UCD9090A: About V33A RC filter

minoru.takeuchi

Part Number: UCD9090A
Other Parts Discussed in Thread: UCD90SEQ48EVM-560, UCD9090

We are currently designing the peripheral circuit for UCD9090A.
The documentation recommends a 5Ω resistor and 4.7uF capacitor for the connection from V33D to V33A.
However, the 5Ω resistor that is inserted into the power line is generally a shunt resistor for current measurement.

This is expensive and even less available.
Are there any other options?
By the way, in the UCD90SEQ48EVM-560 document (slvu464a), a 220Ω ferrite bead (BLM21PG221SN) is selected.

8 months ago

0 yihe 8 months ago

TI__Guru 60100 points

the 4.99ohm + CAP is to formal a good low-pass filter on the V33A which is the source for the internal analog circuity.

Regards

Yihe

0 minoru.takeuchi 8 months ago in reply to yihe

Prodigy 60 points

Hi Yihe,

Thank you for your reply.

We don't want to know why we use 4.99ohm, we don't want to use 4.99, so we want a replacement part.
The cutoff frequency of the 4.99ohm and 4.7uF Low Pass filters is 7KHz, but it does not necessarily have to be such a cutoff frequency.
We think this is the reason why TI's UCD9090 evaluation board uses a 220Ω ferrite bead (BLM21PG221SN).

0 yihe 8 months ago in reply to minoru.takeuchi

TI__Guru 60100 points

We recommend this based on the latest design advice and the EVM was developed before.

Regards

Yihe

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UCD9090A: About V33A RC filter