MEMS display pixel control circuits and methods
This disclosure provides novel latching circuits, and pixel circuits and display devices that include such latching circuits. The latches herein include a switch positioned on an inverter coupling interconnect which couples two cross-coupled inverters of the latch. The switch is configured to control a passage of a current between the first and second inverters. By switching the switch OFF at a time a data voltage is transferred to the inverters, any leak current between the inverters can be interrupted. As a result, a malfunctioning of the data latch is prevented.
1. An apparatus, comprising:
a plurality of MEMS devices arranged in an array; and
a control circuit coupled to the plurality of MEMS devices to communicate data and drive voltages to the MEMS devices, the control circuit, for each MEMS device, including:
a latch configured to actuate a shutter of the MEMS device, the latch including:
first and second cross-coupled inverters, each including at least two transistors; and
an inverter coupling interconnect coupling gates of the at least two transistors of the first inverter to drains of the at least two transistors of the second inverter; and
an inverter coupling interconnect switch including a transistor positioned on the inverter coupling interconnect configured to control a passage of a current between the first and second inverters;
a second switch including a transistor that is coupled to the inverter coupling interconnect and to the gate of the at least two transistors of the first inverter and is configured to communicate the data to the gate of the at least two transistors of the first inverter;
a latching control line coupled to the inverter coupling interconnect switch; and
a data transfer control line coupled to the second switch,
wherein a latch control signal from the latching control line causes the inverter coupling interconnect switch to switch to an OFF state at a time that the second switch communicates the data to the gate of the at least two transistors of the first inverter based on a data transfer control signal from the data transfer control line.
2. The apparatus of claim 1 , wherein the latch is coupled to a first actuator and a second actuator and is configured to maintain difference in voltages on the first and second actuators, and wherein the first and second actuators actuate the shutter based on the difference in voltages.
3. The apparatus of claim 1 , wherein the inverter coupling interconnect switch includes an n-type transistor.
4. The apparatus of claim 1 , wherein the inverter coupling interconnect switch includes a p-type transistor.
5. The apparatus of claim 1 , wherein, in operation, the inverter coupling interconnect switch is switched to an ON state after the time that the second switch communicates the data to the gate of the at least two transistors of the first inverter.
6. The apparatus of claim 1 , wherein a drain of the second switch is coupled to the inverter coupling interconnect and to the gate of the at least two transistors of the first inverter.
7. The apparatus of claim 1 , wherein the latching control line is coupled to respective gates of the inverter coupling interconnect switch and the second switch.
8. The apparatus of claim 7 , wherein the transistor of the inverter coupling interconnect is of a different conductivity type from the transistor of the second switch.
9. The apparatus of claim 7 , wherein a gate of the inverter coupling interconnect switch is coupled to the latching control line.
10. The apparatus of claim 7 , wherein a gate of the second switch is coupled to the data transfer control line.
11. The apparatus of claim 1 , wherein the apparatus is a display apparatus and the MEMS device comprises a shutter, wherein the latch is coupled to a first actuator and a second actuator and is configured to maintain difference in voltages on the first and second actuator, and wherein the first and second actuators actuate the shutter based on the difference in voltages.
12. An apparatus, comprising:
a plurality of MEMS devices arranged in an array; and
a control circuit coupled to the plurality of MEMS devices to communicate data and drive voltages to the MEMS devices, the control circuit, for each MEMS device, including:
a latch configured to actuate a shutter of the MEMS device, the latch including:
two cross-coupled inverters, each of a first inverter and a second inverter of the two cross-coupled inverters including at least two transistors; and
inverter coupling interconnect switch;
wherein an inverter coupling interconnect couples a common gate of the at least two transistors of the first inverter to a common drain of the at least two transistors of the second inverter; and
wherein the inverter coupling interconnect switch is positioned on the inverter coupling interconnect;
a second switch that is coupled to the inverter coupling interconnect and to the gate of the at least two transistors of the first inverter; and
a third switch that is coupled to a power supply line, to the second switch and to the gate of the at least two transistors of the first inverter.
13. The apparatus of claim 12 , wherein the second switch is configured to communicate the data to the gate of the at least two transistors of the first inverter.
14. The apparatus of claim 12 , wherein the second switch includes a transistor, and wherein the third switch is coupled to a drain of the second switch.
15. The apparatus of claim 12 , wherein the latch further includes a fourth switch that is connected between the common gate of the at least two transistors of the first inverter to a common drain of the at least two transistors of the first inverter.
16. The apparatus of claim 15 , wherein the latch further includes a capacitor that couples the third switch to the gate of the at least two transistors of the first inverter, and wherein the latch is configured such that the inverter coupling interconnect switch is in an OFF state at a time that (i) the third switch and the fourth switch are switched to an OFF state and subsequently switched to an ON state, and (ii) at a subsequent time that the second switch communicates the data to the gate of the at least two transistors of the first inverter through the capacitor.
17. The apparatus of claim 12 , wherein the latch is coupled to a first actuator and a second actuator and configured to maintain difference in voltages on the first and second actuators, and wherein the first and second actuators actuate the shutter based on the difference in voltages.