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Hyper RAM

New Contributor

My application will use a NXP imxRT1050 FlexSPI summunication with two memory devices:

  Cypress S27KS0641DPBHV020

  Cypress S26KS256SDPBHV020

Cypress Document AN211622, section 4.1 recommends that the connecting transmission lines have 50 ohms characteristic impedance. 

The question:  Why 50 ohms characteristic impedance?  Neither the memory device drivers and receivers nor, insofar as I know, the FlexSPI port drivers and receivers, have 50 homs characteristic impedance.

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Moderator
Moderator

Hello,

We suggest you to perform signal integrity simulations using IBIS models to decide the series termination required on PCB traces.

You can download IBIS models for our devices from below links,

1. S26KS256S - https://www.cypress.com/ibis/s26ks256s-ibis

2. S27KS0641 - https://www.cypress.com/ibis/s27ks0641-ibis

Thanks and Regards,

Sudheesh

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7 Replies
Moderator
Moderator

Hello,

50ohms is the most commonly used T-line impedance in the industry. Normal practice is to match the driver/receiver impedance using series resistors or simulate to see if user can do without such resistors.

Thanks and Regards,

Sudheesh

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New Contributor

Hello Sudesh,

Thank you for the information.

Since 50 ohms is just normal practice, and neither HyperFlash nor HypeRAM are 50 ohms, is there any good reason not to set the microstrip impedance to some value other than 50 ohms?

This application will have three devices on the Hyperbus, arranged in this order on the transmission lines:

1 uP: NXP imxRT1052 FlexSPI, 8 bits wide

2. HyperFlash NOR: Cypress S26KS256SDPBHV020

3. HyperRAM: Cypress S27KS0641DPBHV020

The imxRT1052 FlexSPI drivers a characteristic impedance ranging from approximately 30 ohms to 150 ohms, including 52 ohms, depending on user selectable pin drive strength.  Neither Cypress device has a specified characteristic impedance, but have a specified capacitance.  Therefore, the series termination, if any, should go at the imxRT1052 end, correct?

Thank you,

M.Reich

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Moderator
Moderator

Hello,

We suggest you to perform signal integrity simulations using IBIS models to decide the series termination required on PCB traces.

You can download IBIS models for our devices from below links,

1. S26KS256S - https://www.cypress.com/ibis/s26ks256s-ibis

2. S27KS0641 - https://www.cypress.com/ibis/s27ks0641-ibis

Thanks and Regards,

Sudheesh

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New Contributor

Hello Sudheesh,

Thank you for the information.

You answered the question.

Thank you,

M.Reich

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New Contributor

Hello Sudheesh,

Another question, if it is possible to continue this conversation:

Please provide a link to the model for S71KS512SC0BHV000.

To reduce design risk, this design will use a combination device.

Thank you,

M.Reich

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Moderator
Moderator

Hello,

IBIS model for our device S71KS512S is available at: https://www.cypress.com/documentation/models/ibis-s71ks512s-hyperflash-and-hyperram-mcp .

Thanks and Regards,

Sudheesh

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New Contributor

Hello Sudheesh,

Thank you.

Searching did not find it.

Thank you,

M.Reich

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