LTC2498 Linear Technology, LTC2498 Datasheet - Page 19

• Manufacturer Part Number: LTC2498
• Description: 24-Bit 8-/16-Channel ADC
• Manufacturer: Linear Technology

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APPLICATIONS INFORMATION
up to 15Hz with no latency). When IM = 1 (temperature
measurement), SPD will be ignored and the device will
operate in 1x mode. The confi guration remains valid until
a new input word with EN = 1 (the fi rst 3 bits are 101) and
EN2 = 1 is shifted into the device.
Rejection Mode (FA, FB)
The LTC2498 includes a high accuracy on-chip oscillator
with no required external components. Coupled with an
integrated 4th order digital low pass fi lter, the LTC2498 re-
jects line frequency noise. In the default mode, the LTC2498
simultaneously rejects 50Hz and 60Hz by at least 87dB. If
more rejection is required, the LTC2498 can be confi gured
to reject 50Hz or 60Hz to better than 110dB.
Speed Mode (SPD)
Every conversion cycle, two conversions are combined to
remove the offset (default mode). This result is free from
offset and drift. In applications where the offset is not
critical, the auto-calibration feature can be disabled with
the benefi t of twice the output rate. While operating in the
2x mode (SPD = 1), the linearity and full-scale errors are
Table 4. Converter Confi guration
1
1
1
0
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
0
0
0
0
EN
0
1
0
1
1
1
1
1
1
1
1
SGL
X
X
X
X
X
X
X
X
X
X
X
ODD
X
X
X
X
X
X
X
X
X
X
X
A2
X
X
X
X
X
X
X
X
X
X
X
A1
X
X
X
X
X
X
X
X
X
X
X
A0
X
X
X
X
X
X
X
X
X
X
X
EN2
X
0
X
1
1
1
1
1
1
1
1
unchanged from the 1x mode performance. In both the 1x
and 2x mode there is no latency. This enables input steps
or multiplexer changes to settle in a single conversion
cycle easing system overhead and increasing the effective
conversion rate. During temperature measurements, the 1x
mode is always used independent of the value of SPD.
Temperature Sensor
The LTC2498 includes an integrated temperature sensor.
The temperature sensor is selected by setting IM = 1.
During temperature readings, MUXOUTN/MUXOUTP
remains connected to the selected input channel. The
ADC internally connects to the temperature sensor and
performs a conversion.
The digital output is proportional to the absolute tem-
perature of the device. This feature allows the converter
to perform cold junction compensation for external
thermocouples or continuously remove the temperature
effects of external sensors.
The internal temperature sensor output is 28mV at 27°C
(300°K), with a slope of 93.5μV/°C independent of V
IM
X
X
X
0
0
0
0
0
1
1
1
FA
X
X
X
0
0
1
0
0
0
0
1
FB
X
X
X
0
1
0
0
1
0
1
0
SPD
X
X
X
X
X
X
0
0
0
1
1
Keep Previous (Change Channel)
CONVERTER CONFIGURATION
External Input (See Table 3)
External Input (See Table 3)
External Input (See Table 3)
External Input (See Table 3)
External Input (See Table 3)
50Hz/60Hz Rejection, 1x
50Hz/60Hz Rejection, 2x
50Hz/60Hz Rejection, 1x
Measure Temperature
Measure Temperature
Measure Temperature
50Hz Rejection, 1x
60Hz Rejection, 1x
50Hz Rejection, 2x
50Hz Rejection, 1x
60Hz Rejection, 1x
Keep Previous
Keep Previous
LTC2498
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REF
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