Portable electronic device power manager with current limit feedback control loop modification for stabilizing an external power supply

1. A portable electronic device comprising:

a battery to provide power to operate the device;

a connector including a power supply pin to be coupled to an external power supply; and

a power manager having a battery charger circuit that draws current through the power supply pin to charge the battery,

the power manager having a current limit feedback control loop that limits the drawn current in accordance with a predetermined output current rating of the external power supply,

the power manager to automatically change behavior of the control loop to stabilize operation of the coupled external power supply by at least one of a) changing a bias current of an error amplifier to one of increase and decrease bandwidth of the control loop, and b) changing a frequency response of a filter to change a resonant frequency of the control loop.

2. The portable device of claim 1 wherein the power manager is to change the behavior of the control loop in response to learning that the external power supply is operating outside of its voltage specification.

3. The portable device of claim 1 wherein the power manager is to change the behavior of the control loop in response to monitoring voltage of the power supply pin, wherein the monitoring indicates that the coupled external power supply is operating abnormally.

4. The portable device of claim 1 wherein the power manager is to signal that a predetermined impulse-type load be applied on the power supply pin, measure response of the coupled external power supply to the impulse-type load, and on that basis change the behavior of the control loop.

5. The portable device of claim 4 wherein the power manager is to calculate a resonant frequency of the coupled external power supply based on the measured response, and on that basis change the behavior of the control loop.

6. The portable device of claim 5 wherein the power manager is to change the behavior of the control loop by changing bandwidth of the control loop to avoid the calculated resonant frequency.

7. A power manager circuit comprising:

a current limit feedback control loop for limiting dc current drawn from a power supply line so as not to exceed a specified maximum steady state current for the power supply line;

means for charging a battery using the drawn current;

means for monitoring voltage of the power supply line while drawing said current; and

means for changing behavior of the current limit feedback control loop in response to the power supply line voltage moving outside of a predetermined range by at least one of a) changing a bias current of an error amplifier to one of increase and decrease bandwidth of the control loop, and b) changing a frequency response of a filter to change a resonant frequency of the control loop.

8. A method for controlling a current limit feedback control loop process in a portable electronic device, comprising:

measuring power supply current and voltage in a portable electronic device, wherein the power supply current and voltage are being sourced from an external power supply that is coupled to the portable electronic device;

comparing the measured power supply current to a threshold, wherein the threshold represents a maximum steady state current available from the external power supply;

adjusting the power supply current based on the comparison, wherein the measuring, comparing and adjusting are part of a current limit feedback control loop process;

analyzing the measured power supply voltage to determine whether or not the external power supply is operating outside of its specification; and

modifying the control loop process based on the analysis by at least one of changing a bias current of an error amplifier to one of increase and decrease bandwidth of the control loop, and changing a frequency response of a filter to change a resonant frequency of the control loop.

9. The method of claim 8 further comprising:

applying a predetermined load to the coupled external power supply to elicit a response from the external power supply;

measuring the response; and

analyzing the measured response to determine a characteristic of the external power supply, wherein the control loop process is modified further based on the analyzed response.

10. The method of claim 9 wherein said analyzing the measured response comprises:

calculating a resonant frequency of the coupled external power supply based on the measured response.

11. The method of claim 10 wherein said modifying the control loop process comprises:

changing loop bandwidth of the process to avoid the calculated resonant frequency.

12. A power manager circuit comprising:

a current limit feedback control loop circuit to limit dc current in a power supply line;

a battery charger circuit to charge a battery using some of the dc current; and

a controller circuit to monitor voltage on the power supply line and in response signal a change in behavior of the control loop circuit without affecting the dc current limiting function of said control loop circuit, wherein said change in behavior consists of at least one of a) changing a bias current of an error amplifier to one of increase and decrease bandwidth of the control loop, and b) changing a frequency response of a filter to change a resonant frequency of the control loop.

13. The power manager circuit of claim 12 wherein the controller circuit is to signal that a predetermined load be applied to the power supply line, wherein the voltage being monitored is a response to the applied load.

14. The power manager circuit of claim 13 wherein the controller circuit is to calculate a resonant frequency based on the monitored voltage, and wherein the change is designed to distance a resonant frequency of the control loop circuit from the calculated one.