
LTC2492
20
2492fd
APPLICATIONS INFORMATION
Figure 4. Internal PTAT Digital Output vs Temperature
from the output code (DATAOUT24) for a 5V reference
using the following formula:
TK = DATAOUT24/314 in Kelvin
If a different value of VREF is used, the temperature output
is:
TK = DATAOUT24 VREF/1570 in Kelvin
If the value of VREF is not known, the slope is determined by
measuring the temperature sensor at a known temperature
TN (in °K) and using the following formula:
SLOPE = DATAOUT24/TN
This value of slope can be used to calculate further
temperature readings using:
TK = DATAOUT24/SLOPE
All Kelvin temperature readings can be converted to TC
(°C) using the fundamental equation:
TC = TK – 273
SERIAL INTERFACE TIMING MODES
The LTC2492’s 4-wire interface is SPI and MICROWIRE
compatible. This interface offers several exible modes
of operation. These include internal/external serial clock,
3- or 4-wire I/O, single cycle or continuous conversion. The
following sections describe each of these timing modes
in detail. In all cases, the converter can use the internal
oscillator (fO = LOW) or an external oscillator connected to
the fO pin. For each mode, the operating cycle, data input
format, data output format, and performance remain the
same. Refer to Table 5 for a summary.
Figure 5. Absolute Temperature Error
Table 5. Serial Interface Timing Modes
CONFIGURATION
SCK
SOURCE
CONVERSION
CYCLE CONTROL
DATA OUTPUT
CONTROL
CONNECTION AND
WAVEFORMS
External SCK, Single Cycle
Conversion
External
CS and SCK
Figures 6, 7
External SCK, 3-Wire I/O
External
SCK
Figure 8
Internal SCK, Single Cycle
Conversion
Internal
CS↓
Figures 9, 10
Internal SCK, 3-Wire I/O,
Continuous Conversion
Internal
Continuous
Internal
Figure 11
TEMPERATURE (K)
0
DATAOUT
24
60000
80000
100000
120000
140000
400
2492 F04
40000
0
300
200
100
20000
VCC = 5V
VREF = 5V
SLOPE = 314 LSB24/K
TEMPERATURE (°C)
–55
–30
–5
ABSOLUTE
ERROR
(°C)
5
4
3
2
1
–4
–3
–2
–1
0
120
95
70
45
20
2492 F05
–5