ADS1294CZXGR datasheet(46/114 Pages) TI2

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Respiration

Modulation

Generator

RESP_PH[2:0]

CLK

(2.048MHz)

ModulationClock

DemodulationClock

GPIO4

GPIO3

GPIO2

GPIO3

GPIO4

GPIO2

BLKDLY

(DemodulationClock)

(Blocki g

n Si n l)

g a

PHASE

(ModulationCl ck)

ADS1294, ADS1294R, ADS1296, ADS1296R, ADS1298, ADS1298R

SBAS459K – JANUARY 2010 – REVISED AUGUST 2015

www.ti.com

9.3.1.7.8

Respiration

As shown in Table 8, the ADS129xR provide three options for respiration impedance measurement: external

respiration, internal respiration using on-chip modulation signals, and internal respiration using user-generated

modulation signals. The ADS129x provides only external respiration impedance measurement.

Table 8. Respiration Control

RESP.RESP_CTRL[1]

RESP.RESP_CTRL[0]

DESCRIPTION

MODE AVAILABLE

Respiration disabled

ADS129x, ADS129xR

Generates modulation and demodulation signals for external

respiration circuitry. RESP_CLK signals on GPIO2, GPIO3,

ADS129x, ADS129xR

and GPIO4.

Respiration measurement using internally-generated

ADS129xR

RESP_MOD signals.

Respiration measurement using user-generated modulation

ADS129xR(1)

and blocking signal.

(1)

Do not set RESP_CTRL[1:0] = 11 if CLKSEL = 1 (internal master clock).

For more information on respiration impedance measurement, see Respiration Rate Measurement Using

Impedance Pneumography, SBAA181.

9.3.1.7.8.1

External Respiration Circuitry (RESP_CTRL = 01b)

With this option, GPIO2, GPIO3, and GPIO4 are automatically configured as outputs. The phase relationship

between the signals is shown in Figure 47. GPIO2 is the exclusive-OR of GPIO3 and GPIO4, as shown in

Figure 48. GPIO3 is the modulation signal, and GPIO4 is the demodulation signal. While using this option, the

general-purpose pin functions of GPIO2, GPIO3, and GPIO4 are not available. The modulation frequency is set

to either 64 kHz or 32 kHz by using the RESP_FREQ[2:0] bits in the CONFIG4 register. The remaining bit

options of RESP_FREQ[2:0] generate square waves on GPIO3 and GPIO4. The exclusive-OR out on GPIO2 is

only available in 64-kHz or 32-kHz. The phase of GPIO4, relative to GPIO3, is set by RESP_PH[2:0] bits in the

RESP register.

Use this option to implement custom respiration impedance circuitry external to the ADS129x.

Figure 47. External Respiration (RESP_CTRL = 01b)

Figure 48. External Respiration (RESP_CTRL = 01b) Block

Timing

Diagram

Table 9. Switching Characteristics for Figure 47(1)

2.7 V

≤ DVDD ≤ 3.6 V

1.65 V

≤ DVDD ≤ 2 V

PARAMETER

MIN

TYP

MAX

MIN

TYP

MAX

UNIT

tPHASE

Respiration phase delay, set by RESP.RESP_PH[2:0]

22.5

157.5

22.5

157.5

Degrees

tBLKDLY

Modulation clock rising edge to XOR signal

(1)

Specifications apply from –40°C to 85°C.

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Product Folder Links: ADS1294 ADS1294R ADS1296 ADS1296R ADS1298 ADS1298R

ADS1294CZXGR Datasheet(PDF) 46 Page - Texas Instruments

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