Dual-mode filtering actuator driver apparatus, systems and methods

Patent metadata

Field	Value
Publication number	US-2016156337-A1
Application number	US-201414558718-A
Country	US
Kind code	A1
Filing date	Dec 2, 2014
Priority date	Dec 2, 2014
Publication date	Jun 2, 2016
Grant date	—

Abstract

A dual-mode driver includes a transition stage and a static stage. The transition stage switches a bias voltage or an RF ground potential to an output pad to change the state of an RF actuator device connected at the output pad. After waiting a predetermined period of time for the RF actuator device to change state, the transition stage of the driver is disabled. A high-side or low-side static stage transistor maintains the driver output state through an isolation resistor. The isolation resistor and a capacitor formed at the driver output pad form an RC low-pass filter to block spurious noise generated at the driver. The RC filter also blocks RF energy that might otherwise enter the actuator driver from the actuator. Some embodiments also include a second RC filter located proximate to the output pad to prevent RF energy generated in the RF actuator from entering the driver.

First claim

What is claimed is:

1 . A dual-mode filtering actuator driver apparatus, comprising:
a transition stage including at least two transition stage transistors, the two transition stage transistors having a first current path coupled in series between a power supply voltage rail and a radio frequency (“RF”) ground rail, the two transition stage transistors joined at an output node, at least one of the transition stage transistors to conduct during a state change at the output node and to be turned off at an end of a predetermined period of time after the state change; a static stage communicatively coupled to the transition stage, the static stage including at least two static stage transistors, the two static stage transistors having a second current path coupled in series between the supply voltage rail and the RF ground rail and joined at an isolation node, at least one of the static stage transistors to continue to conduct following the predetermined period of time after the state change in order to maintain the state change after the transition stage becomes inactive; an isolation resistor coupled between the isolation node and the output node; and a pad capacitor with a first terminal at a connector pad communicatively coupled to the output node and a second terminal coupled to the RF ground rail, the isolation resistor and the pad capacitor to form a low-pass filter to filter RF harmonics from the actuator driver to actuator circuitry and to filter RF energy generated outside of the actuator driver at the actuator driver output.

2 . The dual-mode filtering actuator driver apparatus of claim 1 , the actuator being an element of a micro-electromechanical (“MEMS”) array.

3 . The dual-mode filtering actuator driver apparatus of claim 2 , the MEMS array being a selected one of a group consisting of a MEMS RF switching array, a MEMS tunable inductor array, a MEMS capacitor array, a MEMS switched capacitor array, and a MEMS varactor array.

4 . The dual-mode filtering actuator driver apparatus of claim 1 , a voltage associated with the power supply rail being substantially equal to an actuation bias voltage associated with the actuator.

5 . The dual-mode filtering actuator driver apparatus of claim 1 , the pad capacitor further comprising:
a metallic top plate formed by the connector pad; a metallic bottom plate formed at a layer under the connector pad; and a dielectric layer formed between the metallic top plate and the metallic bottom plate.

6 . The dual-mode filtering actuator driver apparatus of claim 1 , further comprising:
a resistance/capacitance (“RC”) pad filter proximate to the connector pad to filter RF energy from the actuator to the actuator driver.

7 . The dual-mode filtering actuator driver apparatus of claim 6 , the RC pad filter further comprising:
a pad filter resistor coupled to the connector pad; and a metal capacitor coupled between the pad filter resistor and the RF ground rail.

8 . The dual-mode filtering actuator driver apparatus of claim 7 , the metal capacitor further comprising:
a silicon epitaxial layer on a silicon substrate; an n-well formed in the silicon epitaxial layer, the n-well coupled to the RF ground rail; a field oxidation dielectric layer formed on the n-well; a cathode of the metal capacitor formed as a lower metallic layer on the field oxidation layer; a metal capacitor dielectric layer formed on the lower metallic layer; and an anode of the metal capacitor formed as an upper metallic layer on the metal capacitor dielectric layer.

