19-1209; Rev 0; 10/97 KIT ATION EVALU E L B AVAILA Low-Voltage IF Transceiver with Limiter and RSSI The MAX2511 is a complete, highly integrated IF transceiver for applications employing a dual-conversion architecture. Alternatively, the MAX2511 can be used as a single-conversion transceiver if the RF operating frequency ranges from 200MHz to 440MHz. In a typical application, the receiver downconverts a high IF/RF (200MHz to 440MHz) to a 10.7MHz low IF using an image-reject mixer. Functions include an image-reject downconverter with 34dB of image suppression followed by an IF buffer that can drive an offchip IF filter; an on-chip limiting amplifier offering 90dB of monotonic received-signal-strength indication (RSSI); and a robust limiter output driver. The transmit imagereject mixer generates a clean output spectrum to minimize filter requirements. It is followed by a 40dB variable-gain amplifier that maintains IM3 levels below -35dBc. Maximum output power is 2dBm. A VCO and oscillator buffer for driving an external prescaler are also included. The MAX2511 operates from a 2.7V to 5.5V supply and includes flexible power-management control. Supply current is reduced to 0.1µA in shutdown mode. For applications using in-phase (I) and quadrature (Q) baseband architecture for the transmitter, Maxim offers a corresponding transceiver product: the MAX2510. The MAX2510 has features similar to those of the MAX2511, but upconverts I/Q baseband signals using a quadrature upconverter. ____________________________Features ♦ Single +2.7V to +5.5V Supply ♦ Complete Receive Path: 200MHz to 440MHz (first IF) to 8MHz to 13MHz (second IF) ♦ Limiter with Differential Outputs (adjustable level) ♦ RSSI Function with 90dB Monotonic Dynamic Range ♦ Complete Transmit Path: 8MHz to 13MHz (second IF) to 200MHz to 440MHz (first IF) ♦ On-Chip Oscillator with Voltage Regulator and Buffer ♦ Advanced System Power Management (four modes) ♦ 0.1µA Shutdown Supply Current ______________Ordering Information PART MAX2511EEI TEMP. RANGE PIN-PACKAGE -40°C to +85°C 28 QSOP __________________Pin Configuration TOP VIEW ________________________Applications PWT1900 Wireless Handsets and Base Stations PACS, PHS, DECT and Other PCS Wireless Handsets and Base Stations 400MHz ISM Transceivers IF Transceivers Wireless Data Links Typical Operating Circuit appears at end of data sheet. LIMIN 1 28 VREF CZ 2 27 MIXOUT CZ 3 26 GND RSSI 4 25 RXIN GC 5 24 TXOUT TANK 6 23 TXOUT GND 7 22 RXIN VCC 8 21 VCC TANK 9 MAX2511 20 GND GND 10 19 VCC VCC 11 18 TXEN OSCOUT 12 17 RXEN LIMOUT 13 16 TXIN LIMOUT 14 15 TXIN QSOP ________________________________________________________________ Maxim Integrated Products 1 For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800. For small orders, phone 408-737-7600 ext. 3468. MAX2511 _______________General Description MAX2511 Low-Voltage IF Transceiver with Limiter and RSSI ABSOLUTE MAXIMUM RATINGS VCC to GND .............................................................-0.3V to 8.0V VCC to Any Other VCC ........................................................±0.3V TXIN, TXIN Input Voltage............................