S-8353 Seiko Instruments, S-8353 Datasheet - Page 17

• 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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Rev.1.4
STEP-UP, PWM CONTROL or PWM / PFM SWITCHABLE BUILT-IN TRANSISTOR SWITCHING REGULATOR
4. Operation
The following are the basic equations [(1) through (7)] of the step-up switching regulator. (Refer to Figure 11 .)
Voltage at CONT pin at the moment M1 is turned ON (V
The change in I
Integration of equation (2) (I
I
The peak current (I
The energy stored in L is represented by 1/2 • L (I
When M1 is turned OFF (t
Then, the reverse voltage (V
The voltage at CONT pin rises only by V
The change in the current (I
L
flows while M1 is ON (t
V
I
I
dI
V
dI
L
PK
_00
dt
dt
A
L
L
L
=
= V
*1. Current flowing through L (I
*2. Non-saturated voltage of M1.
*1. Diode forward voltage
=
= (V



=
=



V
S
V
V
L
IN
V
L
OUT
L
L
IN
*2
L
−
=
=
L
−
V
+ V
L
V
V
V
S
S
OUT
over time :
IN

• 

L

• 

D
−
PK
*1
t
V
+
) after t
) − V
t
ON
L
S
V
Figure 11 Step-Up Switching Regulator Circuit for Basic Equation
D
ON
VIN
−
IN
OFF
). The time of t
V
L
L
ON
L
) flowing through the diode into V
) :
IN
), the energy stored in L is emitted through a diode to the output capacitor.
) is generated :
:
L
L
) is zero.
OUT
Seiko Instruments Inc.
M1
ON
+
V
CONT
is determined by the oscillation frequency of OSC.
D
.
PK
)
2
.
A
)
*1
EXT
D
:
OUT
during t
VOUT
VSS
OFF
:
+
−
S-8353/8354 Series
C
L
(1)
(2)
(3)
(4)
(5)
(6)
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