8

LTC1392

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

SELECT

1

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

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

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

The LTC1392 measures supply voltage through the on-

10-bit, unipolar format. Table 3 describes the exact rela-

[(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

from 3.63V to 6.353V.

Table 3. Codes for Voltage Supply Conversion

OUTPUT CODE

1011110110

6.003V

1011110101

5.998V

...

...

1000100010

5.001V

...

...

0110111001

4.504V

0110111000

4.500V