A constant current drive chip power-on reset circuit

Abstract

The invention discloses a power on reset circuit for a constant-current driving chip, which comprises a power following control module, a schmidt trigger module and a phase inverting module, wherein the power following control module is used for controlling the voltage at a trigger end of the schmidt trigger module to change with a power voltage VDD when the power voltage VDD fluctuates; the schmidt trigger module is used for outputting a power on reset signal according to the voltage at the trigger end; and the phase inverting module is used for inversely outputting the power on reset signal.

Description

technical field [0001] The invention relates to the field of integrated circuit design, in particular to a constant current drive chip power-on reset circuit. Background technique [0002] For a general circuit system, the power supply voltage has not yet reached a stable expected state at the initial stage of power-on, so the voltage and logic state of many circuit components (such as semiconductor devices, etc.) and circuit nodes are unstable. If the voltage or logic state of electrical components or circuit nodes changes at the initial stage of power-on, the circuit system is likely to generate unexpected errors, which will affect the normal operation after power-on. In order to make the circuit system start to operate from the state expected by the designer every time it is powered on, the general practice is to use a special power-on reset circuit to generate a reset signal at the beginning of power-on (generally called "POR") Signal), within a period of time after the...

AI Technical Summary

Problems solved by technology

[0005] First, because the rising speed of the power supply VDD depends on many factors, such as the transient response and output impedance of the power supply used, the resistance of the connection line between the power supply and the circuit system, the size of the capacitance between the power supply and ground, the circuit system The size of the initial power consumption current, etc., when the rise time of the power supply VDD is longer than the delay time of the resistor R1 and capacitor C1, there will be no T1 time period, that is, when the power supply VDD is in a stable state, the POR1 signal has already In the high-level state, at this time, the high-level voltage is the actual output voltage of the power supply VDD, and the two rise synchronously along the slope, so the power-on reset signal POR1 cannot be effectively generated within the expected time; If it is necessary to ensure that the delay time of the delay circuit 100 is much longer than the rise time of the power supply VDD in the integrated circuit, it is difficult to realize it only by relying on the internal resistance R1 and the electric capacity C1 of the integrated circuit, unless a resistor of mega-ohm level and a microfarad are used outside the integrated circuit Level capacitance, which will occupy an integrated circuit pin and increase the number of peripheral components of the integrated circuit. Moreover, due to the uncertainty of the rising speed of the power supply VDD, it cannot guarantee that the power-on reset signal of the circuit system can be effective under all circumstances. produce

[0006] Second, if the power supply VDD suddenly loses power, the charge stored in the capacitor C1 needs to be discharged to the power supply VDD through the resistor R1. Since the values ​​of the resistor R1 and the capacitor C1 are both large, the charge stored in the capacitor C1 will take a long time to discharge. Finish

[0008] First, the internal structure of the voltage monitor 200 is relatively complicated, and generally includes a reference voltage generating circuit, a power supply voltage divider circuit, a comparator, etc., and these circuits will consume static power supply current, thereby increasing the power consumption of the circuit system to a certain extent, especially When the circuit system is in standby state, this part of the increased power consumption may be more prominent

[0009] Second, the threshold value Vg of the voltage monitor 200 is more difficult to choose: if it is set too high, once the power supply VDD fluctuates during the operation of the circuit system, the voltage monitor 200 may be triggered, causing the circuit system to reset incorrectly, causing serious damage. Consequences, and, in most cases, the designer's original intention is to hope that the circuit system can work normally in a wide power supply voltage range; if the threshold value Vg of the voltage monitor 200 is set too low, in many cases It cannot play the role of forced reset of the circuit system

[0010] therefore, figure 2 The power-on reset circuit disclosed in not only consumes a lot of power, but its performance is also unstable

Images