LTC1392C View Datasheet(PDF) - Linear Technology
Part Name
Description
MFG CO.
'LTC1392C' PDF : 12 Pages View PDF
LTC1392
APPLICATIONS INFORMATION
Measurement Mode Selections
The two bits of the input word following the Start Bit assign
the measurement mode for the requested conversion.
Table 1 shows the mode selections. Whenever there is a
mode change from another mode to temperature mea-
surement, a temperature mode initializing cycle is needed.
The first temperature data measurement after a mode
change should be ignored.
Table 1. Measurement Mode Selections
SELECT
1
SELECT
0
MEASUREMENT MODE
0
0
Temperature
0
1
Power Supply Voltage
1
0
Differential Input, 1V Full Scale
1
1
Differential Input, 0.5V Full Scale
MSB-First/LSB-First (MSBF)
The output data of the LTC1392 is programmed for
MSB-first or LSB-first sequence using the MSBF bit. When
the MSBF bit is a logical one, data will appear on the DOUT
line in MSB-first format. Logical zeros will be filled in
indefinitely following the last data bit to accommodate
longer word lengths required by some microprocessors.
When the MSBF bit is a logical zero, LSB-first data will
follow the normal MSB-first data on the DOUT line.
CONVERSIONS
Temperature Conversion
The LTC1392 measures temperature through the use of an
on-chip, proprietary temperature measurement technique.
The temperature reading is provided in a 10-bit, unipolar
format. Table 2 describes the exact relationship of output
data to measured temperature or equation 1 can be used
to calculate the temperature.
Temperature (°C) = Output Code/4 – 130
(1)
Note that the LTC1392C is only specified for operation
over the 0°C to 70°C temperature range and the LTC1392I
over the – 40°C to 85°C range. Performance at tempera-
tures outside these specified temperature ranges is not
guaranteed and errors may be greater than those shown in
the Electrical Characteristics table.
Table 2. Codes for Temperature Conversion
OUTPUT CODE
TEMPERATURE (°C)
1111111111
125.75
1111111110
125.50
...
...
1001101101
25.25
1001101100
25.00
1001101011
24.75
...
...
0000000001
– 129.75
0000000000
– 130.00
Voltage Supply (VCC) Monitor
The LTC1392 measures supply voltage through the on-
chip VCC supply line. The VCC reading is provided in a
10-bit, unipolar format. Table 3 describes the exact rela-
tionship of output data to measured VCC or equation (2)
can be used to calculate the measured VCC.
Measured VCC =
[(Output Code) • 4.84/1024] + 2.42
(2)
The guaranteed supply voltage monitor range is from 4.5V
to 6V. Typical parts are able to maintain measurement
accuracy with VCC as low as 3.25V. The typical INL and
DNL error plots shown on page 4 are measured with VCC
from 3.63V to 6.353V.
Table 3. Codes for Voltage Supply Conversion
OUTPUT CODE
1011110110
Supply Voltage (VCC)
6.003V
1011110101
5.998V
...
...
1000100010
5.001V
...
...
0110111001
4.504V
0110111000
4.500V
8
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