Datasheet

LTC2492
20
2492fd
APPLICATIONS INFORMATION
Figure 4. Internal PTAT Digital Output vs Temperature
from the output code (DATAOUT
24
) for a 5V reference
using the following formula:
T
K
= DATAOUT
24
/314 in Kelvin
If a different value of V
REF
is used, the temperature output
is:
T
K
= DATAOUT
24
• V
REF
/1570 in Kelvin
If the value of V
REF
is not known, the slope is determined by
measuring the temperature sensor at a known temperature
T
N
(in °K) and using the following formula:
SLOPE = DATAOUT
24
/T
N
This value of slope can be used to calculate further
temperature readings using:
T
K
= DATAOUT
24
/SLOPE
All Kelvin temperature readings can be converted to T
C
(°C) using the fundamental equation:
T
C
= T
K
– 273
SERIAL INTERFACE TIMING MODES
The LTC2492’s 4-wire interface is SPI and MICROWIRE
compatible. This interface offers several fl 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 (f
O
= LOW) or an external oscillator connected to
the f
O
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 CS and SCK Figures 6, 7
External SCK, 3-Wire I/O External SCK SCK Figure 8
Internal SCK, Single Cycle
Conversion
Internal
CS↓ 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
300200100
20000
V
CC
= 5V
V
REF
= 5V
SLOPE = 314 LSB
24
/K
TEMPERATURE (°C)
–55 –30 –5
ABSOLUTE ERROR (°C)
5
4
3
2
1
–4
–3
–2
–1
0
12095704520
2492 F05
–5