Method of using a field-effect transistor as a current sensing device

Patent metadata

Field	Value
Publication number	US-2016178705-A1
Application number	US-201514705600-A
Country	US
Kind code	A1
Filing date	May 6, 2015
Priority date	Dec 23, 2014
Publication date	Jun 23, 2016
Grant date	—

Abstract

An apparatus may include one or more registers configured to store a plurality of values, and an analog-to-digital converter (ADC). Each value of the plurality of values may correspond to a characteristic of a transistor at a respective temperature value. The ADC may be configured to generate a digital value corresponding to a difference in voltage levels between a first terminal and a second terminal of the transistor. The apparatus may further include a sensor configured to measure a temperature, and control logic configured to generate a first voltage level at a control terminal of the transistor and receive the digital value from the ADC. The control logic may be further configured to determine, during a first operational mode, a current passing through the transistor dependent upon the digital value, at least one value of the plurality of values, and the temperature.

First claim

What is claimed is:

1 . An apparatus comprising:
one or more registers configured to store a plurality of values, wherein each value of the plurality of values corresponds to a characteristic of a transistor at a respective one of a plurality of temperature values; an analog-to-digital converter (ADC) configured to generate a first digital value corresponding to a difference in voltage levels between a first terminal and a second terminal of the transistor; a sensor configured to measure a temperature; and control logic configured to:
generate a control voltage level at a control terminal of the transistor;
receive the first digital value from the ADC; and
determine, during a first operational mode, a current passing through the transistor dependent upon the first digital value, at least one value of the plurality of values, and the temperature.

2 . The apparatus of claim 1 , wherein the control logic is further configured to:
determine, during a second operational mode, that the temperature is at a higher temperature value than each of the plurality of values stored in the one or more registers; determine, during the second operational mode, a new value for the characteristic of the transistor; and replace, in the one or more registers, at least one value of the plurality of values with the new value.

3 . The apparatus of claim 1 , wherein the control logic is further configured to:
determine, during a second operational mode, that the temperature is at a lower temperature value than each of the plurality of values stored in the one or more registers; determine, during the second operational mode, a new value for the characteristic of the transistor; and replace, in the one or more registers, at least one value of the plurality of values with the new value.

4 . The apparatus of claim 3 , wherein the second operational mode corresponds to a battery charging mode.

5 . The apparatus of claim 4 , wherein to determine a new value for the characteristic of the transistor, the control logic is further configured to receive a value of a charging current from a charger circuit.

6 . The apparatus of claim 1 , wherein to generate the control voltage level at the control terminal of the transistor, the control logic is further configured to enable a charge pump.

7 . The apparatus of claim 6 , wherein the charge pump is further configured to adjust the first voltage level at the control terminal of the transistor dependent upon a voltage level of an output of the charge pump.

8 . A method, comprising:
generating a first voltage level at a first terminal of a transistor during a first operational mode; measuring a difference between a second voltage level of a second terminal of the transistor and a third voltage level of a third terminal of the transistor; measuring a temperature; retrieving, from one or more registers, at least one value of a plurality of values, wherein each value of the plurality of values corresponds to a characteristic of the transistor at a respective one of a plurality of temperature values; and determining a current passing through the transistor dependent upon the difference between the second voltage level and the third voltage level, the temperature, and the at least one value.

9 . The method of claim 8 , further comprising:
determining, during a second operational mode, that the temperature is at a lower temperature value than each of the plurality of values stored in the one or more registers; determining, during the second operational mode, a new value for the characteristic of the transistor; and replacing, in the one or more registers, at least one value of the plurality of values with the new value.

10 . The method of claim 8 , further comprising:
determining, during a second operational mode, that the temperature is at a higher temperature value than each of the plurality of values stored in the one or more registers; determining, during the second operational mode, a new value for the characteristic of the transistor; and replacing, in the one or more registers, at least one value of the plurality of values with the new value.

11 . The method of claim 10 , wherein the second operational mode corresponds to a battery charging mode.

12 . The method of claim 8 , wherein generating the first voltage level at the first terminal of the transistor further comprises enabling a charge pump.

13 . The method of claim 12 , further comprising adjusting the first voltage level dependent upon a measurement of the first voltage level.

14 . The method of claim 8 , wherein the characteristic of the transistor corresponds to a resistance between the second terminal of the transistor and the third terminal of the transistor.

15 . A system comprising:
a transistor, wherein a first terminal of the transistor is coupled to a power supply unit and a second terminal of the transistor is coupled to a power supply terminal of a circuit; and a power management circuit coupled to the transistor, wherein the power management circuit is configured to:
store, in one or more registers, a plurality of values wherein each value of the plurality of values corresponds to a characteristic of the transistor at a respective one of a plurality of temperature values;
generate a first voltage level at a third terminal of the transistor;
measure a temperature;
measure a difference between a second voltage level at the first terminal and a third voltage level at the second terminal; and
determine, during a first operational mode, a current flowing through the transistor dependent upon the difference, the temperature, and at least one value of the plurality of values.

16 . The system of claim 15 , wherein the power management circuit is further configured to adjust the first voltage level dependent upon a measured value of the first voltage level.

17 . The system of claim 15 , wherein the power supply unit includes at least one battery.

18 . The system of claim 15 , wherein the power management circuit is further configured to:
determine, during a second operational mode, that the temperature has been determined at a lower temperature value than each of the plurality of values stored in the one or more registers; determine, during the second operational mode, a new value for the characteristic of the transistor, wherein a predetermined current passes through the transistor in the second operational mode; and replace at least one value of the plurality of values with the new value.

19 . The system of claim 15 , wherein the power management circuit is further configured to:
determine, during a second operational mode, that the temperature has been determined at a higher temperature value than each of the plurality of values stored in the one or more registers; determine, during the second operational mode, a new value for the characteristic of the transistor, wherein a predetermined current passes through the transistor in the second operational mode; and replace at least one value of the plurality of values with the new value.

20 . The system of claim 15 , wherein the transistor comprises a metal-oxide semiconductor field-effect transistor.

Assignees

• Apple Inc

Inventors

• Stirk Gary L
• Kadirvel Karthik

Classifications

• H02J7/865

  Battery or charger load switching, e.g. concurrent charging and load supply (H02J7/50 takes precedence) · CPC title

• H03K19/017509 Primary

  Interface arrangements · CPC title

• G01R31/374

  with means for correcting the measurement for temperature or ageing · CPC title

• H02J2207/20

  Charging or discharging characterised by the power electronics converter · CPC title

• G06F13/4256

  using a clocked protocol · CPC title