Datasheet

ADS1293

SNAS602B –FEBRUARY 2013–REVISED MARCH 2013

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Table 10. Typical Common-Mode Detector Bandwidth, Capacitive Drive and

Power Consumption

CMDET

BW C

LOAD

SUPPLY

CMDET_BW CMDET_CAPDRIVE

(kHz) (nF)

(µA)

0: Low BW 00: Low Cap Drive 50 2 39

mode

0: Low BW 01: Medium Low Cap Drive 50 3.3 45

mode

0: Low BW 10: Medium High Cap Drive 50 4.5 56

mode

0: Low BW 11: High Cap Drive 50 8 75

mode

1: High BW 00: Low Cap Drive 150 0.4 43

mode

1: High BW 01: Medium Low Cap Drive 150 0.65 49

mode

1: High BW 10: Medium High Cap Drive 150 1 60

mode

1: High BW 11: High Cap Drive 150 1.6 79

mode

Common-Mode Output Range (CMOR)

The Common-Mode Detector incorporates an out-of-range alarm to sense if the common-mode voltage is outside

of the common-mode voltage range of the ADS1293. A Common-Mode Out-of-Range Alarm is created in the

CMOR bit of the ERROR_STATUS register when the common-mode drops below 0.75V or exceeds VDD-0.75V.

System alarms are filtered by the digital circuitry (see Error Filtering), and for this reason, the master clock must

be active in order to capture an alarm.

Right Leg Drive (RLD)

The RLD is a programmable operational amplifier that is intended to control the common-mode level of the

patient connected through electrodes to the ADS1293 and thereby improving the AC CMRR of the overall ECG

system. In a typical ADS1293 application, the common-mode level of the patient's body is measured by the

Common-Mode Detector described in the previous section. The CMOUT is compared by the RLD to the

reference voltage present on the RLDREF pin. When used in an inverting amplifier topology, the right leg

electrode is driven by the RLD to counter any differences between the reference voltage and the detected

common-mode level. This reduces the amount of power-line common-mode interference.

Figure 22. Right-Leg Drive Circuit

Product Folder Links: ADS1293