ADS1294CZXGR datasheet(89/114 Pages) TI2

89 / 114 page

10M

470pF

40.2k

0.1µF

2.2nF

AVDD

AVSS

Left Arm Lead

RESP_MODP

IN1P

IN2P

Right Arm Lead

RESP_MODN

IN2N

40.2k

0.1µF

2.2nF

470pF

10M

AVDD

AVSS

IN1N

ADS1294R/6R/8R

ADS1294, ADS1294R, ADS1296, ADS1296R, ADS1298, ADS1298R

www.ti.com

SBAS459K – JANUARY 2010 – REVISED AUGUST 2015

10.2 Typical Applications

10.2.1 ADS129xR Respiration Measurement Using Internal Modulation Circuitry

The respiration measurement circuitry on the ADS129xR employs out-of-band amplitude modulation and

demodulation to measure changes in thoracic impedance that correspond to breathing. When respiration mode is

enabled, channel 1 cannot be used to acquire ECG signals because the internal demodulation circuitry is unique

to that channel. ECG signals can still be acquired with the same electrodes used for respiration measurement if

they are also connected to another channel. Note the configuration shown in Figure 97.

NOTE: Patient and input protection circuitry not shown.

Figure 97. Typical Respiration Circuitry

10.2.1.1 Design Requirements

Table 36 shows the design requirements for the components shown in Figure 97.

Table 36. Respiration Design Requirements

DESIGN PARAMETER

VALUE

Modulation frequency

32 kHz or 64 kHz

Input high-pass filter cutoff

≈ 68 Hz

ADC reference voltage

2.4 V

Maximum ac body current

100

μA

Minimum resistance R1 + R2

24 k

10.2.1.2 Detailed Design Procedure

To configure the ADS129xR to use its internal modulation circuitry, set RESP register bits[6:7] to enable both the

internal modulation and demodulation circuitry. RESP register bits[4:2] determine the phase of the demodulation

blocking signal. To configure the device to use the internally generated signals for internal respiration

measurement, configure RESP register bits[1:0] to 10b.

The RESP_MODP and RESP_MODN pins produce a 32 kHz or 64 kHz square wave depending on the

CONFIG4 regsiter bits[7:5] when configured to use the internal circuitry. The REP_MODP and RESP_MODN pin

voltages toggle between VREFP and VREFN at opposite phases at the specified frequency.

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ADS1294CZXGR Datasheet(PDF) 89 Page - Texas Instruments

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