LTC2984 datasheet(21/78 Pages) AD

21 / 78 page

LTC2984

2984fb

For more information www.linear.com/LTC2984

BitsB4toB0determinewhichinputchanneltheconversion

is performed upon and are simply the binary equivalent

of the channel number (see Table 7). These bits are also

usedforEEPROMreadandwriteoperations(seeTable14).

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.

State 4: Conversion

The measurement cycle starts after the initiate conversion

command is written into RAM location 0x000 (Table 6).

The LTC2984 simultaneously measures the selected input

sensor, sense resistors (RTDs and thermistors), and cold

junction temperatures if applicable (thermocouples).

Once the conversion is started, the user is locked out of

the RAM, with the exception of reading status data stored

in RAM memory location 0x000.

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.Detailsdescribingthesemodesaredescribed

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 com-

mandstatusregisterinRAMmemorylocation0x000(startbit,

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).

APPLICATIONS INFORMATION

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 resolution. Included with the conver-

sion result are seven sensor fault bits and a valid bit.

These bits are set to a 1 if there was a problem as-

sociated 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 accuracy 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.

Oncethedatareadiscomplete,thedeviceisreadyforanew

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.

Table 8. Conversion Result Memory Map

CONVERSION

CHANNEL

START

ADDRESS

END ADDRESS SIZE (BYTES)

CH1

0x010

0x013

CH2

0x014

0x017

CH3

0x018

0x01B

CH4

0x01C

0x01F

CH5

0x020

0x023

CH6

0x024

0x027

CH7

0x028

0x02B

CH8

0x02C

0x02F

CH9

0x030

0x033

CH10

0x034

0x037

CH11

0x038

0x03B

CH12

0x03C

0x03F

CH13

0x040

0x043

CH14

0x044

0x047

CH15

0x048

0x04B

CH16

0x04C

0x04F

CH17

0x050

0x053

CH18

0x054

0x057

CH19

0x058

0x05B

CH20

0x05C

0x05F

LTC2984 Datasheet(PDF) 21 Page - Analog Devices

LTC2984 Datasheet(HTML) 21 Page - Analog Devices

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78

Datasheet Download

Link URL