US 12,591,282 B2 · Reset circuit and method for designing reset circuit

Abstract

The reset circuit according to the disclosure includes a resistor, a diode, a capacitor, a power input terminal, a power return terminal, and an output terminal which outputs a reset signal. The power input terminal, the resistor, the capacitor, and the power return terminal are connected in series in this order. The diode is connected in parallel with the resistor between the power input terminal and the capacitor. The output terminal is connected to a high potential side of the capacitor. When a reverse resistance of the diode at temperature T, the resistor's resistance, and the capacitor's capacitance are each denoted as RD(T), R, and C, a time constant of the reset circuit at the temperature T is given by CRRD(T)/(R+RD(T)), whereby the time needed for output signal to rise from zero to the reset release threshold voltage was made longer than the specified time for the reset operation.

Claims8

Dependent claims

A method for designing a reset circuit which outputs a reset signal to a CPU in a high temperature environment,

the reset circuit including a resistor, a diode, a capacitor, a power input terminal, a power return terminal, and an output terminal which outputs a reset signal,
the power input terminal, the resistor, the capacitor, and the power return terminal being connected in series in an order of the power input terminal, the resistor, the capacitor, and the power return terminal,
the diode being connected in parallel with the resistor between the power input terminal and the capacitor in a manner such that a cathode is on a side closer to the power input terminal and an anode is on a side closer to the capacitor, and
the output terminal being connected to the capacitor on a side being closer to the resistor,
the method comprising:
measuring a reverse resistance RD(T) of the diode at high temperature T, at which the reset circuit is operated;
obtaining specified time td for a reset operation, the specified time td being specified by the CPU, a drive voltage VCC of the reset circuit, and a reset release voltage VT;
and
determining capacitance C of the capacitor and a resistance R of the resistor so that the capacitance C and the resistance R satisfy a following formula:
t
d
≤
C
⁢
R
⁢
R
D
(
T
)
R
+
R
D
(
T
)
⁢
log
⁢
(
V
C
⁢
C
V
C
⁢
C
-
V
T
)
.

42 more elements

A reset circuit which outputs a reset signal to a CPU in a high temperature environment, the reset circuit comprising:

a resistor;
a diode;
a capacitor;
a power input terminal;
a power return terminal;
and an output terminal which outputs a reset signal, wherein
the power input terminal, the resistor, the capacitor, and the power return terminal are connected in series in an order of the power input terminal, the resistor, the capacitor, and the power return terminal,
the diode is connected in parallel with the resistor between the power input terminal and the capacitor in a manner such that a cathode is on a side closer to the power input terminal and an anode is on a side closer to the capacitor,
the output terminal is connected to the capacitor on a side being closer to the resistor,
when a reverse resistance of the diode at high temperature T, at which the reset circuit is operated, is denoted as RD(T), a resistance of the resistor is denoted as R, and capacitance of the capacitor is denoted as C, a time constant of the reset circuit at the high temperature T is given by a following formula:
C
⁢
R
⁢
R
D
(
T
)
R
+
R
D
(
T
)
,
and
time during which the reset signal rises from zero volt to a reset release threshold voltage at the high temperature T, the time being referred to as rise time, is equal to or longer than specified time for a reset operation, the specified time being specified by the CPU.

26 more elements

Dependencies are inferred from the claim text.

Reset circuit and method for designing reset circuit

Life of this patent

Reset circuit and method for designing reset circuit

Life of this patent

Abstract

Claims8