9 . The dual-mode filtering actuator driver apparatus of claim 6 , further comprising:
a shielded conductive route to couple the connector pad to the pad filter resistor.

10 . The dual-mode filtering actuator driver apparatus of claim 9 , the shielded conductive route further comprising:
an upper metallic layer to couple between the connector pad and the pad filter resistor; an isolated lower metallic layer to provide an RF shield to the upper metallic layer; and a route dielectric formed between the upper metallic layer and the isolated lower metallic layer.

11 . A dual-mode filtering actuation system, comprising:
an array of dual-mode actuator drivers, each actuator driver to include a transition stage to initiate a state change of a driver output signal, a static stage to maintain the state change of the driver output signal, and an isolation resistor to couple the output signal from the static stage to an output node of the actuator driver during a static mode of operation; an array of pad capacitors, each pad capacitor with a first terminal at a connector pad communicatively coupled to the output node and a second terminal coupled to a radio frequency (“RF”) ground rail, the isolation resistor and the pad capacitor to form a low-pass filter to filter RF harmonics from the actuator driver to actuator circuitry and to filter RF energy generated outside of the actuator driver at the actuator driver output; and an array of RF actuator elements, a state of each element of the RF actuator array to be controlled by a corresponding actuator driver in the actuator driver array.

12 . The dual-mode filtering actuation system of claim 11 , the array of RF actuator elements a micro-electromechanical (“MEMS”) array selected from a group consisting of a MEMS RF switching array, a MEMS tunable inductor array, a MEMS capacitor array, a MEMS switched capacitor array, and a MEMS varactor array.

13 . The dual-mode filtering actuation system of claim 11 , states of the driver output signal to include a high bias voltage state substantially equal to a voltage of a power supply voltage rail, a low voltage state substantially equal to a voltage potential of the RF ground rail, and a high impedance state.

14 . The dual-mode filtering actuation system of claim 11 , the transition stage further comprising:
at least two transition stage transistors, the two transition stage transistors having a first current path coupled in series between a power supply voltage rail and the RF ground rail, the two transition stage transistors joined at an output node, at least one of the transition stage transistors to conduct during a state change at the output node and to be turned off at the end of a predetermined period of time after the state change at the output node.

15 . The dual-mode filtering actuation system of claim 14 , the static stage further comprising:
at least two static stage transistors, the two static stage transistors having a second current path coupled in series between the supply voltage rail and the RF ground rail and joined at an isolation node, at least one of the static stage transistors to continue to conduct following the predetermined period of time after the state change in order to maintain the state change after the transition stage becomes inactive.

16 . The dual-mode filtering actuation system of claim 11 , further comprising:
an array of resistance/capacitance (“RC”) low-pass pad filters, each RC pad filter proximate to a corresponding connector pad to filter RF energy from a corresponding actuator element to a corresponding actuator driver.

17 . A method of generating a filtered radio frequency (“RF”) actuator control signal at an actuator driver including a transition stage and a static stage, the transition stage including a high-side transition transistor coupled between a high voltage power supply rail and a driver output node and a low-side transition transistor coupled between the driver output node and an RF ground rail and the static stage i

Assignees

• Texas Instruments Inc

Inventors

• Shay Michael John
• Xu Jialei
• Chappel Randy A

Classifications

• H03H9/00

  Networks comprising electromechanical or electro-acoustic elements; Electromechanical resonators (electro-acoustic transducers such as loudspeakers, microphones or gramophone pick-ups H04R; piezoelectric, electrostrictive or magnetostrictive devices with mechanical input or output, e.g. actuators or sensors, H10N30/00, H10N35/00) · CPC title

• H03H11/04

  Frequency selective two-port networks · CPC title

• H03H1/0007

  of radio frequency interference filters · CPC title

• H03H1/02 Primary

  RC networks, e.g. filters · CPC title

• H03H21/0007 Primary

  comprising switched capacitor [SC] devices · CPC title