General
Review and verify the following for the custom
schematic design:
- Above sections, including relevant application notes and
FAQ links
- Pin attributes, signal description, and electrical
specifications
- Electrical characteristics, timing parameters, and any
additional available information
- Connection of address, clock, control and data signals,
follow the processor-specific DDR design
guidelines
- Routing topology based on number of memory
devices connected (data bus topology is always point-to-point). 1x 16
(point-to-point) and 2x 8 (daisy) are the allowed configurations
- Connection of signals based on the selected
memory size (CS0, BG0-1)
- Differential clock termination using 2x resistors
and filter capacitor for point-to-point and daisy chain memory interface
configuration
- DDR0_CAL0, DDRSS IO pad calibration resistor (240Ω, 1%)
connected to VSS
- Resistor divider configuration (1kΩ, 1%) for DDR
reference generation DDR_VREFCA. Place decoupling
capacitor 0.1μF across the resistor divider and near
to the memory pin
- Termination (VTT) of address and control signals
when x2 memory device are used (optional for point-to-point connection)
- VTT resistor and capacitor (1 for every 2 VTT resistors)
quantity and values - follow EVM and design
guide
- VTT termination LDO implementation and
configuration for when x2 memory devices are used
- ZQ0-1, Memory device IO calibration resistor
(240Ω, 1%) connected to VSS
- Connection of alert (10kΩ pullup) and TEN (1kΩ
pulldown)
- Connection of ODT from DDRSS to memory device - external
pull is optional
- Connection of processor DDRSS RESETn signal
directly to DDR_RESETn memory reset input. To hold the signal low during
power-on initialization, add pulldown (10kΩ) and placed near the memory
device reset pin
- Connection of unused DDRSS interface signals as per pin
connectivity requirements
- DDR design guidelines for swapping of the data group
signals
- Connection of required DDRSS signals for memory
expansion
Schematic Review
Follow the below list for the custom
schematic design:
- Compare the bulk and decoupling capacitors used
and the values with EVM schematics
- Value and tolerance used for
the calibration resistors
- Value of the VTT resistors
and capacitors
- DDR reference voltage divider
value and tolerance
- Reset pulldown value and
connection of alert, TEN pulls
- Memory selected confirms to
the JEDEC standards
- Supply rails connected follow
the ROC
Additional
- Refer TMDS64EVM for implementing
VTT terminations for DDR4 address and control signals and LDO for generating VTT
supply
- Add layout notes on the schematic (for DDR
routing to follow the recommended guidelines)