DDR3 ODT signal with I.MX6 processors

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DDR3 ODT signal with I.MX6 processors

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Contributor III

Hello

On Sabre ref. design i see pull-down resistors (10K) on few DDR3 lines like ODT and RESET.
Are they needed? I have never seen those on ISSI and Micron datasheet. IMHO IMX6 ODT pin should be connected with DDR3 ODT pin without a pull-down resistor. Am i wrong?

Thanks

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NXP TechSupport
NXP TechSupport

Hello,

 

   There is no need for DDR3 ODT pulling down. 

DDR3 DRAM_RESET should be pulled down to  meet the JEDEC sequence until the controller is
configured and starts driving. DRAM_RESET should be kept high when DDR3 enters self-refresh mode.

 

DDR3  SDCKE[1:0] pull-down is used in the SDP\B, although it is not recommended.
DRAM_SDCKE0 and DRAM_SDCKE1 require external resistors (such as 10 kΩ) to GND to minimize current
drain during deep sleep mode (DSM).
The BSP (Board Support Package) uses a common DDR routine for both fly-by and T-topology designs.
Fly-by designs have parallel resistor termination on address lines, while T-topology does not.

During low-power self refresh, the BSP programs pad control register GRP_CTLDS to 0x00000000. Therefore,
DRAM_SDCKE0, DRAM_SDCKE1, and other associated GRP_CTLDS I/O are forced to the high-impedance state.

Because DRAM_SDCKE0 and DRAM_SDCKE1 are forced to high-Z, external pull-down resistors are required to
avoid floating outputs during standby.

Have a great day,

Yuri

 

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