Y1
U1
U2
TP4
GND
TP3
GND
TP2
GND
TP1
GND
VDD Set
VR1
J6
GND TP5
TP7
VDD_IN
J3
J2
CLK
TP8
VIN
J5
National
Semiconductor
ADC121S101 Evaluation Board
Rev. 1
J7
ADC121S101
ADC101S101
ADC081S101
Figure 1. The Evaluation Board
4.0 Functional Description
is 2.7V to 5.25V, this is also the range of the reference
voltage.
The ADC121S101 Evaluation Board component locations
are shown in
Figure 1
. The board schematic is shown in
Figure 2
.
4.3 ADC clock circuit
The clock signal applied to the ADC can comes from
BNC J2 or from an on-board oscillator at position Y1 or
Y2. Y1 is for a through-hole TTL oscillator, while Y2 is for
a surface mounted TTL oscillator. Only one oscillator
should be mounted at a time and either an oscillator or
an external generator should be connected. When using
an external clock source, be sure that there is a 51 Ohm
resistor at position R2 near BNC J2. Resistor R2 should
be removed if the on-board oscillator is used. These
boards are shipped without R2 populated.
4.1 Input (signal conditioning) circuitry
The input signal to be digitized should be applied to BNC
connector J3 through an appropriate filter. This 50 Ohm
input is intended to accept a low-noise sine wave signal
of peak-to-peak amplitude up to the power supply level.
To accurately evaluate the ADC121S101 dynamic
performance, the input test signal should be a single
frequency passed through a high-quality band pass filter
as described in Section 5.0.
4.5 Digital Data Output.
The input signal may be either a.c. or d.c. coupled to the
ADC121S101 with the setting of the jumper on J4. See
schematic
Figure 2
.
The digital output data from the ADC121S101 is available
at Header J7 for connection to a logic analyzer. Data is
transferred over FutureBus J5 for use with the
WaveVision data capture board.
4.2 The ADC reference
4.6 Power Supply Connections
The reference voltage for the ADC121S101 is the device
supply voltage. Therefore, adjusting this voltage will
change the full scale range of the ADC121S101 . Since
the operational supply voltage range of the ADC121S101
Power to this board is supplied through power connector
J6. The only Voltage needed for the ADC121S101
evaluation board is a 2.7V to +5.6V supply.
5
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