RF2174 Preliminary 2 3V DCS POWER AMPLIFIER Typical Applications • Commercial and Consumer Systems • 3V DCS1900 (PCS) Cellular Handsets • Portable Battery-Powered Equipment • 3V Dual-Band/Triple-Band Handsets • GPRS Compatible Product Description 2 Optimum Technology Matching® Applied Si Bi-CMOS ü 0.45 0.28 3.75 The RF2174 is a high power, high efficiency power amplifier module offering high performance in GSM or GPRS applications. The device is manufactured on an advanced GaAs HBT process, and has been designed for use as the final RF amplifier in DCS1800/1900 hand-held digital cellular equipment and other applications in the 1700MHz to 2000MHz band. On-board power control provides over 65dB of control range with an analog voltage input, and provides power down with a logic "low" for standby operation. The device is self-contained with 50Ω input and the output can be easily matched to obtain optimum power and efficiency characteristics. The RF2174 can be used together with the RF2173 for dual-band operation. The device is packaged in an ultra-small plastic package, minimizing the required board space. Si BJT 2 GaAs HBT GaAs MESFET SiGe HBT Si CMOS 1 0.80 TYP 0.75 0.50 3.75 + 1 1.60 4.00 12° 1.50 SQ INDEX AREA 3 3.20 0.75 0.65 4.00 1.00 0.90 0.05 0.00 NOTES: 1 Shaded Pin is Lead 1. 2 Dimension applies to plated terminal and is measured between 0.10 mm and 0.25 mm from terminal tip. The terminal #1 identifier and terminal numbering convention 3 shall conform to JESD 95-1 SPP-012. Details of terminal #1 identifier are optional, but must be located within the zone indicated. The identifier may be either a mold or marked feature. 4 5 Pins 1 and 9 are fused. Package Warpage: 0.05 max. Package Style: LCC, 16-Pin, 4x4 Features GND VCC2 VCC2 VCC2 2F0 • Single 2.7V to 4.8V Supply Voltage 1 16 15 14 13 • +33dBm Output Power at 3.5V • 27dB Gain with Analog Gain Control • 51% Efficiency AT_EN 2 12 RF OUT RF IN 3 11 RF OUT GND1 4 10 RF OUT • 1700MHz to 1950MHz Operation 9 GND 8 VCC 7 APC2 6 APC1 VCC1 5 Functional Block Diagram Rev A6 010720 • Supports DCS1800 and PCS1900 Ordering Information RF2174 RF2174 PCBA 3V DCS Power Amplifier Fully Assembled Evaluation Board RF Micro Devices, Inc. 7628 Thorndike Road Greensboro, NC 27409, USA Tel (336) 664 1233 Fax (336) 664 0454 http://www.rfmd.com 2-231 POWER AMPLIFIERS • 3V DCS1800 (PCN) Cellular Handsets RF2174 Preliminary Absolute Maximum Ratings Parameter POWER AMPLIFIERS 2 Supply Voltage Power Control Voltage (VAPC) Enable Voltage (VAT_EN) DC Supply Current Input RF Power Duty Cycle at Max Power Output Load VSWR Operating Case Temperature Storage Temperature Parameter Rating Unit -0.5 to +6.0 -0.5 to +3.0 -0.5 to +3.0 1500 +13 50 10:1 -40 to +85 -55 to +150 VDC V V mA dBm % 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). °C °C Specification Min. Typ. Max. Unit Overall Operating Frequency Range Usable Frequency Range Maximum Output Power Total Efficiency Recommended Input Power Range Output Noise Power +32 +31.5 +29.5 45 +5 Forward Isolation -37 -40 -60 -65 Second Harmonic Third Harmonic All Other Non-Harmonic Spurious Input Impedance Input VSWR Output Load VSWR 1710 to 1785 1850 to 1910 1700 to 2000 +33 +32.8 +31.5 +31 +30 51 51 15 10 +7 +9 MHz MHz MHz dBm dBm dBm dBm dBm % % % % dBm -79 dBm -30 -35 -45 -50 -36 dBm dBm dBc dBc dBm Temp=25 °C, VCC =3.5V, VAPC1,2 =2.6V, VAT_EN =2.6V, PIN =+6dBm, Freq=1710MHz to 1910MHz, 25% Duty Cycle, pulse width=1154µs See application schematic for tuning details. A different tuning is required. Temp=25 °C, VCC =3.5V, VAPC1,2 =2.6V Temp=+25 °C, VCC =3.2V, VAPC1,2 =2.6V Temp=+85 °C, VCC =3.2V, VAPC1,2 =2.6V Temp=25 °C, VCC =2.7V, VAPC1,2 =2.6V Temp=+85 °C, VCC =2.7V, VAPC1,2 =2.6V At POUT,MAX, VCC =3.5V At POUT,MAX, VCC =3.0V POUT =+20dBm POUT =+10dBm RBW=100kHz, 1805MHz to 1880MHz and 1930MHz to 1990MHz, POUT,MIN <POUT <POUT,MAX, PIN,MIN <PIN <PIN,MAX, VCC =3.0V to 5.0V VAPC1,2 =0.2V, PIN =+9dBm VAPC1,2 =0.2V, PIN =+6dBm POUT <+32.5dBm Ω 50 2.2:1 3:1 10:1 Output Load Impedance Condition Ω 4.5-j3.9 POUT,MAX-5dB<POUT <POUT,MAX POUT <POUT,MAX-5dB Spurious<-36dBm, VAPC1,2 =0.2V to 2.6V, RBW=100kHz Load Impedance presented at RF OUT pin Power Control Power Control “ON” 2.6 Power Control “OFF” 0.2 0.5 Attenuator Enable “ON” Attenuator Enable “OFF” 2.5 0.2 2.6 0.5 2-232 V V 2.85 V V Maximum POUT, Voltage supplied to the input Minimum POUT, Voltage supplied to the input For maximum isolation when VAPC is low For power down mode Rev A6 010720 RF2174 Parameter Power Control Range Specification Min. Typ. Max. 62 Gain Control Slope APC Input Capacitance APC Input Current 68 dB 100 4.5 AT_EN Input Current Turn On/Off Time Unit 10 5 10 500 10 100 dB/V pF mA µA µA µA ns 4.8 5.5 V V V 300 10 10 A mA µA µA Condition VAPC1,2 =0.2V to 2.6V, VAT_EN =2.6V, PIN =+9dBm POUT =-10dBm to +33dBm DC to 2MHz VAPC1,2 =2.6V VAPC1,2 =0V VAT_EN =2.6V, VAPC1,2 =0V VAT_EN =0V, VAPC1,2 =0V 2 Power Supply Power Supply Voltage 3.5 2.7 Power Supply Current 1.3 50 1 1 Rev A6 010720 Specifications Nominal operating limits, POUT <+33dBm With maximum output load VSWR 6:1, POUT <+33dBm DC Current at POUT,MAX Idle Current, PIN <-30dBm PIN <-30dBm, VAPC1,2 =0.2V PIN <-30dBm, VAPC1,2 =0.2V, Temp=+85°C 2-233 POWER AMPLIFIERS Preliminary RF2174 Pin 1 2 Function GND AT_EN POWER AMPLIFIERS 2 3 RF IN Preliminary Description Interface Schematic Internally connected to the ground slug. See pin 15. Control input for the PIN diode. The purpose of the PIN diode is to attenuate the RF input drive level when the VAPC is low. This serves both to reduce the leakage through the device cause by self biasing when driving with high level at the RF input, as well as to maintain a good input match when the bias of the input stage is turned off. When this pin is “high” the PIN diode control is turned on. See the Theory of Operation for more details. RF Input. This is a 50Ω input, but the actual impedance depends on the interstage matching network connected to pin 5. An external DC blocking capacitor is required if this port is connected to a DC path to ground or a DC voltage. To PIN diode 3k Ω AT_EN GND1 VCC1 RF IN PIN From Attn control circuit 4 GND1 5 VCC1 6 APC1 GND 1 From Bias Stages Ground connection for the pre-amplifier stage. Keep traces physically See pin 3. short and connect immediately to the ground plane for best performance. It is important for stability that this pin has it’s own vias to the groundplane, to minimize any common inductance. Power supply for the pre-amplifier stage and interstage matching. This See pin 3. pin forms the shunt inductance needed for proper tuning of the interstage match. Please refer to the application schematic for proper configuration, and note that position and value of the components are important. Power Control for the driver stage and pre-amplifier. When this pin is APC VCC "low," all circuits are shut off. A "low" is typically 0.5V or less at room temperature. A shunt bypass capacitor is required. During normal operation this pin is the power control. Control range varies from about 1.0V for -10dBm to 2.6V for +33dBm RF output power. The maximum power that can be achieved depends on the actual output matching; see the application information for more details. The maximum current into this pin is 5mA when VAPC1 =2.6V, and 0mA when VAPC =0V. To RF Stages GND GND 7 8 9 10 APC2 VCC GND RF OUT Power Control for the output stage. See pin 6 for more details. See pin 6. Power supply for the bias circuits. See pin 6. Internally connected to the ground slug. RF