Ischia, 21-23 giugno 2006Riunione Annuale GE 2006

Università di CataniaFacoltà di IngegneriaDIEESCatania - ITALY

STMicroelectronicsCatania site

Lumped Modeling of Lumped Modeling of Differentially Driven Differentially Driven

Symmetric Inductors for RF Symmetric Inductors for RF IC DesignIC Design

Egidio Ragonese, Angelo Scuderi, Tonio Biondi, Alessandro Italia, and Giuseppe Palmisano

Radio Frequency Advanced Design Center (RF-ADC)

Sistemi Elettronici Integrati – B25

Ischia, 21-23 giugno 2006Riunione Annuale GE 2006

IntroductionIntroduction In RF ICs symmetrical inductors are profitable

exploited instead of two separate spirals lower area full electrical symmetry higher Q-factor and fSR

A profitable exploitation of integrated inductors requires simple, accurate and geometrically scalable models

Most inductor models are developed only for single-ended spirals, while the few models for symmetric inductors are not validated for single-ended structures

Ischia, 21-23 giugno 2006Riunione Annuale GE 2006

Modeling of integrated inductors Modeling of integrated inductors on Sion Si

Both single-ended and differential inductors were fabricated using a bipolar process supplied by ST-Microelectronics

Turn number from 1 to 5.5, inner diameter from 50 to 150 µm and metal width from 6 to 20 mm

Ischia, 21-23 giugno 2006Riunione Annuale GE 2006

Modeling of integrated inductors Modeling of integrated inductors on Sion Si

A scalable model for both single-ended and differential inductors

Modified -like topology (only one fitting parameter)

Physics-based equations based on process/layout parameters

Improved current sheet expression of LS (for sub-nH inductors)

Novel equation for series resistance (current crowding)

K·LS K·RS (1-2K)·LS (1-2K)·RS

CS Z1

K=0.16

RG CG

COX

K·LS K·RS

Z2

CG

COX

RG

Ischia, 21-23 giugno 2006Riunione Annuale GE 2006

Model validationModel validation Model validation up to 20 GHz by comparison with on-

wafer measurements of more than 100 spirals (covering 0.2 to 8.3 nH inductance values)

Accuracy, geometrical scalability and compactness promote the model as a reliable time-saving design tool

Average errors on inductance, fSR and Q

are 2%, 5%, and 7%

Ischia, 21-23 giugno 2006Riunione Annuale GE 2006

Model exploitationModel exploitation:: A 5-GHz image-reject down-A 5-GHz image-reject down-

converterconverter Extensively exploitation of integrated inductors (designed

with the proposed model)

Differential inductors are used in image-rejection filters

Ischia, 21-23 giugno 2006Riunione Annuale GE 2006

Model exploitation Model exploitation A 5-GHz image-reject down-A 5-GHz image-reject down-

converterconverter

Ischia, 21-23 giugno 2006Riunione Annuale GE 2006

See you later….See you later….

Poster B25Poster B25