E202075_HD404889 Datasheet, PDF (164/202 Pages) Renesas Technology Corp – Low-Voltage AS Microcomputers with On-Chip LCD Circuit

HD404889/HD404899/HD404878/HD404868 Series
PROM Reliability after Programming: In general, semiconductor devices retain their reliability,
provided that some initial defects can be excluded. These initial defects can be detected and rejected by
screening. Baking devices under high-temperature conditions is one method of screening that can rapidly
eliminate data-hold defects in memory cells. (Refer to the previous Principles of Programming/Erasure
section.)
ZTAT™ microcomputer devices are extremely reliable because they have been subjected to such a
screening method during the wafer fabrication process, but Hitachi recommends that each device be
exposed to 150°C at one atmosphere for at least 48 hours after it is programmed, to ensure its best
performance. The recommended screening procedure is shown in figure 99.
Note: If programming errors occur continuously during PROM programming, suspend programming and
check for problems in the PROM programmer or socket adapter. If programming verification
indicates errors in programming or after high-temperature exposure, please inform Hitachi.
Programming, verification
Exposure to high temperature, without power
150°C ± 10°C, 48 h ^{+8 h *}
–0 h
Program read check
V_CC = 4.5 V or 5.5 V
Note: Exposure time is measured from when the temperature in the heater reaches 150°C.
Figure 99 Recommended Screening Procedure
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