-0.3V to (VCC + 0.3V) TXIN to TXIN Differential Voltage ....................................±300mV RXIN, RXIN Input Voltage ........................................-0.3V to 1.6V TANK, TANK Voltage ...............................................-0.3V to 2.0V LIMIN Voltage .............................(VREF - 1.3V) to (VREF + 1.3V) LIMOUT, LIMOUT Voltage ..............(VCC - 1.6V) to (VCC + 0.3V) RXEN, TXEN, GC Voltage...........................-0.3V to (VCC + 0.3V) RXEN, TXEN, GC Input Current ............................................1mA RSSI Voltage...............................................-0.3V to (VCC + 0.3V) Continuous Power Dissipation (TA = +70°C) QSOP (derate 11mW/°C above 70°C) ...........................909mW Operating Temperature Range MAX2511EEI ......................................................-40°C to +85°C Junction Temperature ......................................................+150°C Storage Temperature Range .............................-65°C to +165°C Lead Temperature (soldering, 10sec) .............................+300°C Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. DC ELECTRICAL CHARACTERISTICS (VCC = +2.7V to +5.5V, 0.01µF across CZ and CZ; TANK = TANK; MIXOUT tied to VREF through a 165Ω resistor; GC open, RXIN = RXIN; TXOUT = TXOUT = VCC; TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER CONDITIONS Operating Voltage Range Digital Input Voltage High RXEN, TXEN Digital Input Voltage Low RXEN, TXEN MIN TYP MAX UNITS 2.7 3.0 5.5 V 2.0 Digital Input Current High 23 Digital Input Current Low Typical Supply Current V -5 VCC = 3.0V TA = +25°C Worst-Case Supply Current VREF Voltage Rx mode, RXEN = high, TXEN = low 24 Tx mode, RXEN = low, TXEN = high, VGC = 0.5V 26 Standby mode, RXEN = high, TXEN = high 9.5 Shutdown mode, RXEN = low, TXEN = low 0.1 2 32 µA µA mA µA 38.5 Tx mode, RXEN = low, TXEN = high, VGC = 0.5V 45 Standby mode, RXEN = high, TXEN = high 14.5 Shutdown mode, RXEN = low, TXEN = low 5 (Note 1) Internally terminated to 1.35V mA µA VCC / 2 - VCC / 2 VCC / 2 + 100mV 100mV V 2 kΩ LIMOUT, LIMOUT Differential Output Impedance GC Input Resistance V -1 Rx mode, RXEN = high, TXEN = low VCC = 2.7V to 5.5V, TA = -40°C to +85°C 0.4 60 80 _______________________________________________________________________________________ 125 kΩ Low-Voltage IF Transceiver with Limiter and RSSI (MAX2511 test fixture, VCC = +3.0V, RXEN = TXEN = low, 0.01µF across CZ and CZ, MIXOUT tied to VREF through 165Ω resistor, TXIN, TXIN tied to VREF through 50Ω resistor, TXOUT and TXOUT loaded with 100Ω differential, GC open, LIMOUT, LIMOUT loaded with 2kΩ differential, TANK and TANK driven with -2.5dBm from a 100Ω source; OSCOUT AC-terminated with 50Ω, 330pF at RSSI pin, 0.1µF at VREF pin, Rx inputs and Tx outputs differentially coupled, PRXIN, RXIN = -28dBm (200Ω system), fRXIN, RXIN = 425MHz, fLO = 435.7MHz, fTXIN, TXIN = 10.7MHz, TA = +25°C, unless otherwise noted.) PARAMETER CONDITIONS MIN TYP MAX 21.5 23.6 25.5 UNITS DOWNCONVERTER (RXEN = high) Downconverter Mixer Voltage Gain TA = +25°C TA = -40°C to +85°C (Note 1) 20 Downconverter Mixer