Current to frequency conversion, apparatus and methods

• US 8,183,834 B2
• Filed: 01/28/2009
• Issued: 05/22/2012
• Est. Priority Date: 01/28/2009
• Status: Active Grant

• Current Assignee: Atmel Corporation (Microchip Technology Incorporated)
• Original Assignee: Atmel Corporation (Microchip Technology Incorporated)
• Inventors: Haddani, Idir, Manai, Bilal, Rabeyrin, Xavier
• Primary Examiner(s): Phan, Huy Q
• Assistant Examiner(s): CHAN, EMILY Y
• Application Number:
  US12/361,145
• Publication Number:
  US 20100188049A1
• Time in Patent Office: 1,210 Days
• Field of Search: 320124-167
• US Class Current: 320/134
• CPC Class Codes: G01R 31/3832 without measurement of battery voltage
• CPC Class Codes: H03K 7/06 Frequency or rate modulation, i.e. PFM or PRM

Abstract

Electronic apparatus, methods of forming the electronic apparatus, and methods of operating the electronic apparatus include features of current to frequency conversion that may be implemented in a variety of applications. Additional apparatus, systems, and methods are disclosed.

Claims

1. An apparatus comprising:

a sensing element through which a battery operatively charges and discharges;

a current-to-current converter coupled to the sensing element to generate a first current and a second current, the two currents correlated to current flowing through the sensing element such that the first current is zero relative to a nonnegative reference current when the second current is non-zero relative to the nonnegative reference current and the second current is zero relative to the nonnegative reference current when the first current is non-zero relative to the nonnegative reference current; and

a capacitor coupled to the current-to-current converter, the current-to-current converter operatively delivers a difference current at a node of the capacitor, the difference current being the difference between the first current and the second current.

2. The apparatus of claim 1, wherein the nonnegative reference current has a value equal to zero.

3. The apparatus of claim 1, further comprising:

a switching circuit; and

a voltage comparator coupled to the switching circuit, the voltage comparator having a first voltage threshold and a second voltage threshold, the first voltage threshold being greater than the second voltage threshold, the voltage comparator responsive to a voltage at the node of the capacitor such that the voltage comparator operatively controls the switching circuit to discharge the capacitor when the voltage reaches the first threshold voltage until the voltage of reaches the second voltage threshold.

4. The apparatus of claim 3, further comprising a counter configured to increment a count each time the capacitor discharges to the second voltage threshold and to increment another count each time charges to the first voltage threshold.

5. The apparatus of claim 1, wherein the sensing element includes a resistor.

6. The apparatus of claim 1, wherein the current to current converter comprises:

a first transresistor coupled to a first node of the sensing element;

first transconductor coupled to the first transresistor to generate the first current;

a second transresistor coupled to a second node of the sensing element; and

a second transconductor coupled to the second transresistor to generate the second current.

7. The apparatus of claim 1, further comprising a variable offset adder to provide a current offset to the current-to-current converter.

8. A method comprising:

generating a first current and a second current correlated to currents flowing through a sensing element through which a battery operatively charges and discharges, the first and two currents related to each other such that the first current is zero relative to a nonnegative reference current when the second current is non-zero relative to the nonnegative reference current and the second current is zero relative to the nonnegative reference current when the first current is non-zero relative to the nonnegative reference current; and

providing a difference current at a node of a capacitor, the difference current being the difference between the first current and the second current.

9. The method of claim 8, wherein the nonnegative reference current has a value equal to zero.

10. The method of claim 8, further comprising:

comparing a voltage of the capacitor to a threshold voltage; and

discharging the capacitor when the voltage of the capacitor reaches a first threshold voltage until the voltage of the capacitor reaches a second voltage threshold.

11. The method of claim 10, further comprising:

counting each time the capacitor discharges to the second voltage threshold; and

counting each time the capacitor charges to the first voltage threshold.

12. The method of claim 11, further comprising providing an indication of a charge capacity of the battery.

13. The method of claim 12, further comprising providing the indication on a display of a mobile telephone.

14. A method comprising:

providing a sensing element having a node to couple to a battery such that the battery operatively charges and discharges through the sensing element;

coupling a current-to-current converter to the sensing element, the current-to-current converter arranged to generate a first current and a second current correlated to current flowing through the sensing element, the current-to-current converter arranged such that the first current is zero relative to a nonnegative reference current when the second current is non-zero relative to the nonnegative reference current and the second current is zero relative to the nonnegative reference current when the first current is non-zero relative to the nonnegative reference current; and

coupling a capacitor to the current-to-current converter such that the capacitor operatively receives a difference current at a node of the capacitor, the difference current being the difference between the first and second currents.

15. The method of claim 14, wherein the nonnegative reference current has a value equal to zero.

16. The method of claim 14, further comprising:

providing a voltage comparator, the voltage comparator arranged to have a first voltage threshold and a second voltage threshold, the first voltage threshold being greater than the second voltage threshold,

coupling the voltage comparator to a switching circuit; and

coupling the voltage comparator to the capacitor, the voltage comparator, the switching circuit, and the capacitor arranged such that the voltage comparator operatively controls the switching circuit to discharge the capacitor when the voltage of the capacitor reaches the first threshold voltage until the voltage of the capacitor reaches the second voltage threshold.

17. The method of claim 14, further comprising coupling one or more counters to the capacitor, the one or more counters configured to count each time the capacitor charges to the first voltage threshold and to count each time the capacitor discharges to the second voltage threshold.

18. The method of claim 14, wherein providing the sensing element comprises providing a resistor as the sensing element.

19. The method of claim 14, further comprising forming the current-to-Current converter having a current charging path and a current discharging path coupled to current mirrors configured to operatively generate the first and second currents.

20. A system comprising:

a battery;

an application section having a power switching unit to operatively connect the battery to a charging source; and

a battery gauging unit coupled between the battery and the application section, the battery gauging unit including;

a sensing element through which the battery operatively charges and discharges;

a current-to-current converter coupled to the sensing element to generate a first current and to generate a second current, the two currents correlated to current flowing through the sensing element such that the first current is zero relative to a nonnegative reference current when the second current is non-zero relative to the nonnegative reference current and the second current is zero relative to the nonnegative reference current when the first current is non-zero relative to the nonnegative reference current; and

a capacitor coupled to the current-to-current converter, the current-to-current converter operatively delivers a difference current at a node of the capacitor, the difference current being the difference between the first current and the second current.

21. The system of claim 20, wherein the nonnegative reference current has a value equal to zero.

22. The system of claim 20, wherein the battery gauging unit further comprising:

a switching circuit; and

a voltage comparator coupled to the switching circuit, the voltage comparator having a first voltage threshold and a second voltage threshold, the first voltage threshold being greater than the second voltage threshold, the voltage comparator responsive to a voltage at the node such that the voltage comparator operatively controls the switching circuit to discharge the capacitor when the voltage reaches the first threshold voltage until the voltage reaches the second voltage threshold; and

a counter configured to increment a count each time the capacitor discharges to the second voltage threshold and to increment another count each time charges to the first voltage threshold.

23. The system of claim 20, wherein the current to current converter comprises:

a first transresistor coupled to a first node of the sensing element;

first transconductor coupled to the first transresistor to generate the first current;

a second transresistor coupled to a second node of the sensing element; and

a second transconductor coupled to the second transresistor to generate the second current.

24. The system of claim 20, wherein the system includes a mobile telephone.