LTC2487 Linear Technology, LTC2487 Datasheet - Page 19

• Manufacturer Part Number: LTC2487
• Description: 16-Bit 2-/4-Channel ADC
• Manufacturer: Linear Technology

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applicaTions inForMaTion
(see Figures 4 and 5). Slope calibration is not required if
the reference voltage (V
a slope of 2.45 LSBs
from the output code (where DATAOUT
representation of the 16-bit result) for a 5V reference using
the following formula:
If a different value of V
output is:
T
T
K
K
Figure 4. Internal PTAT Digital Output vs Temperature
=
=
DATAOUT
DATAOUT • V
1020
960
800
640
480
320
160
–1
–2
–3
–4
–5
0
5
4
3
2
1
0
–55
Figure 5. Absolute Temperature Error
2 45
0
.
V
V
SLOPE = 2.45 LSB
CC
REF
–30
= 5V
= 5V
16
16
100
16
–5
TEMPERATURE (°C)
TEMPERATURE (K)
in Kelvin
/°C. The temperature is calculated
REF
REF
20
16
REF
) is known. A 5V reference has
/K
200
/12.25 in Kelvin
45
is used, the temperature
70
300
95
16
2487 F05
2487 F04
120
400
is the decimal
If the value of V
by measuring the temperature sensor at a known tempera-
ture T
This value of slope can be used to calculate further tem-
perature readings using:
All Kelvin temperature readings can be converted to T
(ºC) using the fundamental equation:
Initiating a New Conversion
When the LTC2487 finishes a conversion, it automatically
enters the sleep state. Once in the sleep state, the device is
ready for a read operation. After the device acknowledges
a read request, the device exits the sleep state and enters
the data output state. The data output state concludes
and the LTC2487 starts a new conversion once a Stop
condition is issued by the master or all 24 bits of data are
read out of the device.
During the data read cycle, a Stop command may be issued
by the master controller in order to start a new conversion
and abort the data transfer. This Stop command must be
issued during the ninth clock cycle of a byte read when
the bus is free (the ACK/NAK cycle).
LTC2487 Address
The LTC2487 has two address pins (CA0, CA1). Each may
be tied high, low, or left floating enabling one of 9 possible
addresses (see Table 6).
In addition to the configurable addresses listed in Table 6,
the LTC2487 also contains a global address (1110111)
which may be used for synchronizing multiple LTC2487s or
other LTC24XX delta-sigma I
Multiple LTC2487s with a Global Address Call section).
T
SLOPE
T
C
K
= T
N
=
(in K) and using the following formula:
DATAOUT
K
– 273
=
SLOPE
DATAOUT
REF
T
is not known, the slope is determined
16
N
16
2
C devices (see Synchronizing
LTC2487

2487fa
C