AC0801LCN National Semiconductor Corporation, AC0801LCN Datasheet - Page 34

• Manufacturer Part Number: AC0801LCN
• Description: ADC0801 - 8-Bit µP Compatible A/D Converters, Package: Mdip, Pin Nb=20
• Manufacturer: National Semiconductor Corporation

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Functional Description
any output of Port B will source current into node V
raising the voltage at V
more negative. Conversely, a logic “0” (0V) will pull current
out of node V
ential output to become more positive. For the resistor val-
ues shown, V
which will null the offset error term to
Note 26: R2 = 49.5 R1
Note 27: Switches are LMC13334 CMOS analog switches.
Note 28: The 9 resistors used in the auto-zero section can be
X
X
and decrease the voltage, causing the differ-
can move
X
±
and making the output differential
12 mV with a resolution of 50 µV,
FIGURE 18. Gain of 100 Differential Transducer Preamp
1
⁄
4
(Continued)
LSB of full-scale for
±
5% tolerance.
X
thus
34
the ADC0801. It is important that the voltage levels that drive
the auto-zero resistors be constant. Also, for symmetry, a
logic swing of 0V to 5V is convenient. To achieve this, a
CMOS buffer is used for the logic output signals of Port B
and this CMOS package is powered with a stable 5V source.
Buffer amplifier A1 is necessary so that it can source or sink
the D/A output current.
DS005671-91