Datasheet
-
+
CSB
SCLK
SDI
SDO
VSS
VDD
VDDIO
RLDINV
RLDIN
CMOUT
DRDYB
RLDREF
RLDOUT
DIGITAL
CONTROL AND
POWER
MANAGEMENT
Wilson
ref.
Digital
Filter
Σ∆
Modulator
Digital
Filter
Σ∆
Modulator
Digital
Filter
Σ∆
Modulator
-
+
-
+
InA
InA
InA
WCT
-
+
WILSON_EN
RA LA
LL
RL
IN1
IN2
IN3
IN4
IN5
IN6
R
1
R
2
C
1
I
II
SELRLD
XTAL1
XTAL2
CVREF
CM
detect
CMDET_EN
REF for
CM & RLD
-
+
RLD
Amp.
0.1
F
1
F
InA
CH1
CH2
ALARMB
4.096
MHz
5V
0.1 F
3.3V
0.1 F
22 pF
5V 5V
22 pF
VSSIO
CLK
SYNCB
1 MΩ
3.3V
1 MΩ
RSTB
3.3V
ADS1293
www.ti.com
SNAS602B –FEBRUARY 2013–REVISED MARCH 2013
APPLICATION INFORMATION
Example Applications
3-Lead ECG Application
A 3-Lead ECG system can be implemented using two channels as shown in Figure 32. In this example, the right
arm (RA), left arm (LA), left leg (LL) and right leg (RL) are connected to the IN1, IN2, IN3 and IN4 pins
respectively. The ADS1293 uses the Common-Mode Detector block 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
(1)
. The output of the RLD amplifier is connected internally to the IN4 pin, which is connected to
the right leg electrode, to drive the common-mode of the patient’s body. 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 32. 3-Lead ECG Application
Follow the next steps to program the ADS1293 in a 3-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: Connects channel 2’s INP to IN3 and INN to IN1.
3. Set address 0x0A = 0x07: Enables the common-mode detector on input pins IN1, IN2 and IN3.
4. Set address 0x0C = 0x04: Connects the output of the RLD amplifier internally to pin IN4.
5. Set address 0x12 = 0x04: Uses external crystal and feeds the output of the internal oscillator module to the
digital.
(1) 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 39
Product Folder Links: ADS1293