External Memory Interface Handbook Volume 2: Design Guidelines

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ID 683385
Date 5/08/2017
Public
Document Table of Contents

7.3.4.1. Setup and Hold Derating for UniPHY IP

The slew rate of the output signals affects the setup and hold times of the memory device, and thus the write margin. You can specify the slew rate of the output signals to see their effect on the setup and hold times of both the address and command signals and the DQ signals, or alternatively, you may want to specify the setup and hold times directly.

For RDIMMs, the slew rate is defined at the register on the RDIMM, instead of at the memory component. For LRDIMMs, the slew rate is defined at the buffer on the LRDIMM, instead of at the memory component.

Note: You should enter information derived during your PCB development process of prelayout (line) and postlayout (board) simulation.

The following table lists the setup and hold derating parameters.

Table 77.  Setup and Hold Derating Parameters

Parameter

Description

LPDDR2/DDR2/DDR3 SDRAM/RLDRAM 3

Derating method

Derating method. The default settings are based on Intel® internal board simulation data. To obtain accurate timing analysis according to the condition of your board, Intel recommends that you perform board simulation and enter the slew rate in the Quartus Prime software to calculate the derated setup and hold time automatically or enter the derated setup and hold time directly.

For more information, refer to the “Timing Deration Methodology for Multiple Chip Select DDR2 and DDR3 SDRAM Designs” section in the Analyzing Timing of Memory IP chapter.

CK/CK# slew rate (differential)

CK/CK# slew rate (differential).

Address/Command slew rate

Address and command slew rate.

DQS/DQS# slew rate (Differential)

DQS and DQS# slew rate (differential).

DQ slew rate

DQ slew rate.

tIS

Address/command setup time to CK.

tIH

Address/command hold time from CK.

tDS

Data setup time to DQS.

tDH

Data hold time from DQS.

RLDRAM II

tAS Vref to CK/CK# Crossing

For a given address/command and CK/CK# slew rate, the memory device data sheet provides a corresponding "tAS Vref to CK/CK# Crossing" value that can be used to determine the derated address/command setup time.

tAS VIH MIN to CK/CK# Crossing

For a given address/command and CK/CK# slew rate, the memory device data sheet provides a corresponding "tAS VIH MIN to CK/CK# Crossing" value that can be used to determine the derated address/command setup time.

tAH CK/CK# Crossing to Vref

For a given address/command and CK/CK# slew rate, the memory device data sheet provides a corresponding "tAH CK/CK# Crossing to Vref" value that can be used to determine the derated address/command hold time.

tAH CK/CK# Crossing to VIH MIN

For a given address/command and CK/CK# slew rate, the memory device data sheet provides a corresponding "tAH CK/CK# Crossing to VIH MIN" value that can be used to determine the derated address/command hold time.

tDS Vref to CK/CK# Crossing

For a given data and DK/DK# slew rate, the memory device data sheet provides a corresponding "tDS Vref to CK/CK# Crossing" value that can be used to determine the derated data setup time.

tDS VIH MIN to CK/CK# Crossing

For a given data and DK/DK# slew rate, the memory device data sheet provides a corresponding "tDS VIH MIN to CK/CK# Crossing" value that can be used to determine the derated data setup time.

tDH CK/CK# Crossing to Vref

For a given data and DK/DK# slew rate, the memory device data sheet provides a corresponding "tDH CK/CK# Crossing to Vref" value that can be used to determine the derated data hold time.

tDH CK/CK# Crossing to VIH MIN

For a given data and DK/DK# slew rate, the memory device data sheet provides a corresponding "tDH CK/CK# Crossing to VIH MIN" value that can be used to determine the derated data hold time.

Derated tAS

The derated address/command setup time is calculated automatically from the "tAS", the "tAS Vref to CK/CK# Crossing", and the "tAS VIH MIN to CK/CK# Crossing" parameters.

Derated tAH

The derated address/command hold time is calculated automatically from the "tAH", the "tAH CK/CK# Crossing to Vref", and the "tAH CK/CK# Crossing to VIH MIN" parameters.

Derated tDS

The derated data setup time is calculated automatically from the "tDS", the "tDS Vref to CK/CK# Crossing", and the "tDS VIH MIN to CK/CK# Crossing" parameters.

Derated tDH

The derated data hold time is calculated automatically from the "tDH", the "tDH CK/CK# Crossing to Vref", and the "tDH CK/CK# Crossing to VIH MIN" parameters.

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