5 PICOSCALE HARDWARE
5.3.3 BOB analog GPIOs
The Breakout-Box buffers and normalizes the analog GPIOs to single ended signals with an ampli-
tude of
±
10 V
.
At the input ADC1 the single ended
±
10 V
signal is converted to a differential signal with an ampli-
tude equivalent to a full scale modulation of the ADC. Due to component toler
ances, o
ff
sets and
gains can vary slightly so that
±
10 V
is not exactly equivalent to the ADC
’
s resolution. For an ex-
act mapping of voltage to ADC resolution it is recommended to do a calibration of the ADC input.
The input impedance of the ADC1 input is approx.
2.4 k
Ω
. The inputs ADC2 and ADC3 input are
converted a di
ff
erential signal. Again, it is recommended to do a calibration to get an exact map-
ping from voltage to ADC resolution. The input impedance is approx.
34 k
Ω
. For a performance
overview see table 5.5 and 5.6.
Table 5.5: Main performance data of ADC1
Parameter
Typical Value
Unit
Full-scale input voltage
±
10
V
Sample-rate
10
MS /s
Resolution
16
Bit
Bandwidth
f
1
dB
2-2.5
MHz
Table 5.6: Main performance data of ADC2 and ADC3
Parameter
Typical Value
Unit
Full-scale input voltage
±
10
V
Sample-rate
100
kS /s
Resolution
16
Bit
Bandwidth
f
1
dB
35-45
kHz
The Breakout-Box converts the di
ff
erential DAC1 signal from the
PICO
SCALE
Controller to a single
ended
±
10 V
output signal. The output can drive currents up to
35 mA
and a capacitive load up to
33 pF
. DAC2-DAC5 are the
PICO
SCALE
DAC signals normalized to
±
10 V
.
I
f a single DAC channel
is connected, it can drive currents up to
±
30 mA
and a capacitive load of up to
200 pF
. With more
channels connected, the maximum current reduces correspondingly. For a performance overview
see table 5.7 and 5.8.
39
PicoScale User Manual
