RF2721 Preliminary 2 QUADRATURE DEMODULATOR Typical Applications • UHF Digital and Analog Receivers • Commercial and Consumer Systems • Digital Communication Systems • Portable Battery-Powered Equipment • Spread-Spectrum Communication Systems • General Purpose Frequency Conversion Product Description 0.156 0.148 üSi Bi-CMOS GaAs HBT GaAs MESFET SiGe HBT Si CMOS 0.010 0.004 0.347 0.339 0.050 7 0.252 0.236 0.059 0.057 8° MAX 0° MIN 0.0500 0.0164 Optimum Technology Matching® Applied Si BJT .018 .014 QUADRATURE DEMODULATORS The RF2721 is a monolithic integrated quadrature demodulator intended for use in digital mobile radio receivers. In this application it is used to recover the inphase and quadrature baseband signals from the amplified and filtered IF. The RF2721 is intended for IF systems where the IF frequency ranges from 100kHz to 500MHz, and the LO frequency is two times the IF. The IC contains all of the required components to implement the demodulation function of the receiver and contains a digital divider type 90° phase shifter, two double-balanced mixers, and baseband amplifiers designed to interface with analog to digital converters. The output DC offset may be slaved to the reference of the ADCs to maintain DC accuracy. 0.010 0.007 Package Style: SOIC-14 Features • 5V Power Supply • On-Chip Active Device for Oscillator IF1+ 1 14 IF IN- GND 2 13 VCC • Low LO Power Requirement OSCB 3 12 PD • Digitally Controlled Power Down Mode OSCE 4 11 GND • 100kHz to 500MHz IF Operation POWER CONTROL GND 5 • ADC Compatible Outputs 10 I OUT 5 kΩ LO2- 6 LO2+ 7 QUAD DIV. BY 2 9 REF IN 5 kΩ 8 Q OUT Functional Block Diagram Rev A2 010509 Ordering Information RF2721 RF2721 PCBA Quadrature Demodulator 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 2-27 RF2721 Preliminary Absolute Maximum Ratings Parameter Rating Unit Supply Voltage Power Down Voltage (VPD) IF Input Level -0.5 to +7.0 -0.5 to VCC 2.0 VDC VDC VPP LO Input Power Operating Ambient Temperature Storage Temperature +10 -40 to +85 -40 to +150 dBm °C °C Parameter 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 0.1 to 500 DC to >10 DC to 1 3 5000 >1.25 14 0.1 ±1 1.5 to 3.5 MHz MHz MHz kΩ Ω VPP dB dB ° V T=25°C, VCC =5.0V Overall IF Frequency Range Baseband Frequency Range QUADRATURE DEMODULATORS 7 Input Impedance Output Impedance Maximum Output Gain I/Q Amplitude Balance I/Q Phase Accuracy Reference Voltage Condition 13 DC Offset 3 3 0.5 ±5 20 20 mV mV Load Impedance >5kΩ, CSHUNT <1pF Load Impedance >5kΩ, CSHUNT <10pF At 70MHz, each input With 250mV input Small-signal, 100mV input The reference voltage input should provide a low impedance at the I/Q frequency. The voltage sets the DC level seen on the I and Q ports. I to Q I or Q to REF IN LO Oscillator Frequency Level Input Impedance Use provided transistor or external LO. Twice (2x) the IF frequency. 0.1-1 400-j1200 VPP Ω At 140MHz <100 >50 2.5 0.8 ns kΩ V V Threshold voltage; Part is “ON”. Threshold voltage; Part is “OFF”. V V mA µA Specifications Operating limits Operating Power Down Power Down Turn On/Off Time Input Resistance VIH VIL 0 VCC Power Supply Voltage Current 2-28 5 4.5 to 5.5 4.5 300 7.2 500 Rev A2 010509 RF2721 Preliminary Pin 1 Function IF IN+ Description Balanced IF input. An input level of 400mVPP gives full output swing; a level of maximum 250mVPP is recommended for linear operation. This pin has no internal DC block, and an external capacitor of 100nF is needed if connected to a DC path. Interface Schematic IF IN+ IF IN- 1500 Ω 1500 Ω 350 Ω 2 GND 3 OSC B Ground connection. For best performance, keep traces physically short and connect immediately to ground plane. Base of the LO transistor. This pin is not connected to anything else. This transistor can be used for an oscillator. The collector of the transistor is connected to VCC. 350 Ω VCC OSC B OSC E OSC E GND LO2- 7 LO2+ 8 Q OUT 9 REF IN Rev A2 010509 Emitter of the LO transistor. This pin is not connected to anything else. See pin 3. Same as pin 2. Balanced input for the doubled LO. An internal divide-by-2 network generates the actual LO for the mixers. The divided signal is not accessible. When the LO is driven single ended this pin should be connected to a 100nF capacitor to ground. This pin has an internal pull-up resistor to VCC and an external DC blocking capacitor of 100nF is recommended. 