DSC Test Results

The main purpose is to check the DSC's functionality. We have to check, if the Read Bit (RBI) will be clocked through the Domino pipeline and if the DSC gives out the sampled signal, which is put to the input. In figure 1 you will see the output seen on a digital scope (Tektronix TDS 540). The upper signal is the passed RBI (Read Bit Out, RBO), the lower channel shows the output for a gaussian-like input on the DSC.

DSC Output on Scope Figure 1: DSC Output on Scope. You can see the Read Bit Out and the sampled signal.
 

From 517 chips 499 have been okay, which means 97% are working fine.
After cutting the chips (6 chips on 1 wafer), we have tested some of them (random).

The complete worksheet of the chips you will find on the  DSC Database .

We found out, that there is a spread (40 mV FWHM) of the threshold voltage (see figure 2), seen by the DSC comparator, which may cause trouble for the operation of the DSC.

threshold voltage histogram Figure 2: Threshold Voltages Histogram

This effect is just an offset from chip to chip, not linear. So it is possible to adjust this threshold voltage for any chip individually (figure 3).
 

Threshold Voltage Linearity Figure 3: DSC Threshold Voltage Linearity For 6 Different DSC

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H.P. Wirtz, Dec-1998
last update 09-Aug-2000