Receiver testing (Rx) was never a concern for DDR design. Until now. The margin for error ran out, and now Rx testing is getting standardized. We sit down with Stephanie Rubalcava to explore the challenges of this new ground.
This is the first time in the industry that high-accuracy, standardized receiver measurements need to be done
DDR is very different from traditional memory in terms of testing
Process of getting specs defined
What a DDR receiver test (DDR Rx Test) looks like
Even being just 100 mV off when testing can make a part appear to fail
The BERT sends out a signal to test the channel, but what’s really being tested is the DIMM and device’s ability to receive data under certain conditions
Receiver types across different devices? There’s a DQS data clock signal, and a data signal. There are also command and address lines in DDR.
For Rx testing, we’re calibrating the signal going into the receiver
JEDEC develops a lot of the testing standards
Two components of test standards: compliance and characterization. Compliance asks “do I meet the spec?” Characterization asks “how well does my system perform, and where is my fail point?”
Receiver test as whole is a challenge for engineers
They need new kinds of calibration, DDR fixtures, and tests.
DDR Transmitters (DDR Tx) are progressing with DDR5 as well as receivers. We do have the DDR Tx history testing all the way back to DDR1.
There are similar specifications for characteristics of DDR transmitters and DDR receivers.
DDR Transmitter testing is at “the ball of the part” and checks for signal characteristics.