AN4243

Designing an application with the L6230

Doc ID 024199 Rev 1

7/29

Equation 1

so the supply voltage ripple is:

Equation 2

With fast decay, instead, recirculating current recharges the capacitor, causing the supply

voltage to exceed the nominal voltage. This can be very dangerous if the nominal supply

voltage is close to the maximum recommended supply voltage (52 V). In fast decay the

supply voltage ripple is about:

Equation 3

always assuming that the power supply does not recharge the capacitor, and neglecting the

output current ripple and the deadtime.

Usually (if C > 100 µF) the capacitance role is much less than the ESR, then supply voltage

ripple can be estimated as:

Equation 4

Equation 5

should be lower than:

Equation 6

Equation 7

reverse recovery charge of internal freewheeling diodes. The duration of these peaks is,

tough, very short and can be filtered using a small value (100 ÷ 200 nF), good quality

The bulk capacitor is chosen with maximum operating voltage 25% greater than the

maximum supply voltage, considering also power supply tolerances.

V

S

I

out

ESR

t

on

C

-------

+

⎝⎠

⎛⎞

⋅

–

V

S

I

out

ESR

t

on

C

-------

+

⎝⎠

⎛⎞

⋅

–

I

OUT

2ESR

t

ON

t

OF F

+

c

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

+

⋅

⎝⎠

⎛⎞

⋅

I

OUT

ESR

in slow decay

⋅

I

OUT

ESR

in fast decay

⋅

ESR

0.5V

1A

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

500m

Ω in slow decay

=

<

ESR

1

2

---

0.5V

1A

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

⋅

250 500

()mΩ in fast decay

=

<