DP83869EVM: 100M media converter chip selection

Aneesh Kumar Gopalakrishnan

Part Number: DP83869EVM
Other Parts Discussed in Thread: DP83869,

Tool/software:

Hi,

We are currently developing a 100M media converter (100base-TX to 100base-FX) using the DP83869. However, this chip has more functions than we need, and it seems over-designed for our application.

Can you suggest any other chips that only perform the intended function of 100base-TX to 100base-FX without using micro controller? We are looking for a small form factor and lower cost compared to the DP83869.

Thank You

Aneesh

7 months ago

0 Evan Mayhew 7 months ago

TI__Mastermind 21722 points

Hi Aneesh,

DP83869 is our only PHY that can support 100base-TX/FX media conversion. This can be achieved through straps alone, without configuration via MCU. However, we recommend MDC/MDIO access for debug.

Thank you,

Evan

0 Aneesh Kumar Gopalakrishnan 6 months ago

Prodigy 60 points

Thank you for your comments!

Below is my schematic of a 100M media converter (100base-TX to 100base-FX) using the DP83869. I referred to the DP83869EVM development board. Please provide your comments.

My question is, why can’t we use a 2.2k resistor instead of a 2.49k resistor? Do we have any internal ADC for reference?

0 Evan Mayhew 6 months ago in reply to Aneesh Kumar Gopalakrishnan

TI__Mastermind 21722 points

Hi Aneesh,

Please refer to Tables 7-9 / 7-10 to calculate acceptable strap resistor ranges.

PHY will sample voltage at pin on startup - as long as sampled voltage is between Vmin and Vmax for the intended mode, the strap resistor used is valid.

"Ideal resistor" values are selected to provide good margin between Vmin and Vmax for each mode, as the PHY's internal pull-down resistor has +/-25% tolerance.

Thank you,

Evan

0 Aneesh Kumar Gopalakrishnan 6 months ago in reply to Evan Mayhew

Prodigy 60 points

Thank you for answering my question.

And I have one more question. I don’t have the DP83869EVM development board. As per guideline we configure the hardware straps for 100M media converter application. Is it really important for debugging our converter’s reading register settings, or can we do it without the development board?

Thank You

G. Aneesh Kumar

+1 Evan Mayhew 6 months ago in reply to Aneesh Kumar Gopalakrishnan

TI__Mastermind 21722 points

Hi Aneesh,

The development board is not required, but will provide a good baseline reference if you encounter issues.

I recommend providing external test points for MDC/MDIO connections in your design, and using MSP-EXP430F5529LP as a debugging tool for external register access.

Thank you,

Evan

+1 Aneesh Kumar Gopalakrishnan 6 months ago in reply to Evan Mayhew

Prodigy 60 points

Hi Evan,

Thanks for answering my question! my proto board working fine.

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DP83869EVM: 100M media converter chip selection