AN RFMD® APPLICATION NOTE SZA-5044 Biasing, VPC Selection, and Performance versus Supply Voltage RFMD Multimarket Products Group Overview The SZA-5044 is a very flexible amplifier in terms of biasing. It can be run deep class AB for best efficiency and up to near class A for the best linearity. The power on/off control voltages are accessible for each of the three stages and nominal currents are set via externally chosen series resistors for each stage. It can support power on voltage logic (VPC) from +2.9V to +5V by simply choosing the right resistor network for the desired quiescent current and VPC power enable voltage. This application note addresses VPC resistor selection, VPC voltage selection, associated performance tradeoffs of the various configurations over temperature, and performance over supply voltage variation. If VCC < 3.6V is required. The STA-6033(Z) is recommended. VPC Power Enable Bias Resistor Selection for Various VPC Voltage Levels The schematic and table shown below describe the two recommended IQ settings of 220mA and 270mA for V+=VCC =5V. The IQ=220mA bias has the best combination of POUT over temperature at 3% EVM (802.11a 54Mb/s). The IQ=270mA bias point has the best IM3 performance as compared to IQ=220mA. Table 1 shows resistor values for VCC =5V and VPC range of 2.9V– 5V. Table 2 shows resistor values for other combinations of VCC and VPC levels. Figure 1. Application Schematic RF MICRO DEVICES®, RFMD®, Optimum Technology Matching®, Enabling Wireless Connectivity™, PowerStar®, POLARIS™ TOTAL RADIO™ and UltimateBlue™ are trademarks of RFMD, LLC. BLUETOOTH is a trademark owned by Bluetooth SIG, Inc., U.S.A. and licensed for use by RFMD. All other trade names, trademarks and registered trademarks are the property of their respective owners. ©2006, RF Micro Devices, Inc. AN062 090416 7628 Thorndike Road, Greensboro, NC 27409-9421 · For sales or technical support, contact RFMD at (+1) 336-678-5570 or [email protected]. 1 of 5 SZA-5044 Biasing, VPC Selection, and Performance versus Supply Voltage Table 1 VPC =2.9V to 5.0V ICQ =220mA VCC =5V Stage 1 (41mA) Stage 2 (94mA) VPC R1 (Ω) R2 (Ω) R3 ICQ =270mA Stage 3 (85mA) R4 (Ω) R5 Stage 1 (41mA) Stage 2 (94mA) R1 (Ω) R2 (Ω) Stage 3 (135mA) R3 R4 (Ω) R5 2.9 0 698 OUT 221 OUT 0 698 OUT 10 OUT 3 174 1.10K OUT 604 OUT 174 1.10K OUT 261 OUT 3.1 348 1.37K OUT 909 OUT 348 1.37K OUT 499 OUT 3.2 511 1.78K OUT 1.24K OUT 511 1.78K OUT 750 OUT 3.3 698 2.15K OUT 1.50K OUT 698 2.15K OUT 1.00K OUT 5 3.74K 2.49K 7.5K 7.15K OUT 3.74K 2.49K 7.5K 2.6K 7.5K Table 2 VCC =4.9V to 5.5V and VPC =2.9V to 5.0V ICQ =220mA Stage 1 (41mA) Stage 2 (94mA) R1 (Ω) R2 (Ω) ICQ =270mA Stage 3 (85mA) Stage 1 (41mA) Stage 2 (94mA) R1 (Ω) R2 (Ω) Stage 3 (135mA) VCC (V) VPC (V) 4.9 2.9 0 200 OUT 249 OUT 0 200 OUT 0 OUT 4.9 3 182 412 OUT 562 OUT 182 412 OUT 237 OUT R3 R4 (Ω) R5 R3 R4 (Ω) R5 4.9 3.1 365 604 OUT 909 OUT 365 604 OUT 475 OUT 4.9 3.2 562 825 OUT 1.21K OUT 562 825 OUT 698 OUT 4.9 3.3 698 1.02K OUT 1.50K OUT 698 1.02K OUT 1.00K OUT 5.1 2.9 0 243 OUT 301 OUT 0 243 OUT 20 OUT 5.1 3 182 442 OUT 619 OUT 182 442 OUT 274 OUT 5.1 3.1 340 665 OUT 1.00K OUT 340 665 OUT 511 OUT 5.1 3.2 511 825 OUT 1.24K OUT 511 825 OUT 750 OUT 5.1 3.3 698 1.10K OUT 1.62K OUT 698 1.10K OUT 1.02K OUT 5.1 5 3.74K 2.61K 7.5K 7.32K OUT 3.74K 2.61K 7.5K 2.8K 7.5K 5.2 