Patent ID: 7626416
Filing Date: 2009-12-01
Classification: H03K,H04L

Abstract:
1. A method of controlling an output impedance of an electronic device having an impedance control terminal to which an external load is to be connected, a predetermined value of the voltage at said control terminal being used to control said output impedance of said device, said method comprising: comparing a reference voltage to a voltage at an impedance control terminal; producing a variable count signal representing a count value in response to said comparing; varying the impedance of a variable impedance circuit in response to said count signal, wherein the impedance of said variable impedance circuit controls the voltage at said impedance control terminal; and operating a device connected in parallel with said variable impedance circuit using a periodic pulse train having a predetermined pulse frequency equal to twice a frequency at which said count value is produced to periodically change the impedance of said variable impedance circuit.