Multifunctional μP monitoring chip IMP706 and its application

    In recent years, microprocessors have been widely used in industrial control fields and intelligent products. In the development and design process of systems and products, in order to improve their anti-interference ability, the application of monitoring μP monitoring chips is one of the preferred technical measures. The monitoring chip can provide power-on and power-off reset functions for the system, and can also provide other functions, such as backup battery management, memory protection, low-voltage alarm or watchdog, etc. The system μP monitoring chip produced by the American IMP Company has the characteristics of multiple functions, low power consumption, wide operating temperature range (-40 ~ +80℃), easy to use, low price, and can be combined with μP monitoring chips from MAXIM, AD and other companies The product is fully compatible. We have used the IMP706 chip in many projects such as "IC Card Electronic Energy Meter" and "Gas Power Rock Drill Performance Test System" with good results.

1 Content structure and pin functions

    The internal structural block diagram of IMP706 is shown in Figure 1. It can generate a reset signal during power-on, power-down or manual conditions. It contains a 4.40V power supply voltage monitor with a 1.6s watchdog timer. In addition, there is a 1.25V threshold power failure alarm circuit that can be used to detect battery voltage and non-5V power supplies.

    IMP706 is available in various package forms such as 8-pin DiP and Sot Micro SO. Figure 2 is the pin diagram of IMP706. The functions of each pin are as follows:

    MP(1): manual reset input;

    VCC (2): +5V power input;

    GND (3): the reference ground for all signals;

    PFI (4): Power failure voltage monitoring input. When PFI is less than 1.25V, PFO becomes low level;

    PFO(5): power failure output;

    WDI (6): Watchdog input. When WDI remains high or low for 1.6s, the internal timer can complete counting and set WDO low;

    RESET(7): active low reset output;

    WDO(8): Watchdog output, if connected to MR, the reset signal will be triggered.

2 Typical application circuit

    The typical application circuit of IMP706 is shown in Figure 3. This circuit can be used to implement power-on, power-off, manual reset, power supply voltage monitoring, watchdog and other functions. It can also monitor the backup battery voltage or other non-5V power supplies as needed.

3 Precautions for use

    You should pay attention to the following two points when using IMP706:

    (1) When Vcc drops below 1.1V, the RESET output of IMP706 is uncertain. At this time, a 100kΩ pull-down resistor can be connected to the RESET pin to absorb stray charges to ground and keep RESET low.

    (2) The IMP706's power fault circuit can also monitor negative supply voltages. When the negative supply is normal, PFO is low; when the negative supply becomes bad (not negative enough), PFO is high (the opposite is true for the positive supply being monitored). In order to deactivate the reset, PFO needs to be inverted and connected to the MR terminal, as shown in Figure 4.