2.9 10 249 OUT 332 OUT 10 249 OUT 49.9 OUT 5.2 3 174 475 OUT 665 OUT 174 475 OUT 301 OUT 5.2 3.1 348 681 OUT 1.02K OUT 348 681 OUT 562 OUT 5.2 3.2 562 887 OUT 1.37K OUT 562 887 OUT 825 OUT 5.2 3.3 698 1.10K OUT 1.69K OUT 698 1.10K OUT 1.10K OUT 5.2 5 3.74K 2.61K 7.5K 7.50K OUT 3.74K 2.61K 7.5K 2.87K 7.5K 5.3 2.9 10 274 OUT 348 OUT 10 274 OUT 82.5 OUT 5.3 3 196 499 OUT 698 OUT 196 499 OUT 340 OUT 5.3 3.1 357 750 OUT 1.02K OUT 357 750 OUT 604 OUT 5.3 3.2 511 909 OUT 1.37K OUT 511 909 OUT 825 OUT 5.3 3.3 698 1.15K OUT 1.74K OUT 698 1.15K OUT 1.10K OUT 5.3 5 3.74K 2.67K 7.5K 7.68K OUT 3.74K 2.67K 7.5K 3.0K 7.5K 5.4 2.9 0 287 OUT 374 OUT 0 287 OUT 100 OUT 5.4 3 182 511 OUT 750 OUT 182 511 OUT 348 OUT 5.4 3.1 357 750 OUT 1.10K OUT 357 750 OUT 604 OUT AN062 090416 7628 Thorndike Road, Greensboro, NC 27409-9421 · For sales or technical support, contact RFMD at (+1) 336-678-5570 or [email protected]. 2 of 5 SZA-5044 Biasing, VPC Selection, and Performance versus Supply Voltage Table 2 5.4 3.2 562 1.00K OUT 1.37K OUT 562 1.00K OUT 887 OUT 5.4 3.3 698 1.18K OUT 1.78K OUT 698 1.18K OUT 1.13K OUT 5.4 5 3.74K 2.67K 7.5K 7.68K OUT 3.74K 2.67K 7.5K 3.16K 7.5K 5.5 2.9 0 301 OUT 383 OUT 0 301 OUT 100 OUT 5.5 3 174 511 OUT 750 OUT 174 511 OUT 357 OUT 5.5 3.1 340 750 OUT 1.10K OUT 340 750 OUT 619 OUT 5.5 3.2 511 1.00K OUT 1.47K OUT 511 1.00K OUT 909 OUT 5.5 3.3 698 1.21K OUT 1.78K OUT 698 1.21K OUT 1.18K OUT 5.5 5 3.74K 2.67K 7.5K 8.06K OUT 3.74K 2.67K 7.5K 3.32K 7.5K The temperature range and required performance of the application should be considered when choosing a VPC power enable voltage. The higher VPC values have better performance over temperature because IQ varies less with temperature. Below is Figure 2 that shows IQ variation over temperature for VPC enable set voltages ranging from 2.9V to 5V. . Figure 2. SZA-5044 ICQ versus VPC versus Temperature AN062 090416 7628 Thorndike Road, Greensboro, NC 27409-9421 · For sales or technical support, contact RFMD at (+1) 336-678-5570 or [email protected]. 3 of 5 SZA-5044 Biasing, VPC Selection, and Performance versus Supply Voltage Another consideration is the variation in VPC enable voltage and the impact on performance. Performance is optimized when the VPC power enable is regulated and controlled. This is the case for the Atheros chip set where a regulated VPC enable=2.9V is available. Figure 3 shows IQ versus swept VPC for the nominal cases of VPC enable=2.9V to 5V at 25°C. . Figure 3. SZA-5044 ICQ versus Swept VPC, Constant VCC =5V, T=25°C The variation in current over temperature has impact on EVM over temperature. Figure 4 shows the EVM at POUT =21.5dBm versus temperature and VPC enable set voltage. . Figure 4. EVM (%) at POUT =21.5dBm versus VPC versus Temp AN062 090416 7628 Thorndike Road, Greensboro, NC 27409-9421 · For sales or technical support, contact RFMD at (+1) 336-678-5570 or [email protected]. 4 of 5 SZA-5044 Biasing, VPC Selection, and Performance versus Supply Voltage The variation in VCC also has an impact on EVM. Figure 5 shows the POUT at 3% EVM versus temperature and fixed VPC voltage=5.0V. . Figure 5. POUT at 3% EVM versus VCC, F=2.4GHz, Constant VPC =5V, ICQ=302mA AN062 090416 7628 Thorndike Road, Greensboro, NC 27409-9421 · For sales or technical support, contact RFMD at (+1) 336-678-5570 or [email protected]. 5 of 5