V1
-
+
R
L
D
IN
V
C
M
O
U
T
R
L
D
O
U
T
DIGITAL
CONTROL AND
POWER
MANAGEMENT
Wilson
ref.
Digital
Filter
Σ∆
Modulator
Digital
Filter
Σ∆
Modulator
Digital
Filter
Σ∆
Modulator
-
+
-
+
InA
InA
InA
WCT
-
+
RA
LA
LL
RL
IN1
IN2
IN3
IN4
IN5
IN6
R
1
R
2
C
1
I
II
V
S
E
L
R
L
D
WILSON_EN
CM
detect
CMDET_EN
-
+
RLD
Amp.
V
S
S
V
D
D
V
D
D
IO
X
T
A
L
1
X
T
A
L
2
C
V
R
E
F
5V
InA
CH1
CH2
CSB
SCLK
SDI
SDO
DRDYB
ALARMB
R
L
D
IN
R
L
D
R
E
F
CH3
5V
5V
0.1 F
1 F
4.096
MHz
0.1 F
3.3V
0.1 F
22 pF
22 pF
CLK
V
S
S
IO
S
Y
N
C
B
1 MΩ
3.3V
REF for
CM & RLD
1 MΩ
R
S
T
B
3.3V
www.ti.com
Theory of Operation
3
Theory of Operation
3.1
5-Lead ECG Application
Figure 5
shows the ADS1293 device in a 5-Lead ECG system setup. The ADS1293 device uses the
Common-Mode Detector to measure the common-mode of the patient’s body by averaging the voltage of
input pins IN1, IN2 and IN3, and uses this signal in the right leg drive feedback circuit.
NOTE:
The ideal values of R
1
, R
2
and C
1
will vary per system/application; typical values for these
components are: R
1
= 100k
Ω
, R
2
= 1M
Ω
and C
1
= 1.5nF.
The output of the RLD amplifier is connected to the right leg electrode, which is IN4, to drive the common-
mode of the patient’s body. The Wilson Central Terminal is generated by the ADS1293 and is used as a
reference to measure the chest electrode, V1. The chip uses an external 4.096MHz crystal oscillator
connected between the XTAL1 and XTAL2 pins to create the clock sources for the device.
Figure 5. 5-Lead ECG Application
CC2541 Communication
The CC2541 device communicates to the ADS1293 device through SPI interface. The CC2541 device
implements the application software to run this application through the 8051 microcontroller core in
addition to running the BLE stack. For additional information, see
Section 4.4
.
9
TIDU195A – January 2014 – Revised July 2014
Wireless Heart Rate Monitor Reference Design
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