Display column driver devices with offset cancellation
An electronic device may include a display having an array of pixels that receive data signals from multiple column driver integrated circuits. Each column driver integrated circuit may include gamma amplifiers that are used to set gamma references for driving the data signals. Each gamma reference can be set using first and second (redundant) gamma amplifiers in an alternating fashion to perform auto-zeroing. The auto-zeroing operation can be combined with a chopping operation to minimize amplifier offset across the different column driver integrated circuits. The auto-zeroing and/or the chopping function can be spatially alternated across the different rows in the array and temporally alternated across the different display frames.
1. A display comprising:
an array of pixels arranged in rows and columns;
a plurality of column driver circuits configured to generate data signals for corresponding columns of pixels in the array; and
first and second gamma amplifiers configured to set a gamma reference that is used to drive the data signals at the plurality of column driver circuits, wherein
the first gamma amplifier is configured to operate in an offset-hold phase while the second gamma amplifier operates in an offset-sampling phase and is configured to operate in the offset-sampling phase while the second gamma amplifier operates in the offset-hold phase,
the first gamma amplifier is used to set the gamma reference for driving data signals to a first row of pixels in the array during first and second consecutive frames while operating in the offset-hold phase,
the second gamma amplifier is used to set the gamma reference for driving data signals to a second row of pixels in the array during the first and second consecutive frames while operating in the offset-hold phase, and
the first gamma amplifier, during the first frame, has a first polarity when setting the gamma reference for driving data signals to the first row of pixels in the array and has a second polarity opposite the first polarity when setting the gamma reference for driving data signals to a third row of pixels in the array.
2. The display of claim 1 , wherein the second gamma amplifier has the first polarity when setting the gamma reference for driving data signals to the second row of pixels in the array and has the second polarity when setting the gamma reference for driving data signals to a fourth row of pixels in the array.
3. The display of claim 1 , wherein the first gamma amplifier has the second polarity when setting the gamma reference for driving data signals to the first row of pixels during the second frame.
4. The display of claim 1 , wherein the second gamma amplifier, during the first frame, has the first polarity when setting the gamma reference for driving data signals to the second row of pixels and has the second polarity when setting the gamma reference for driving data signals to a fourth row of pixels in the array.
5. The display of claim 4 , wherein the second gamma amplifier has the second polarity when setting the gamma reference for driving data signals to the second row of pixels during the second frame.
6. The display of claim 5 , wherein the first gamma amplifier has the second polarity when setting the gamma reference for driving data signals to the third row of pixels during the first frame and has the first polarity when setting the gamma reference for driving data signals to the third row of pixels during the second frame.
7. The display of claim 6 , wherein the second gamma amplifier has the second polarity when setting the gamma reference for driving data signals to the fourth row of pixels during the first frame and has the first polarity when setting the gamma reference for driving data signals to the fourth row of pixels during the second frame.
8. The display of claim 1 , wherein the first gamma amplifier has the first polarity when setting the gamma reference for driving data signals to the first row of pixels during the second frame.
9. The display of claim 8 , wherein the second gamma amplifier has the first polarity when setting the gamma reference for driving data signals to the second row of pixels during the first and second frames.
10. The display of claim 9 , wherein the first gamma amplifier has the second polarity when setting the gamma reference for driving data signals to the first row of pixels during third and fourth consecutive frames following the second frame.
11. The display of claim 10 , wherein the second gamma amplifier has the second polarity when setting the gamma reference for driving data signals to the second row of pixels during the third and fourth frames.
12. The display of claim 1 , wherein the first gamma amplifier has the first polarity when setting the gamma reference for driving data signals to a first additional row of pixels adjacent to the first row of pixels during the first frame.
13. The display of claim 12 , wherein the second gamma amplifier has the first polarity when setting the gamma reference for driving data signals to a second additional row of pixels adjacent to the third row of pixels during the first frame.
14. The display of claim 13 , wherein the first gamma amplifier has the second polarity when setting the gamma reference for driving data signals to a third additional row of pixels adjacent to the third row of pixels during the first frame.
15. A method of operating display circuitry, comprising:
using first and second gamma amplifiers to set a gamma reference for driving data signals to an array of pixels;
using the first gamma amplifier to set the gamma reference for driving data signals to a first row of pixels in the array during first and second frames, the first gamma amplifier having a first chopping polarity during the first frame and having a second chopping polarity opposite of the first chopping polarity during the second frame; and
using the second gamma amplifier to set the gamma reference for driving data signals to a second row of pixels in the array during the first and second frames, the second gamma amplifier having the first chopping polarity during the first frame and having the second chopping polarity during the second frame.
16. The method of claim 15 , further comprising:
using the first gamma amplifier having the second chopping polarity to set the gamma reference for driving data signals to a third row of pixels in the array during the first frame; and
using the second gamma amplifier having the second chopping polarity to set the gamma reference for driving data signals to a fourth row of pixels in the array during the first frame.
17. The method of claim 15 , further comprising:
using the first gamma amplifier having the first chopping polarity to set the gamma reference for driving data signals to the first row of pixels during an additional frame following the first frame and preceding the second frame; and
using the second gamma amplifier having the first chopping polarity to set the gamma reference for driving data signals to the second row of pixels during an additional frame following the first frame and preceding the second frame.
18. The method of claim 15 , further comprising:
during the first frame, using the first gamma amplifier having the first chopping polarity to set the gamma reference for driving data signals to a first additional row of pixels adjacent to the first row of pixels; and
during the first frame, using the second gamma amplifier having the first chopping polarity to set the gamma reference for driving data signals to a second additional row of pixels adjacent to the second row of pixels.
19. A display comprising:
an array of pixels formed on a substrate; and
a plurality of column driver integrated circuits, each having at least first and second gamma amplifiers configured to set a gamma reference that is used to drive data signals to the array of pixels, wherein
the first gamma amplifier is used to set the gamma reference for driving data signals to a first row of pixels in the array across multiple frames,
the second gamma amplifier is used to set the gamma reference for driving data signals to a second row of pixels in the array across multiple frames, and
the first and second gamma amplifiers have a chopping polarity that alternates every frame or every group of consecutive frames.
20. The display of claim 19 , wherein the chopping polarity of the first and second gamma amplifiers changes every two rows or every four rows during a given frame.