TPS53353: About TPS53353 datasheet ripple injection formula

Frank Xiao

Genius 12055 points

Part Number: TPS53353

Hi team,

We find the TPS53353 datasheet talk about the ripple injection circuit.

we want to check:

1. what does Ton mean? D*T?

2. How to get the formula and N value?

3. Why VINJ_SW need to be less than 50mv? And which value should be better?

Thanks.

over 7 years ago

0 JohnTucker over 7 years ago

TI__Guru**** 191445 points

Frank,

Ton is the on time. Ton = Vout / (Vin * Fsw)

For N, use 2 for Vout less than or equal 10 1.8 V. N = 3 for Vout between 1.8 and 3.3 V. N = 4 for Vout greater or equal to 3.3 V or any time Lout less than 250 nH. There is no formula other than that.

50 mV is the maximum recommended ripple injection. You should try for 15 to 20 mV.

0 Frank Xiao over 7 years ago in reply to JohnTucker

TI__Genius 12055 points

Hi John,

Why 50mv is max, in my opinion, larger ripple will only cause accuracy problem. Thanks.

0 JohnTucker over 7 years ago in reply to Frank Xiao

TI__Guru**** 191445 points

Lower ripple can cause excessive jitter. Increasing ripple reduces jitter but can slow transient response. Excessive ripple may cause instability.

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TPS53353: About TPS53353 datasheet ripple injection formula