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| Preliminary RF2721 QUADRATURE DEMODULATOR 2 Typical Applications * UHF Digital and Analog Receivers * Digital Communication Systems * Commercial and Consumer Systems * Portable Battery-Powered Equipment * Spread-Spectrum Communication Systems * General Purpose Frequency Conversion Product Description 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. Optimum Technology Matching(R) Applied 0.156 0.148 .018 .014 0.010 0.004 0.347 0.339 0.050 0.252 0.236 7 0.059 0.057 8 MAX 0 MIN 0.0500 0.0164 0.010 0.007 Package Style: SOIC-14 uSi Bi-CMOS IF1+ 1 GND 2 OSCB 3 OSCE 4 GND 5 Si BJT GaAs HBT SiGe HBT GaAs MESFET Si CMOS Features * 5V Power Supply * On-Chip Active Device for Oscillator 14 IF IN13 VCC 12 PD 11 GND 10 I OUT 5 k 9 REF IN 5 k 8 Q OUT * ADC Compatible Outputs * Low LO Power Requirement * Digitally Controlled Power Down Mode * 100kHz to 500MHz IF Operation POWER CONTROL LO2- 6 LO2+ 7 QUAD DIV. BY 2 Ordering Information RF2721 RF2721 PCBA Quadrature Demodulator Fully Assembled Evaluation Board Functional Block Diagram RF Micro Devices, Inc. 7628 Thorndike Road Greensboro, NC 27409, USA Tel (336) 664 1233 Fax (336) 664 0454 http://www.rfmd.com Rev A2 010509 2-27 QUADRATURE DEMODULATORS RF2721 Absolute Maximum Ratings Parameter Supply Voltage Power Down Voltage (VPD) IF Input Level LO Input Power Operating Ambient Temperature Storage Temperature Preliminary Rating -0.5 to +7.0 -0.5 to VCC 2.0 +10 -40 to +85 -40 to +150 Unit VDC VDC VPP 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). Parameter Overall IF Frequency Range Baseband Frequency Range Input Impedance Output Impedance Maximum Output Gain I/Q Amplitude Balance I/Q Phase Accuracy Reference Voltage Specification Min. Typ. Max. 0.1 to 500 DC to >10 DC to 1 3 5000 >1.25 14 0.1 1 1.5 to 3.5 Unit MHz MHz MHz k VPP dB dB V Condition T=25C, VCC =5.0V Load Impedance >5k, CSHUNT <1pF Load Impedance >5k, CSHUNT <10pF At 70MHz, each input With 250mV input Small-signal, 100mV input 7 QUADRATURE DEMODULATORS 13 0.5 5 DC Offset 3 3 20 20 mV mV 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 Use provided transistor or external LO. Twice (2x) the IF frequency. LO Oscillator Frequency Level Input Impedance 0.1-1 400-j1200 <100 >50 2.5 0.8 5 4.5 to 5.5 4.5 300 VPP ns k V V V V mA A At 140MHz Power Down Turn On/Off Time Input Resistance VIH VIL VCC 0 Threshold voltage; Part is "ON". Threshold voltage; Part is "OFF". Specifications Operating limits Operating Power Down Power Supply Voltage Current 7.2 500 2-28 Rev A2 010509 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. RF2721 Interface Schematic IF IN+ 1500 350 350 IF IN1500 2 3 GND 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. VCC OSC B OSC E 4 5 6 OSC E GND LO2- Emitter of the LO transistor. This pin is not connected to anything else. 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. See pin 3. 200 LO2+ 200 LO2- 7 QUADRATURE DEMODULATORS 7 LO2+ 8 Q OUT 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 5k resistor to the collectors of this push-pull output. This results in an output impedance of 5k 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. 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 5k resistors. This pin should have an external decoupling capacitor large enough to decouple the lowest baseband frequency. 5 k REF IN I/Q OUT 9 REF IN Rev A2 010509 2-29 RF2721 Pin 10 Function I OUT Description 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 5k resistor to the collectors of this push-pull output. This results in an output impedance of 5k 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. 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. Preliminary Interface Schematic See pin 8. 11 12 GND PD VCC PD 13 14 VCC IF IN- 7 QUADRATURE DEMODULATORS 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. See pin 1. 2-30 Rev A2 010509 Preliminary Evaluation Board Schematic (Download Bill of Materials from www.rfmd.com.) C4 100 nF 1 R1 51 2 3 4 C2 100 nF R2 51 C3 100 nF 2721400- RF2721 J1 IF1 50 strip C1 100 nF 14 13 12 11 10 5 k 6 7 QUAD DIV. BY 2 9 5 k 8 C5 100 nF VCC P1-1 P1 1 2 VCC GND PD POWER CONTROL PD C6 100 nF J3 I OUT P1-3 3 CON3 P2 P2-1 1 2 3 REF IN GND NC 5 J2 LO IN REF IN C7 100 nF J4 Q OUT CON3 7 QUADRATURE DEMODULATORS Rev A2 010509 2-31 RF2721 Evaluation Board Layout Board Thickness 1.5" x 1.5" Board Thickness 0.031", Board Material FR-4 Preliminary 7 QUADRATURE DEMODULATORS 2-32 Rev A2 010509 |
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