Rainbow Electronics LM80 - Manual (Page 16)

Functional Description
(Continued)
7.0 TEMPERATURE MEASUREMENT SYSTEM
The LM80 bandgap type temperature sensor and ADC per-
form 9-bit or a 12-bit two’s-complement conversions of the
temperature. An 8-bit digital comparator is also incorporated
that compares the readings to the user-programmable Hot
and Overtemperature setpoints, and Hysteresis values.
7.1 Temperature Data Format
Temperature data can be read from the Temperature, T
hot
,
T
hot hyst
, T
os
and T
os hyst
setpoint registers; and written to the
T
hot
, T
hot hyst
, T
os
and T
os hyst
setpoint registers. T
hot
set
point, T
hot hyst
set point, T
os
set point and T
os hyst
tempera-
ture data is represented by an 8-bit, two’s complement word
with an LSB (Least Significant Bit) equal to 1˚C:
Temperature Digital Output
Binary Hex
+125˚C 0111 1101 7Dh
+25˚C 0001 1001 19h
+1.0˚C 0000 0001 01h
+0˚C 0000 0000 00h
−1.0˚C 1111 1111 FFh
−25˚C 1110 0111 E7h
−55˚C 1100 1001 C9h
DS100040-20
(Non-Linear Scale for Clarity)
FIGURE 8. 9-bit Temperature-to-Digital Transfer
Function
DS100040-16
(Non-Linear Scale for Clarity)
FIGURE 9. 12-bit Temperature-to-Digital Transfer
Function
LM80
www.national.com 16