S-8352 Seiko Instruments, S-8352 Datasheet - Page 18

• Manufacturer Part Number: S-8352
• Description: (S-8351 / S-8352) SMALL PACKAGE PFM CONTROL STEP-UP SWITCHING REGULATOR
• Manufacturer: Seiko Instruments

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18
STEP-UP, SUPER-SMALL PACKAGE, PFM CONTROL SWITCHING REGULATOR / SWITCHING REGULATOR CONTROLLER
S-8351/8352 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
=
t
ON
PK
=
1
=
OFF
=
=
=
=
I (
(time) from when M1 is turned OFF (after t
I
I
, the energy is stored in L and is not transmitted to V
L
PK
+
∫
PK
−
PK
I (
∆
∆
, and the voltage of C
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
Q
OUT
(
=
I
OUT
−
C
PK
C
IN
1
P
P
1
1
+
)
I

•  

L
PK
L
) ) when the current flowing through into V
−
•
which is charged in C




L
)
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
.
−
)
dt
L
IN
+
•
+
), 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) :
Q
t
OUT
I
PK
I
OUT
−

• 

PK

• 

L
1
t
1
V
rises rapidly. V
:
+
to be consumed during t
1 t
t
2
IN
+
1
2
L
ON
+
I
OUT
I
+
) is consumed. As a result, the pin voltage of C




OUT
L
V
). When M1 is turned OFF, the energy stored in L is transmitted through the



D
I
PK

• 

L
−
•
Seiko Instruments Inc.
during t
t
+
V
R
1
2
IN
I
ESR
OUT
•
∫

• 

1
1 t
0
OUT
:
tdt
ON
R
ESR
) to when V
is a time function, and therefore indicates the maximum value
=
I
PK
−
I
1
OUT
•
and the Equivalent Series Resistance (R
OUT
C
t
1
L
•
−
OUT
t
and load current (I
OUT
1
V
OUT
. When receiving the output current (I
reaches the maximum level :
+
L
V
D
−
V
IN
•
OUT
1
2
t
1
) match.
L
2
is reduced, and goes to the
ESR
Rev.2.0
) of C
OUT
L
) from
(10)
(11)
(12)
(13)
(14)
(15)
(16)
:
(7)
(8)
(9)
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