ZXLD1370Q

Document number: DS37117 Rev. 4 - 2

20 of 39

www.diodes.com

February 2018

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ZXLD1370Q

As the regulated frequency is known, and we have already found D from Equation 7 or the approximation Equation 7a, this allows calculation of

The ZXLD1370Q

ripple current control is also modulated by other circuit parameters as follows.

I

ADJ

_

GI

D

1

V

V

12

.

0

03

.

0

I

COIL

REF

ADJ

LMAX





































I

ADJ

_

GI

D

1

V

V

04

.

0

01

.

0

I

COIL

REF

ADJ

LMIN





































Equation 20

I

ADJ

_

GI

D

1

V

V

08

.

0

02

.

0

I

COIL

REF

ADJ

LMID





































If ADJ is connected to REF, this simplifies to:

I

ADJ

_

GI

D

1

15

.

0

I

COIL

LMAX







I

ADJ

_

GI

D

1

05

.

0

I

COIL

LMIN







Equation 20a

I

ADJ

_

GI

D

1

1

.

0

I

COIL

LMID







W

The chosen coil should have a saturation current higher than the peak sensed current. This saturation current is the DC current for which the

inductance has decreased by 10% compared to the low current value.

Assuming ±10% ripple current, we can find this peak current from Equation 8, adjusted for ripple current:

for Buck

for Boost

Equation 21

for Buck-Boost

The mean current rating is also a factor, but normally the saturation current is the limiting factor.

The following websites may be useful in finding suitable components:

www.coilcraft.com

www.niccomp.com

www.we-online.com/web/en/wuerth_elektronik/start.php