Application note

L5953

26/31

Part list on evaluation board

6.1

REG1 output voltage

Timing capacitor

output voltage.

6.2

Feedback resistors for REG2

where VLR is the required output voltage for REG2.

6.3

External components for PWM regulator

6.3.1

Bootstrap capacitor

The suggested value for the bootstrap capacitor is C6 = 100nF

Here following you find the criteria for the selection of the inductor L1, the free-wheeling

diode D2, the output filter capacitor C7, the feedback resistor R1, R2 and the compensation

network R3, C8, R4, C9 to have a Buck regulator working in continuous mode. Continuous

mode operation is recommended in order to reduce the stress of the output capacitor and of

the free-wheeling diode.

6.3.2

Inductor selection

The minimum value of the inductor L7 has to be so that the maximum inductor current ripple

ΔI

C1 = 470

μF

C2 = 220 nF

C3 = 470

μF

C4 = 10

μFC5 = 1 μF

C6 = 100 nF

C7 = 470

μF

ESR=65 m

Ω

C8 = 56nF

C9 = 2.7 nF

C10 = 10

μF

C11 = 4.7 nF

R1 = 2.2 k

Ω

R2 = 2 x 1.5 k

Ω in

parallel

R3 = 10 k

Ω

R4 = 220 k

Ω

R5 = 3.3 k

Ω

R6 = 1 k

Ω

L1 = 180

μH

D1 = 1N4007 or

MBR160

D2 = MBR360

C11

I

⋅

0.5 V

STBY

⋅

() V

CTLHy

+

----------------------------------------------------------------

=

R5

R6

V

LR

V

ref REG2

,

---------------------------- 1

–

⎝⎠

⎜⎟

⎛⎞

⋅

=