2.1.19 Prescaler Range
The prescaler range is determined by the Maximum Input Voltage field. Use the following table to determine the appropriate prescaler range.
| Scaling Factor: Pad to ADC Input | LSB for 8‑bit conversion (mV) | LSB (10‑bit) (mV) | LSB (12‑bit) (mV) | Full‑Scale Voltage (V) | Range Name (V) |
|---|---|---|---|---|---|
| 0.15625 | 64 | 16 | 4 | 16.368 | 16 |
| 0.3125 | 32 | 8 | 2 | 8.184 | 8 |
| 0.625 | 16 | 4 | 1 | 4.092 | 4 |
| 1.25 | 8 | 2 | 0.5 | 2.046 | 2 |
| 2.5 | 4 | 1 | 0.25 | 1.023 | 1 |
| 5.0 | 2 | 0.5 | 0.125 | 0.5115 | 0.5 |
| 10.0 | 1 | 0.25 | 0.0625 | 0.25575 | 0.25 |
| 20.0 | 0.5 | 0.125 | 0.03125 | 0.127875 | 0.125 |
If the maximum input voltage exceeds the selected range, ASB automatically selects the next higher range. The corresponding ranges for negative polarity are identical.
The prescaler logic in the AB has a maximum settling time of 10 µs. This settling time is application‑dependent and must be accounted for when setting the acquisition and hold time for each channel. A recommended default value is inserted by ASB when configuring a new Voltage Monitor, but it may be reduced at the cost of reduced sampling accuracy.
If the maximum input voltage is greater than the given range, it will select the higher range. The corresponding ranges for negative polarity is the same.