Revision 1.8

16 - 20

AS3833

Datasheet - D e t a i l e d D e s c r i p t i o n

Peak current:

RMS inductor current:

This peak current is flowing through MN1 during phase 1 and through D1 during phase 2 of each cycle. Therefore this peak current is important

for a proper diode , MOSFET and inductor selection.

Note:

The saturation current of the inductor should be about 20 to 30% larger than the peak current

8.4.5

Input Capacitor

The input capacitor has to supply the delta inductor current and it should be selected according to:

8.4.6

Output Capacitor

The output capacitor must be chosen according to the max allowable output ripple at high load.

8.4.7

Current Sense Resistor

Note:

Low inductance, specific designed current sensing resistors should be used, e.g. Stackpole Electronics CSR/CSRN series of sensing

resistors with less than 0.2nH (typ.).

8.4.8

Compensation Network

A typical choice for values of the compensation network is C10 = 100pF, C11 = 10nF, R11 = 100K

Ω. Use these values as initial choice and

evaluate the transient response of the system to verify the behavior at output load change.

(EQ 14)

I

pk

I

L

I

L

∆

2

--------

I

OUT

1

D

–

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

D

V

IN

×

2

f

S

×

L

×

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

+

=

+

=

(EQ 15)

I

RMS

I

L

2

1

12

------

I

L

∆

×







+

=

(EQ 16)

C

IN

I

L

∆

4

V

IN

∆

×

f

SW

×

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

>

(EQ 17)

ESR

V

IN

∆

2

I

L

∆

×

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

<

(EQ 18)

C

OUT

I

OUT

max

–

D

×

V

OUT

∆

f

SW

×

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

>

(EQ 19)

ESR

V

OUT

∆

I

OUT

1

D

–

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

V

IN

D

×

2

L

×

f

SW

×

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

+









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

<

(EQ 20)

R

S

max

–

V

SEN SE

I

L

0 5

,

I

L

∆

×

+

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

=

(EQ 21)

P

RS

I

2

L

rms

–

R

S

D

×

×

=