S-9365AAAAAI6TIG2 SII [Seiko Instruments Inc], S-9365AAAAAI6TIG2 Datasheet - Page 18

• Manufacturer Part Number: S-9365AAAAAI6TIG2
• Description: STEP-UP, SUPER-SMALL PACKAGE, 1.2 MHz PWM CONTROL or PWM/PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
• Manufacturer: SII [Seiko Instruments Inc]

18
S-8365/8366 Series
STEP-UP, SUPER-SMALL PACKAGE, 1.2 MHz PWM CONTROL or PWM/PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
1. Continuous current mode
The following explains the current that flows into the inductor when the step-up operation stabilizes in a certain
status and I
When the Nch power MOS FET is turned on, current (I
current (I
Current change of inductor within t
When the Nch power MOS FET is turned off, the voltage of the CONT pin is stepped up to V
voltage on both ends of the inductor becomes V
is ignored.
Current change of inductor within t
The input power equals the output power in an ideal situation where there is no loss by components.
The current that flows in the inductor consists of a ripple current that changes due to variation over time and a
direct current.
From Figure 15 :
Above, the continuous mode is the operation mode when I
continuously flows.
While the output current (I
critical point of the continuous mode.
As shown in equations (2) and (3), the direct current component (I
t
When the output current decreases below I
as shown in Figure 17. This is the discontinuous mode.
ON
∆I
I
I
I
IN(AV)
IN(AV)
OUT(0)
L(ON)
can be calculated using equation (1).
∆I
P
I
∴I
I
I
:
:
IN(AV)
IN(AV)
OUT(0)
when I
IN
= I
L(OFF)
L
IN(AV)
) at this time gradually increases in proportion with the ON time (t
= P
L
OUT
max. − I
× V
=
= I
= I
= I
OUT
=
=
=
IN(DC)
is sufficiently large.
IN
IN(DC)
IN(DC)
IN(DC)
2 × L × V
V
V
V
t
L
= I
ON
V
IN
OUT
OUT
reaches 0 (critical point) :
IN
L
OUT
+
+
+
× V
L
min.
× t
− V
2 × L
∆I
V
× I
× V
ON
2
IN
V
OUT
OUT
IN
L
2
IN
2 × L
OUT
OUT
OUT
× t
− V
) continues to decrease, I
.................. (2)
× t
OFF
IN
ON
ON
OFF
.......... (3)
× t
:
:
OFF
Seiko Instruments Inc.
OUT(0)
OUT
, the current flowing in the inductor stops flowing in the t
+ V
D
1
− V
IN(DC)
) flows in the direction shown in Figure 14. The inductor
IN(DC)
IN
. However, it is assumed here that V
reaches 0 as shown in Figure 16. This point is the
> 0 as shown in Figure 15 and the inductor current
IN(DC)
) depends on I
ON
) of the Nch power MOS FET.
OUT
.
OUT
OUT
+ V
Rev.1.1
>> V
OFF
D
D
and the
and V
period
_00
D