353
• Description: (S-8353 / S-8354) PWM Control Switchable Built-in Transistor Switching Regulator
• Manufacturer: Seiko Instruments

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18
STEP-UP, PWM CONTROL or PWM / PFM SWITCHABLE BUILT-IN TRANSISTOR SWITCHING REGULATOR
S-8353/8354 Series
Integration of the equation (6) is as follows :
During t
V
lowest level after M1 is turned ON (t
diode to C
(ripple voltage (V
Next, the ripple voltage is determined as follows.
I
When M1 is turned OFF (t
When substituting equation (10) for equation (9) :
Electric charge
When substituting equation (12) for equation (9) :
A rise in voltage (V
When taking into consideration I
When substituting equation (11) for equation (15) :
Therefore to reduce the ripple voltage, it is important that the capacitor connected to the output pin has a large
capacity and a small R
OUT
OUT
∴
I
I




t
∆
∆
V
V
V
L
OUT
vs. t
, the energy of the capacitor (C
1
V
Q
Q
P
P
P
t
=
=
1
−
−
−
OUT
1
1
P
P
P
I
ON
=
t
PK
=
1
=
OFF
=
=
=
=
I (
, the energy is stored in L and is not transmitted to V
(time) from when M1 is turned OFF (after t
I
L
I
PK
+
∫
PK
−
PK
, and the voltage of C
I (
∆
∆
C
L
0
C
1 t
V
−
PK



Q
Q
−
I
−
L
L
D
−
L
V




1
1
dt
I 2



−
I
I
OUT
−
2
1
OUT
OUT
I
∆
=
=
V
PK
PK
I
P
V
OUT
(
Q
=
I
OUT
−
C
PK
C
IN
P
P
1
1
+
)
1
I

•  

L
PK
L
) ) when the current flowing through into V
−
•




L
which is charged in C
)
P
V
−
•
2
•
+




) due to
=
D
t
I
•
ESR



L
OFF
OUT



•
V
V
−
I
t
∫
I
OUT
PK
I
PK
D
OFF
t
OFF
PK
C
OFF
1 t
0
V
.
−
)
L
IN
dt
+
•
+
), I
2
2
V
+
t
I
I

• 

OUT
+
IN
−
1
OUT
L
V
L
∆
=



D

• 

V
= 0 (when the energy of the inductor is completely transmitted). Based on equation (7) :
t
Q
OUT
I
L
PK
I
OUT
−

• 

PK

• 

rises rapidly. V
1
t
1
V
+
L
:
ON
to be consumed during t
1 t
t
2
IN
+
) is consumed. As a result, the pin voltage of C
1
2
+
I
OUT
I
+
). When M1 is turned OFF, the energy stored in L is transmitted through the




OUT
L
V



D
I
PK

• 

−
L
•
Seiko Instruments Inc.
during t
t
V
+
R
1
2
IN
I
ESR
OUT
•
∫

• 

OUT
1 t
0
1
tdt
ON
R
:
is a time function, and therefore indicates the maximum value
ESR
) to when V
=
I
PK
−
I
1
OUT
•
and the Equivalent Series Resistance (R
OUT
t
C
OUT
1
L
−
•
t
. When receiving the output current (I
and load current (I
OUT
V
1
OUT
reaches the maximum level :
+
L
V
D
−
V
IN
•
1
2
OUT
L
t
is reduced, and goes to the
1
) match.
2
ESR
Rev.1.4
OUT
) of C
) from
L
(10)
(11)
(12)
(13)
(14)
(15)
(16)
:
(7)
(8)
(9)
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