LTC2983C View Datasheet(PDF) - Linear Technology
Part Name
Description
MFG CO.
'LTC2983C' PDF : 72 Pages View PDF
LTC2983
Applications Information
Bits B4 to B0 determine which input channel the conversion
is performed upon and are simply the binary equivalent
of the channel number (see Table 7).
Bit B5 should be set to 0.
Bits B7 and B6 serve as start/done bits. In order to start
a conversion, these bits must be set to “10” (B7=1 and
B6=0). When the conversion begins, the INTERRUPT
pin goes LOW. Once the conversion is complete, bits B7
and B6 will toggle to “01” (B7=0 and B6=1) (Address =
0x000) and the INTERRUPT pin will go HIGH, indicating
the conversion is complete and the result is available.
Table 8. Conversion Result Memory Map
CONVERSION
CHANNEL
START
END ADDRESS SIZE (BYTES)
ADDRESS
CH1
0x010
0x013
4
CH2
0x014
0x017
4
CH3
0x018
0x01B
4
CH4
0x01C
0x01F
4
CH5
0x020
0x023
4
CH6
0x024
0x027
4
CH7
0x028
0x02B
4
CH8
0x02C
0x02F
4
CH9
0x030
0x033
4
State 4: Conversion
CH10
0x034
0x037
4
CH11
0x038
0x03B
4
The measurement cycle starts after the initiate conversion
CH12
0x03C
0x03F
4
command is written into RAM location 0x000 (Table 6).
CH13
0x040
0x043
4
The LTC2983 simultaneously measures the selected input
CH14
0x044
0x047
4
sensor, sense resistors (RTDs and thermistors), and cold
CH15
0x048
0x04B
4
junction temperatures if applicable (thermocouples).
CH16
0x04C
0x04F
4
Once the conversion is started, the user is locked out of
CH17
0x050
0x053
4
the RAM, with the exception of reading status data stored
CH18
0x054
0x057
4
in RAM memory location 0x000.
CH19
0x058
0x05B
4
Once the conversion is started the INTERRUPT pin goes
low. Depending on the sensor configuration, two or three
82ms cycles are required per temperature result. These
correspond to conversion rates of 167ms and 251ms,
respectively. Details describing these modes are described
in the 2- and 3-cycle Conversion Modes section of the
data sheet.
The end of conversion can be monitored either through
the interrupt pin (LOW to HIGH transition), or by reading
the command status register in RAM memory location
0x000 (start bit, B7, toggles from 1 to 0 and DONE bit,
B6, toggles from 0 to 1).
State 5: Read Results
Once the conversion is complete, the conversion results
can be read from RAM memory locations corresponding
to the input channel (see Table 8).
The conversion result is 32 bits long and contains both
the sensor temperature (D23 to D0) and sensor fault data
(D31 to D24) (see Tables 9A and 9B).
CH20
0x05C
0x05F
4
The result is reported in °C for all temperature sensors with a
range of –273.16°C to 8192°C and 1/1024°C resolution or in
°F with a range of –459.67°F to 8192°F with 1/1024°F reso-
lution. Included with the conversion result are seven sensor
fault bits and a valid bit. These bits are set to a 1 if there was a
problem associated with the corresponding conversion result
(see Table 10). Two types of errors are reported: hard errors
and soft errors. Hard errors indicate the reading is invalid
and the resulting temperature reported is –999°C or °F. Soft
errors indicate operation beyond the normal temperature
range of the sensor or the input range of the ADC. In this
case, the calculated temperature is reported but the ac-
curacy may be compromised. Details relating to each fault
type are sensor specific and are described in detail in the
sensor specific sections of this data sheet. Bit D24 is the
valid bit and will be set to a 1 for valid data.
Once the data read is complete, the device is ready for a new
initiate conversion command. In cases where new channel
configuration data is required, the user has access to the
RAM in order to modify existing channel assignment data.
2983fa
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