Datasheet

LTC2492
19
2492fd
a new input word with EN = 1 (the fi rst three bits are 101)
and EN2 = 1 is shifted into the device.
Rejection Mode (FA, FB)
The LTC2492 includes a high accuracy on-chip oscillator
with no required external components. Coupled with an
integrated 4th order digital lowpass fi lter, the LTC2492 re-
jects line frequency noise. In the default mode, the LTC2492
simultaneously rejects 50Hz and 60Hz by at least 87dB. If
more rejection is required, the LTC2492 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
unchanged from the 1× mode performance. In both the
1× and 2× 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 1×
mode is always used independent of the value of SPD.
Temperature Sensor
The LTC2492 includes an integrated temperature sensor.
The temperature sensor is selected by setting IM = 1. The
digital output is proportional to the absolute temperature
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
REF
(see Figures 4 and 5). Slope calibration is not required if
the reference voltage (V
REF
) is known. A 5V reference has
a slope of 314 LSBs
24
/°C. The temperature is calculated
APPLICATIONS INFORMATION
Table 4. Converter Confi guration
1 0 EN SGL ODD A2 A1 A0 EN2 IM FA FB SPD CONVERTER CONFIGURATION
100XXXXXXXXXX Keep Previous
101XXXXX0XXXX Keep Previous
000XXXXXXXXXX Keep Previous
101XXXXX10000 External Input (See Table 3)
50Hz/60Hz Rejection, 1x
101XXXXX10010 External Input (See Table 3)
50Hz Rejection, 1x
101XXXXX10100 External Input (See Table 3)
60Hz Rejection, 1x
101XXXXX10001 External Input (See Table 3)
50Hz/60Hz Rejection, 2x
101XXXXX10011 External Input (See Table 3)
50Hz Rejection, 2x
101XXXXX10101 External Input (See Table 3)
60Hz Rejection, 2x
101XXXXX1100X Measure Temperature
50Hz/60Hz Rejection, 1x
101XXXXX1101X Measure Temperature
50Hz Rejection, 1x
101XXXXX1110X Measure Temperature
60Hz Rejection, 1x
101XXXXX1X11X Reserved, Do Not Use