ADC12034 National Semiconductor Corporation, ADC12034 Datasheet - Page 33

• Manufacturer Part Number: ADC12034
• Description: Self-calibrating 12-bit Plus Sign Serial I/o A/d Converters With Mux And Sample/hold
• Manufacturer: National Semiconductor Corporation

1.7 Reading the Data Without Starting a Conversion
The data from a particular conversion may be accessed with-
out starting a new conversion by ensuring that the CONV line
is taken high during the I/O sequence. See the Read Data
timing diagrams. Table 6 describes the operation of the
CONV pin.
2.0 THE ANALOG MULTIPLEXER
For the ADC12038, the analog input multiplexer can be con-
figured with 4 differential channels or 8 single ended channels
A/DIN1 and A/DIN2 can be assigned as the + or − input
CH0, CH2, CH4, and CH6 can be assigned to the MUXOUT1
pin in the differential configuration, while CH1, CH3, CH5, and
CH7 can be assigned to the MUXOUT2 pin. In the differential
configuration, the analog inputs are paired as follows: CH0
with CH1, CH2 with CH3, CH4 with CH5 and CH6 with CH7.
The A/DIN1 and A/DIN2 pins can be assigned positive or
negative polarity.
With the single-ended multiplexer configuration CH0 through
CH7 can be assigned to the MUXOUT1 pin. The COM pin is
always assigned to the MUXOUT2 pin. A/DIN1 is assigned as
the positive input; A/DIN2 is assigned as the negative input.
(See Figure 10).
Configuration
4 Differential
Differential
Channels
1135438
1135440
FIGURE 10.
FIGURE 9.
33
A/DIN1 is + input
A/DIN2 is − input
with the COM input as the zero reference or any combination
thereof (see Figure 9). The difference between the voltages
on the V
span (V
ative digital output codes result when V
voltage at V
The Multiplexer assignment tables for the ADC12030,2,4,8
(Tables 2, 3, 4) summarize the aforementioned functions for
the different versions of A/Ds.
2.1 Biasing for Various Multiplexer Configurations
Figure 11 is an example of biasing the device for single-ended
operation. The sign bit is always low. The digital output range
is 0 0000 0000 0000 to 0 1111 1111 1111. One LSB is equal
to 1 mV (4.1V/4096 LSBs).
REF
REF
). The analog input voltage range is 0 to V
IN
+
−
and V
8 Single-Ended Channels
or V
as Zero Reference
IN
REF
Configuration
+
Single-Ended
cannot go below AGND.
with COM
−
pins determines the input voltage
1135439
1135441
IN
−
> V
IN
+
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. The actual
A
+
. Neg-