Datasheet

ADS1293
SNAS602B –FEBRUARY 2013–REVISED MARCH 2013 www.ti.com
The output of Wilson Central Terminal generated by the ADS1293, as seen in Figure 20, is defined as:
WCT
OUT
= (BUF
1
+ BUF
2
+ BUF
3
)/3
The user could program the WILSON_EN1 register to connect the RA electrode to BUF
1
, program the
WILSON_EN2 register to connect the LA electrode to BUF
2
, and program the WILSON_EN3 register to connect
the LL electrode to BUF
3
.
When the Wilson reference is enabled, its output is present at the WCT pin, except when the analog pace
channel is routed to the WCT pin (see Analog Pace Channel). In such a configuration, the Wilson terminal can
still be made available at an external pin by programming the WILSONINT bit to 1. Setting this bit connects the
output of the Wilson reference internally to the IN6 pin.
Goldberger Terminals
Augmented leads in 3-lead, 5-lead or 12-lead ECG are typically calculated digitally based on the measurement
results of Lead I and Lead II. The augmented leads are defined as:
• aVR = -(I + II)/2 = RA - (LA + LL)/2 = RA - G1
• aVL = I - II/2 = LA - (RA + LL)/2 = LA - G2
• aVF = II - I/2 = LL - (RA + LA)/2 = LL - G3
Augmented leads can also be measured directly with the Goldberger terminals to give the best SNR. The
Goldberger terminals generated by the ADS1293, as seen in Figure 20, are defined as:
• G1 = (BUF
2
+ BUF
3
)/2
• G2 = (BUF
1
+ BUF
3
)/2
• G3 = (BUF
1
+ BUF
2
)/2
In this case, the user must program the WILSON_EN1 register to connect the RA electrode to BUF
1
, program
the WILSON_EN2 register to connect the LA electrode to BUF
2
, and program the WILSON_EN3 register to
connect the LL electrode to BUF
3
.
The Goldberger output terminals, G1, G2 and G3 can be made available on external pins programming the
GOLDINT bit to 1. Setting this bit connects the Goldberger terminals internally to the IN4, IN5 and IN6 pins.
• IN4 = G1
• IN5 = G2
• IN6 = G3
Note that multiple ADS1293 chips are required if both the augmented leads and the three basic leads need to be
converted directly.
The WILSONINT and GOLDINT bits must not be programmed to 1 simultaneously because it will short-circuit the
Wilson output terminal and the third Goldberger output terminal. The options described in these sections are
summarized in Table 9.
Table 9. Wilson and Goldberger Reference Control
TERMINAL OUTPUTS
GOLDINT WILSONINT PACE2WCT
WCT PIN IN4 PIN IN5 PIN IN6 PIN
0 0 0 WCT
OUT
General input General input General input
0 1 0 WCT
OUT
General input General input WCT
OUT
1 0 0 WCT
OUT
(BUF
2
+ BUF
3
)/2 (BUF
1
+ BUF
3
)/2 (BUF
1
+ BUF
2
)/2
1 1 X Illegal Illegal Illegal Illegal
0 0 1 Vpaceout General input General input General input
0 1 1 Vpaceout General input General input WCT
OUT
1 0 1 Vpaceout (BU
F2
+ BUF
3
)/2 (BUF
1
+ BUF
3
)/2 (BUF
1
+ BUF
2
)/2
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