Texas Instruments ADS1299, Руководство пользователя

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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 1 2 RESERVE
RESERVE 3 4 RESERVE
GPIO4 5 6 PWDNB
GPIO3 7 8 Daisy_in
AGND 9 10 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 1 2 CLKSEL
CLK 3 4 GND
NC 5 6 GPIO1
CS 7 8 RESETB
NC 9 10 GND
DIN 11 12 GPIO2
DOUT 13 14 NC/START
DRDYB 15 16 SCL
EXT_CLK 17 18 GND
NC 19 20 SDA
16 EEG Front-End Performance Demonstration Kit SLAU443 – May 2012
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