Ambient light sensor

• US 8,400,626 B2
• Filed: 06/10/2010
• Issued: 03/19/2013
• Est. Priority Date: 06/10/2010
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Mahowald, Peter H.
• Primary Examiner(s): NGUYEN, TU T
• Application Number:
  US12/813,287
• Publication Number:
  US 20110304847A1
• Time in Patent Office: 1,013 Days
• Field of Search: None
• US Class Current: 356/218
• CPC Class Codes: G01J 1/32 adapted for automatic variation of the measured or reference value regulation of light intensity G05D25/00
• CPC Class Codes: G01J 1/44 Electric circuits for command of an exposure part G03B7/02
• CPC Class Codes: H03F 3/08 controlled by light

Abstract

Embodiments described herein relate to a light sensing system. In one embodiment, the light sensing system may include a microprocessor including an input pin configured to receive a first voltage from a light sensor. The light sensing system may also include a pull-up resistor coupled to the input pin. The pull-up resistor may include a first gate. The light sensing system may further include a pull-down resistor coupled to the input pin. The pull-down resistor may include a second gate. The first and second gates may allow for connecting or disconnecting the pull-up and pull-down resistors based on the amount or intensity of light detected by the light sensor.

Claims

1. A light sensing system, comprising:

a microprocessor including an input pin, the input pin configured to receive a first voltage from a light sensor;

a pull-up resistor coupled to the input pin, the pull-up resistor including a first gate; and

a pull-down resistor coupled to the input pin, the pull-down resistor including a second gate.

2. The light sensing system of claim 1, wherein the light sensor is a photodiode.

3. The light sensing system of claim 1, wherein the light sensor is configured to sense light and convert the sensed light to the first voltage.

4. The light sensing system of claim 1, wherein the first gate is configured to connect the pull-up resistor to a source voltage.

5. The light sensing system of claim 4, wherein the first gate is configured to connect the pull-up resistor based on whether the first voltage is greater than a threshold voltage level.

6. The light sensing system of claim 1, wherein the second gate is configured to connect the pull-down resistor to ground.

7. The light sensing system of claim 6, wherein the second gate is configured to connect the pull-down resistor based on whether the first voltage is less than a threshold voltage level.

8. The light sensing system of claim 1, wherein the light sensor is connected to a source voltage.

9. The light sensing system of claim 1, wherein the input pin is connected to a controller.

10. The light sensing system of claim 1, wherein the first gate is a CMOS circuit.

11. A method for detecting levels of light, comprising:

receiving a first voltage from a light sensor;

connecting a pull-down resistor to obtain a first logic value;

sampling a digital signal at an I/O pin; and

determining a first light level based on the first logic value.

12. The method of claim 11, further comprising:

connecting a pull-up resistor if the first logic value is a logical output of 1; and

afterwards, disconnecting the pull-up and pull-down resistors.

13. The method of claim 11, further comprising:

connecting a pull-up resistor to obtain a second logic value if the first logic value is a logical output of 0.

14. The method of claim 13, further comprising:

sampling the digital signal at the I/O pin to determine whether the second logic value is a logical output of 1 or 0; and

determining, based on the second logic value, that a second light level is lower than the first light level.

15. The method of claim 14, further comprising:

determining, based on the second logic value, that a third light level is lower than the second light level.

16. The method of claim 14, further comprising:

connecting the pull-down resistor if the second logic value is a logical output of 0; and

afterwards, disconnecting the pull-up and pull-down resistors.

17. The method of claim 14, further comprising:

connecting the pull-down resistor if the second logic value is a logical output of 1; and

afterwards, disconnecting the pull-up and pull-down resistors.

18. An electronic device comprising:

a light sensor configured to sense light and convert the sensed light to a first voltage;

a microprocessor coupled to the light sensor, the microprocessor including a digital I/O pin and configured to receive the first voltage from the light sensor;

a pull-up resistor coupled to the digital I/O pin; and

a pull-down resistor coupled to the digital I/O pin;

the microprocessor operative to selectively connect the pull-up resistor to the digital I/O pin at least partially in response to the first voltage; and

the microprocessor operative to selectively connect the pull-down resistor to the digital I/O pin at least partially in response to the first voltage.

19. The electronic device of claim 18, further comprising a controller coupled to the I/O pin.

20. The electronic device of claim 19, further comprising a controlled component coupled to the controller.