US 10,650,946 B1Granted

Trimming method of DCR sensing circuits

AssigneeFlex Ltd.

InventorsMikael Appelberg, Andreas Larsson

Life of this patent

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Abstract

A circuit and method provide improved trimming of a DCR sensing circuit where a sensing element is sensitive to self-heating or having a large tolerance. The circuit includes a resistive divider circuit coupled to a sensing element. The resistive divider circuit includes a trim resistor and two test points. Prior to trimming the trim resistor, an actual resistance of the sensing element is determined. A target voltage across the trim resistor to be trimmed is calculated according to the determined sensing element resistance and a known small trim current that is to be injected into the circuit during the trimming process. This injected trim current has a low current value so there is no self-heating of the sensing element. Then, the trim resistor is trimmed while injecting this small trim current into the resistive divider circuit and the voltage across the trim resistor is monitored.

Claims13

Dependent claims

A method of sensing current using direct current resistance sensing, the method comprising:

a. configuring a circuit having a current sensing element, a load coupled to the current sensing element, and a resistive divider circuit having a trim resistor, the resistive divider circuit coupled across the current sensing element, wherein the current sensing element has an unknown resistance value;
b. measuring the resistance value of the current sensing element;
c. calculating a target voltage value across the trim resistor according to the measured resistance value and a predetermined known trim current value;
d. injecting a trim current having the predetermined known trim current value into the circuit such that the trim current passes through the trim resistor;
e. trimming the trim resistor while the trim current is being injected, wherein a trim resistor voltage across the trim resistor is monitored during trimming, and the trim resistor is trimmed until the monitored trim resistor voltage equals the target voltage value.

2 more elements

Dependencies are inferred from the claim text.

Facts

Application: 16/058,742Filed 8 Aug 2018
Granted: 12 May 2020
Term ends: Not estimatedThe source records don’t support an estimate.

Classification12 codes

H01C 17/24
Adapted for trimming: by removing or adding resistive material
G01R 19/0092
Arrangements for measuring currents or voltages or for indicating presence or sign thereof: measuring current only
G01R 35/005
Testing or calibrating of apparatus covered by the other groups of this subclass: calibrating; Standards or reference devices, e.g. voltage or…
H01C 17/267
By chemical or thermal treatment, e.g. oxydation, reduction, annealing: by passage of voltage pulses or electric current