Light sensor
A light sensor is provided that includes an exposed light transducer for accumulating charge in proportion to light incident thereon over an integration period; and a light-to-pulse circuit in communication with the exposed light transducer, the light-to-pulse circuit operative to output a pulse having a pulse width based on the charge accumulated by the exposed light transducer. The light-to-pulse circuit may include a one shot logic circuit that contributes to generation of the pulse. The light sensor may include an input/output pad, a capacitor provided at the input/output pad for blocking static electricity, an input low pass filter provided at the input/output pad for blocking electromagnetic interference, and/or a bandgap voltage reference circuit connected to a power source having a supply voltage level in a range of about 3.3V to about 5.0V, and for generating a set of stable reference voltages throughout the supply voltage level range.
1. A light sensor package comprising:
an enclosure having a window for receiving light, the enclosure admitting at least a power connection pad, a ground connection pad, and an input/output pad;
an input low pass filter provided at the input/output pad for blocking electromagnetic interference;
an exposed light transducer disposed within the enclosure, the exposed light transducer operative to accumulate charge in proportion to light received through the window incident on the exposed light transducer over an integration period; and
a light-to-pulse circuit in communication with the exposed light transducer, the light-to-pulse circuit operative to output a pulse on the input/output pad, the pulse width based on the charge accumulated by the exposed light transducer.
2. The light sensor package of claim 1 , wherein the input low pass filter comprises a resistance at the input/output pad and a capacitor coupled between the resistance and ground.
3. The light sensor package of claim 2 , wherein the capacitor is configured such that the light sensor package is rated for at least 2 kV static protection.
4. The light sensor package of claim 2 , wherein the resistance is an integral part of the input/output pad.
5. The light sensor package of claim 1 and further comprising a nonvolatile memory within the enclosure for storing data from which calibration data may be obtained for the exposed light transducer.
6. The light sensor of claim 1 and further comprising a bandgap reference circuit for receiving power from a power source having a supply voltage level in a range of about 3.3V to about 5.0V, and for generating a set of stable reference voltages throughout the supply voltage level range to the light-to-pulse circuit.
7. The light sensor of claim 1 and further comprising a bandgap voltage reference circuit for receiving power from a power source and for generating a set of stable reference voltages to the light-to-pulse circuit, wherein the bandgap voltage reference circuit generates constant currents from the supply voltage supplied by the power supply and wherein the bandgap voltage reference circuit comprises resistive ladders through which the constant currents are passed to generate the set of stable reference voltages.
8. A rearview assembly for a vehicle comprising:
a rearview device for providing a rearward view to a driver of the vehicle;
the light sensor package of claim 1 ; and
a mounting mechanism adapted for mounting the rearview device and the light sensor to the vehicle.
9. The rearview assembly of claim 8 and further comprising a display carried by the mounting mechanism, and a display brightness control circuit coupled to the display and the light sensor package for controlling a brightness of the display in response to light levels sensed by the light sensor package.
10. The rearview assembly of claim 8 and further comprising an electro-optic mirror element carried by the mounting mechanism, and a mirror reflectivity control circuit coupled to the electro-optic mirror element and the light sensor package for controlling a reflectivity of the electro-optic mirror element in response to light levels sensed by the light sensor package.