The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jun. 18, 1996
Filed:
Aug. 09, 1994
Niraj Kumar, Fremont, CA (US);
Zilog, Inc., Campbell, CA (US);
Abstract
A two-step flash ADC includes a MSB reference ladder having a first plurality resistors of resistance r and a second plurality of resistors of resistance R, serially connected together on an alternating basis starting and ending with one of the first plurality of resistors. A LSB reference ladder having a total resistance R.sub.L is initially connected across a predetermined (2r+R) leg of the MSB reference ladder. The resistances r, R, and R.sub.L are selected such that the effective resistance resulting from connecting the LSB reference ladder in parallel with a (2r+R) leg of the MSB reference ladder is equal to a (r+R) leg of the MSB reference ladder. In a first step of the two-step flash ADC, MSB reference voltages are picked-off the MSB reference ladder from actual or effective (r+R) legs of the MSB reference ladder, compared against an analog input voltage, and used to generate the most-significant-bits of a digital number corresponding to the analog input voltage. In a second step of the two-step flash ADC, the LSB reference ladder is connected to a portion of the MSB reference ladder determined by the analog input voltage, LSB reference voltages are picked-off the LSB reference ladder from which the least-significant-bits of the digital number corresponding to the analog input voltage is generated. Carryover logic generates the digital number corresponding to the analog input voltage from the most-significant-bits and least-significant-bits thus generated.