Compact dual oscillator and power on reset for MCU

Would you consider connecting an IC with dual-speed oscillator and a power-on reset to you MCU. This is what MAX7378 does. This is a good replacement for ceramic resonators, crystals and other oscillator modules and discrete reset circuits as well. Good thing here is that at any time you can select either low frequency 32.768kHz or a high frequency from range 600kHz to 10MHz.Clock frequency can be switched at any time without glitches.

MAX7378.PNG

MAX7378 can be powered from 2,7V to 5,5V, so it is suitable for most of MCU types. Comparing to Crystal resonators it is resistive to vibrations and EMI. It is good solution for automotive and industrial environment. High frequency oscillator error reaches of ±2% at 25°C at 5V power supply. In other words speaking oscillator frequency stability is about ±325ppm (when crystal stability is from ±10ppm to ±100ppm). So it doesn’t correspond to crystal accuracy, but it suits for most non time critical applications. 32.768kHz oscillator is more accurate with an error of 1%, but it still a bit much for time measurements.

Reset circuitry takes care that reset will occur after 100us after clock startup. Reset output is available in three different options: two of them are push-pull types (active LOW or active HIGH) and third one is open drain and requires an external pull-up resistor (dashed in picture bellow).

 

MAX7378_to_MCU.PNG

Reset signal becomes active if voltage drops bellow threshold. IC is coated in small 8-pin package and has dimensions of only 3,05×5,03mm including pins.

Leave a Reply

Your email address will not be published. Required fields are marked *