BL4S100 User’s Manual
27
3.4 A/D Converter Inputs
The single A/D converter chip used in the BL4S100 has a resolution of 12 bits (11 bits for
the value and one bit for the polarity). The A/D converter chip has a programmable-gain
amplifier. Each external input has circuitry that provides scaling and filtering. All 8 external
inputs are scaled and filtered to provide the user with an input impedance of 1 M
and a
variety of single-ended unipolar, and differential bipolar ranges as shown in Table 6.
Figure 11 shows a pair of A/D converter input circuits. The resistors form an approx. 10:1
attenuator, and the capacitors filter noise pulses from the A/D converter inputs.
Figure 11. Buffered A/D Converter Inputs
The A/D converter chip can only accept positive voltages. By pairing the analog inputs,
differential bipolar measurements are possible, and can be configured for each channel pair
with the
opmode
parameter in the
anaInConfig()
software function call. The available
voltage ranges are listed in Table 6.
ADC
953 k
W
10 pF
AIN0
AGND
AIN1
10 pF
105 k
W
105 k
W
953 k
W
