Vdd brownouts are among the most common antipodes of microcontroller design – they are especially annoying, as their presence is not easy to detect. Diodes Incorporated provides a new family of easy-to-use supply voltage monitor ICs.
From a principal point of view, the parts are not difficult to understand. Simply connect them to VCC and ground, thereby allowing the chip to keep an eye on the supply. After that, a pull-up resistor is needed to provide current to the open drain active-low reset output which resets the microprocessor.
The addition of the resistor shown in figure one is intentional – some (odd or high-end) microcontrollers can also assert the reset line on their own.
A question of the part number
The lack of external pins limits the configuration possibilities – the part behaves just like you ordered it. One interesting aspect is that Diodes Incorporated provides a series of different voltage levels, which are shown in the table.
In addition to that, three timeout durations exist – they govern how long the microcontroller is held in reset if a voltage drop out is detected. Their configuration is also shown in figure three…
Diodes Inc also covers you if your microcontroller needs more time to reset itself
The tables can then be used to find out more about the part at hand. We recently saw significant search interest for the APX803S-31SA-7 – it works with a voltage trip level of 3.1V, and has a sleep time of 240ms.
Furthermore, all of the parts boast with an impressively low standby current consumption. The datasheet claims consumption in the range of 10 yA – this should be acceptable, especially when combined with high-end microcontrollers.