An on-chip input driver for a high-voltage SAR ADC

This thesis describes the design of a novel on-chip input driver for a SAR ADC. The driver achieves performance gains relative to off-chip alternatives by being integrated into the signal path of the ADC between the sampling switches and sampling capacitor. This placement allows for auto-zeroing the offset of the driver and reducing flicker noise. Additional performance benefits are possible because the driver can be optimized for the specific load and timings of the ADC. The most important benefit of an on-chip input driver is that it simplifies the design process for the ADC user by eliminating the external op-amp and reducing the constraints on the external filter by reducing input current load. Design simplicity is especially important to users in high-voltage SAR ADC applications, so the input driver is designed for an ADC with a +/- 10.24 V input range and +/- 15 V supply rails. This high-voltage input relaxes noise and headroom constraints, but makes device overvoltage a significant concern. The driver is designed in a BiCMOS process, and simulation results with a computer-modeled ADC are presented here. In these simulations, the driver achieves a THD of -124.7 dB at 2 kHz and a noise voltage spectral density of 5.5 nV / [square root of] Hz with a power consumption of 27.6 mW. The LT1469, an example of a state-of-the-art external input driver, has a THD of -123 dB at 2 kHz, a noise voltage spectral density of 5 nV / [square root of] Hz, and a power consumption of 123 mW.

Department dc:contributor.department

Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2014

Author dc:creator

• Linke, Kevin Robert

Advisor dc:contributor.advisor

• Micah G. O'Halloran and Charles G. Sodini.

• Electrical Engineering and Computer Science.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/91837

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/91837