Table 4-1 Brownout and Device Reset Power Ramp Requirementsover recommended ranges of supply voltage and operating temperature (unless otherwise noted)
|| Brownout power-down level(1)(2)
||| dDVCC/dt | < 3 V/s(3)
|| dDVCC/dt | > 300 V/s(3)
||Brownout power-up level(2)
||| dDVCC/dt | < 3 V/s(4)
(1) In case of a supply voltage brownout, the device supply voltages need to ramp down to the specified brownout power-down level VVCC_BOR- before the voltage is ramped up again to ensure a reliable device start-up and performance according to the data sheet including the correct operation of the on-chip SVS module.
(2) Fast supply voltage changes can trigger a BOR reset even within the recommended supply voltage range. To avoid unwanted BOR resets, the supply voltage must change by less than 0.05 V per microsecond (±0.05 V/µs). Following the data sheet recommendation for capacitor CDVCC should limit the slopes accordingly.
The brownout levels are measured with a slowly changing supply. With faster slopes the MIN level required to reset the device properly can decrease to 0 V. Use the graph in Figure 4-3
to estimate the VVCC_BOR-
level based on the down slope of the supply voltage. After removing VCC the down slope can be estimated based on the current consumption and the capacitance on DVCC: dV/dt = I/C with dV/dt: slope, I: current, C: capacitance.
(4) The brownout levels are measured with a slowly changing supply.
Figure 4-3 Brownout Power-Down Level vs Supply Voltage Down Slope
Table 4-2 lists the characteristics of the SVS.