Timing parameters
DDR Tool uses default timing parameter values, compliant with LPDDR4 JEDEC standard specifications. There are 2 types of parameters:
- Density dependent parameters (e.g. refresh cycle times, average refresh interval, etc.)
- Data rate dependent parameters (e.g. read/write latencies)
All the timing parameters are automatically calculated based on JEDEC formulas and the DRAM settings inputted in DDR View (clock frequency, density per channel, number of channels, etc.).
For example, considering a dual rank, dual channel DRAM, with 4Gb density per channel and running at 1600 MHz DDR clock frequency (3200 MT/s data rate) the following values are used:
| Symbol | Parameter | Value |
| RL | Read-Latency with no DBI | 28 nCK |
| WL | Write-Latency of set A | 14 nCK |
| nWR | Number of clock cycles used to determine the starting point of an internal Precharge operation after a Write burst with AP | 30 nCK |
| nRTP | Number of clock cycles used to determine the starting point of an internal Precharge operation after a Read burst with AP | 12 nCK |
| tREFI | Average Refresh Interval (all banks) | 3904 us |
| tREFIpb | Average Refresh Interval (per bank) | 488 ns |
| tRFCab | Refresh Cycle Time (all banks) | 180 ns |
| tRFCpb | Refresh Cycle Time (per bank) | 90 ns |
| tpbR2pbR | Per-bank refresh to Per-bank refresh time (different bank) | 90 ns |
| tSR | Minimum Self-Refresh time (entry to exit) | 15 ns |
| tXSR | Self-Refresh exit to next valid command delay | 187.5 ns |
| tXP | Exit Power-Down to next valid command delay | 7.5 ns |
| tRPbp | Row precharge time (single bank) | 18 ns |
| tRPab | Row precharge time (all banks) | 21 ns |
| tRAS min | Minimum time between activate and precharge to the same bank | 42 ns |
| … | … | … |