C8051F064-EK
Rev. 0.4
11
9.5. Analog Inputs (J4, J5, J6, J8, J16, ADC0 [J13], ADC1 [J12])
Two BNC connectors (J13 (ADC0) and J12 (ADC1)) are provided on the C8051F064 board for easy evaluation of
the 16-bit on-chip ADCs. These analog inputs can be used to input an ac analog signal to the ADCs, ADC0 and
ADC1. Additionally, front-end circuitry is provided to condition the analog signals. To use this circuitry, follow the
guidelines listed below in conjunction with the schematic located in Section 10.
See "AN190: Understanding ADC
Specifications" for a detailed discussion of issues related to ADC performance.
Select the 5 V supply voltage for the Voltage References U3 and U6 at header J4. Place a shorting block on J4,
Pin 1 and Pin 2, to select the DATA VBUS signal. Place a shorting block on J4, Pin 2 and Pin 3, to select the
DEBUG VBUS signal.
A single-supply voltage option is provided on the evaluation board for the op-amps. Place a shorting block on J6
to connect the "V+" op-amp supply to AV+. Additionally, place a shorting block on J8 to connect the "V–"
op-amp supply to GND.
Provide a dual-supply voltage to the op-amps for optimal performance by removing the shorting blocks on
headers J6 and J8. To supply the voltages, +5 V and –5 V signals will need to be provided at the J3 terminal
block (Pin 1 and Pin 2).
Note:
Remove shorting blocks from J6 and J8 BEFORE applying voltages to the J3 terminal block. Voltages applied to J3
while shorting blocks are on J6 and J8 could cause damage to the evaluation board.
Provide an external Conversion Start signal to ADC0 at header J5 Pin 1.
Provide an external Conversion Start signal to ADC1 at header J5 Pin 2.
Differential measurement from one test source: input signal to ADC0 and place shorting block on header J16.
9.6. Analog I/O (Terminal Block [J3])
J3 is used to provide off-board voltage supply and voltage references for better noise performance evaluation in a
lab environment. Refer to Table 3 for terminal block connections.
Table 3. Terminal Block (J3) Pin Descriptions
Pin #
Description
1
–5 V
2
+5 V
3
AGND
4
GND
5
+3.3 VIN
6
5VDD
