L5953

20/24

PART LIST on Evaluation Board

REG1 OUTPUT VOLTAGE

Timing Capacitor

Feedback resistors for REG2

where VLR is the required output voltage for REG2.

External components for PWM regulator

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 Continuos mode. Continuous mode operation is recommended in order to reduce the stress

of the output capacitor and of the free-wheeling diode.

Inductor Selection

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

Output Capacitor Selection

The criteria for the selection of the capacitor C7 is based on the output voltage ripple requirements. The ripple

on the output voltage is due to a capacitive contribute, often negligible, equal to

C1 = 470

µF

C2 = 220 nF

C3 = 470

µF

C4 = 10

µF

C5 = 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

CT 1

T

d

⋅

0.5 V

STBY

⋅

() V

CTL Ry

+

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

=

R5

R6

V

LR

V

ref R EG 2

,

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



 1

–

⋅

=

L

min

V

O

∆I

Lm ax

,

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

V

O

V

im ax

,

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

1

f

sw m in

,

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

⋅

–

⋅

=