Texas Instruments TLV320DAC26EVM, Руководство пользователя

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Circuit Description
3-7 Operation
and the TAS SPI switch SW1-3 is turned on. The firmware resides in the serial
EEPROM chip (U2). U5 only loads firmware from U2 when U2’s A1 address
line is pulled low. To disable firmware loading, A1 must be high, by having JM3
removed.
When the firmware is loaded and active, D2 (a yellow LED) is lit.
If no firmware is loaded, the U3 outputs are in 3-state, allowing the external SPI
bus to drive the DAC26 and turn off SW1-3 to ensure the isolation of the
TAS1020B from the SPI bus. When the firmware is loaded, the PC software
enables the microprocessor to control the SPI bus.
Do not drive the external SPI bus when the firmware is loaded and
the onboard microprocessor is active. Disable the micro-
processor by removing JMP3, turn off SW1-3, and cycle power to
the DAC26EVM in order to use the external SPI bus.
Each signal from the SPI inputs is connected directly to the DAC26. As such,
signals on these pins must not exceed the power supply voltage of the DAC26,
which is 3.3 V on this EVM.
Likewise, the I
2
S signals for the digital audio can be driven either externally by
J11 or by the USB audio controller, U5.
Do not drive the external I
2
S bus when the firmware is loaded and
the onboard microprocessor is active. Disable the micro-
processor by removing JMP3, turn off SW1-1 and SW1-2, and cycle
power to the DAC26EVM in order to use the external I
2
S bus.
3.4.2 Power Supply
Power to the DAC26EVM can be derived directly from the USB interface or
externally supplied through the J9 terminal block or the J10 barrel jack
connector. Supply voltages of 6 VDC to 10 VDC must be supplied from an
external supply. Because it is regulated on the DAC26EVM, this input voltage
does not need to be regulated, as long as it falls within this range. D1 prevents
damage to the board in the event a power supply is connected in reverse
polarity.
U6 regulates the input supply voltage to provide 1.8 V for the DAC26 digital
core, or the digital IO power supply if the IOVDD is selected as 1.8 V by JMP9.
Also, J3 provides the 3.3 V for the remaining hardware. The regulated supply
voltages have LEDs attached that alert the user that the supply is working. D4
(red) is the indicator for the 1.8-V power supply, and D3 (green) is the indicator
for the 3.3-V power supply.