200 Ω LO2+ 7 200 Ω LO2- Balanced input for the doubled LO. The input frequency should be See pin 6. twice (2x) the IF frequency. An internal divide-by-2 network generates the actual LO for the mixers. This pin has an internal pull-up resistor to VCC, and an external DC blocking capacitor of 100nF is recommended. LO frequencies below 100kHz are acceptable, providing that the LO signal is square wave. Above 100kHz a sine wave signal is acceptable. The quadrature accuracy of the LO/2 frequency into the mixers is affected by the duty cycle of the LO input signal. Square wave signals with other than 50% duty cycle will degrade the quadrature accuracy of the LO signal, thereby adversely affecting the I and Q quadrature accuracy. Since the LO input is AC coupled, asymmetric sine waves and sine waves clipped on either the top or bottom half will not have 50% duty cycles relative to the internal DC reference point. For this reason, distorted LO sine wave signals will degrade performance in a fashion similar to non-50% duty cycle square waves. A sine wave input with even harmonics less than -15dBc is recommended. The internal limiting buffer amplifier ensures the amplitude stability of the demodulator. Demodulated baseband Q output. The reference DC level of this pin is set by the voltage of pin 9 (REF IN), which is connected to this pin through a 5kΩ resistor to the collectors of this push-pull output. This results in an output impedance of 5kΩ if the REF IN pin is connected to a low impedance source. The capacitance of the load determines the maximum baseband frequency. A very low capacitive load may stretch the 3dB bandwidth over 10MHz. Another way to increase bandwidth is by connecting a shunt resistor. This will trade-off gain for bandwidth. QUADRATURE DEMODULATORS 4 5 6 5 kΩ REF IN I/Q OUT Reference voltage input for the baseband outputs. This pin can be con- See pin 8. nected to the reference voltage source of the Analog to Digital Converter. It is connected to the I and Q outputs through 5kΩ resistors. This pin should have an external decoupling capacitor large enough to decouple the lowest baseband frequency. 2-29 RF2721 Pin 10 Function I OUT 11 12 GND PD 13 VCC 14 IF IN- Description Interface Schematic Demodulated baseband I output. The reference DC level of this pin is set by the voltage of pin 9 (REF IN), which is connected to this pin through a 5kΩ resistor to the collectors of this push-pull output. This results in an output impedance of 5kΩ if the REF IN pin is connected to a low impedance source. The capacitance of the load determines the maximum baseband frequency. A very low capacitive load may stretch the 3dB bandwidth over 10MHz. Another way to increase bandwidth is by connecting a shunt resistor. This will trade gain for bandwidth. Same as pin 2. See pin 8. Power down control. When this pin is "low", all circuits are shut off. A "low" is typically 0.8V or less at room temperature. When this pin is "high", all circuits are operating normally. Power supply pin. An external 100nF bypass capacitor is recommended if no other bypass capacitor is nearby. Balanced IF input. An input level of 400mVPP gives full output swing; a level of maximum 250mVPP is recommended for linear operation. This pin has no internal DC block and an external capacitor of 100nF is needed if connected to a DC path. If the IF is driven by a single-ended source, connect this pin to an 100nF capacitor to ground. VCC PD See pin 1. QUADRATURE DEMODULATORS 7 Preliminary 2-30 Rev A2 010509 RF2721 Preliminary Evaluation Board Schematic (Download Bill of Materials from www.rfmd.com.) J1 IF1 50 Ω µstrip C4 100 nF C1 100 nF 1 R1 51 Ω C2 100 nF J2 LO IN POWER CONTROL 12 4 11 5 10 PD 7 2 GND 3 PD REF IN P2-1 1 REF IN 2 GND 3 NC CON3 C7 100 nF J4 Q OUT 7 QUADRATURE DEMODULATORS 2721400- VCC P2 9 C3 100 nF 1 CON3 J3 I OUT 5 kΩ 8 P1-3 C6 100 nF 5 kΩ QUAD DIV. BY 2 P1 P1-1 13 3 6 R2 51 Ω VCC 14 2 C5 100 nF Rev A2 010509 2-31 RF2721 Preliminary Evaluation Board Layout Board Thickness 1.5” x 1.5” Board Thickness 0.031”, Board Material FR-4 QUADRATURE DEMODULATORS 7 2-32 Rev A2 010509