Current-sensing power-on reset circuit for integrated circuits
AssigneeTexas Instruments Incorporated
InventorsTim M. Coffman, Phat C. Truong, Sung-Wei Lin, T. Damodar Reddy, Dennis R. Robinson
Life of this patent
Estimating the term…
Abstract
The power-on reset circuit of this invention includes a current-sensing circuit, a pulse-stretching circuit, and a voltage-reference circuit. The voltage-reference circuit consists, for example, of one N-Channel and one P-Channel MOS transistor. The circuit of this invention uses a static voltage reference comprised of CMOS transistors to detect the power-up condition. The circuit of this invention improves detection of a transient power-supply voltage Vcc loss and detects that power-supply voltage transient on both rising and falling edges.
Claims16
A power-on reset circuit having a supply-voltage terminal, a reference-potential terminal and an output, said circuit comprising:
- a current-bias circuit coupled to said supply-voltage terminal and said reference-potential terminal and having an output;
- a voltage-reference circuit having an input and having first and second outputs, said input of said voltage-reference circuit coupled to said output of said current-bias circuit;
- a current-sensing circuit having first, second and third inputs and an output, said first input of said current-sensing circuit coupled to said output of said current-bias circuit and said second and third inputs of said current-sensing circuit coupled to respective first and second outputs of said voltage-reference circuit;
- and
- a pulse-stretching circuit having first and second inputs and an output, said first input of said pulse-stretching circuit coupled to said output of said current-sensing circuit, said second input of said pulse stretching circuit coupled to said second output of said voltage-reference circuit, said output of said pulse-stretching circuit coupled to said output of said power-on reset circuit.
A method for indicating that a power-supply voltage is below a certain level, said method comprising:
- establishing a maximum current responsive to said power-supply voltage;
- mirroring said maximum current to a voltage-reference circuit and to a current-sensing circuit, said current-sensing circuit including a current-summing circuit and a reset-detection circuit;
- coupling outputs of said voltage-reference circuit to said current-summing circuit and to said reset-detection circuit;
- and
- coupling the output of said reset-detection circuit to a pulse stretching circuit;
- the output of said pulse-stretching circuit providing a signal if said power-supply voltage is below said certain level.
Dependencies are inferred from the claim text.