S-8355 Seiko Instruments, S-8355 Datasheet - Page 26

• Manufacturer Part Number: S-8355
• Description: (S-8355 - S-8358) PWM/PFM SWITCHING CONTROL STEP-UP SWITCHING REGULATOR
• Manufacturer: Seiko Instruments

www.DataSheet4U.com
26
STEP-UP, SUPER-SMALL PACKAGE, 600 kHz, PWM CONTROL or PWM/PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
S-8355/56/57/58 Series
4. Operation
The following are the basic equations [(1) through (7)] of the step-up switching regulator. (Refer to Figure 15 .)
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
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
*2
IN
L
−
=
=
L
−
V
+ V
V
V
L
V
S
S
OUT
over time :
IN

• 

L

• 

D
−
PK
*1
t
V
+
) after t
) − V
t
ON
L
S
V
Figure 15 Step-Up Switching Regulator Circuit for Basic Equation
D
ON
VIN
−
IN
). The time of t
V
L
L
ON
L
) :
) flowing through the diode into V
IN
) is generated :
OFF
:
), the energy stored in L is emitted through a diode to the output capacitor.
L
L
) is zero.
OUT
ON
Seiko Instruments Inc.
M1
+
V
is determined by the oscillation frequency of OSC.
CONT
D
.
PK
)
2
.
A
)
*1
EXT
D
:
OUT
during t
VOUT
VSS
OFF
:
+
−
C
L
Rev.6.6
(1)
(2)
(3)
(4)
(5)
(6)
_00