RF2472 Preliminary 4 2.4GHZ LOW NOISE AMPLIFIER WITH ENABLE Typical Applications • TDMA/CDMA PCS LNA • Low Noise Transmit Driver Amplifier • TDMA/CDMA/FM Cellular LNA • General Purpose Amplification • ISM Band LNA/Driver • Commercial and Consumer Systems Product Description 4 0.15 0.05 GENERAL PURPOSE AMPLIFIERS The RF2472 is a general purpose, low-cost, high-performance amplifier designed for operation from a 2.7V to 4V supply with low current consumption. The device is optimized for 2.4GHz LNA applications, but is also useful for 1.9GHz PCS and K-PCS, 900MHz ISM, and 1.5GHz GPS applications. The RF2472 is available in a very small industry-standard SOT23 5-lead surface mount package, enabling compact designs which conserve board space. 1.60 + 0.01 0.400 1 2.90 + 0.10 0.950 2.80 + 0.20 3° MAX 0° MIN 1.44 1.04 Dimensions in mm. 0.127 0.45 + 0.10 Optimum Technology Matching® Applied Si BJT GaAs HBT Si Bi-CMOS üSiGe HBT Package Style: SOT 5 Lead GaAs MESFET Si CMOS Features • DC to >6GHz Operation • 2.7V to 4.0V Single Supply • High Input IP3 VCC 1 5 RF OUT • 1.5dB Noise Figure at 2400MHz • 14dB Gain at 2400MHz GND 2 • Low Current Consumption of 6mA at 3V RF IN 3 4 PD Ordering Information RF2472 2.4GHz Low Noise Amplifier with Enable RF2472 PCBA-410Fully Assembled Evaluation Board, 2.4GHz RF2472 PCBA-411Fully Assembled Evaluation Board, 1.9GHz Functional Block Diagram Rev A6 011023 RF Micro Devices, Inc. 7628 Thorndike Road Greensboro, NC 27409, USA Tel (336) 664 1233 Fax (336) 664 0454 http://www.rfmd.com 4-87 RF2472 Preliminary Absolute Maximum Ratings Parameter Supply Voltage Input RF Level Operating Ambient Temperature Storage Temperature Parameter Rating Unit -0.5 to 4.0 0 -40 to +85 -40 to +150 V dBm °C °C Caution! ESD sensitive device. RF Micro Devices believes the furnished information is correct and accurate at the time of this printing. However, RF Micro Devices reserves the right to make changes to its products without notice. RF Micro Devices does not assume responsibility for the use of the described product(s). Specification Min. Typ. Max. Unit DC to >6000 MHz Overall GENERAL PURPOSE AMPLIFIERS 4 T=27°C, VCC =3.0V Frequency Range T=27°C, VCC =3.0V, Freq=2440MHz 2.4GHz LNA Operation Gain Noise Figure Input IP3 Input P1dB Condition 13.0 +8.0 14.6 1.5 +10.0 -10 17.0 +20.0 dB dB dBm dBm PCS and K-PCS LNA Operation Two tones at 1MHz spacing, -15dBm output T=27°C, VCC =3.0V, Freq=1960MHz Gain Noise Figure Input IP3 Input P1dB 16.3 1.4 +8 -12 dB dB dBm dBm Two tones at 1MHz spacing, -12dBm output Power Supply Operating Voltage Operating Current 4-88 4.0 2.7 to 3.6 6.0 <1.0 8.0 3.0 V mA µA VCC =3.0V, PD =3.0V VCC =3.0V, PD =0V Rev A6 011023 RF2472 Preliminary Pin 1 Function VCC 2 GND 3 RF IN Description Interface Schematic Supply connection. An external bypass capacitor may be required in some applications. Ground connection. Keep traces physically short and connect immediately to ground plane for best performance. RF input pin. This pin is DC coupled and matched to 50Ω at 2.4GHz. See pin 3. VCC PD BIAS RF OUT RF IN PD 5 RF OUT Rev A6 011023 Power down pin.This pin enables the bias to the amplifier. To turn the amplifier on, this pin should be connected to VCC. Connecting this pin to ground, will turn the amplifier off and reduce the current draw to below 1µA. This pin is a CMOS input. There is no DC current draw other than the transient current required to charge or discharge the gate capacitance (less than 5pF). LNA Output pin.This pin is an open-collector output. It must be biased to VCC through a choke or matching inductor. This pin is typically matched to 50Ω with a shunt bias/matching inductor and series blocking/matching capacitor. Refer to application schematics. 4 GENERAL PURPOSE AMPLIFIERS 4 See pin 3. 4-89 RF2472 Preliminary Theory of Operation GENERAL PURPOSE AMPLIFIERS 4 The RF2472 is a low-noise amplifier with internal bias circuitry. It is DC-coupled on the input and output; therefore, it can be used to arbitrarily low frequency. It has useful gain to above 6GHz. Its design is optimized for use at 2.4GHz. Because of the high-frequency gain, the designer must take care to ensure that the device will remain stable outside the desired operating frequency. The RF2472 is capable of providing outstanding linearity, but to achieve this high performance, the circuit designer must pay attention to the terminations that are presented to low-frequency intermodulation products. Stability The RF2472 must be stabilized for frequencies outside of the desired operating