Output and power supply for the output stage. Bias voltage for the final stage is provided through this wide output pin. An external matching network is required to provide the optimum load impedance. RF OUT From Bias GND Stages PCKG BASE 11 12 13 RF OUT RF OUT 2F0 14 VCC2 2-234 Same as pin 10. Same as pin 10. Same as pin 10. Same as pin 10. Connection for the second harmonic trap. This pin is internally connected to the RF OUT pins. The bonding wire together with an external capacitor form a series resonator that should be tuned to the second harmonic frequency in order to increase efficiency and reduce spurious outputs. Same as pin 15. Same as pin 10. Rev A6 010720 RF2174 Preliminary Pin 15 Function VCC2 Description Interface Schematic Power supply for the driver stage and interstage matching. This pin forms the shunt inductance needed for proper tuning of the interstage match. Please refer to the application schematic for proper configuration, and note that position and value of the components are important. VCC2 From Bias GND2 Stages VCC2 GND Rev A6 010720 Same as pin 15. 2 Same as pin 15. Ground connection for the output stage. This pad should be connected to the groundplane by vias directly under the device. A short path is required to obtain optimum performance, as well as to provide a good thermal path to the PCB for maximum heat dissipation. POWER AMPLIFIERS 16 Pkg Base 2-235 RF2174 Preliminary Theory of Operation and Application Information POWER AMPLIFIERS 2 The RF2174 is a three-stage device with 28 dB gain at full power. Therefore, the drive required to fully saturate the output is +5dBm. Based upon HBT (Heterojunction Bipolar Transistor) technology, the part requires only a single positive 3V supply to operate to full specification. Power control is provided through a single pin interface, with a separate Power Down control pin. The final stage ground is achieved through the large pad in the middle of the backside of the package. First and second stage grounds are brought out through separate ground pins for isolation from the output. These grounds should be connected directly with vias to the PCB ground plane, and not connected with the output ground to form a so called “local ground plane” on the top layer of the PCB. The output is brought out through the wide output pad, and forms the RF output signal path. The amplifier operates in near Class C bias mode. The final stage is "deep AB", meaning the quiescent current is very low. As the RF drive is increased, the final stage self-biases, causing the bias point to shift up and, at full power, draws about 1500mA. The optimum load for the output stage is approximately 4.5Ω. This is the load at the output collector, and is created by the series inductance formed by the output bond wires, vias, and microstrip, and 2 shunt capacitors external to the part. The optimum load impedance at the RF Output pad is 4.5-j3.9Ω. With this match, a 50Ω terminal impedance is achieved. The input is internally matched to 50Ω with just a blocking capacitor needed. This data sheet defines the configuration for GSM operation. The input is DC coupled; thus, a blocking cap must be inserted in series. Also, the first stage bias may be adjusted by a resistive divider with high value resistors on this pin to VPC and ground. For nominal operation, however, no external adjustment is necessary as internal resistors set the bias point optimally. When the device is driven at maximum input power self biasing would occur. This results in less isolation than one would expect, and the maximum output power would be about -15dBm. If the drive power to the PA is turned on before the GSM ramp-up, higher isolation is required. In order to meet the GSM system specs under those conditions, a PIN diode attenuator connected to the input can be turned on. The figure below shows how the attenuator and its controls are connected. 