5

RADIATION HARDNESS

The UT28F256 PROM incorporates special design and layout

features which allow operation in high-level radiation

environments. UTMC has developed special low-temperature

processing techniques designed to enhance the total-dose

radiation hardness of both the gate oxide and the field oxide while

maintaining the circuit density and reliability. For transient

radiation hardness and latchup immunity, UTMC builds all

radiation-hardened products on epitaxial wafers using an

advanced twin-tub CMOS process. In addition, UTMC pays

special attention to power and ground distribution during the

design phase, minimizing dose-rate upset caused by rail collapse.

Note:

1. The PROM will not latchup during radiation exposure under recommended operating conditions.

Figure 2. PROM Read Cycle

t

ELQV

t

AVQV

t

AXQX

A(14:0)

CE

OE

DQ(7:0)

Total Dose

1E6

rad(Si)

Latchup LET Threshold

>128

MeV-cm

Memory Cell LET Threshold

>128

Transient Upset LET Threshold

54

1E-6