range. Ground connections should be kept as short as possible. Wherever practical, ground should be provided by a via hole directly to a continuous ground layer. Highly reflective terminations to the RF input and output pins should be avoided whenever possible. In most circumstances, a resistor in parallel with an inductor in the bias line on pin 5 will improve the stability of the circuit. See the application schematics for examples. The 10nH inductor in the bias line is part of an output impedance matching circuit. At higher frequencies, the impedance of the matching circuit, alone, would become highly inductive. The large reactive termination of the output port could cause the circuit to oscillate at a high frequency. The resistance in parallel with the inductor adds a real part to the high-frequency termination that will have a stabilizing effect on the circuit. Linearity The 22nF bypass and coupling capacitors in the application schematics may seem excessively large for circuits intended to operate at 1.9GHz and 2.4GHz. These large capacitors provide a low impedance path to ground for second-order mixing products that leads to improved third-order intermodulation performance. The effect is most easily seen for the input coupling capacitor. A 100pF capacitor would provide low enough impedance to couple a 2.4GHz signal into the input pin of the RF2472. However, low-frequency intermodulation products caused by second-order nonlinearities would be presented with a large reactive impedance at the input pin. Relatively large voltages for these low-frequency products would be allowed to mix with the fundamental signals at the input pin, resulting in relatively large, in-band, third-order products. With a large coupling capacitor, the low-frequency products would be presented with a low impedance, via the input source impedance, resulting in a lower voltage at the input pin. These products, in turn, would mix at a lower level with the fundamental signals to produce lower in-band, third-order products. Some designers may be concerned about the self-resonant frequency of large coupling capacitors. A 22nF capacitor will probably pass through self resonance below 100MHz. Beyond resonance, the reactance of the capacitor will turn inductive, but the internal losses of the capacitor will usually prevent the component from exhibiting a large reactive impedance. Third-Order Intercept versus 1-dB Compression Point For many devices, the third-order intercept point is approximately 10dB higher than the 1-dB compression point. This rule of thumb does not apply for the RF2472. It is normal to find that the third-order intercept point is 20 dB higher than the 1-dB compression point. This behavior is common for SiGe devices. The reason for the difference is that the 10dB rule is based on a simple third-order polynomial model for device nonlinearities. For SiGe devices this simple model is not a good fit. 4-90 Rev A6 011023 RF2472 Preliminary Application Schematic - 1.9GHz VCC 22 pF VCC 1.8 kΩ 10 nH 22 nF 1 22 nF RF OUT 5 4 5.6 nH GENERAL PURPOSE AMPLIFIERS 2 22 nF 2.7 nH RF IN 3 PD 4 22 nF 0.5 pF Application Schematic - 2.4GHz VCC 22 pF VCC 1.0 kΩ 10 nH 22 nF 22 nF 1 RF OUT 5 5.6 nH 2 22 nF RF IN 3 PD 4 22 nF Rev A6 011023 4-91 RF2472 Preliminary Evaluation Board Schematic - 1.9GHz (Download Bill of Materials from www.rfmd.com.) P2 P1 P1-1 1 PD 2 GND P2-1 1 VCC 2 GND C6 3 pF R3 10 Ω C7 15 nF VCC C2 15 nF VCC GENERAL PURPOSE AMPLIFIERS 4 R4 1.8 kΩ U1 1 50 Ω µstrip J1 RF IN L3 2.7 nH 50 Ω µstrip 50 Ω µstrip 5 L2 5.6 nH 2 C1 10 nF L1 10 nH C4 15 nF J2 RF OUT R1 1 kΩ 50 Ω µstrip 3 PD 4 C3 0.5 pF C8 15 nF Evaluation Board Schematic - 2.4GHz P2 P1 P1-1 1 PD 2 GND P2-1 1 VCC1 2 GND C6 3 pF R3 10 Ω C7 15 nF VCC C2 15 nF VCC J1 RF IN 1 50 Ω µstrip C1 15 nF 4-92 L1 10 nH 50 Ω µstrip 5 L2 5.6 nH 2 3 2472400- R4 1.0 kΩ U1 C4 15 nF J2 RF OUT R1 1 kΩ PD 4 C8 15 nF Rev A6 011023 RF2472 Preliminary Evaluation Board Layout - 1.9GHz Board Size 1.0” x 1.0” Board Thickness 0.031”; Board Material FR-4 GENERAL PURPOSE AMPLIFIERS 4 Evaluation Board Layout - 2.4GHz Board Size 1.0” x 1.0” Board Thickness 0.031”; Board Material FR-4 Rev A6 011023 4-93 RF2472 Preliminary Gain versus Frequency 25.0 20.0 S21 (dB) 15.0 10.0 4 GENERAL PURPOSE AMPLIFIERS 5.0 0.0 0.0 1.0 2.0 3.0 4.0 5.0 Frequency (GHz) Swp Max 5.00069GHz 2. 0 6 0. 0.8 1.0 Smith Chart 0. 4 0 3. 0 4. 5.0 0.2 10.0 5.0 4.0 3.0 2.0 1.0 0.8 0.6 0.4 0 0.2 10.0 S1,1 -10.0 2 -0. -4 .0 -5. 0 S2,2 -3 .0 4-94 .0 -2 -1.0 -0.8 -0 .6 .4 -0 Swp Min 0.1GHz Rev A6 011023