2-236 VCC RF IN 750 Ω 500 Ω 5 kΩ APC PIN From Bias Stages 2 kΩ AT_EN The current through the PIN diode is controlled by two signals: AT_EN and APC. The AT_EN signal allows current through the PIN diode and is an on/off function. The APC signal controls the amount of current through the PIN diode. Normally, the AT_EN signal will be derived from the VCO ENABLE signal available in most GSM handset designs. If maximum isolation is needed before the ramp-up, the AT_EN signal needs to be turned on before the RF power is applied to the device input. The current into this pin is not critical, and can be reduced to a few hundred micro amps with an external series resistor. Without the resistor, the pin will draw about 700µA. Because of the inverting stage at the APC input, the current through the PIN diode is inverted from the APC voltage. Thus, when VAPC is high for maximum output power, the attenuator is turned off to obtain maximum drive level for the first RF stage. When VAPC is low for maximum isolation, the attenuator is be turned on to reduce the drive level and to avoid self-biasing. The PIN diode is dimensioned such that a low VAPC the impedance of the diode is about 50 Ohm. Since the input impedance of the first RF stage become very high when the bias is turned off, this topology will maintain a good input impedance over the entire VAPC control range. Rev A6 010720 VCC1 and VCC2 provide supply voltage to the first and second stage, as well as provides some frequency selectivity to tune to the operating band. Essentially, the bias is fed to this pin through a short microstrip. A bypass capacitor sets the inductance seen by the part, so placement of the bypass cap can affect the frequency of the gain peak. This supply should be bypassed individually with 100pF capacitors before being combined with VCC for the output stage to prevent feedback and oscillations. The RF OUT pin provides the output power. Bias for the final stage is fed to this output line, and the feed must be capable of supporting the approximately 1.5A of current required. Care should be taken to keep the losses low in the bias feed and output components. A narrow microstrip line is recommended because DC losses in a bias choke will degrade efficiency and power. While the part is safe under CW operation, maximum power and reliability will be achieved under pulsed conditions. The data shown in this data sheet is based on a 12.5% duty cycle and a 600µs pulse, unless specified otherwise. RF2174 The HBT breakdown voltage is >20V, so there is no issue with overvoltage. However, under worst-case conditions, with the RF drive at full power during transmit, and the output VSWR extremely high, a low load impedance at the collector of the output transistors can cause currents much higher than normal. Due to the bipolar nature of the devices, there is no limitation on the amount of current the device will sink, and the safe current densities could be exceeded. High current conditions are potentially dangerous to any RF device. High currents lead to high channel temperatures and may force early failures. The RF2174 includes temperature compensation circuits in the bias network to stabilize the RF transistors, thus limiting the current through the amplifier and protecting the devices from damage. The same mechanism works to compensate the currents due to ambient temperature variations. To avoid excessively high currents it is important to control the VAPC when operating at supply voltages higher than 4.0V, such that the maximum output power is not exceeded. The part will operate over a 3.0V to 5.0V range. Under