Datasheet

Max(INP INN)<-
V
REF
Gain
Full-ScaleRange=
±V
REF
Gain
;
−160
−150
−140
−130
−120
−110
−100
−90
−80
−70
−60
−50
−40
−30
−20
−10
0
0.001 0.01 0.1 1
Normalized Frequency (f
IN
/f
MOD
)
Power Spectral Density (dB)
G001
ADS1194, ADS1196
ADS1198
www.ti.com SBAS471C –APRIL 2010– REVISED NOVEMBER 2011
Input Differential Dynamic Range
The differential (INP – INN) signal range depends on the analog supply and reference used in the system. This
range is shown in Equation 3.
(3)
The 3V supply, with a reference of 2.4V and a gain of 6 for ECGs, is optimized for power with a differential input
signal of approximately 300mV. For higher dynamic range, a 5V supply with a reference of 4V (set by the
VREF_4V bit of the CONFIG3 register) can be used to increase the differential dynamic range.
ADC ΔΣ Modulator
Each channel of the ADS1194/6/8 has a 16-bit ΔΣ ADC. This converter uses a second-order modulator
optimized for low-power applications. The modulator samples the input signal at the rate of f
MOD
= f
CLK
/8. As in
the case of any ΔΣ modulator, the noise of the ADS1194/6/8 is shaped until f
MOD
/2, as shown in Figure 20. The
on-chip digital decimation filters explained in the next section can be used to filter out the noise at higher
frequencies. These on-chip decimation filters also provide antialias filtering. This feature of the ΔΣ converters
drastically reduces the complexity of the analog antialiasing filters that are typically needed with nyquist ADCs.
Figure 20. Modulator Noise Spectrum Up To 0.5 × f
MOD
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