S-8327 Seiko, S-8327 Datasheet - Page 12

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

The following are basic equations [(1) through (7)] of the step-up switching regulator (see Figure 5.)
Voltage at CONT pin the moment M1 is turned ON (current I
The change in I
Integration of the above equation (I
I
The peak current (I
The energy stored in L is represented with 1/2 L (I
When M1 is turned OFF (t
voltage (V
The voltage at CONT pin rises only by the voltage corresponding to V
The change in the current flowing through the diode into V
Integration of the above equation is as follows:
During t
energy of the capacitor (C
M1 is turned ON (t
voltage of C
current flowing through the diode into V
Next, the ripple voltage is found out as follows:
I
When M1 is turned ON (after t
L
OUT
flows while M1 is ON (t
vs t
ON
1
(time) from when M1 is turned OFF (after t
, the energy is stored in L and is not transmitted to V
L
) is generated.
V
V
(V
OUT
dI
I
I
dt
L
I
dI
PK
A
L
=
dt
L
L
D
= (V
=I
=V
L
=
L
rises drastically. V
: Diode forward voltage)
I
t
PK
OUT
1
over time:
V
S
= (I
=
SMALL PACKAGE PWM CONTROL STEP-UP SWITCHING REGULATOR
OUT
ON
OUT
(V
=
V
PK
V
-
=I
V
IN
). When M1 is turned OFF, the energy stored in L is transmitted through the diode to C
PK
S
L
) after t
IN
+V
+V
PK
: Non-saturated voltage of M1)
L
V
- V
L
L
L
- V
V
L
- I
L
-
D
D
OUT
ON
=
OUT
S
) - V
S
OUT
- V
=
OFF
). The time of t
V
+V
ON
V
)
IN
) is consumed. As a result, the pin voltage of C
IN
), the energy stored in L is transmitted through a diode to the output capacitor. Then reverse


OUT
OFF
:
D
L
IN
- V
V
L




- V
OUT
+V
.........................................................................(1)
), IL=0 (when the energy of the inductor is completely transmitted). Based on equation (7),
t
L
=
t
V
OUT
S
ON
L
IN
OUT
D
):
+V
t
I
OFF
PK
is a time function that indicates the maximum value (ripple voltage: V
- V
L
+V
D
OUT


IN
L
- V
D
............................................................(2)
t
ON
.......................................................... (3)
- V
and load current (I
Seiko Instruments Inc.
.........................................................(5)
IN
.........................................................(4)
is determined by the oscillation frequency of the OSC.


IN
t
1
PK
.............................................(6)
............................................. (7)
ON
)
.............................................(10)
2
................................................ (8)
................................................ (9)
.
) to when V
OUT
L
OUT
flowing through L is zero):
during t
OUT
) match.
OUT
. When receiving output current (I
reaches the maximum level:
OFF
OUT
:
+V
D
.
OUT
is reduced, and goes to the lowest level after
S-8323/8327 Series
OUT
) from V
P-P
OUT
) when the
OUT
, and the
, the
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