Ic Functions; Led Functions; Reset; Ad1940Eb/Ad1941Eb Differences - Analog Devices EVAL-AD1940EB Manual

IC FUNCTIONS

Table 4 explains the function of each IC on the evaluation
boards. The two large Lattice CPLDs (U13 and U15) are used
only for routing signals on the board and do not perform
decoding or signal conditioning.
Table 4. IC Functions
Reference
Designator Function
U1 AD1940/AD1941 SigmaDSP audio processor
U10 AD1939 4 ADC/8 DAC audio codec
U9 AD1871 stereo ADC
U13, U15 Lattice M4A5-128/64 CPLDs for signal routing
U14, AD8606 dual op amps for analog audio I/O
U17 to U20, buffering
U26 to U31
U11 ADP3303-5 LDO Regulator, 5.0 V analog supply
U8 LM317AT, 5.0 V digital supply
U12 ADM811 reset generator
U32, U33 74HC125 for external MCLK I/O buffering
U3 74HC04 for driving LEDs
U22 74HC541 for buffering SPI signals
U2 CS8414 S/PDIF receiver
U4 CS8404 S/PDIF transmitter

LED FUNCTIONS

The four LEDs on the evaluation boards are useful components
that indicate the boards are properly powered and set up. Table
5 explains what each LED indicates.
Table 5. LED Functions
Reference
Designator Function
D1
When lit, U2 is receiving no data, or an invalid
S/PDIF stream.
When dim, U2 is receiving valid S/PDIF data.
D2 When lit, the SPI or I
When dim, an SPI or I
established.
When blinking, an SPI or I
occurring.
D6 Indicates +5 V DV
D11 Indicates +5 V AV
2
C connection is inactive.
2 C connection has been
2
C transaction is
DD
DD

RESET

The AD1940EB/1941EB can be reset with push-button switch
SW1. This reset signal is debounced by the ADM811 (U12).
This reset signal affects the AD1940/AD1941, AD1939,
AD1871, and S/PDIF receiver and transmitter. The boards can
also be reset by disconnecting the power. After reset, the
AD1940EB/AD1941EB do not pass audio and a control port write
has to be performed so that signals are output again. See the
Using SigmaStudio section for additional information.

AD1940EB/AD1941EB DIFFERENCES

The main difference between the AD1940EB and AD1941EB is
the control port. The AD1940EB uses an SPI control port,
whereas the AD1941EB uses an I
for both assemblies, with slight modifications. To accommodate
2
for I C communication, the AD1941EB's CPLDs have slightly
different programs than those of the AD1940EB. Also, the
AD1941EB has Resistor R56, Resistor R57, Resistor R72, and
Resistor R73, while the AD1940EB does not.
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EVAL-AD1940EB/AD1941EB
2
C port. The same PCB is used