Reference voltage circuit allowing fast power up from low power standby condition

Claim 1

In an integrated circuit analog-to-digital converter, a reference voltage circuit comprising in combination: (a) a band gap circuit having an output conductor and producing thereon a first reference voltage; (b) a first field effect transistor coupling the output conductor of the band gap circuit to a first conductor, the first conductor being coupled to a first external bypass capacitor means; (c) a buffer circuit; (d) a second field effect transistor coupling the first conductor to a non-inverting input of the buffer circuit; (e) means for turning the first and second field effect transistors off when low power standby operation of the analog-to-digital converter is desired to prevent discharging of the first external bypass capacitor and thereby avoid a need to recharge the first external bypass capacitor when the first and second field effect transistors are turned back on, the first field effect transistor and the first bypass capacitor means coacting with output impedance of the band gap circuit when the first and second field effect transistors are on to filter high frequency noise produced on the first reference voltage by the band gap circuit to thereby apply a second reference voltage that is more regulated than the first reference voltage to the non-inverting input of the buffer circuit, the reference voltage circuit replicating the second reference voltage to produce a third reference voltage that is more regulated than the first reference voltage at the output of the buffer circuit.

Claim 13

A method of producing a precise, low noise reference voltage with low average power dissipation, comprising the steps of: (a) powering up a band gap circuit having an output conductor and producing thereon a first reference voltage; (b) coupling the output conductor of the band gap circuit to a first conductor by turning on a first field effect transistor, the first conductor being coupled to a first external bypass capacitor, and simultaneously filtering high frequency noise produced on the first reference voltage by the band gap circuit to thereby produce a second reference voltage that is more regulated than the first reference voltage on the first conductor; (c) coupling the first conductor to a non-inverting input of a buffer circuit means of a second field effect transistor to thereby produce the second reference voltage on the non-inverting input of the buffer circuit, the buffer circuit means replicating the second reference voltage to produce a third reference voltage that is more regulated than the first reference voltage; (d) turning the first and second field effect transistors on during powered up operations by a utilization circuit, to cause the channel resistance of the first field transistor and the output impedance of the band gap circuit to coact with the first bypass capacitor to produce the filtering; (e) turning the first and second field effect transistors off to begin a power down operation and to prevent discharge of the first bypass capacitor and thereby avoid a need to recharge the first bypass capacitor when the first and second field effect transistors are turned back on.

Claim 14

A method of producing a precise, low noise reference voltage with low average power dissipation, comprising the steps of: (a) powering up a band gap circuit having an output conductor and producing thereon a first reference voltage; (b) coupling the output conductor of the band gap circuit to a first conductor by turning on a first field effect transistor, the first conductor being coupled to a first external bypass capacitor, and simultaneously filtering high frequency noise produced on the first reference voltage by the band gap circuit to thereby produce a second reference voltage that is more regulated than the first reference voltage on the first conductor; (c) coupling the first conductor to a non-inverting input of a buffer circuit means of a second field effect transistor to thereby produce the second reference voltage on the non-inverting input of the buffer circuit, the buffer circuit means replicating the second reference voltage to produce a third reference voltage that is more regulated than the first reference voltage; (d) turning the first and second field effect transistors on during powered up operations by a utilization circuit, to cause the channel resistance of the first field transistor and the output impedance of the band gap circuit to coact with the first bypass capacitor to produce the filtering; (e) turning the first and second field effect transistors off to begin a power down operation and to prevent discharge of the first bypass capacitor and thereby avoid a need to recharge the first bypass capacitor when the first and second field effect transistors are turned back on.