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USE OF THE SAME MCU I/O LINE TO DRIVE A POWER MOSFET AND TO DETECT OVERLOAD

IP.com Disclosure Number: IPCOM000006542D
Original Publication Date: 1992-Aug-01
Included in the Prior Art Database: 2002-Jan-14
Document File: 2 page(s) / 88K

Publishing Venue

Motorola

Related People

Charles-Edouard Cordonnier: AUTHOR

Abstract

The idea consists in using the same MCU I/O port to drive a power mosfet device containing some logic (such as Smartdiscretes C) or Smartmos C)) and to detect an overload present in the power mosfet device.

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MOTOROLA INC. Technical Developments Volume 16 August 1992

USE OF THE SAME MCU I/O LINE TO DRIVE A POWER MOSFET AND TO DETECT OVERLOAD

by Charles-Edouard Cordonnier

  The idea consists in using the same MCU I/O port to drive a power mosfet device containing some logic (such as Smartdiscretes C) or Smartmos C)) and to detect an overload present in the power mosfet device.

  As shown in Figure 1, an MCU has two current sources which are driven by a write register to function either as a dc current source/sink of either polarity, or an under dimensioned push/pull arrangement. The I/O port of the MCU is coupled to a power mosfet device containing components coupled to the gate of the power mosfet for performing predetermined logic functions. The I/O port is also connected via an operational ampli- fier and falter to a read register and to a line providing an interrupt vector.

Thus in operation, the MCU 110 port functions either in an output (write) mode or in an input (read) mode.

Behaviour as an output (write mode):

  The output port is either a pure current source/sink or an under-dimensioned Push-Pull which can only sup- ply a limited current. When the Smartdiscrete input capacitance is filled and reaches 5 Volts, the current sources only supplies the current necessary to complete the leakage current. The turn off is done in a similar Way.

Behaviour as an input (read mode):

  The particularity of the smartdiscrete described in Figure 1 is to clamp its input voltage around its thresh- old (2 volts) when the current limit is reached. The. port of the MCU used as an input just needs to sense the Sm...