Datasheet
V1
-
+
RLDINV
CMOUT
RLDOUT
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
SELRLD
WILSON_EN
CM
detect
CMDET_EN
-
+
RLD
Amp.
VSS
VDD
VDDIO
XTAL1
XTAL2
CVREF
5V
InA
CH1
CH2
CSB
SCLK
SDI
SDO
DRDYB
ALARMB
RLDIN
RLDREF
CH3
5V 5V
0.1 F
1
F
4.096
MHz
0.1 F
3.3V
0.1 F
22 pF 22 pF
CLK
VSSIO
SYNCB
1 MΩ
3.3V
REF for
CM & RLD
1 MΩ
RSTB
3.3V
ADS1293
www.ti.com
SNAS602B –FEBRUARY 2013–REVISED MARCH 2013
5-Lead ECG Application
Figure 33 shows the ADS1293 in a 5-Lead ECG system setup. Similar to the 3-Lead application, the ADS1293
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
(2)
. 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 33. 5-Lead ECG Application
The following steps configure the ADS1293 for a 5-lead application with an ECG bandwidth of 175Hz and an
output data rate of 853Hz; it is assumed that the device registers contain their default power-up values.
1. Set address 0x01 = 0x11: Connects channel 1’s INP to IN2 and INN to IN1.
2. Set address 0x02 = 0x19: Connect channel 2’s INP to IN3 and INN to IN1.
3. Set address 0x03 = 0x2E: Connects channel 3’s INP to IN5 and INN to IN6.
4. Set address 0x0A = 0x07: Enables the common-mode detector on input pins IN1, IN2 and IN3.
5. Set address 0x0C = 0x04: Connects the output of the RLD amplifier internally to pin IN4.
6. Set addresses 0x0D = 0x01, 0x0E = 0x02, 0x0F = 0x03: Connects the first buffer of the Wilson reference to
the IN1 pin, the second buffer to the IN2 pin, and the third buffer to the IN3 pin.
7. Set address 0x10 = 0x01: Connects the output of the Wilson reference internally to IN6.
(2) The ideal values of R
1
, R
2
and C
1
will vary per system/application; typical values for these components are: R
1
= 100kΩ, R
2
= 1MΩ and
C
1
= 1.5nF.
Copyright © 2013, Texas Instruments Incorporated 41
Product Folder Links: ADS1293