ZHCSLA7C December 2019 – September 2023 AM6526 , AM6528 , AM6546 , AM6548
PRODUCTION DATA
The VDDA_VSYS_MON pin provides a way to monitor the system power supply and is not fail-safe, unless implemented with the appropriate resistor voltage divider source. This pin should be sourced with a resistor voltage divider that receives its power from the system power supply.
The output of the resistor voltage divider is connected to the VDDA_VSYS_MON pin which has a trigger voltage of 0.5 V ± 5%. The resistor voltage divider should be implemented such that it has a reference current in the range of 1 µA to 50 µA, output voltage that never exceeds the maximum value defined in Section 6.1, Absolute Maximums Ratings, and output voltage of 0.54 V when the system supply drops to its lowest desired operating voltage.
The recommended output voltage of 0.54 V provides 40 mV of margin that includes 5% for tolerance of the voltage monitor, 1% for tolerance of each resistor, plus 5 mV of potential error introduced by input leakage current. This value ensures the voltage monitor will never trigger before reaching the expected trigger voltage.
Figure 8-5 presents an example, when the system power supply voltage is nominally 5 V and the desired trigger threshold is -10% or 4.5 V.
In this example the voltage divider ratio should be (4.5 V / 0.54 V) = 8.33 V. This ratio produces a 0.54 V potential on the VDDA_VSYS_MON pin when the system power supply is 4.5 V. In this case, the voltage monitor will trigger in the range of 3.88 V to 4.5 V. Precision 1% resistors with similar thermal coefficient are recommended for implementing the resistor voltage divider.