TLC32046CFN Datasheet, PDF (39/56 Pages) Texas Instruments – Wide-Band Analog Interface Circuit

4 Parameter Measurement Information
IN +
R
or
AUX IN +
IN –
R
or
AUX IN –
Rfb
–
+
–
+
Rfb
To Multiplexer
Rfb = R for D6 = 1 and D7 = 1
D6 = 0 and D7 = 0
Rfb = 2R for D6 = 1 and D7 = 0
Rfb = 4R for D6 = 0, and D7 = 1
Figure 4–1. IN + and IN – Gain Control Circuitry
Table 4–1. Gain Control Table (Analog Input Signal Required for
Full-Scale Bipolar A/D Conversion Twos Complement)^†
INPUT
CONFIGURATIONS
CONTROL REGISTER BITS
D6
D7
ANALOG
INPUT^{‡ §}
A/D CONVERSION
RESULT
1
Differential configuration
0
Analog input = IN + – IN –
= AUX IN + – AUX IN –
1
0
1
0
VID = ± 6 V
± full scale
0
VID = ± 3 V
± full scale
1
VID = ± 1.5 V
± full scale
1
Single-ended configuration
0
Analog input = IN + – ANLG GND
= AUX IN + –ANLG GND
1
1
0
VI = ± 3 V
0
VI = ± 3 V
± half scale
± full scale
0
1
VI = ± 1.5 V
± full scale
† _{VCC+ = 5 V, VCC – = – 5 V, VDD = 5 V}
‡ _{VID = Differential Input Voltage, VI = Input voltage referenced to ground with IN – or AUX IN – connected to GND.}
§ _{In this example, Vref is assumed to be 3 V. In order to minimize distortion, it is recommended that the analog input not}
exceed 0.1 dB below full scale.
4–1