Over voltage and over current protection integrated circuit

Abstract

An integrated circuit is disclosed including a primary input for receiving an input voltage, a battery voltage input for receiving a battery voltage signal and an output for providing an output voltage higher than the battery voltage. First circuitry responsive to the input voltage is provided for turning off the output voltage responsive to an input over voltage condition. Second circuitry responsive to the battery voltage signal is provided for turning off the output voltage responsive to a battery over voltage condition. Third circuitry provides for over current protection.

What is claimed is: 
     
       1. A method for protecting a load operating at a set operating voltage, comprising the steps of:
 receiving on a primary input an input voltage at a level above the set operating voltage; 
 driving on an output a voltage translating circuit that is operable to lower the input voltage level to the set operating voltage level; 
 connecting the primary input to the output with a switch; 
 detecting an input over voltage condition wherein the input voltage exceeds a predetermined input over voltage limit; 
 generating an input over voltage control signal responsive to detection of the input over voltage condition; 
 detecting a battery over voltage condition wherein a variable battery voltage level to which a battery is currently charged exceeds the set operating voltage by a predetermined battery over voltage limit; 
 generating a battery over voltage control signal responsive to detection of the battery over voltage condition; 
 disconnecting the primary input from the output using a switch responsive to the input over voltage control signal when an input voltage limit is exceeded by the input voltage; and 
 disconnecting the primary input from the output using the switch responsive to the battery over voltage control signal when the battery voltage level exceeds the battery over voltage limit. 
 
     
     
       2. The method of  claim 1 , and further comprising the step of detecting an over current condition where the current through the switch exceeds a predetermined current limit and generating an over current control signal responsive thereto. 
     
     
       3. The protection circuit method of  claim 2 , wherein the load is a battery. 
     
     
       4. The method of  claim 3 , wherein the voltage translating circuit comprises a battery charger which has associated therewith internal protection circuitry for protecting for an input over voltage condition above a predetermined voltage level and for protecting the battery from a battery over voltage condition. 
     
     
       5. An integrated circuit, comprising:
 a primary input for receiving an input voltage; 
 a battery voltage input for receiving a variable battery voltage level defining a current voltage level to which a battery is charged by a regulated charging voltage; 
 an output for providing an output voltage higher than the variable battery voltage level to a battery charger for generating the regulated charging voltage for charging the battery; 
 first circuitry responsive to the input voltage for generating an input over voltage control signal responsive to a determination that the input voltage exceeds an input over voltage limit; 
 second circuitry responsive to the variable battery voltage level for generating a battery over voltage control signal responsive to a determination that the variable battery voltage level exceeds a battery over voltage limit; and 
 a switch connecting said primary input to said output, wherein said switch is responsive to the input over voltage control signal for controlling said switch to disconnect the primary input from the output when the input voltage limit is exceeded by the input voltage and further wherein said switch is also responsive to the battery over voltage control signal for controlling said switch to disconnect the primary input from the output when the battery over voltage limit is exceeded by the battery voltage level. 
 
     
     
       6. An integrated circuit, comprising:
 an input node configured to receive an input voltage;   an output node configured to be coupled to a battery charger that is configured to charge a battery;   a sense node configured to receive a battery voltage across the battery;   a switch coupled between the input and output nodes and configured to conduct a switch current; and   logic circuitry coupled to the input node, sense node, and switch, and configured to open the switch in response to at least two of a magnitude of the input voltage exceeding an input-voltage threshold, a magnitude of the battery voltage exceeding a battery-voltage threshold, and   a magnitude of the switch current exceeding a switch-current threshold.   
     
     
       7. The integrated circuit of claim 6 wherein the switch includes a PMOS transistor. 
     
     
       8. The integrated circuit of claim 6 wherein the logic circuitry is configured to open the switch within approximately 1 microsecond. 
     
     
       9. The integrated circuit of claim 6 further comprising:
 an input-voltage sensor configured to signal the logic circuitry in response to the magnitude of the input voltage exceeding the input-voltage threshold;   a battery-voltage sensor configured to signal the logic circuitry in response to a magnitude of the battery voltage exceeding the battery-voltage threshold; and   a current sensor configured to signal the logic circuitry in response to a magnitude of the switch current exceeding a switch-current threshold.   
     
     
       10. The integrated circuit of claim 6, further comprising:
 wherein the switch includes a transistor configured to conduct the switch current in response to a control signal; and   a disable circuit configured to disable, until the magnitude of the control signal exceeds a turn-on threshold, the logic circuitry from turning off the transistor in response to the magnitude of the switch current exceeding the switch-current threshold.   
     
     
       11. The integrated circuit of claim 6, further comprising a disable circuit configured to disable, for a delay period, the logic circuitry from opening the switch in response to the magnitude of the battery voltage exceeding the battery-voltage threshold. 
     
     
       12. The integrated circuit of claim 6, further comprising:
 a counter configured to count a number of times that the logic circuitry opens the switch; and   a disable circuit configured to maintain the switch open in response to the number of times exceeding a count threshold.   
     
     
       13. The integrated circuit of claim 6, further comprising:
 wherein the switch includes a transistor; and   a driver configured to turn on the transistor slowly enough to prevent a current through the transistor from exceeding an inrush threshold while the driver is turning on the transistor.   
     
     
       14. A system, comprising:
 a battery charger having a charger input node, and having a charger output node configured to provide a charging signal to a battery; and   a protection circuit, including a protection-circuit input node configured to receive an input voltage, a protection-circuit output node coupled to the charger input node, a sense node configured to receive a battery voltage across the battery;   a switch coupled between the protection-circuit input and output nodes and configured to conduct a switch current; and   logic circuitry coupled to the protection-circuit input node, the sense node, and the switch, and configured to turn off the switch in response to at least two of
 a magnitude of the input voltage exceeding an input-voltage threshold, 
 a magnitude of the battery voltage exceeding a battery-voltage threshold, and 
 a magnitude of the switch current exceeding a switch-current threshold. 
   
     
     
       15. The system of claim 14 wherein the charging signal includes a substantially constant voltage. 
     
     
       16. The system of claim 14 wherein the charging signal includes a substantially constant current. 
     
     
       17. The system of claim 14 wherein the battery charger and the protection circuit are disposed on a same integrated circuit. 
     
     
       18. The system of claim 14 wherein the battery charger and the protection circuit are disposed on respective integrated circuits. 
     
     
       19. A system, comprising:
 a battery configured to generate a battery voltage;   a battery charger having a charger input node, and having a charger output node coupled to the battery; and   a protection circuit, including
 a protection-circuit input node configured to receive an input voltage, 
 a protection-circuit output node coupled to the charger input node, 
 a sense node configured to receive the battery voltage; 
 a switch coupled between the protection-circuit input and output nodes and configured to conduct a switch current; and 
 logic circuitry coupled to the protection-circuit input node, the sense node, and the switch, and configured to deactivate the switch in response to at least two of
 a magnitude of the input voltage exceeding an input-voltage threshold, 
 a magnitude of the battery voltage exceeding a battery-voltage threshold, and 
 a magnitude of the switch current exceeding a switch-current threshold. 
 
   
     
     
       20. The system of claim 19 wherein the battery includes a lithium-ion battery. 
     
     
       21. The system of claim 19, further comprising operating circuitry coupled to the charger output node.