ADS1259
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SBAS424C –JUNE 2009–REVISED MARCH 2010
Settling Time While Continuously Converting
OFFSET AND GAIN
If there is a step change on the input signal while
continuously converting, the next data represent a
combination of the previous and current input signal
and should therefore be discarded; see Figure 53 for
this step change. Table 10 shows the number of
conversion cycles for completely settled data while
continuously converting.
The ADS1259 features low offset (40mV, typ) and low
gain errors (0.05%, typ). The offset and gain errors
can be corrected by sending calibration commands to
the ADS1259; see the Calibration section.
The ADS1259 also features very low offset drift
(0.05mV/°C, typ) and very low gain drift (0.5ppm/°C,
typ). The offset and gain drift are calculated using the
box method, as described by Equation 5 and
Equation 6:
Table 10. Settling Time While Continuously
Converting DRDY Periods(1)
V
OFFMAX - VOFFMIN
SETTLING TIME (tSET) (Conversions)
DATA RATE
(SPS)
Offset Drift =
sinc1
sinc2
Temp Range
(5)
10
16.6
50
2
2
2
2
2
2
3
6
3
3
3
3
3
3
4
7
GainErrorMAX - GainErrorMIN
Gain Drift =
Temp Range
60
where:
400
VOFFMAX, VOFFMIN, GainErrorMAX, and GainErrorMIN
are the maximum and minimum offset and gain
error readings recorded over the Temp Range
1200
3600
14,400
(–40°C to +105°C)
(6)
(1) Settling time is defined as the number of DRDY periods after
the input signal has settled following an input step change.
For best data throughput in multiplexed applications, issue a
START condition (START pin or Start command) after the
input has settled following a multiplexer change; see the
Setling Time Using START section.
tSET
New VIN
VIN = AINP - AINN
DRDY
Old VIN
Mix of
Old and New
VIN Data
Fully Settled
Old VIN Data
New VIN Data
Settled
Data
DOUT
Figure 53. Step Change on VIN while Continuously Converting
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