ZSLS7025 Datasheet

© 2016 Integrated Device Technology, Inc.

23

April 20, 2016

kHz

63

100

22

'

f

f

≈

×

=

2

2

1

TH

_

OVP

OVP

R

)

R

R

(

V

V

+

×

=

The recommended switching frequency, 20KHz < f < 200KHz, according to the switching frequency, is inversely

proportional to the inductor value; for example, select L1

=100 μH.

Therefore

(28)

The saturation current of the inductor must exceed the input peak current (IIN_PEAK).

4.4.7

R1 and R2 for Setting OVP

Set VOVP = VOUT + 5V = 45V

(29)

Choose R

2

=10kΩ, then R

1

= 470kΩ.

4.4.8

Q1 External MOSFET and D1 Diode

Power losses in the Q1 external MOSFET should be minimized. Conduction losses increase with RDS(on), and

switching losses increase with gate/drain charge and frequency. Therefore, selecting a MOSFET with low RDS(on) and

low gate/drain charge for the Q1 external MOSFET will help to optimize efficiency.

The MOSFET’s current rating must be higher than the input peak current IIN_PEAK. Q1 must have a VDS rating that

exceeds the maximum over-voltage protection (OVP) level configured for the application.

The average and peak current of the diode D1 must exceed the output average current and input peak current. The

diode’s maximum reverse voltage rating must exceed the over-voltage protection of the application.