Application Note SKY65111-348LF: Amplifier Layout Optimization Introduction Evaluation Board Circuit Description Skyworks SKY65111-348LF is a high performance 3-stage power amplifier IC. Typical applications include automatic meter readers and RFID. The IC is manufactured on an advanced InGaP HBT process and packaged in a small 3 x 3 mm QFN package. Figure 2 describes the application circuit schematic used for the wideband 700–1200 MHz tuning. The operation of each device pin is detailed below. Typically the SKY65111-348LF is used in the 800–1100 MHz frequency band. It is tuned for very high efficiency, input and output return loss, and gain while still maintaining good output third order intercept (OIP3) and harmonic performance. The SKY65111-348LF data sheet references long lengths of two lines on VCC3, RFOUT, and VCC2. In efforts to reduce the overall board space required by the device and matching circuit, this application note describes how to replace these traces with surface mount inductors. As a result, the bandwidth of operation has been expanded to 700–1200 MHz. DC bias variation and harmonic filtering are also described. Ground, (Pins 1, 3, 8, 14). Attach all ground pins to the RF ground plane with multiple largest diameter, lowest inductance vias that the layout will allow. It is extremely important that the device paddle be sufficiently grounded for both thermal and stability reasons. RFIN, (Pin 2). A lumped element matching structure for good in-band return loss has been realized on the RF input, Pin 2. This structure is comprised of a DC blocking capacitor (C1), low pass LC filter (L1 and C2) and finally at the device input a series capacitor (C25). This combination of devices will yield a return loss of better than -11 dB over the entire 700–1200 MHz band. The actual placement of C1 is not critical; it can be moved as close to L1, C2 and C25 as desired. C25 should be placed as close to the device pin as possible to replicate performance when measured on the applications board. VCC1, (Pin 4). VCC1 is the collector bias input for the first amplifier stage in the SKY65111. Multiple bypass capacitors, C3–C5, C17 and a series inductor L2, have been utilized to ensure stability both in and out of the usable bandwidth of the device. L2 and C3 should be placed in the approximate location shown on the applications board layout, but absolute placement is not critical. VAPC1, (Pin 5). VAPC1 is the bias control voltage input for amplifier stages 1 and 2. Nominal operating range is between 2.6 V and 3.0 V, with 3.0 V producing maximum gain. VAPC1 can also be set to 0 V, if it is desired to place amplifier stages 1 and 2 into standby mode to reduce current consumption. Figure 1. SKY65111 Evaluation Board Without Layout Optimizations VAPC2, (Pin 6). VAPC2 is the bias control voltage input for amplifier stage 3. Nominal operating range is between 2.6 V and 3.0 V, with 3.0 V producing maximum gain. VAPC2 can also be set to 0 V, if it is desired to place amplifier stage 3 into standby mode to reduce current consumption. In most applications the VAPC1 and VAPC2 pins are tied directly together and biased from the same control voltage. VAPC1 and VAPC2 may also be split if independent control is desired. Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 200976 Rev. A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • November 10, 2008 1 Application Note • SKY65111-348LF: Amplifier Layout Optimization VREF, (Pin 7). VREF is the bias reference voltage input for amplifier stages 2 and 3. VREF should be operated over the same voltage range as VCC, with a nominal voltage of 3.5 V. Bypassing of VREF is accomplished with C23 and C24, both of which should be placed close to the device pin. proper RF bypassing and should be placed closely to L5 as shown in the applications circuit. Output matching