Noise Figure 27 dB 14 dB (Note 2) -16 dBm Input Third-Order Intercept Two tones at 424MHz and 425MHz, -30dBm per tone -11 dBm Image Rejection fIMAGE = fLO + fIF = 446.4MHz Downconverter Mixer Input 1dB Compression Level 25 MIXOUT Maximum Voltage Swing Power-Up Time 34 dB 2 Vp-p Standby to RX or TX (Note 3) 5 LIMITING AMPLIFIER AND RSSI (RXEN = high) VGC = 0.8V (Note 4) 120 µs 160 Limiter Output Level VGC = open 475 950 Phase Variation VGC = 2.0V (PLIMIN = +5dBm) -75dBm to 5dBm from 50Ω 3.6 degrees Minimum Linear RSSI Range -75dBm to 5dBm from 50Ω 80 dB Minimum Monotonic RSSI Range -80dBm to 10dBm from 50Ω 90 dB RSSI Slope -75dBm to 5dBm from 50Ω 10.6 mV/dB RSSI Maximum Intercept (Note 5) -82 -75 TA = +25°C ±1 ±2 RSSI Relative Error 625 mVp-p 1100 TA = -40°C to +85°C (Note 1) ±2.5 dBm dB RSSI Rise Time Rise time to within 1dB accuracy; using a 100pF capacitor from RSSI to GND Minimum-Scale RSSI Voltage At LIMIN input of -75dBm 50 90 135 mV Maximum-Scale RSSI Voltage At LIMIN input of 5dBm 850 940 1025 mV OSCILLATOR (TXEN = RXEN = high) Frequency Range Phase Noise Maximum LO Frequency Pulling (Note 7) At 10kHz offset Standby mode to TX or RX mode 200 440 -88 ±36 MHz dBc/Hz kHz LO Leakage At RXIN port -65 dBm Oscillator Buffer Output Power Maximum Power-Up Time 6.4 TA = +25°C (Note 8) -12 TA = -40°C to +85°C (Notes 1 and 8) -13 Shutdown to standby mode (Note 9) -9 220 µs dBm µs _______________________________________________________________________________________ 3 MAX2511 AC ELECTRICAL CHARACTERISTICS MAX2511 Low-Voltage IF Transceiver with Limiter and RSSI AC ELECTRICAL CHARACTERISTICS (continued) (MAX2511 test fixture, VCC = +3.0V, RXEN = TXEN = low, 0.01µF across CZ and CZ, MIXOUT tied to VREF through 165Ω resistor, TXIN, TXIN tied to VREF through 50Ω resistor, TXOUT and TXOUT loaded with 100Ω differential, GC open, LIMOUT, LIMOUT loaded with 2kΩ differential, TANK and TANK driven with -2.5dBm from a 100Ω source; OSCOUT AC-terminated with 50Ω, 330pF at RSSI pin, 0.1µF at VREF pin, Rx inputs and Tx outputs differentially coupled, PRXIN, RXIN = -28dBm (200Ω system), fRXIN, RXIN = 425MHz, fLO = 435.7MHz, fTXIN, TXIN = 10.7MHz, TA = +25°C, unless otherwise noted.) PARAMETER CONDITIONS MIN TRANSMITTER (TXEN = high, VTXIN and VTXIN = 100mVp-p differential) VGC = 0.5V, TA = +25°C Output Power TYP MAX UNITS -44 VGC = open, TA = +25°C -19 VGC = 2.0V, TA = +25°C -5 VGC = 2.0V, TA = -40°C to +85°C (Note 1) -6 dBm -2 Image Rejection 34 25 dBc LO Rejection 40 30 dBc Output 1dB Compression Point VGC = 2.0V Output IM3 Level 0.5V < VGC < 1.87V -40dBm < POUT < -10dBm (Note 10) 2 -40 VGC = 2.0V -35 dBm dBc Note 1: Guaranteed by design and characterization. Note 2: Driving RXIN or RXIN with a power level greater than the 1dB compression level forces the input stage out of its linear range, causing harmonic and intermodulation distortion. The RSSI output increases monotonically with increasing input levels beyond the mixer’s 1dB compression level. Note 3: Assuming the supply voltage has been applied, this includes settling of the limiter offset correction and the Rx or Tx bias stabilization