In Resolution Adjust Mode it is possible to adjust the resolution precisely via software. The adjusted resolution becomes completely independent of temperature, so no more calibration of the measuring circuit is necessary. The resolution remains stable due to the changes in the measurement core voltage, which is regulated via PLL (Phase Locked Loop). For that purpose, the TDC-GPX phase output provides a pulse width modulated signal for the external PLL regulation loop. This signal is derived from TDC-GPX reference clock and regulates the TDC-GPX core voltage. As soon as the PLL has locked, the resolution becomes stable. The absolute precision of the resolution only depends upon the used reference oscillator at this point. The range for resolution adjustment can reach values from -30% up to +8% of the normal resolution at 5 V and 25°C, so you should however realize that not every resolution is compatible with the full permissible temperature range. Before setting the resolution parameter, potential temperature variations should be considered, since they need voltage margin for compensation. A careless choice may end up in an undefined resolution. This would be the case e.g. when regulated voltage is close to maximum permitted voltage (say 5 volts) and temperature rises so high, that voltage being regulated right up to 5 volts, the high end, becomes insufficient. The PLL comes to the limit and then locks off.
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