Macro-pixel display backplane
A micro-light emitting diode (micro-LED) display backplane includes a plurality of macro-pixels. Each macro-pixel includes: a contiguous two-dimensional (2-D) array of bitcells storing display data bits for driving a set of micro-LEDs of a 2-D array of micro-LEDs; and drive circuits configured to generate, based on the display data bits stored in the contiguous 2-D array of bitcells, pulse-width modulated (PWM) drive signals for driving the set of micro-LEDs of the 2-D array of micro-LEDs. In one example, the plurality of macro-pixels is grouped into a plurality of sub-arrays, where each sub-array of the plurality of sub-arrays includes a set of macro-pixels and a local periphery circuit next to the set of macro-pixels. The local periphery circuit includes, for example, a buffer, a repeater, a clock gating circuit for gating an input clock signal to the sub-array, and/or a sub-array decoder for selecting the sub-array.
1. A display device comprising:
a first die including a two-dimensional (2-D) array of micro-light emitting diodes (micro-LEDs) in a display area; and
a second die vertically bonded with the first die, the second die including a micro-LED driver backplane that includes a 2-D array of sub-arrays, wherein each sub-array of the 2-D array of sub-arrays comprises:
drive circuits configured to generate pulse-width modulated (PWM) drive signals to drive a set of micro-LEDs of the 2-D array of micro-LEDs; and
a local periphery circuit for controlling the drive circuits of the sub-array, the local periphery circuit within the display area and including at least one of a buffer, a repeater, a clock gating circuit for gating an input clock signal to the sub-array, or a sub-array decoder for selecting the sub-array,
wherein the micro-LED driver backplane includes a periphery circuit outside of the 2-D array of sub-arrays, and
wherein the repeater is configured to replicate a control signal generated by the periphery circuit and for controlling the drive circuits of the sub-array.
2. The display device of claim 1 , wherein each sub-array of the 2-D array of sub-arrays comprises an array of macro-pixels, each macro-pixel of the array of macro-pixels comprising a contiguous 2-D array of bitcells storing display data bits for driving a subset of micro-LEDs of the set of micro-LEDs.
3. The display device of claim 2 , wherein:
each bitcell of the contiguous 2-D array of bitcells includes a six-transistor (6T) static random access memory (SRAM) cell that includes a world line, two bit lines, and two internal state storage nodes for storing a respective display data bit of the display data bits; and
each bitcell of the contiguous 2-D array of bitcells is configured to read the respective display data bit of the display data bits from the bitcell through the two bit lines.
4. The display device of claim 2 , wherein each macro-pixel of the array of macro-pixels further comprises:
a respective current driver for each micro-LED in the subset of micro-LEDs, the respective current driver configured to provide a drive current to the micro-LED;
a comparator for the subset of micro-LEDs, the comparator configured to compare, for each micro-LED in the subset of micro-LEDs, the display data bits for driving the micro-LED with a counter value; and
a respective PWM latch for each micro-LED in the subset of micro-LEDs, the respective PWM latch configured to generate, based on an output for the micro-LED generated by the comparator, a PWM control signal for modulating the drive current of the respective current driver for the micro-LED to generate a respective PWM drive signal of the PWM drive signals.
5. The display device of claim 4 , wherein the respective current drivers for two or more micro-LEDs in the subset of micro-LEDs are arranged contiguously in a region of the macro-pixel, the region separated from regions of the macro-pixel for other circuits by a transition region.
6. The display device of claim 5 , wherein the respective current drivers for the subset of micro-LEDs are connected to the subset of micro-LEDs in the 2-D array of micro-LEDs by an interconnect layer that includes re-distribution routing interconnects.
7. The display device of claim 4 , wherein the respective PWM latches for two or more micro-LEDs in the subset of micro-LEDs are arranged contiguously in a region of the macro-pixel.
8. The display device of claim 4 , wherein the comparator is configured to:
read and compare the display data bits for driving a first micro-LED of the subset of micro-LEDs in a first time window; and
read and compare the display data bits for driving a second micro-LED of the subset of micro-LEDs in a second time window.
9. The display device of claim 2 , wherein each macro-pixel of the array of macro-pixels further comprises a respective design-for-test (DFT) circuit for each micro-LED in the subset of micro-LEDs.
10. The display device of claim 2 , wherein each macro-pixel of the array of macro-pixels further comprises a respective input/output circuit configured to read display data bits stored in each row or column of the contiguous 2-D array of bitcells.
11. The display device of claim 2 , wherein the contiguous 2-D array of bitcells includes at least 6 bitcells for each micro-LED of the subset of micro-LEDs.
12. The display device of claim 2 , wherein the subset of micro-LEDs includes 8 or more micro-LEDs.
13. The display device of claim 1 , wherein a plurality of sub-arrays in the 2-D array of sub-arrays is included in a slice of the micro-LED driver backplane, the slice comprising a slice periphery circuit for controlling the plurality of sub-arrays.
14. The display device of claim 13 , wherein the slice periphery circuit comprises at least one of a counter or a look-up table for gamma correction.
15. The display device of claim 1 , wherein the periphery circuit includes at least one of a counter or a look-up table for gamma correction, the look-up table storing display data codes and corresponding counter values.
16. The display device of claim 15 , wherein the corresponding counter value for at least one display data code in the look-up table is different from an ideal counter value determined for the at least one display data code based on a gamma value.
17. The display device of claim 1 , wherein the periphery circuit is configurable to send a control signal to the clock gating circuit for gating the input clock signal to the sub-array to disable the drive circuits configured to generate the PWM drive signals.
