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ADS1299EEG-FE Daughter Card Hardware Introduction

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A 2.048MHz oscillator available for +3V and +1.8V DVDD is the FXO-HC735-2.048MHz and SiT8002AC-

34-18E-2.048, respectively. The EVM is shipped with the external oscillator enabled.

4.3

Reference

The ADS1299 has an on-chip internal reference circuit that provides reference voltages to the device.

Alternatively, the internal reference can be powered down and VREFP can be applied externally. This

configuration is achieved with the external reference generator (U3) and driver buffer. The EVM has the

footprints for the necessary circuitry, but the components are not installed at the factory.

The external reference voltage can be set to 4.096V. Measure TP3 to make sure the external reference is

correct. The setting for the external reference is described in Table 6.

Table 6. External Reference Jumper Options

Internal Reference

External Reference

ADS1299 Reference

VREF = 4.5V

VREFP = 4.096V

JP3

Not Installed

Installed

The software uses the VREF value entered in the Global Registers control tab (refer to Section 5.2) to

calculate the input-referred voltage value for all the tests. The default value is 4.5V. If any other value is

used, the user must update this field in the Global Registers control tab.

4.4

Accessing ADS1299 Analog Signals

Some ADS1299 output signals are provided as test points for probing purposes through J5. Table 7 lists

the various test signals with the corresponding test points.

Table 7. Test Signals

Signal

J5 Pin Number

Signal

RESERVE

GPIO4

PWDNB

GPIO3

Daisy_in

AGND

RESERVE

4.5

Accessing ADS1299 Digital Signals

The ADS1299 digital signals (including SPI interface signals, some GPIO signals, and some of the control

signals) are available at connector J3. These signals are used to interface to the MMB0 board DSP. The

pin out for this connector is given in Table 8.

Table 8. Serial Interface Pin Out

Signal

J3 Pin Number

Signal

START/CS

CLKSEL

CLK

GND

GPIO1

RESETB

GND

DIN

GPIO2

DOUT

NC/START

DRDYB

SCL

EXT_CLK

GND

SDA

EEG Front-End Performance Demonstration Kit

SLAU443 – May 2012

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