A 1mm2 Two Stage LNA and SP2T Switch RFIC FEM for WLAN 802.11a Application January 18, 2012 Lei Ma, Cody Hale, Bob Baeten Motivation / Outline Motivation: • Low Cost, Low NF LNA for high band WLAN 4.9-5.85GHz • Highly integrated MMIC single chip solution for PA/LNA/Switch Outline: • pHEMT device Noise Figure FOM • RFMD E/D-mode pHEMT Device Noise Figure Characteristics • RF5540 LNA design and data • Summary pHEMT LNA Noise Figure FOM - Fukui equations s s e c o t i r f p t i e u c m r i a c s t i t f i t m f n t o i i i t e f u r l f u c a t c r i v u i s r i i sc u c c T g r q E i m t e c F t n g π n l l 2 e m e t l a l a n o a ~ v r e r i v l f o i u a f u y q e i v q B c n e c u e d e u q e m n e n l a m a u i o t q i o r m r t v c e f o a o f e r f n m e p r f c e a n n a s c i a R e s a c e n r t g c a e u c t n c g r s t a r g i i n u e t u s R f e t s e d o e i r e n s s r r s m o e e m i u r c a c g o c r s e n a r y n t e u t l p y t a a a c i f f Ta g o r g s n n t u f m g e i n u T T T T K t i p t q T E E E E t F i E e F F 1 O F r F F F s g g m f F O F OK f f T g C R Reference: Optimal noise figure of microwave GaAs MESFET's Fukui, H.; Electron Devices, IEEE Transactions Volume 26, Issue 7, Jul 1979 Page(s):1032 - 1037 C t ︶ ︵ ︶ ︵ Rs NF at 5GHz Scaling Rule based Prediction m m W Ω U n * s N R s Ω s s m g G π 2 z H G ︶ C ︵ s R g R * m g ︶ R n s n m g 2 n m W U n g R g More fingers reduces Gate resistance ︵ Ft does not scale due to cancellation of Cgs and Gm scale, so Noise Figure f fT * kf 1 ︶ Reducing UW will decrease Rg, but increase Rs F 1 N * g T W * U g L * ρ g Ω ︵ g T W * U g L * ρ g Ω ︵ g R N fingers g R One finger ︶ fT Lg ︵ W U * N * m m / S ︵ ︶ ︵ ︵ ︶ ︵ R W U * N * m m / F p D ︵ N / W U * Ω UWg Cm Tg ︵ nnS gs Ωg n Ig n g g RF gpS Ω s ggm RCG ︵ Id Assuming Normalized Gmn, Rgn, Rsn does Not change, reducing UW will reduce noise figure • Normalized Rg should be only dependent on gate metal resistivity, Gate length and gate thickness. • Due to layout difference, there should also be additional routing resistance (gate access resistance) added to gate resistance. Device Noise Pull E-Mode device Noise parameters 3V 40mA/mm 5.4GHz Wg S11* Sopt & S11* 8x35 8x30 8x25 8x20 8x15 8x10 6x40 6x30 6x25 4x40 4x35 4x30 Gopt freq (5.400GHz to 5.400GHz) • Lower NF for smaller UW as expected • Trade off between NF and noise match inductance E-Mode 8x25um device Noise Parameters Vds=3.5V 5mA/mm 10mA/mm 15mA/mm 20mA/mm 25mA/mm 30mA/mm 40mA/mm 60mA/mm 80mA/mm Raw symbol smoothed line E-Mode 8x25um NFmin vs. Vds and Idn Idn = Id/gate width Normalized drain current NFmin is flat over Vds And increases slightly at higher Idn Input Noise Match Width (um) L (nH) R(Ohm) Q 150x150 3.75 10 1.37 5.15 9.03 310x200 2.5 22 1.94 4.22 15.8 310x200 2.5 25 1.67 3.94 14.6 310x190 2.25 22 1.61 3.08 17.9 310x220 2.5 25 1.76 3.3 18 310x310 1.75 28 1.50 2.16 23.9 310x330 1.75 29 1.56 2.24 23.8 Inductor size N NF performance for input match with different Q 5GHz • NF improve with larger first stage FET from 80um to 200um • NF improve with higher Q input match RF5540 Circuit Micro-photograph 916um x 950um SP2T Bypass switch • Full die Momentum simulation is necessary to predict RF performance • Sensitivity of Coupling for critical RF path esp. Noise match has to be considered Stage 1 Bias network Stage 2 • Stand alone LNA with NF=1.1dB is possible with less than half of the die size RF5540 NF performance • Note: this is one of the best performing part to date at this frequency RF5540 RX LNA mode S parameters Gain IRL ORL RF5540 RX Bypass mode S parameters Gain ORL IRL 0 -10 -10 -20 -20 0 1 2 3 4 5 freq, GHz 6 7 8 9 RX BYPASS IRL and ORL (dB) RX BYPASS GAIN (dB) 0 RF5540 TX mode S parameters 0 0 -1 -20 -30 -2 -40 0 1 2 3 4 5 freq, GHz 6 7 8 9 TX IRL and ORL and ISO (dB) -10 TX IL (dB) IL IRL ORL ISO RFMD and Competitor’s LNA in high band WLAN 4.9-5.85GHz • RF5540 has over 1dB loss on SP2T switch, so the NF of the LNA is 1.1dB Reference: Ref [1]: TQL5000, LNA for 5GHz UNI I Band 802.11a Systems. Triquint Semiconductor data sheet, www. Triquint.com Ref [2]: ALM-2812, Dual-Band(2.4-2.5)GHz&(4.9-6)GHz WLAN Low-Noise Amplifier, Avago Technologies data sheet, www.avagotech.com Ref [3]: MGA-675T6, Low Noise Amplifier with Shutdown Mode in Low Profile Package for 4.9-6GHz Application, Avago Technologies data sheet, www. avagotech.com Ref [4]: SKY65404-21, 5GHz Low Noise Amplifier, Skyworks Solutions Inc data sheet, www.skyworksinc.com RF5540 block diagram Summary/Conclusion • Competitive NF performance is achieved in RFMD’s low cost E/D-mode pHEMT process using high Q and narrow band matching at WLAN high band 4.9-5.85GHz • The LNA NF at 5GHz is close to the limit of RFMD’s E-mode pHEMT device capability. (1.1dB RF5540 excluding switch loss vs. 1.0dB 8x25um) • High Q inductor has to be used for lower loss and higher NF. • Stand alone LNA with 1dB NF is possible with less than half of the size of RF5540. • Lower noise figure 0.5dB at 5GHz is possible to achieve but at a higher processing cost than is acceptable for handset BOMs (RFMD E/D pHEMT vs. RFMD FSS25) • RFMD E/D-mode pHEMT process provide a technology for highly integrated RFIC solution with PA/LNA/Switch on the same die. Acknowledgement • Fab Device engineering: John Fendrich, Dain Miller • Cooperate Engineering: Bill Clausen, Joe Gering