EVALUATION BOARD HARDWARE
The AD7793 evaluation board is powered via the 5 V supply from the USB connector, J1. This 5 V supply can be used to power the AD7793 directly. A 3.3 V regulated voltage from the on-board ADP3303 (a high precision, low power, 3.3 V output voltage regulator) can also be used. Alternatively, the AD7793 can be powered using an external 3 V or 5 V power supply via J3.
Seven link options must be set for the required operating setup before using the evaluation board. The functions of these link options are outlined in Table 1.
Care should be taken before applying power and signals to the evaluation board to ensure that all link positions are set per the required operating mode. Table 2 shows the position in which all the links are initially set.
There are five sockets relevant to the operation of the AD7793 on this evaluation board. The functions of these sockets are outlined in Table 3.
Table 1. Evaluation Board Link Settings
This link is used to externally short AIN1(+) to AIN1(−). If VBIAS is enabled and directed to AIN1(−), a noise analysis can be performed in this configuration. With this link out, an external voltage can be applied to AIN1(+)/AIN(−) using the SMB connectors.
LK2 to LK6
These links are used to connect the on-board temperature demonstration circuit to the ADC and must all be in place when attempting to measure the ambient temperature.
When the on-board temperature demonstration circuit is selected in software, LK6 allows current from the on-chip current source of the AD7793 to flow through the temperature demonstration circuit. When LK4 and LK5 are in place, the 1 kΩ thermistor is connected to AIN2(+)/AIN2(−). When LK2 and LK3 are in place, the 5 kΩ precision resistor is used to generate the reference for the AD7793 so that a ratiometric configuration of the temperature demonstration circuit is achieved.
LK7 is used to select the power source for AVDD on the AD7793. LK7 in Position A selects an external power supply, supplied via J3. LK7 in Position B selects the 3.3 V regulated output from the on-board ADP3303 voltage regulator. LK7 in Position C selects the 5 V supply from the USB connector, J1.
Socket AIN1+ AIN1− REFIN1+
Description Subminiature BNC (SMB) Connector. The analog input signal for the AIN1(+) input of the AD7793 is applied to this socket. Subminiature BNC (SMB) Connector. The analog input signal for the AIN1(−) input of the AD7793 is applied to this socket.
Subminiature BNC (SMB) Connector. This socket is used in conjunction with REFIN1− to apply an external reference to the AD7793. The voltage for the REFIN(+) input of the AD7793 is applied to this socket.
Subminiature BNC (SMB) Connector. This socket is used in conjunction with REFIN1+ to apply an external reference to the AD7793. The voltage for the REFIN(−) input of the AD7793 is applied to this socket.
16-Pin (2 × 8) Straight Header. This socket is used in conjunction with the prototype area to interface any signal to the AD7793.
LK1 LK2 to LK3 LK4 to LK5 LK6 LK7
In Out Out Out B
AIN1(+) and AIN1(−) are shorted. Internal reference is used. AIN2(+) and AIN2(−) are not connected to the temperature demonstration circuit. IOUT2 is not connected to the temperature demonstration circuit. The 3.3 V supply is used as AVDD for the AD7793.
Table 2. Initial Link and Switch Positions
Table 3. Socket Functions
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