Patent Application
20090134934
1. Field of the Invention
The present invention relates to electronic devices, and particularly to an electronic device with a switch circuit for protecting an integrated circuit of the electronic device when the integrated circuit is reset.
2. Description of Related Art
Integrated circuits (IC) are widely used in electronic devices for processing data or power management. Generally, a complex IC (e.g., a microcontroller unit) performs a reset function to clear any pending errors or events so as to return to a normal condition or initial state. When performing the reset function, the IC becomes unstable and is vulnerable to voltage spikes and current surges.
Therefore, an improved electronic device is needed to address the aforementioned deficiency and inadequacies.
An electronic device includes a power interface for transmitting power, an integrated circuit capable of resetting, and a switch circuit. The switch circuit is connected to the power interface for transmitting the power to the integrated circuit after the integrated circuit is reset and to stop transmitting the power to the integrated circuit if the integrated circuit is resetting.
Other advantages and novel features of the present invention will become more apparent from the following detailed description of an embodiment/embodiments when taken in conjunction with the accompanying drawings, in which:
Referring to
There are two types of reset: internal reset (e.g., power on reset) and external reset (reset after receiving the reset signal from the reset circuit 340). While performing the reset procedure, the integrated circuit 330 sends a reset-in-process signal to the switch circuit 320. When the reset-in-process signal is transmitted to the switch circuit 320, the switch circuit 320 disconnects the power interface 310 to the integrated circuit 330. During the reset procedure, the integrated circuit 330 receives power from other power interface with a standard voltage. When the reset procedure is completed, the integrated circuit 330 sends a reset-completed signal to the switch circuit 320. After receiving the reset-completed signal, the switch circuit 320 conducts and connects the power interface 310 to the integrated circuit 330. The integrated circuit 330 performs power management function according to the detected power transmitted from the external or internal power source via the switch circuit 320.
Referring to
The switch circuit 320 includes a first resistor 321, a second resistor 322, a third resistor 323, a fourth resistor 324, and a NPN Bipolar Junction Transistor (BJT) 325. The first resistor 321 is connected between the base of the BJT 325 and the state node 333. The second resistor 322 is connected between the collector of the BJT 325 and the power interface 310. The third resistor 323 is connected between the emitter of the BJT 325 and the ground. The fourth resistor 324 is connected between the emitter of the BJT 325 and the detect pin 331. The resistors 321, 322, 323, 324 are used for providing a suitable voltage to the integrated circuit 330. In other alternative embodiments, some of the resistors can be omitted, or have more resistors. The BJT 325 is used for connecting the power interface 310 to the integrated circuit 330 after receiving the reset-completed signal (i.e., high voltage level) from the state node 333.
For example, a voltage supplied by the power interface 310 may be 9.5 volts. The integrated circuit 330 will initiate the reset after receiving the reset signal from the reset circuit 340. The reset signal is a low voltage from reset circuit 340, this low voltage is outputted to the pin connected to the state node 333. This results in the state node 33 being pulled low and the BJT 325 being off. After the integrated circuit 330 performs the reset procedure, the integrated circuit 330 outputs a high voltage to the base of the BJT 325 via the state node 333, thus the BJT 325 is on and the power is transmitted to the detect pin 331 via the BJT 325. Therefore, the integrated circuit 330 is able to receive and detect the power received by the detect pin 331 to perform power management function. After the reset procedure of integrated circuit 330 is completed, the integrated circuit 330 is able to withstand electric power having voltage spikes and current surges because built-in internal protection circuitry will operate and protect the IC during normal operation.
In other alternative embodiments, the BJT 325 can be replaced by other transistors that conduct under low voltage level, such as field effect transistors. That is, the state node 333 of the integrated circuit 330 is low voltage level after the integrated circuit 330 is reset. In addition, the reset circuit 340 is optional, since the integrated circuit 330 is able to start reset according to software command or start reset automatically when powered on.
It is to be understood, however, that even though numerous characteristics and advantages of the present embodiments have been set forth in the foregoing description, together with details of the structures and functions of the embodiments, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.
| Number | Date | Country | Kind |
|---|---|---|---|
| 200710202677.3 | Nov 2007 | CN | national |
