Rail-to-rail input hysteresis comparator

• US 9,264,031 B2
• Filed: 12/30/2014
• Issued: 02/16/2016
• Est. Priority Date: 03/17/2014
• Status: Active Grant

• Current Assignee: Shanghai Huahong Grace Semiconductor Manufacturing Corporation (Hua Hong Semiconductor Limited)
• Original Assignee: Shanghai Huahong Grace Semiconductor Manufacturing Corporation (Hua Hong Semiconductor Limited)
• Inventors: Xiao, Jun
• Primary Examiner(s): Tra, Quan
• Application Number:
  US14/585,711
• Publication Number:
  US 20150263718A1
• Time in Patent Office: 413 Days
• Field of Search: 327/63, 327/65, 327/67, 327/205, 327/206
• US Class Current: 1/1
• CPC Class Codes: H03K 5/125 Discriminating pulses measuring characteristics of individual pulses G01R29/02; separation of synchronising signals in television systems H04N5/08
• CPC Class Codes: H03K 5/2481 with at least one differential stage

Abstract

A rail-to-rail input hysteresis comparator includes: an input hysteresis comparator module, a transmission module, an output comparator, a switching signal module and a bias module. Compared to the conventional device, the rail-to-rail input hysteresis comparator of the present invention can turn off an output of the N-type input hysteresis comparator of the input hysteresis comparator module when the common mode input voltage is relatively low and turn off an output of the P-type input hysteresis comparator of the input hysteresis comparator module when the common mode input voltage is relatively high, thereby avoiding operating in a linear mode and hence achieving a stable CMRR.

Claims

1. A rail-to-rail input hysteresis comparator, comprising an input hysteresis comparator module, a transmission module, an output comparator, a switching signal module and a bias module, wherein:

the input hysteresis comparator module comprises a P-type input hysteresis comparator and an N-type input hysteresis comparator, the P-type input hysteresis comparator having a first input terminal, a second input terminal, a first output terminal, a second output terminal and a P-type common mode voltage control signal output terminal, the N-type input hysteresis comparator having a first input terminal, a second input terminal, a first output terminal, a second output terminal and an N-type common mode voltage control signal output terminal, the input hysteresis comparator module configured to receive a P-type input signal and an N-type input signal and to output a P-type hysteresis signal and an N-type hysteresis signal, each with hysteresis and steeper rise and fall edges relative to a respective one of the P-type input signal and the N-type input signal, to the transmission module and simultaneously a P-type common mode voltage control signal and an N-type common mode voltage control signal;

the switching signal module is configured to convert the P-type and N-type common mode voltage control signals output from the input hysteresis comparator module to switching signals for the transmission module;

the output comparator comprises a P-type comparator and an N-type comparator, both coupled to the transmission module;

the transmission module selectively couples one of the P-type and N-type hysteresis signals to the output comparator, under control of the switching signals, such that when the input P-type common mode voltage control signal is as low as to cause a decrease in a common mode rejection ratio, an output of the N-type input hysteresis comparator of the input hysteresis comparator module is disabled and an input voltage of the P-type comparator of the output comparator is set to a high level, thereby rendering the P-type comparator of the output comparator out of operation, and when the input N-type common mode voltage control signal is as high as to cause a decrease in the common mode rejection ratio, an output of the P-type input hysteresis comparator of the input hysteresis comparator module is disabled and an input voltage of the N-type comparator of the output comparator is set to a low level, thereby rendering the N-type comparator of the output comparator out of operation; and

the bias module is configured to generate a bias current and a bias voltage, for each of the input hysteresis comparator module, the transmission module, the output comparator and the switching signal module.

2. The rail-to-rail input hysteresis comparator of claim 1, wherein the output comparator comprises first to seventh NMOS transistors and first to seventh PMOS transistors, wherein the first to third NMOS transistors form the N-type comparator, the fourth and fifth PMOS transistors and the fourth and fifth NMOS transistors form a constant current source load, the first to third PMOS transistors form the P-type comparator, and the sixth and seventh PMOS transistors and the sixth and seventh NMOS transistors form an output buffer circuit.

3. The rail-to-rail input hysteresis comparator of claim 1, wherein the first input terminals of the P-type and N-type input hysteresis comparators are configured to receive the P-type input signal and the second input terminals of the P-type and N-type input hysteresis comparators are configured to receive the N-type input signal.

4. The rail-to-rail input hysteresis comparator of claim 3, wherein:

the transmission module comprises a first P-type comparator transmission gate, a second P-type comparator transmission gate, a third P-type comparator transmission gate, a fourth P-type comparator transmission gate, a first N-type comparator transmission gate, a second N-type comparator transmission gate, a third N-type comparator transmission gate and a fourth N-type comparator transmission gate.

