LTC1392CS8 View Datasheet(PDF) - Linear Technology
Part Name
Description
MFG CO.
'LTC1392CS8' PDF : 12 Pages View PDF
LTC1392
APPLICATIONS INFORMATION
Differential Voltage Conversion
The LTC1392 measures the differential input voltage
through pins + VIN and – VIN. Input ranges of 0.5V or 1V
full scale are available for differential voltage measure-
ment with resolutions of 10 bits. Tables 4a and 4b describe
the exact relationship of output data to measured differen-
tial input voltage in the 1V and 0.5V input range. Equations
(3) and (4) can be used to calculate the differential voltage
in the 1V and 0.5V input voltage range respectively. The
output code is in unipolar format.
Differential Voltage = 1V • (10-bit code)/1024 (3)
Differential Voltage = 0.5V • (10-bit code)/1024 (4)
Table 4a. Codes for 1V Differential Voltage Range
OUTPUT
CODE
INPUT
VOLTAGE
INPUT
RANGE = 1V
REMARKS
1111111111 1V – 1LSB
999.0mV
1111111110 1V – 2LSB
998.0mV
...
...
...
0000000001
1LSB
0.977mV
1LSB = 1/1024
0000000000
0LSB
0.00mV
Table 4b. Codes for 0.5V Differential Voltage Range
OUTPUT
CODE
INPUT
VOLTAGE
INPUT
RANGE = 0.5V
REMARKS
1111111111 0.5V – 1LSB
499.5mV
1111111110 0.5V – 2LSB
499.0mV
...
...
...
0000000001
1LSB
0.488mV
1LSB = 0.5/1024
0000000000
0LSB
0.00mV
Thermal Coupling/Airflow
The supply current of the LTC1392 is 700µA typically
when running at the maximum conversion rate. The equiva-
lent power dissipation of 3.5mW causes a temperature
rise of 0.455°C in the SO8 and 0.35°C in PDIP packages
due to self-heating effects. At sampling rates less than 400
samples per second, less than 20µA current is drawn from
the supply (see Typical Performance Characteristics) and
the die self-heating effect is negligible. This LTC1392 can
be attached to a surface (such as microprocessor chip or
a heat sink) for precision temperature monitoring. The
package leads are the principal path to carry the heat into
the device; thus any wiring leaving the device should be
held at the same temperature as the surface. The easiest
way to do this is to cover up the wires with a bead of epoxy
which will ensure that the leads and wires are at the same
temperature as the surface. The thermal time constant of
the LTC1392 in still air is about 22 seconds (see the graph
in the Typical Performance Charateristics section). At-
taching an LTC1392 to a small metal fin (which also
provides a small thermal mass) will help reduce thermal
time constant, speed up the response and give the steadi-
est reading in slow moving air.
9
Share Link: 
