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TB087
| Title |
Title
Using Voltage Supervisors with PICmicro MCU Systems which implement...
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|---|---|
| Name |
Name
TB087
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| Date |
Date
06/24/2015
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| Product Categories |
Product Categories
Power Management ICs /
Voltage Detectors
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| Description |
Description
Even though many microcontrollers offer an on-chip brown-out function, it may be desirable to use an external voltage supervisor. This may be due to the microcontroller?s limited trip point selections or the additional current requirement for enabling the brown-out function. In these cases, an external voltage supervisor device may be preferable. Many standard microcontrollers are Flash memory devices. This means that the device can be programmed in-circuit. Typically, to enter the in-circuit programming mode, some non-typical state needs to be forced. For PICmicro® microcontrollers, the mode is called In-Circuit Serial Programming? (ICSP?). A typical microcontroller ? ICSP system is shown in Figure 1. ICSP can be used to program the device after assembly as well as for firmware updates in the field. In most cases, entering the ICSP mode requires that the MCLR pin go from a low voltage (VIL) to the programming high voltage (VIHH). The VIHH is dependent on the PICmicro microcontroller and typically ranges from a minimum of the PICmicro microcontroller?s VDD + 3.5V to a maximum of 14V. As can be expected, these voltages are beyond the maximum voltage specification of the voltage supervisor output pin. This technical brief will show how the MCP111 and MCP121 may be used in PICmicro microcontroller systems where ICSP is required.
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