Low-voltage detection circuit

• US 7,259,597 B2
• Filed: 06/23/2005
• Issued: 08/21/2007
• Est. Priority Date: 01/07/2005
• Status: Active Grant

• Current Assignee: Winbond Electronics Corporation
• Original Assignee: Winbond Electronics Corporation
• Inventors: Wu, Li-Te
• Primary Examiner(s): Wells; Kenneth B.
• Application Number:
  US11/165,648
• Publication Number:
  US 20060152250A1
• Time in Patent Office: 789 Days
• Field of Search: 327/78, 327/79, 327/143, 320/136
• US Class Current: 327/78
• CPC Class Codes: G01R 19/16542 for batteries charge condition monitoring in G01R31/36

Abstract

A low-voltage detection circuit detects a terminal voltage of a power supply terminal. The low-voltage detection circuit includes a first voltage-dividing circuit, a second voltage-dividing circuit, and a comparator. The second voltage-dividing circuit includes a bias circuit and a metal-oxide-semiconductor (MOS) transistor. The comparator compares and receives a voltage generated by the first voltage-dividing circuit and a voltage generated by the second voltage-dividing circuit to generate a voltage detection signal.

Claims

1. A low-voltage detection circuit to detect a terminal voltage of a power supply terminal, comprising:

a first voltage-dividing circuit coupled to the power supply terminal to divide the terminal voltage into a first compare voltage;

a second voltage-dividing circuit comprising a bias circuit and a metal-oxide-semiconductor (MOS) transistor, the second voltage-dividing circuit being coupled to the power supply terminal to divide the terminal voltage into a second compare voltage, wherein a gate of the MOS transistor receives the terminal voltage; and

a comparator receiving and comparing the first compare voltage and the second compare voltage to generate a voltage detection signal.

2. The low-voltage detection circuit of claim 1, wherein the first voltage-dividing circuit comprises:

a first resistor, a terminal of the first resistor being coupled to the power supply terminal;

a second resistor, a terminal of the second resistor being coupled to another terminal of the first resistor, another terminal of the second resistor being coupled to the comparator; and

a third resistor, a terminal of the third resistor being coupled to the another terminal of the second resistor, another terminal of the third resistor being grounded.

3. The low-voltage detection circuit of claim 2, wherein the bias circuit of the second voltage-dividing circuit comprises:

a fourth resistor, a terminal of the fourth resistor being coupled to the power supply terminal, another terminal of the fourth resistor being coupled to the MOS transistor; and

a fifth resistor, a terminal of the fifth resistor being coupled to the MOS transistor and the comparator, another terminal of the fifth resistor being grounded.

4. The low-voltage detection circuit of claim 1, wherein the second voltage-dividing circuit comprises:

a first resistor, a terminal of the first resistor being coupled to the power supply terminal, another terminal of the first resistor being coupled to the MOS transistor; and

a second resistor, a terminal of the second resistor being coupled to the MOS transistor and the comparator, another terminal of the second resistor being grounded.

5. The low-voltage detection circuit of claim 3, characterized in that:

a resistance of the first resistor is equal to a resistance of the fourth resistor; and

a resistance of the third resistor is equal to a resistance of the fifth resistor.

6. The low-voltage detection circuit of claim 1, wherein if the terminal voltage is higher than a threshold voltage of the MOS transistor of the second voltage-dividing circuit, a transmission resistance of the MOS transistor is a first value;

if the terminal voltage is lower than a threshold voltage of the MOS transistor of the second voltage-dividing circuit, a transmission resistance of the MOS transistor is a second value, wherein the first value is smaller than the second value.

7. The low-voltage detection circuit of claim 1, wherein the MOS transistor is disposed in a to-be-tested integrated circuit.

8. The low-voltage detection circuit of claim 1, wherein if the first compare voltage is higher than the second compare voltage, which is measured by the comparator, the voltage detection signal is logic 1.

9. The low-voltage detection circuit of claim 1, wherein if the first compare voltage is lower than, or equal to the second compare voltage, which is measured by the comparator, the voltage detection signal is logic 0.

10. A low-voltage detection circuit for detecting a first terminal voltage of a first power supply terminal and a second terminal voltage of a second power supply terminal;

comprising;

a first voltage-dividing circuit coupled to the first power supply terminal and the second power supply terminal to divide the first terminal voltage and the second terminal voltage into a first compare voltage;

a second voltage-dividing circuit comprising a bias circuit and a metal-oxide-semiconductor (MOS) transistor, the second voltage-dividing circuit being coupled to the first power supply terminal and the second power supply terminal to divide the first terminal voltage and the second terminal voltage into a second compare voltage, wherein a gate of the MOS transistor receives the terminal voltage; and

a comparator, receiving and comparing the first compare voltage and the second compare voltage to generate a voltage detection signal.

11. The low-voltage detection circuit of claim 10, wherein the first voltage-dividing circuit comprises:

a first resistor, a terminal of the first resistor being coupled to the first power supply terminal;

a second resistor, a terminal of the second resistor being coupled to another terminal of the first resistor, another terminal of the second resistor being coupled to the comparator; and

a third resistor, a terminal of the third resistor being coupled to the another terminal of the second resistor, another terminal of the third resistor being coupled to the second power supply terminal.

12. The low-voltage detection circuit of claim 11, wherein the bias circuit of the second voltage-dividing circuit comprises:

a fourth resistor, a terminal of the fourth resistor being coupled to the first power supply terminal, another terminal of the fourth resistor being coupled to the MOS transistor; and

a fifth resistor, a terminal of the fifth resistor being coupled to the MOS transistor and the comparator, another terminal of the fifth resistor being coupled to the second power supply terminal.

13. The low-voltage detection circuit of claim 10, wherein the second voltage-dividing circuit comprises:

a first resistor, a terminal of the first resistor being coupled to the first power supply terminal, another terminal of the first resistor being coupled to the MOS transistor; and

a second resistor, a terminal of the second resistor being coupled to the MOS transistor and the comparator, another terminal of the second resistor being coupled to the second power supply terminal.

14. The low-voltage detection circuit of claim 12, characterized in that:

a resistance of the first resistor is equal to a resistance of the fourth resistor; and

a resistance of the third resistor is equal to a resistance of the fifth resistor.

15. The low-voltage detection circuit of claim 10, wherein if the sum of the first terminal voltage and the second terminal voltage is higher than a threshold voltage of the MOS transistor of the second voltage-dividing circuit, a transmission resistance of the MOS transistor is a first value;

if the sum of the first terminal voltage and the second terminal voltage are lower than a threshold voltage of the MOS transistor of the second voltage-dividing circuit, a transmission resistance of the MOS transistor is a second value, wherein the first value is smaller than the second value.

16. The low-voltage detection circuit of claim 10, wherein if the first compare voltage is higher than the second compare voltage, which is measured by the comparator, the voltage detection signal is logic 1.

17. The low-voltage detection circuit of claim 10, wherein if the first compare voltage is lower than, or equal to the second compare voltage, which is measured by the comparator, the voltage detection signal is logic 0.

18. The low-voltage detection circuit of claim 10, wherein the MOS transistor is disposed in a to-be-tested integrated circuit.