Wide supply range precision startup current source

Abstract

A start-up circuit for a bandgap reference voltage generator circuit, including a first native transistor with a drain connected to a supply voltage of the bandgap reference voltage generator circuit and a source connected to a gate of the first native transistor; a low voltage transistor with a source connected to ground, a drain connected to the source of the first native transistor, and a gate connected to a resistor; a second native transistor with a source connected to the resistor, a gate connected to the source of the first native transistor; a high voltage transistor with a drain connected to a drain of the second native transistor and a source connected to the supply voltage; and a transistor with a gate connected to the gate of the first high voltage transistor and a drain which provides a start-up current for the bandgap reference voltage generator circuit.

1 . A start-up circuit for a bandgap reference voltage generator circuit, the startup circuit comprising:
 a first transistor having a drain connected to a supply voltage of the bandgap reference voltage generator circuit and a source connected to its own gate;   a voltage reference resistor configured to flow an electric current through the voltage reference resistor when the supply voltage of the bandgap reference voltage generator is increased above a threshold voltage;   an amplifier formed by a second transistor with a drain connected to the source of the first transistor and a gate coupled to the voltage reference resistor, the amplifier having a bias current;   a third transistor having a source connected to the voltage reference resistor and a gate connected to a node between the first transistor and second transistor; and   a current mirror configured to duplicate the electric current flowing through the voltage reference resistor as a startup current for the start-up circuit.   
     
     
         2 . The start-up circuit according to  claim 1  in which the current mirror comprises:
 a fourth transistor with a drain connected to a drain of the third transistor and a source connected to the supply voltage of the bandgap reference voltage generator circuit; and 
 a fifth transistor having a gate coupled to a gate of the fourth transistor, the fifth transistor configured to provide the start-up current for the bandgap reference voltage generator circuit. 
 
     
     
         3 . The start-up circuit of  claim 1  further comprising a sixth transistor configured to turn off the start-up circuit after the bandgap reference voltage generator circuit reaches an operating voltage. 
     
     
         4 . The start-up circuit of  claim 1  wherein the first transistor and the second transistor are the same type of transistor. 
     
     
         5 . The start-up circuit of  claim 4  wherein the first and second transistors are n-channel metal-oxide semiconductor transistors. 
     
     
         6 . The start-up circuit of  claim 4  wherein the second transistor has a gate oxide thickness approximately the same thickness as the first transistor. 
     
     
         7 . The start-up circuit of  claim 1  wherein the first transistor has a threshold voltage less than approximately 0.5 v. 
     
     
         8 . The start-up circuit of  claim 7  wherein the threshold voltage of the first transistor is approximately 0V. 
     
     
         9 . The start-up circuit of  claim 1  wherein a threshold voltage of the first transistor and the second transistor varies over a temperature of the start-up circuit. 
     
     
         10 . The start-up circuit of  claim 1  wherein the third resistor has a threshold voltage less than approximately 0.5 v. 
     
     
         11 . The start-up circuit of  claim 1 , wherein the first transistor forms a self-biased current source. 
     
     
         12 . A start-up circuit in a bandgap reference voltage generator circuit, comprising:
 a first transistor with a drain connected to a supply voltage of the bandgap reference voltage generator circuit and a source connected to its own gate;   a second transistor with a drain connected to the source of the first transistor;   a voltage reference resistor connected to a gate of the second transistor and configured to flow an electric current through the voltage reference resistor when the supply voltage of the bandgap reference voltage generator is increased to approximately the threshold voltage of the second transistor;   a third transistor with a source connected to the voltage reference resistor and a gate connected to a node between the first transistor and second transistor; and   a current mirror configured to duplicate the electric current flowing through the voltage reference resistor as a startup current for the start-up circuit.   
     
     
         13 . The start-up circuit of  claim 12  wherein the first transistor has a threshold voltage less than approximately 0.5 v. 
     
     
         14 . The start-up circuit of  claim 12  wherein the second transistor has a gate oxide thickness approximately the same thickness as the first transistor 
     
     
         15 . The start-up circuit of  claim 12  wherein the third transistor has a threshold voltage less than approximately 0.5 v. 
     
     
         16 . A self-biased current source for a bandgap reference voltage generator circuit, comprising:
 a first transistor with a drain connected to a supply voltage and a source connected to its own gate;   a voltage reference resistor configured to flow an electric current through the voltage reference resistor that is related to a reference voltage when the supply voltage of the bandgap reference voltage generator is increased;   a second transistor with a drain connected to the source of the first transistor, a source coupled to the reference voltage, and a gate coupled to the voltage reference resistor;   a third transistor with a gate connected to a node between the first transistor and the second transistor and a source coupled to the voltage reference resistor, the third resistor configured to flow an electric current through the third transistor when the supply voltage of the bandgap reference voltage generator is increased to approximately a threshold voltage of the second transistor; and   a current mirror structured to duplicate the electric current flowing through the reference resistor as a startup current.   
     
     
         17 . The self-biased current source of  claim 16  in which the second transistor has a gate oxide thickness approximately the same thickness as the first transistor. 
     
     
         18 . The self-biased current source of  claim 16  in which a threshold voltage of the first transistor is approximately 0 volts. 
     
     
         19 . The self-biased current source of  claim 16  in which a threshold voltage of the third transistor is approximately 0 volts. 
     
     
         20 . The self-biased current source of  claim 16  in which each of the first transistor, the second transistor, and the third transistor are n-channel metal oxide semiconductor transistors.