LTC2495
18
2495f
The first bit of the second word is the enable bit for the
conversion configuration (EN2). If this bit is set to 0, then
the next conversion is performed using the previously
selected converter configuration.
If the EN2 bit is set to a 1, a new configuration can be
loaded into the device (see Table 4). The first bit (IM) is
used to select the internal temperature sensor. If IM = 1,
the following conversion will be performed on the internal
temperature sensor rather than the selected input channel.
The next two bits (FA and FB) are used to set the rejection
frequency. The next bit (SPD) is used to select either the
1x output rate if SPD = 0 (auto-calibration is enabled and
the offset is continuously calibrated and removed from
the final conversion result) or the 2x output rate if SPD =
1 (offset calibration disabled, multiplexing output rates up
to 15Hz with no latency). The final three bits (GS2, GS1,
GS0) are used to set the gain. When IM = 1 (temperature
measurement) SPD, GS2, GS1 and GS0 will be ignored
and the device will operate in 1x mode.
The configuration remains valid until a new input word
with EN = 1 (the first three bits are 101 for the first word)
and EN2 = 1 (for the second write byte) is shifted into
the device.
Rejection Mode (FA, FB)
The LTC2495 includes a high accuracy on-chip oscillator
with no required external components. Coupled with an
integrated fourth order digital low pass filter, the LTC2495
rejects line frequency noise. In the default mode, the
LTC2495 simultaneously rejects 50Hz and 60Hz by at least
87dB. If more rejection is required, the LTC2495 can be
configured to reject 50Hz or 60Hz to better than 110dB.
APPLICATIONS INFORMATION
Table 4. Converter Configuration
1
0
EN
SGL ODD A2
1
0
0
1
0
1
1
0
1
1
0
1
1
0
1
1
0
1
1
0
1
1
0
1
1
0
1
1
0
1
1
0
1
1
0
1
1
0
1
1
0
1
1
0
1
1
0
1
1
0
1
1
0
1
1
0
1
1
0
1
1
0
1
1
0
1
1
0
1
1
0
1
1
0
1
1
0
1
A1
A0
EN2
X
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
IM
X
X
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1
1
FA
X
X
FB
X
X
SPD
X
X
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
GS2 GS1 GS0
X
X
X
X
0
0
0
0
0
1
0
1
1
0
1
0
1
1
1
1
0
0
0
0
0
1
0
1
1
0
1
0
1
1
1
1
CONVERTER CONFIGURATION
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External Input, Gain = 1, Autocalibration
External Input, Gain = 4, Autocalibration
External Input, Gain = 8, Autocalibration
External Input, Gain = 16, Autocalibration
External Input, Gain = 32, Autocalibration
External Input, Gain = 64, Autocalibration
External Input, Gain = 128, Autocalibration
External Input, Gain = 264, Autocalibration
External Input, Gain = 1, 2x Speed
External Input, Gain = 2, 2x Speed
External Input, Gain = 4, 2x Speed
External Input, Gain = 8, 2x Speed
External Input, Gain = 16, 2x Speed
External Input, Gain = 32, 2x Speed
External Input, Gain = 64, 2x Speed
External Input, Gain = 128, 2x Speed
External Input, Simultaneous 50Hz/60Hz Rejection
External Input, 50Hz Rejection
External Input, 60Hz Rejection
Reserved, Do Not Use
Temperature Input, Simultaneous 50Hz/60Hz Rejection
Temperature Input, 50Hz Rejection
Temperature Input, 60Hz Rejection
Reserved, Do Not Use
Any
Input
Channel
X
X
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
Any
Rejection
Mode
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
Any
Speed
Any
Gain
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X