Reset Circuit Design of ARM Microcontroller

Whether in mobile phones, high-end handheld instruments or embedded systems, 32-bit ARM microcontrollers occupy an increasing share, and ARM has
become the de facto industrial standard for high-end products. Due to ARM's high speed, low power consumption, and low operating voltage, its noise tolerance is low, which is a challenge to the limits of digital circuits. It also puts forward higher requirements on power supply ripple, transient response performance, clock source stability, power supply monitoring reliability and many other aspects. ARM monitoring technology is complex and very important.

The monitoring circuit implemented by discrete components is greatly affected by external factors such as temperature, humidity, and pressure, and the impact on different components is inconsistent. The board area is large, too many and too long pins are prone to introduce radio frequency interference, and the high power consumption is also unacceptable for many applications. Integrated circuits can solve such problems very well. At present, there are also many microprocessors with integrated monitoring circuits. Due to manufacturing costs and process technology reasons, most of these monitoring circuits are implemented with low-voltage CMOS technology. Compared with dedicated monitoring circuits manufactured with high-voltage, high-linearity bipolar processes, there is still a gap in performance.

The conclusion is that using ARM without dedicated monitoring circuits may result in more harm than good. Experience also tells us that using dedicated monitoring circuits can avoid many strange problems. ARM application engineers, remember to avoid detours.

ARM reset circuit implemented with PHILIPS MAX708

The figure is a practical and reliable ARM reset circuit. The operating voltage of the ARM core is low. R1 can ensure that the voltage is lower than the working
power of MAX708 and can be reset reliably. The TRST signal is used for the JTAG interface. HC125 can realize multiple reset sources to reset ARM,
such as resetting ARM through the PC serial port or JTAG interface.