SCPS199D August 2014 – October 2016 TCA9538
In the event of a glitch or data corruption, the TCA9538 can be reset to its default conditions by using the power-on reset feature. Power-on reset requires that the device go through a power cycle to be completely reset. This reset also happens when the device is powered on for the first time in an application.
The two types of power-on reset are shown in and Figure 29.
Table 8 specifies the performance of the power-on reset feature for the TCA9538 for both types of power-on reset.
|VCC_FT||Fall rate||See Figure 29||1||ms|
|VCC_RT||Rise rate||See Figure 29||0.1||ms|
|VCC_TRR||Time to re-ramp (when VCC drops to VPOR_MIN – 50 mV or when VCC drops to GND)||See Figure 29||2||μs|
|VCC_GH||Level that VCC can glitch down to, but not cause a functional disruption when VCC_GW = 1 µs||See Figure 30||1.2||V|
|VCC_GW||Glitch width that does not cause a functional disruption when VCC_GH = 0.5 × VCC (For VCC > 3 V)||See Figure 30||10||μs|
Glitches in the power supply can also affect the power-on reset performance of this device. The glitch width (VCC_GW) and height (VCC_GH) are dependent on each other. The bypass capacitance, source impedance, and device impedance are factors that affect power-on reset performance. Figure 30 and Table 8 provide more information on how to measure these specifications.
VPOR is critical to the power-on reset. VPOR is the voltage level at which the reset condition is released and all the registers and the I2C/SMBus state machine are initialized to their default states. The value of VPOR differs based on the VCC being lowered to or from 0. Figure 31 and Table 8 provide more details on this specification.