Theory of Operation
b)
Minimum Data Retention Time:
Total Current Drain = Clock + RAM + Buffer
=
1 uA + 50 uA + 80 uA
= 111 uA
Battery Life =
1 AHr
x
1 Day
x
1
-----
---
(24-8)Hr
111 uA
= 563 Days (1.5 years)
2.
Real-time clock, 32 Kbyte static RAM, one 128 Kbyte static
RAM (monolithic part assumed)
a)
Typical Data Retention Time:
Total Current Drain = Clock + RAM + 128 Kbyte RAM
=
1 uA + 1 uA + 8 uA + 1 uA
= 11 uA
Battery Life =
1 AHr
x
1 Day
x
1
-----
---
(24-8)Hr
11 uA
= 5896 Days (16.1 years)
Note: Again, the typical shelf life is 10 years, which would
become the limit here.
b)
Minimum Data Retention Time:
Total Current Drain = Clock + RAM + 128 Kbyte RAM
=
1 uA + 50 uA + 80 uA + 50 uA
= 181 uA
Battery Life =
1 AHr
x
1 Day
x
1
-----
---
(24-8)Hr
181 uA
= 345 Days (.95 years)
3-24