5. The rail-to-rail input hysteresis comparator of claim 4, wherein:

the output comparator has first, second, third and fourth input terminals;

each of the first and second P-type comparator transmission gates has one end coupled to a respective one of the first and second output terminals of the P-type input hysteresis comparator and the other end coupled to a respective one of the first and second input terminals of the output comparator;

each of the third and fourth P-type comparator transmission gates has one end grounded and the other end coupled to a respective one of said other ends of the first and second P-type comparator transmission gates and thereby coupled to the respective one of the first and second input terminals of the output comparator;

each of the first and second N-type comparator transmission gates has one end coupled to a respective one of the first and second output terminals of the N-type input hysteresis comparator and the other end coupled to a respective one of the third and fourth input terminals of the output comparator; and

each of the third and fourth N-type comparator transmission gates has one end coupled to a supply voltage and the other end coupled to a respective one of said other ends of the first and second N-type comparator transmission gates and thereby coupled to the respective one of the third and fourth input terminals of the output comparator.

6. The rail-to-rail input hysteresis comparator of claim 5, wherein:

the switching signal module comprises a resistor voltage divider network, first and second comparators, and first, second, third and fourth phase inverters;

each of the first and second comparators is coupled between the supply voltage and ground and has a first input terminal, a second input terminal and an output terminal;

the first input terminals of the first and second comparators are coupled to the P-type and N-type common mode voltage control signals, respectively;

the output terminal of the first comparator is coupled to the first and second phase inverters which are connected in series;

the first phase inverter is configured to output a first switching signal and the second phase inverter is configured to output a second switching signal;

the output terminal of the second comparator is coupled to the third and fourth phase inverters which are connected in series;

the third phase inverter is configured to output a third switching signal and the fourth phase inverter is configured to output a fourth switching signal;

each of the first, second, third and fourth phase inverters is coupled to both the supply voltage and the ground;

the resistor voltage divider network is coupled between the supply voltage and the ground and comprises a first resistor, a second resistor, a third resistor and a fourth resistor which are connected in series between the supply voltage and the ground;

the second input terminal of the first comparator is coupled to a node between the first and second resistors; and

the second input terminal of the second comparator is coupled to a node between the third and fourth resistors.

7. The rail-to-rail input hysteresis comparator of claim 6, wherein:

each of the first, second, third and fourth P-type comparator transmission gates and the first, second, third and fourth N-type comparator transmission gates comprises a PMOS transistor and an NMOS transistor;

a gate terminal of the PMOS transistor of the first P-type comparator transmission gate is coupled to the second switching signal and a gate terminal of the NMOS transistor of the first P-type comparator transmission gate is coupled to the first switching signal;

a gate terminal of the PMOS transistor of the second P-type comparator transmission gate is coupled to the second switching signal and a gate terminal of the NMOS transistor of the second P-type comparator transmission gate is coupled to the first switching signal;

a gate terminal of the PMOS transistor of the third P-type comparator transmission gate is coupled to the first switching signal and a gate terminal of the NMOS transistor of the third P-type comparator transmission gate is coupled to the second switching signal;

a gate terminal of the PMOS transistor of the fourth P-type comparator transmission gate is coupled to the first switching signal and a gate terminal of the NMOS transistor of the fourth P-type comparator transmission gate is coupled to the second switching signal;

a gate terminal of the PMOS transistor of the first N-type comparator transmission gate is coupled to the third switching signal and a gate terminal of the NMOS transistor of the first N-type comparator transmission gate is coupled to the fourth switching signal;

a gate terminal of the PMOS transistor of the second N-type comparator transmission gate is coupled to the third switching signal and a gate terminal of the NMOS transistor of the second N-type comparator transmission gate is coupled to the fourth switching signal;

a gate terminal of the PMOS transistor of the third N-type comparator transmission gate is coupled to the fourth switching signal and a gate terminal of the NMOS transistor of the third N-type comparator transmission gate is coupled to the third switching signal; and

a gate terminal of the PMOS transistor of the fourth N-type comparator transmission gate is coupled to the fourth switching signal and a gate terminal of the NMOS transistor of the fourth N-type comparator transmission gate is coupled to the third switching signal.

8. The rail-to-rail input hysteresis comparator of claim 1, wherein the input hysteresis comparator module, the transmission module, the output comparator, the switching signal module and the bias module are powered either by a same voltage source, or by different voltage sources used in combination with a level converter.