=

1

K

R

C

¦

´

´

=

ON

OFF1

OFF2

T

T

T

T

K

R

C

+

+

=

´

´

OUT

PEAK

PEAK

PEAK

=

ON

OFF1

OFF2

IN

OUT

IN

IN

OUT

IN

V

L I

L I

L

I

T T

T

T

+

+ K R C

+

V

V

V

V

V

V

§

·

u

u

u

u u

¨

¸

©

¹

x

OFF2

OUT

PEAK

IN

OUT

IN

OUT

PEAK

T

=

IN

IN

OUT

IN

V

L

I

K

V

C

R

V

V

V

L

I

= K R C

+

V

V

V

V

R

§

·

u

u

u

¨

¸

§

·

u

©

¹

u

u

¨

¸

©

¹

x

x

IN

OUT

PEAK

IN

K

V

C =

OFF2

OUT

IN

V

L

I

V

+

+

T

R

V

V

R

u

u

u

u

x

PEAK

ON

IN

L

I

T

V

´

=

0

14

TPS61372

SLVSEE7 – JUNE 2018

www.ti.com

Product Folder Links: TPS61372

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Copyright © 2018, Texas Instruments Incorporated

Device Behavior Description (continued)

Figure 12. Switching Cycle at DCM

The switching frequency at DCM could be calculated by Equation 9, Equation 10, Equation 11, Equation 12,

Equation 13, Equation 14, Equation 15

(9)

(10)

(11)

(12)

(13)

(14)

(15)

The switching frequency keeps fairly constant regardless of the input voltage variation. For TPS61372, the K is 3

CCM operation.

8.5.2 Start up

The TPS61372 implements the soft start function to reduce the inrush current during startup. The TPS61372

begins soft start (typically 1 ms ) when the EN pin is pulled high. There are two phases for the startup procedure

shown in :

clamped at VIN – 0.5 V.