
Wi125 Data Sheet #:
SG170
Page 16 of 20
Rev:
04
Date:
11/29/11
Copyright 2011 The Connor-Winfield Corp. All Rights Reserved
Specifications subject to change without notice
8 APPLICATION HINTS
ThefollowingarealistofapplicationhintsthatmayhelpinimplementingsystembasedontheWi125.
8.1 Power Supply
ThepowersupplyrequirementsoftheWi125canallbeprovidedfromasingle3.3Vsupply.Tosimplifysystem
integrationon-boardregulatorsprovidethecorrectvoltagelevelsfortheRFandoscillator(2.9Vor3.0V)andlow
voltagedigitalcore(1.8V).InpowersensitiveapplicationsitisrecommendedthattheDIG_1V8supplyisprovided
fromahighefficiencyexternal1.8Vsourcee.g.switchmodepowersupply,ratherthantheon-boardlinearregula-
tor.
IfthesourceimpedanceofthepowersupplytotheWi125ishighduetolongtracks,filteringorothercauses,local
decouplingofthesupplysignalsmaybenecessary.Careshouldbetakentoensurethatthemaximumsupply
rippleatthepinsoftheWi125is50mVpeaktopeak.
8.2 RF Connection
TheRFconnectiontotheWi125canbedoneintwoways.Thepreferredmethodistousestandardmicrostrip
designtechniquestotrackfromtheantennaelementtotheRF_INcastellation.Thisalsoallowsthesystems
integratortheoptionofdesigninginexternalconnectorssuitablefortheapplication.Theusercaneasilyfitan
externallymountedMCX,SMAorsimilarconnector,provideditisplacedadjacenttotheRF_INcastellation.Ifthe
trackingguidelinesgivenbelowarefollowed,theimpedancematchwillbeacceptable.Thediagrambelowshows
howthiscouldbeachieved.Inthisdiagram,thecentreviaoftheRFconnectorispresumedtobeplatedthrough
withaminimalpadtopandbottom.ThePCBmaterialisassumedtobe1.6mmthickFR4withadielectricconstantof
4.3.Twosituationsareconsidered;onewithnogroundplaneandonewithagroundplaneonthebottomoftheboard,
underneaththeRFconnector.InbothcasesthereisnoinnerlayertrackingundertheRFconnector.
SMA Connector
RF_IN
Top Tracking
Ground Plane
(if used)
PIN 22
Figure 7 RF Tracking Example
ThewidthsoftheRF_INtrackandtheassociatedgapsaregiveninthetablebelow.
Scenario
Track Width (1/1000Inch)
Gap Width (1/1000Inch)
Withoutgroundplane
37
6
56
8
Withgroundplane
32
6
43
8
Table 7 RF Track & Gap Widths
Alternatively,theusercanattachtheantennatotheHiroseH.FL-R-SMTusingaflyingleadfittedwithasuitable
plug.