nominal conditions, the power at 3.5V will be greater than +32dBm at +85°C. As the voltage is increased, however, the output power will increase. Thus, in a system design, the ALC (Automatic Level Control) Loop will back down the power to the desired level. This must occur during operation, or the device may be damaged from too much power dissipation. At 5.0V, over +36dBm may be produced; however, this level of power is not recommended, and can cause damage to the device. Rev A6 010720 2-237 2 POWER AMPLIFIERS Preliminary RF2174 Preliminary Application Schematic VCC 12 pF POWER AMPLIFIERS 2 Very close to pin 15/16 1 nF Instead of a stripline, an inductor of ~6 nH can be used 15 pF 1.0 pF 1 16 15 14 13 AT_EN 2 12 RF IN 3 11 VCC Instead of a stripline, an inductor of 2.2 nH can be used Quarter wave length 33 pF 50 Ω µstrip 33 pF 4 Distance between edge of device and capacitor is 0.240" to improve the "off" isolation 5 10 6 7 VCC 15 pF 15 pF 15 pF 3.6 pF 1.3 pF Note 1 1.3 pF Note 1 9 VCC APC 2-238 8 RF OUT 4.3 pF Distance between edge of device and capacitor is 0.080" Distance center to center of capacitors 0.220" 15 pF Note: All capacitors are standard 0402 multi layer chip Note 1: Using a hi-Q capacitor will increase efficiency slightly Rev A6 010720 RF2174 Preliminary Internal Schematic VCC1 VCC2 RF OUT 2 VCC APC2 VCC POWER AMPLIFIERS APC1 RF IN 750 Ω 500 Ω 500 Ω 200 Ω VCC 320 Ω 5k Ω APC1 3k Ω AT_EN 2.5k Ω 2.5k Ω 1.5k Ω 1.5k Ω GND1 Rev A6 010720 PKG BASE PKG BASE 2-239 RF2174 Preliminary Evaluation Board Schematic (Download Bill of Materials from www.rfmd.com.) VEN VCC P1 + POWER AMPLIFIERS C7 3.3 uF + C6 1 nF C10 1 pF C5 12 pF 1 C21 1 nF 16 15 14 C1 33 pF 2 12 3 11 + C12 1 nF GND P1-3 3 VCC P1-4 4 VCC 5 GND CON5 C9 33 pF Quarter Wave Length C2 33 pF 50 Ω µstrip 4 10 VCC C20 3.3 uF C8 1 nF 13 50 Ω µstrip J1 RF IN VEN 2 C19 3.3 uF C22 1 nF 2 1 P1-1 5 C11 27 pF 6 7 8 9 C3 3.6 pF C26 4.3 pF C4 1.3 pF J2 RF OUT C27 1.5 pF 2174400- C23 10 nF C16 1 nF C13 33 pF C14 33 pF VCC C17 1 nF C15 33 pF C25 10 nF C18 3.3 uF + C24 10 nF 50 Ω µstrip J3 VAPC 2-240 Rev A6 010720 RF2174 Preliminary Evaluation Board Layout Board Size 2.0” x 2.0” Board Thickness 0.032”; Board Material FR-4; Multi-Layer POWER AMPLIFIERS 2 Rev A6 010720 2-241 RF2174 Preliminary Typical Test Setup Power Supply V- S- S+ V+ POWER AMPLIFIERS 2 RF Generator Spectrum Analyzer 3dB 10dB/5W Buffer x1 OpAmp Pulse Generator A buffer amplifier is recommended because the current into the VAPC changes with voltage. As an alternative, the voltage may be monitored with an oscilloscope. Notes about testing the RF2174 The test setup shown above includes two attenuators. The 3dB pad at the input is to minimize the effects that the switching of the input impedance of the PA has on the signal generator. When VAPC is switched quickly, the resulting input impedance change can cause the signal generator to vary its output signal, either in output level or in frequency. Instead of an attenuator an isolator may also be used. The attenuator at the output is to prevent damage to the spectrum analyzer, and should be able to handle the power. It is important not to exceed the rated supply current and output power. When testing the device at higher than nominal supply voltage, the VAPC should be adjusted to avoid the output power exceeding +36dBm. During load-pull testing at the output it is important to monitor the forward power through a directional coupler. The forward power should not exceed +36dBm, and VAPC needs to be adjusted accordingly. This simulates the behavior for the power control loop in this respect. To avoid damage, it is recommended to set the power supply to limiting the current during the burst, not to exceed the maximum current rating. 2-242 Rev A6 010720