18. The display device of claim 1 , wherein a pitch of the 2-D array of micro-LEDs is equal to or less than 2 μm.
19. The display device of claim 1 , wherein the local periphery circuit includes the clock gating circuit for gating the input clock signal to the sub-array or the sub-array decoder for selecting the sub-array.
20. A micro-light emitting diode (micro-LED) display backplane comprising a plurality of macro-pixels, each macro-pixel of the plurality of macro-pixels comprising:
a contiguous two-dimensional (2-D) array of bitcells storing display data bits for driving a set of micro-LEDs of a 2-D array of micro-LEDs; and
drive circuits configured to generate, based on the display data bits stored in the contiguous 2-D array of bitcells, pulse-width modulated (PWM) drive signals for driving the set of micro-LEDs of the 2-D array of micro-LEDs,
wherein the drive circuits include a comparator for the set of micro-LEDs, the comparator configured to compare counter values with display data for different micro-LEDs of the set of micro-LEDs in different time windows.
21. The micro-LED display backplane of claim 20 , wherein,
each bitcell of the contiguous 2-D array of bitcells includes a six-transistor (6T) static random access memory (SRAM) cell that includes a world line, two bit lines, and two internal state storage nodes for storing a respective display data bit of the display data bits; and
each bitcell of the contiguous 2-D array of bitcells is configured to read the respective display data bit of the display data bits from the bitcell through the two bit lines.
22. The micro-LED display backplane of claim 20 , wherein:
each macro-pixel of the plurality of macro-pixels further comprises a respective current driver for each micro-LED in the set of micro-LEDs, the respective current driver configured to provide a drive current to the micro-LED; and
the drive circuits of each macro-pixel of the plurality of macro-pixels include:
the comparator configured to compare, for each micro-LED in the set of micro-LEDs, the display data bits for driving the micro-LED with a counter value; and
a respective PWM latch for each micro-LED in the set of micro-LEDs, the respective PWM latch configured to generate, based on an output for the micro-LED generated by the comparator, a PWM control signal for modulating the drive current of the respective current driver for the micro-LED to generate a respective PWM drive signal of the PWM drive signals.
23. The micro-LED display backplane of claim 22 , wherein the respective current drivers for two or more micro-LEDs in the set of micro-LEDs are arranged contiguously in a region of the macro-pixel separated from regions of the macro-pixel for other circuits by a transition region.
24. The micro-LED display backplane of claim 22 , wherein the respective current driver for each micro-LED in the set of micro-LEDs includes a thick gate-oxide transistor with a channel length greater than 400 nm.
25. The micro-LED display backplane of claim 22 , wherein the drive currents of the respective current drivers of the plurality of macro-pixels are characterized by a standard deviation less than 20 nA.
26. The micro-LED display backplane of claim 22 , wherein the respective PWM latches for two or more micro-LEDs in the set of micro-LEDs are arranged contiguously in a region of the macro-pixel.
27. The micro-LED display backplane of claim 22 , wherein the comparator is configured to:
read and compare the display data bits for driving a first micro-LED of the set of micro-LEDs in a first time window; and
read and compare the display data bits for driving a second micro-LED of the set of micro-LEDs in a second time window.
28. The micro-LED display backplane of claim 20 , wherein each macro-pixel of the plurality of macro-pixels further comprises a respective design-for-test (DFT) circuit for each micro-LED in the set of micro-LEDs.
29. The micro-LED display backplane of claim 20 , wherein each macro-pixel of the plurality of macro-pixels further comprises a respective input/output circuit configured to read display data bits stored in each row or column of the contiguous 2-D array of bitcells.
30. The micro-LED display backplane of claim 20 , wherein the contiguous 2-D array of bitcells includes at least 6 bitcells for each micro-LED of the set of micro-LEDs.
31. The micro-LED display backplane of claim 20 , wherein the set of micro-LEDs includes 8 or more micro-LEDs.
32. The micro-LED display backplane of claim 20 , wherein a pitch of the set of micro-LEDs is equal to or less than 2 μm.
33. The micro-LED display backplane of claim 20 , wherein the plurality of macro-pixels is grouped into a plurality of sub-arrays, each sub-array of the plurality of sub-arrays including a set of macro-pixels and a local periphery circuit next to the set of macro-pixels.
34. The micro-LED display backplane of claim 33 , wherein the local periphery circuit comprises at least one of a buffer, a repeater, a clock gating circuit for gating an input clock signal to the sub-array, or a sub-array decoder for selecting the sub-array.
35. The micro-LED display backplane of claim 34 , wherein the repeater is configured to replicate a control signal for controlling the drive circuits of the set of macro-pixels in the sub-array.
36. The micro-LED display backplane of claim 33 , wherein the plurality of sub-arrays is grouped into a plurality of slices, each slice of the plurality of slices including a set of sub-arrays and a slice periphery circuit next to the set of sub-arrays.
37. The micro-LED display backplane of claim 36 , wherein the slice periphery circuit includes at least one of a counter or a look-up table for gamma correction, the look-up table storing display data codes and corresponding counter values.
38. The micro-LED display backplane of claim 37 , wherein the corresponding counter value for at least one display data code in the look-up table is different from an ideal counter value determined for the at least one display data code based on a gamma value.
39. The micro-LED display backplane of claim 36 , wherein the slice periphery circuit includes a calibration table for calibrating the drive circuits of the macro-pixels in the slice.