POWER-ON DETECTION CIRCUIT FOR DETECTING MINIMUM OPERATIONAL FREQUENCY

• US 20090261870A1
• Filed: 04/18/2008
• Published: 10/22/2009
• Est. Priority Date: 04/18/2008
• Status: Active Grant

• Current Assignee: Nanya Technology Corporation
• Original Assignee: Nanya Technology Corporation
• Inventors: Dale, Bret Roberts, Jurasek, Ryan Andrew, Daudelin, Darin James, Chapmen, Dave Eugene
• Granted Patent: US 7,750,684 B2
• Time in Patent Office: Days
• US Class Current: 327/143
• CPC Class Codes: H03K 3/0315 Ring oscillators

Abstract

A power-on detection circuit for detecting a minimum operational frequency includes: an oscillating circuit, which includes: a ring oscillator, for generating a first oscillating signal; and a high pass filter for filtering the first oscillating signal to generate a second oscillating signal. The power-on detection circuit also includes a rectification device, coupled to the high pass filter, for generating a logic signal once the second oscillating signal reaches a certain frequency.

Claims

1. A power-on detection circuit for detecting a minimum operational frequency, comprising:

an oscillating circuit, for generating an oscillating signal having an upper threshold; and

a rectification device, coupled to the oscillating circuit, for generating a logic signal once the oscillating signal reaches a certain frequency.

2. The power-on detection circuit of claim 1, wherein the oscillating circuit comprises:

a ring oscillator, for generating a first oscillating signal up to the upper threshold; and

a high pass filter, coupled to the ring oscillator, for filtering the first oscillating signal to generate a second oscillating signal to the rectification device, wherein the logic signal is generated once the first oscillating signal reaches the certain frequency.

3. The power-on detection circuit of claim 2, wherein the second oscillating signal is generated at a predetermined frequency and amplitude of the first oscillating signal, and the logic signal is generated after the second oscillating signal is generated.

4. The power-on detection circuit of claim 2, wherein the rectification device comprises:

a transistor, having a gate coupled to the high pass filter and a source coupled to a first reference voltage;

a resistor, coupled between a second reference voltage and a drain of the transistor; and

a logic detect circuit, coupled to the drain of the transistor, for outputting the logic signal when the transistor is turned on by the second oscillating signal.

5. The power-on detection circuit of claim 2, wherein the second oscillating signal is input to the rectification device and the rectification device comprises:

a capacitor, for storing charges when the second oscillating signal is not input to the rectification device and for discharging after the second oscillating signal is input to the rectification device; and

a logic detect circuit, coupled to the capacitor, for outputting the logic signal when the capacitor discharges.

6. The power-on detection circuit of claim 1, wherein the oscillating signal is input to the rectification device and the rectification device comprises:

a transistor that is turned on at the certain frequency, having a gate coupled to the oscillating device and a source coupled to a first reference voltage;

a resistor, coupled between a second reference voltage and a drain of the transistor;

a capacitor, coupled between the resistor and the drain of the transistor, for storing charges when the oscillating signal is below the certain frequency and for discharging when the transistor is turned on by the oscillating signal; and

a logic detect circuit, coupled to the capacitor, for outputting the logic signal when the capacitor discharges.

7-12. -12. (canceled)