LMH1226: Add bypass capacitor to power pin

K. Sasaki14

Part Number: LMH1226

I've heard that it is recommended to add additional 0.01uF capacitor to each power pin (VIN, VDDIO, VDD_LDO and VDD_CDR) of the datasheet Fig 27 configuration.

Is this needed for all power pins?

Our customer has space limitation, so they want to minimize additional parts if it is possible.

Which pin should we add additional bypass capacitor at least?

Is it OK that we add 0.01uF capacitor to only VIN and VDD_CDR pins? Please tell me if we must add to other pins.

Best Regards,
Kohei Sasaki

over 5 years ago

0 Nasser Mohammadi over 5 years ago

TI__Guru* 88835 points

Greetings Sasaki-San,

In general, it is a good desi9gn practice to use very low cap value like 0.01uF - if PCB layout space allows - to attenuated high frequency noise. On VDD_LDO it would be a good idea to put 1uF, 0.1uF, and 0.01uF. It is important to put these as close to the device - pin 23 - as possible. You can send me - through email - your customer pcb layout for review.

Regards,,nasser

0 K. Sasaki14 over 5 years ago in reply to Nasser Mohammadi

Guru 10200 points

Nasser-san,

Thank you for your reply.
Is VDD_LDO more important than VIN or VDD_CDR?
I understood we should add 0.01uF capacitor at least to VDD_LDO pin from your reply.

Please let me ask about customer layout when our customer design their PCB.

Best Regards,
Kohei Sasaki

0 Nasser Mohammadi over 5 years ago in reply to K. Sasaki14

TI__Guru* 88835 points

Sasaki-San,

Your understanding is correct. VDD_LDO is the regulated 1.8V which is used for equalizer analog core. So this is much more important than the other two supply.

Regards,,nasser

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LMH1226: Add bypass capacitor to power pin