Datasheet

Rev 03 Jan 2013 19:42 | Page 8
and therefore take valid measurements soon after connecting the electrodes to the subject. To access
this function, set the jumper P2 connection between pins 1 and 2. To disable, connect pins 2 and 3.
BOARD SETTINGS FOR TWO ELECTRODE CONFIGURATION
The AD8232-CHAR-Z can be configured to suit two-electrode applications, as shown in Table 2.
TABLE 2. Two-electrode configuration
FUNCTION LABEL CONFIGURATION
AC/DC Leads Detection P5 AC method enabled
Input pull-up voltage J3 Pull up inputs to PRLD or place jumper on J1 to connect to VREF
Keep in mind that the gain and filtering may need to be adjusted depending on the location of the
electrodes. Note that narrow bandwidths offer the highest rejection to motion artifacts and other
external interferences, but introduce distortion into the ECG signal.
EVALUATION BOARD COMPONENT EXPLANATION
Input Bias Circuit: R4, R5, J1, J2, J3, J4
In three-electrode configurations, pull-up resistors are necessary for the leads-off functionality to work
correctly. In two-electrode configurations, biasing the inputs within the input range of AD8232 is
necessary for the instrumentation amplifier to work. R4 and R5 are 10 MΩ on the evaluation board.
The resistors may be pulled up to four different values, depending on which jumper is set. Only one
jumper should be connected at a time.
Two-electrode configuration:
J1: Connects pull up resistors to VREF, which is typically at mid-supply.
J3: Connects pull up resistors to the RLD (right-leg drive) amplifier output. This is the recommended
configuration for two electrode configurations
Three-electrode configuration:
J2: Connects pull up resistors to +VS. This is the standard configuration for three-electrode
configurations.
J4: This jumper position allows connecting the pull-up resistors to a voltage provided by the user. This
is useful in systems that expect high power-line noise (50Hz or 60Hz). A higher voltage than the
supply, such as 5V, can help in maintaining the inputs within the common-mode range of the amplifier.
Apply this voltage at the VSETIN pin.
Thoroughly clean the board after performing any solder work around this area, so that residual flux