for optimal power gain is accomplished with capacitors C15, L3 and C16. C15 should be placed about 141 mils (3.6 mm) from the RF output. RFOUT, VCC3 (Pins 9–12). RFOUT and VCC3 are the inputs for the power supply connection to the stage 3 collectors as well as the RF output port. These pins should be tied together to enable current sharing. Bias is applied to the RF output through L5, a high current rated 10 nH inductor. Capacitors C11 through C14 provide VCC2, (Pins 15 and 16). VCC2 is the collector bias input for the second amplifier stage in the SKY65111. Multiple bypass capacitors, C8–C10 have been utilized to ensure stability both in and out of the usable bandwidth of the device. C8 should be placed closely to L4 as shown in the application board layout. VCC2 C10 C9 Pin 13. No connection and must be left open circuit. C8 L4 C11 16 15 14 C1 C13 C14 L5 13 1 C12 12 L1 2 11 C25 C2 RFIN C24 L3 SKY65111-348 3 10 4 9 C15 C16 RFOUT C3 L2 VCC1 C17 C5 5 6 7 8 C4 C22 VAPC1 VAPC2 C23 VREF Figure 2. Application Circuit Schematic 2 Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com November 10, 2008 • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • 200976 Rev. A VCC3 Application Note • SKY65111-348LF: Amplifier Layout Optimization Figure 3. Application Board Layout Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 200976 Rev. A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • November 10, 2008 3 Application Note • SKY65111-348LF: Amplifier Layout Optimization Table 1. SKY65111-348LF Recommended Evaluation Board Component Values 4 Component Value Size Manufacturer Part Number C1 100 pF 0402 Murata GRM1555C1H101JD83E C2 0.5 pF 0402 Murata GRM1555C1H0R5JZ35E C3 4.7 pF 0402 Murata GRM1555C1H4R7JZ35E C4 100 pF 0402 Murata GRM1555C1H101JD83E C5 1000 pF 0402 Murata GRM155R71H102KA01 C8 100 pF 0402 Murata GRM1555C1H101JD83E C9 1000 pF 0402 Murata GRM155R71H102KA01 C10 10 μF 0402 AVX TAJA106M006R C11 100 pF 0402 Murata GRM1555C1H101JD83E C12 1000 pF 0402 Murata GRM155R71H102KA01 C13 10 nF 0402 Murata GRM155R71E103KA01 C14 10 μF 1206 AVX TAJA106M006R C15 15 pF 0402 Murata GJM1555C1H150JB01E C16 6.8 pF 0402 Murata GJM1555C1H6R8CB01E C17 10 μF 1206 AVX TAJA106M006R C22 1000 pF 0402 Murata GRM155R71H102KA01 C23 100 pF 0402 Murata GRM1555C1H101JD83E C24 100 pF 0402 Murata GRM1555C1H101JD83E C25 27 pF 0402 Murata GRM1555C270JZ35E L1 1 nH 0402 Taiyo Yuden HK1005-1N0S L2 1.2 nH 0402 Taiyo Yuden HK1005-1N2S L3 1.8 nH 0402 Taiyo Yuden HK1005-1N8S L4 1 nH 0402 Taiyo Yuden HK1005-1N0S L5 10 nH 0603 Coilcraft 0603HC-10NXJB Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com November 10, 2008 • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • 200976 Rev. A Application Note • SKY65111-348LF: Amplifier Layout Optimization Typical Performance Characteristics 0 0 -5 -10 Output Return Loss (dB) Input Return Loss (dB) VCC1,2,3 = 3.5 V, VREF = 3.5 V, VAPC1,2 = 2.7 V, F = 915 MHz, Z0 = 50 W, T = 25 °C, unless otherwise noted -10 -15 -20 -25 -30 -35 -30 -40 -50 -60 500 1000 1500 2000 2500 3000 3500 4000 0 Frequency (MHz) Figure 4. input Return loss vs. Frequency, pin = -30 dBm Figure 7. output Return loss vs. Frequency, pin = -30 dBm 50 40 30 20 10 0 -10 -20 -30 -40 -50 -60 1100 MHz 800 MHz 1000 MHz 700 MHz 45 40 35 30 25 20 15 10 5 500 1000 1500 2000 2500 3000 3500 4000 0 Frequency (MHz) Figure 5. Small Signal Gain vs. Frequency, pin = -30 dBm 0 32 31 -20 30 -40 -50 -60 -70 25 30 35 26 25 23 1000 1500 2000 2500 3000 3500 4000 20 27 24 500 15 28 -90 0 10 29 -80 -100 5 Figure 8. pAe vs. output power for multiple Frequencies -10 -30 0 Output Power (dBm) Output P1 dB (dBm) Reverse Isolation (dB) 1200 MHz 900 MHz 50 0 500 1000 1500 2000 2500 3000 3500 4000 Frequency (MHz) PAE (%) Small Signal Gain (dB) 0 -20 22 600 700 800 900 1000 1100 Frequency (MHz) Frequency (MHz) Figure 6. Reverse isolation vs. Frequency, pin = -30 dBm Figure 9. op1 dB vs. Frequency Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 200976 Rev. A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • November 10, 2008 1200 5 Application Note • SKY65111-348LF: Amplifier Layout Optimization Typical Performance Characteristics VCC1,2,3 = 3.5 V, VREF = 3.5 V, VAPC1,2 = 2.7 V, F = 915 MHz, Z0 = 50 W, T = 25 °C, unless otherwise noted 2nd Harmonic -30 3rd Harmonic 4th Harmonic 34 32 Output P1 dB (dBm) Harmonic Power (dBc) -40 -50 -60 -70 30 28 26 24 22 -80 20 -90 18 20 22 24 26 28 30 32 2.0 34 40 Output P1 dB (dBm) OIP3 (dBm) 37 36 35 34 33 32 31 4.5 5.0 VCC = 3.5 V VCC = 2.0 V 30 28 26 24 22 700 800 900 1000 1100 1200 20 2.60 1300 Frequency (MHz) 38 37 36 35 20 25 2.75 2.80 30 420 45 370 40 320 35 270 30 220 25 170 20 120 15 70 10 20 2.50 2.55 2.60 2.65 2.70 2.75 2.80 Output Power Per Tone (dBm) VAPC (V) Figure 12. oip3 vs. output power, ∆F = 5 mHz Figure 15. Supply current and Small Signal Gain vs. VApc, Vcc = 3.5 V Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com November 10, 2008 • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • 200976 Rev. A 5 Gain (dB) Total Supply Current (mA) 39 15 2.70 Figure 14. op1 dB vs. VApc, Vcc = 5 V, 3.5 V, 2 V 40 10 2.65 VAPC (V) Figure 11. oip3 vs. Frequency, pin = -20 dBm/tone, ∆F = 5 mHz OIP3 (dBm) 4.0 32 38 6 VCC = 5.0 V 34 39 5 3.5 Figure 13. op1 dB vs. Vcc, VApc = 2.7 V Figure 10. Harmonic power vs. output power 34 3.0 VCC (V) Output Power (dBm) 30 600 2.5 Application Note • SKY65111-348LF: Amplifier Layout Optimization Device Bias Options The SKY65111-348LF is capable of using a wide range of supply voltages while still maintaining good performance. VCC is typically specified at 3.5 V, but can be as low as 2 V or as high as 5 V. 5.6 nH 6.8 nH Changing VCC will directly affect the output 1 dB compression point (OP1 dB) and gain of the device, but input and output return losses will only see small changes. Figure 13 describes the extent OP1 dB is altered by varying the supply voltages. 3.9 pF Changing VAPC changes the bias point and quiescent current draw of the device. Lowering VAPC can actually increase OP1 dB by introducing gain expansion at the compression point. Figure 14 describes the effects of varying VAPC. Figure 16. 915 MHz Harmonic Filter Without Filter 60 40 The filter improves rejection by approximately 13 dB and 34 dB at the 2nd and 3rd harmonics, respectively. Pass band insertion loss is approximately 0.3 dB. Small Signal Gain (dB) 915 MHz Harmonic Filter The SKY65111-348LF has very good 2nd and 3rd harmonic performance, which minimizes interference at these frequency bands. To reduce these harmonics even more, external filtering may be used. Figure 16 shows a simple three component low-pass filter designed to improve harmonic rejection while maintaining low pass band insertion loss for 915 MHz operation. This filter should be placed immediately following the DC blocking capacitor, C24. With Filter 20 0 -20 -40 -60 -80 -100 0 500 1000 1500 2000 2500 3000 3500 4000 Frequency (MHz) Figure 17. Small Signal Gain With and Without the 915 mHz Harmonic Filter Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com 200976 Rev. A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • November 10, 2008 7 Application Note • SKY65111-348LF: Amplifier Layout Optimization Copyright © 2008, Skyworks Solutions, Inc. All Rights Reserved. Information in this document is provided in connection with Skyworks Solutions, Inc. (“Skyworks”) products or services. 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Additional information, including relevant terms and conditions, posted at www.skyworksinc.com, are incorporated by reference. 8 Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com November 10, 2008 • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • 200976 Rev. A