SN54ALS526, SN54ALS527, SN54ALS528

SN74ALS526, SN74ALS527, SN74ALS528

FUSE-PROGRAMMABLE IDENTITY COMPARATORS

SDAS051A – JUNE 1984–REVISED MAY 1986

POST OFFICE BOX 655303

2

description

The ’ALS526 and ’ALS528 are fuse-programmable identity comparators designed for easy programming in

fixed-comparator applications. The ’ALS526 compares a 16-bit data word against a preprogrammed 16-bit data

word while the ’ALS528 compares a 12-bit data word against a preprogrammed 12-bit data word. The P = Q

output will go low when the applied data word (P inputs) matches the preprogrammed data word (Q represents

the preprogrammed data word). Programming is easily accomplished on the bench or with conventional

automatic test equipment. Special equipment such as PROM programmers are not required.

The ’ALS527 is a combination of an 8-bit fuse-programmable comparator and a conventional 4-bit comparator.

For the P = Q output to go low, the applied data word P0 through P7 must match the preprogrammed data word

Q0 through Q7, and the applied data word P8 through P11 must match the applied data word Q8 through Q11.

The SN54ALS526, SN54ALS527, and SN54ALS528 are characterized for operation over the full military

temperature range of – 55

°C to 125°C. The SN74ALS526, SN74ALS527, and SN74ALS528 are characterized

for operation from 0

°C to 70°C.

programming procedure

Before any fuses are blown, the inputs will recognize a low logic level. Therefore, only the bits that are to

input and also to the G input. This permanently programs the pin to recognize a high. Only one input pin should

be programmed at a time.

Step 1.

Step 2.

Step 3.

Step 4.

verification procedure

These devices can be checked to determine which fuses, if any, are blown. Figure 1 shows how verification can

be accomplished during programming.

Step 1.

Step 2.

blown then the output will be low.

Step 3.

output goes high, the fuse is blown.

Step 4.

† For the ’ALS527, P8 through P11 inputs must match the Q8 through Q11 inputs.