101-0599 Rabbit Semiconductor, 101-0599 Datasheet - Page 32

• Manufacturer Part Number: 101-0599
• Description: COMPUTER SNGLBD BL2500 512K FLSH
• Manufacturer: Rabbit Semiconductor

Specifications of 101-0599

• Module/board Type: Single Board Computer Module
• For Use With/related Products: BL2500
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

Based on the standard capacitor discharge formula, this means that the maximum voltage
change will be
This is a ripple of approximately 6 mV peak-to-peak.
Table 4 lists typical uncalibrated DA0 or DA1 voltages measured for various duty cycle
values with a load larger than 1 M.
The full D/A converter voltage range of 0–3.3 V cannot be realized because of the voltage
tolerances associated with the voltage regulator, the Rabbit 3000 PWM output, and the op-
amp rail. The circuit can achieve an actual voltage range of 0.1–3.3 V.
It is important to remember that the DA0 or DA1 output voltage will not be realized instan-
taneously after programming in a value. There is a settling time because of the RC time
constant (24.9 k × 100 nF), which is 2.5 ms. For example, the voltage at any given time is
where V is the voltage at time t, V
DA1 output voltage from the D/A converter, and RC is the time constant (2.5 ms). The
settling will be within 99.326% (or within about 22 mV for a 3.3 V change in voltage)
after five time constants, or 12.5 ms. Six time constants, 15 ms, will allow settling to
within 99.75% (or to within about 8 mV for a 3.3 V change in voltage). Seven time con-
stants, 17.5 ms, will allow settling to within 99.91% (or to within about 3 mV for a 3.3 V
change in voltage).
An LM324 op amp, which can comfortably source 10 mA throughout the D/A converter
range, drives the D/A converter output. If the output voltage is above 1 V, the D/A con-
verter can comfortably sink 10 mA. Below 1 V, the D/A converter can only sink a maxi-
mum of 100 µA.
To summarize, DA0 and DA1 are factory-calibrated, with the calibration constants stored
in flash memory. DA0 and DA1 can be programmed with a resolution of 3 mV and a
peak-to-peak ripple of 6 mV over the range from 0.1 to 3.1 V. The settling time to within 3
mV is 17.5 ms.
26
Table 4. Typical Uncalibrated DA0 or DA1 Voltages for Various Duty Cycles
V = V
1.65 V
P
– (V

Duty Cycle
P
1 e
100
– V
–
(%)
50
0
DA


–
----------------- -
2.5 ms
)e
8.7 µs
(-t/RC)
P


is the programmed voltage, V
=
Voltage
5.73 mV
0.086
1.628
3.244
(V)
Programmed Count
1023
512
1
DA
is the last DA0 or
Coyote (BL2500)