Datasheet
001
010
000
011
100
101
110
IN1
WCT
OUT
SELWILSON1
SELWILSON2
SELWILSON3
IN2
IN3
IN4
IN5
IN6
WILSONINT
GOLDINT
WCT
200kΩ
200kΩ
200kΩ
200kΩ
G1 G2 G3
PACE2WCT
BUF
2
BUF
3
BUF
1
enable
enable
enable
001
010
000
011
100
101
110
001
010
000
011
100
101
110
200kΩ
200kΩ
200kΩ
200kΩ
200kΩ
ADS1293
www.ti.com
SNAS602B –FEBRUARY 2013–REVISED MARCH 2013
Wilson Reference
The ADS1293 features a Wilson reference block consisting of three buffer amplifiers and resistors that can
generate the voltages for the Wilson Central Terminal or Goldberger terminals. Each of the three buffer amplifiers
can be connected to any input pin, IN1 through IN6, by programming the WILSON_EN1, WILSON_EN2, and
WILSON_EN3 registers. A buffer that is not connected to an input pin is automatically disabled. When disabled,
the buffers have a high output impedance.
Figure 20. Wilson Reference Generator Circuit
The output of the Wilson Reference can be routed internally to IN6, and the outputs of the Goldberger reference
can be routed internally to IN4, IN5 and IN6. This is configured in the WILSON_CN register. If routed externally,
it is strongly recommended to shield these connections, which due to their high output impedance, are prone to
pick up external interference.
Wilson Central Terminal
There are three main ECG leads that are measured differentially:
• Lead I: I = LA - RA
• Lead II: II = LL - RA
• Lead III: III = LL - LA
Where LA is the left arm electrode, LL is the left leg electrode, and RA is the right arm electrode.
In a standard 5-lead or 12-lead ECG, the Wilson Central Terminal is used as the reference voltage for the chest
electrodes, which are measured differentially against this reference. The Wilson Central Terminal is defined as
the average of the three limb electrodes, RA, LA and LL:
Wilson Central Terminal = (RA + LA + LL)/3
Copyright © 2013, Texas Instruments Incorporated 23
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