time. Guaranteed by design. Note 4: LIMOUT, LIMOUT loaded with 2kΩ differential. With no load, the output swing is approximately twice as large. Note 5: The RSSI maximum intercept is the maximum input power (over a statistical sample of parts) at which the RSSI output is 0V. This point is extrapolated from the linear portion of the RSSI voltage versus limiter input power. This specification and the RSSI slope define the ideal behavior of the RSSI function (the slope and intercept of a straight line), while the RSSI relative error specification defines the deviations from this line. See the RSSI Output Voltage vs. Limiter Input Power graph in the Typical Operating Characteristics. Note 6: The RSSI relative error is the deviation from the best-fitting straight line of RSSI output voltage versus limiter input power. A 0dB relative error is exactly on this line. The limiter input power range for this test is -75dBm to +5dBm from 50Ω. See the RSSI Relative Error graph in the Typical Operating Characteristics . Note 7: Operation outside this frequency range is possible but has not been characterized. At lower frequencies, it might be necessary to overdrive the oscillator with an external signal source. Note 8: If a larger output level is required, a higher value of load resistance (up to 100Ω) may be used. Note 9: This assumes that the supply voltage has been applied, and includes the settling time of VREF, using the Typical Operating Circuit. Note 10: Using two tones at 10.7MHz and 10.8MHz, 50mVp-p per tone at TXIN, TXIN. See Typical Operating Characteristics. 4 _______________________________________________________________________________________ Low-Voltage IF Transceiver with Limiter and RSSI (MAX2511 test fixture, VCC = +3.0V, 0.01µF across CZ and CZ, MIXOUT tied to VREF through 165Ω resistor, TXIN, TXIN tied to VREF through 50Ω resistor, TXOUT and TXOUT loaded with 100Ω differential, GC open, LIMOUT, LIMOUT loaded with 2kΩ differential, TANK and TANK driven with -2.5dBm from a 100Ω source; OSCOUT AC-terminated with 50Ω, 100pF at RSSI pin, 0.1µF at VREF pin, Rx inputs and Tx outputs differentially coupled, PRXIN, RXIN = -28dBm (200Ω system), fRXIN, RXIN = 425MHz, fLO = 435.7MHz, fTXIN, TXIN = 10.7MHz, TA = +25°C, unless otherwise noted.) SUPPLY CURRENT vs. SUPPLY VOLTAGE Tx MODE 40 45 30 20 Rx MODE 20 15 15 10 10 5 0 0 25 85 Tx MODE 35 30 STANDBY MODE STANDBY MODE 5 -40 40 25 25 Rx MODE 20 2.7 3.0 3.5 4.0 4.5 5.0 5.5 0 0.4 0.8 1.2 1.6 2.0 2.4 TEMPERATURE (°C) VCC (V) GC VOLTAGE (V) SHUTDOWN CURRENT vs. SUPPLY VOLTAGE DOWNCONVERTER MIXER CONVERSION GAIN vs. SUPPLY VOLTAGE DOWNCONVERTER GAIN vs. RXIN FREQUENCY TA = +85°C GAIN (dB) 1.5 TA = -40°C 23 1.0 TA = +25°C 22 TA = +85°C 21 RXEN = HIGH TXEN = LOW 24.5 VOLTAGE GAIN (dB) 2.0 24 25.0 MAX2511-TOC05 25 MAX2511 TOC04 2.5 2.8 3.2 MAX2511/TOC07A Rx MODE ICC (mA) 25 ICC (mA) ICC (mA) 30 ICC (µA) Tx MODE 35 50 MAX2511 TOC02 35 MAX2511 TOC01 40 SUPPLY CURRENT vs. GC VOLTAGE MAX2511 TOC03 SUPPLY CURRENT vs. TEMPERATURE 24.0 23.5 23.0 TA = +25°C 0.5 22.5 20 RXEN = HIGH TXEN = LOW TA = -40°C 0 2.7 3.0 3.5 4.0 4.5 SUPPLY VOLTAGE (V) 5.0 