Trim method for high voltage drivers

Abstract

Methods and circuits are provided to create small, power minimizing, multi-channel high voltage drivers for micro-electromechanical systems (MEMS). A resistor calibration circuit is introduced to allow on chip resistor dividers to be calibrated against a single precision high voltage resistor divider, eliminating the cost and printed circuit board real estate associated with multiple resistor dividers connected to each channel. Additionally, a multiple-power rail configuration is provided to reduce power to the overall system by producing several rails generated by a boost converter or a capacitive charge pump, where the voltage output of the rails is produced to group rails of lesser voltage requirement rather than connecting all channels to the same high voltage rail on a dynamic basis.

Description

CROSS-REFERENCE TO RELATED APPLICATION[0001]This application claims priority of U.S. Provisional Patent Application Ser. No. 61 / 786,310 filed Mar. 15, 2013, which is incorporated herein by referenceFIELD OF THE INVENTION[0002]The present invention in general relates to electronic components and in particular to methods and circuits to create small, power minimizing, multi-channel high voltage drivers for micro-electromechanical systems (MEMS).BACKGROUND OF THE INVENTION[0003]Microelectromechanical systems (MEMS) is the technology of very small devices, that merge at the nano-scale into nanoelectromechanical systems (NEMS) and nanotechnology. MEMS are made up of components between 1 to 100 micrometers in size (i.e. 0.001 to 0.1 mm), and MEMS devices generally range in size from 20 micrometers (20 millionths of a meter) to a few millimeters (i.e. 0.02 to >1.0 mm). MEMS usually consist of a central unit that processes data (the microprocessor) and several components that interact wi...

AI Technical Summary

Benefits of technology

This patent describes methods and circuits for creating small and power-efficient drivers for micro-electromechanical systems (MEMS). It introduces a resistor calibration circuit that allows for the calibration of on-chip resistor dividers against a single precision high-voltage resistor divider, eliminating the cost and space associated with multiple resistor dividers for each channel. Additionally, a multiple power rail configuration is provided to reduce power consumption by creating several rails generated by boost converters or capacitive charge pumps to group outputs of lesser voltage requirement and dynamically selecting the rails for each individual channel as needed. In summary, the patent offers techniques to minimize power consumption and optimize the performance of high-voltage drivers for MEMS.

Problems solved by technology

At these sizes, the standard constructs of classical physics are not always useful.

Unfortunately, high valued resistors of high precision and with tight drift and temperature specifications and high initial accuracy are very expensive and difficult to source.

Furthermore, arraying large numbers of high valued resistors across a printed circuit board creates high impedance nodes which are sensitive to noise coupling and leakage and uses a lot of space.

The result is that most MEMS drivers have poor accuracy, “glitching problems,” poor power characteristics, and are often much larger than the MEMS devices they are trying to drive.

In general high voltage integrated circuits either use internal resistors, in which case their relative accuracy is poor, especially over the drift of the process, or high voltage integrated circuits rely on an external resistor divider for each channel.

Even if multiple on chip resistors are trimmed for good initial accuracy, a costly process, their drift and voltage coefficient specification is still relatively poor.

Exotic materials like SiCr may be used, however, on-chip thermal drift between the different channels, chip topology and the drift of the material itself still do not meet the very tight accuracy requirements of many MEMS drivers or make the cost of such drivers prohibitive.

The power supplies required to generate high voltage rails from a low voltage battery can often be extremely large often requiring more than one stage due to the small duty cycle that would otherwise be required.

Finally, most implementations of these power supplies are not monolithic and take up a great deal of space.

Images