Datasheet LTC1392 (Analog Devices) - 8
| Manufacturer | Analog Devices |
| Description | Micropower Temperature, Power Supply and Differential Voltage Monitor |
| Pages / Page | 12 / 8 — APPLICATIONS INFORMATION. Measurement Mode Selections. Table 2. Codes for … |
| File Format / Size | PDF / 259 Kb |
| Document Language | English |
APPLICATIONS INFORMATION. Measurement Mode Selections. Table 2. Codes for Temperature Conversion. OUTPUT CODE. TEMPERATURE (
Model Line for this Datasheet
Text Version of Document
LTC1392
U U W U APPLICATIONS INFORMATION Measurement Mode Selections
tures outside these specified temperature ranges is not guaranteed and errors may be greater than those shown in The two bits of the input word following the Start Bit assign the Electrical Characteristics table. the measurement mode for the requested conversion. Table 1 shows the mode selections. Whenever there is a
Table 2. Codes for Temperature Conversion
mode change from another mode to temperature mea-
OUTPUT CODE TEMPERATURE (
°
C)
surement, a temperature mode initializing cycle is needed. 1111111111 125.75 The first temperature data measurement after a mode 1111111110 125.50 change should be ignored. ... ...
Table 1. Measurement Mode Selections
1001101101 25.25
SELECT SELECT
1001101100 25.00
1 0 MEASUREMENT MODE
1001101011 24.75 0 0 Temperature ... ... 0 1 Power Supply Voltage 0000000001 – 129.75 1 0 Differential Input, 1V Full Scale 0000000000 – 130.00 1 1 Differential Input, 0.5V Full Scale
Voltage Supply (VCC) Monitor MSB-First/LSB-First (MSBF)
The LTC1392 measures supply voltage through the on- The output data of the LTC1392 is programmed for chip VCC supply line. The VCC reading is provided in a MSB-first or LSB-first sequence using the MSBF bit. When 10-bit, unipolar format. Table 3 describes the exact rela- the MSBF bit is a logical one, data will appear on the DOUT tionship of output data to measured VCC or equation (2) line in MSB-first format. Logical zeros will be filled in can be used to calculate the measured VCC. indefinitely following the last data bit to accommodate Measured V longer word lengths required by some microprocessors. CC = [(Output Code) • 4.84/1024] + 2.42 (2) When the MSBF bit is a logical zero, LSB-first data will follow the normal MSB-first data on the DOUT line. The guaranteed supply voltage monitor range is from 4.5V to 6V. Typical parts are able to maintain measurement
CONVERSIONS
accuracy with VCC as low as 3.25V. The typical INL and DNL error plots shown on page 4 are measured with VCC
Temperature Conversion
from 3.63V to 6.353V. The LTC1392 measures temperature through the use of an
Table 3. Codes for Voltage Supply Conversion
on-chip, proprietary temperature measurement technique.
OUTPUT CODE Supply Voltage (VCC)
The temperature reading is provided in a 10-bit, unipolar 1011110110 6.003V format. Table 2 describes the exact relationship of output 1011110101 5.998V data to measured temperature or equation 1 can be used ... ... to calculate the temperature. 1000100010 5.001V Temperature (°C) = Output Code/4 – 130 (1) ... ... 0110111001 4.504V Note that the LTC1392C is only specified for operation 0110111000 4.500V over the 0°C to 70°C temperature range and the LTC1392I over the – 40°C to 85°C range. Performance at tempera- 8
U U W U APPLICATIONS INFORMATION Measurement Mode Selections
tures outside these specified temperature ranges is not guaranteed and errors may be greater than those shown in The two bits of the input word following the Start Bit assign the Electrical Characteristics table. the measurement mode for the requested conversion. Table 1 shows the mode selections. Whenever there is a
Table 2. Codes for Temperature Conversion
mode change from another mode to temperature mea-
OUTPUT CODE TEMPERATURE (
°
C)
surement, a temperature mode initializing cycle is needed. 1111111111 125.75 The first temperature data measurement after a mode 1111111110 125.50 change should be ignored. ... ...
Table 1. Measurement Mode Selections
1001101101 25.25
SELECT SELECT
1001101100 25.00
1 0 MEASUREMENT MODE
1001101011 24.75 0 0 Temperature ... ... 0 1 Power Supply Voltage 0000000001 – 129.75 1 0 Differential Input, 1V Full Scale 0000000000 – 130.00 1 1 Differential Input, 0.5V Full Scale
Voltage Supply (VCC) Monitor MSB-First/LSB-First (MSBF)
The LTC1392 measures supply voltage through the on- The output data of the LTC1392 is programmed for chip VCC supply line. The VCC reading is provided in a MSB-first or LSB-first sequence using the MSBF bit. When 10-bit, unipolar format. Table 3 describes the exact rela- the MSBF bit is a logical one, data will appear on the DOUT tionship of output data to measured VCC or equation (2) line in MSB-first format. Logical zeros will be filled in can be used to calculate the measured VCC. indefinitely following the last data bit to accommodate Measured V longer word lengths required by some microprocessors. CC = [(Output Code) • 4.84/1024] + 2.42 (2) When the MSBF bit is a logical zero, LSB-first data will follow the normal MSB-first data on the DOUT line. The guaranteed supply voltage monitor range is from 4.5V to 6V. Typical parts are able to maintain measurement
CONVERSIONS
accuracy with VCC as low as 3.25V. The typical INL and DNL error plots shown on page 4 are measured with VCC
Temperature Conversion
from 3.63V to 6.353V. The LTC1392 measures temperature through the use of an
Table 3. Codes for Voltage Supply Conversion
on-chip, proprietary temperature measurement technique.
OUTPUT CODE Supply Voltage (VCC)
The temperature reading is provided in a 10-bit, unipolar 1011110110 6.003V format. Table 2 describes the exact relationship of output 1011110101 5.998V data to measured temperature or equation 1 can be used ... ... to calculate the temperature. 1000100010 5.001V Temperature (°C) = Output Code/4 – 130 (1) ... ... 0110111001 4.504V Note that the LTC1392C is only specified for operation 0110111000 4.500V over the 0°C to 70°C temperature range and the LTC1392I over the – 40°C to 85°C range. Performance at tempera- 8