5.5 22.0 19 2.7 3.0 3.5 4.0 4.5 VCC (V) 5.0 5.5 200 275 350 425 RXIN FREQUENCY (MHz) _______________________________________________________________________________________ 5 MAX2511 __________________________________________Typical Operating Characteristics ____________________________Typical Operating Characteristics (continued) (MAX2511 test fixture, VCC = +3.0V, 0.01µF across CZ and CZ, MIXOUT tied to VREF through 165Ω resistor, TXIN, TXIN tied to VREF through 50Ω resistor, TXOUT and TXOUT loaded with 100Ω differential, GC open, LIMOUT, LIMOUT loaded with 2kΩ differential, TANK and TANK driven with -2.5dBm from a 100Ω source; OSCOUT AC-terminated with 50Ω, 100pF at RSSI pin, 0.1µF at VREF pin, Rx inputs and Tx outputs differentially coupled, PRXIN, RXIN = -28dBm (200Ω system), fRXIN, RXIN = 425MHz, fLO = 435.7MHz, fTXIN, TXIN = 10.7MHz, TA = +25°C, unless otherwise noted.) DOWNCONVERTER-MIXER IMAGE REJECTION vs. TEMPERATURE AND SUPPLY VOLTAGE 30 38 36 VCC = 5.5V 34 VCC = 2.7V 32 VCC = 3.0V 30 30 25 20 15 10 28 200 250 300 350 0 -40 400 425 -20 0 20 40 60 85 0 10 20 30 40 FREQUENCY (MHz) TEMPERATURE (°C) IF FREQUENCY (MHz) DOWNCONVERTER INPUT 1dB COMPRESSION LEVEL RXIN DIFFERENTIAL INPUT IMPEDANCE vs. FREQUENCY LIMITER OUTPUT LEVEL vs. GC VOLTAGE 50 TA = +25°C 40 TA = -40°C 30 20 TXEN = LOW RXEN = HIGH 10 0 150 100 50 0 RX MODE REAL -50 RX MODE IMAGINARY -100 -150 RX OFF IMAGINARY -250 2.7 3.0 3.5 4.0 4.5 VCC (V) 5.0 5.5 1.2 TA = -40°C TA = +25°C 1.0 TA = +85°C .8 .6 .4 .2 -200 200 300 400 FREQUENCY (MHz) 50 MAX2511-TOC11 RX OFF REAL 200 OUTPUT LEVEL (Vp-p) 60 250 MAX2511/TOC10 TA = +85°C REAL AND IMAGINARY IMPEDANCE (Ω) MAX2511-TOC09 70 6 5 26 25 TXEN = LOW RXEN = HIGH 35 IMAGE REJECTION (dB) 35 40 MAX2511 TOC0A2 MAX2511/TOC0A1 40 40 Rx IMAGE REJECTION (dBc) IMAGE REJECTION (dB) 45 DOWNCONVERTER IMAGE REJECTION vs. IF FREQUENCY MAX2511-TOC08 DOWNCONVERTER IMAGE REJECTION vs. RXIN FREQUENCY 1dB COMPRESSION LEVEL (mVrms) MAX2511 Low-Voltage IF Transceiver with Limiter and RSSI TXEN = LOW RXEN = HIGH 0 500 0 0.4 0.8 1.2 1.6 2.0 GC VOLTAGE (V) _______________________________________________________________________________________ 2.4 2.8 3.0 Low-Voltage IF Transceiver with Limiter and RSSI Tx OFF REAL -100 -200 -300 -400 Tx OFF IMAGINARY -500 -600 Tx MODE IMAGINARY -700 -800 -20 MAX2511-TOC16a Tx MODE REAL -30 -40 -50 -60 -70 -80 -90 -900 -100 -1000 0.8 1.2 1.6 2.0 2.7 200 MAX2511tocC -0.5 Tx POUT (dBm) VCC = 2.7V VCC = 5.5V -30 -2.0 -2.5 VCC = 5.5V -3.0 -3.5 -35 -40 VCC = 5.5V VCC = 2.7V VGC = 0.5V -50 -5.0 0 20 40 TEMPERATURE (°C) 1.6 2.0 2.4 2.8 35 30 25 20 15 10 -4.5 -20 1.2 -4.0 -45 -40 0.8 UPCONVERTER IMAGE REJECTION vs. IF FREQUENCY IMAGE REJECTION (dB) -1.5 -15 VGC = OPEN VCC = 2.7V -1.0 0.4 GC VOLTAGE (V) TRANSMITTER OUTPUT POWER vs. TEMPERATURE AND SUPPLY GC VOLTAGE (GC = 2V) VCC = 2.7V VCC = 5.5V 0 500 TRANSMITTER OUTPUT POWER vs. TEMPERATURE, SUPPLY, AND GC VOLTAGE -10 -25 400 FREQUENCY (MHz) VGC = 2V -20 300 GC VOLTAGE (V) 0 -5 2.4 MAX2511 TOC20 0.4 MAX2511TOCD 0 TX PORT (dBm) 0 INTERMODULATION POWER (dBm) 205MHz 260MHz 350MHz 430MHz 100 MAX2511 TOC21 MAX2511TOCB 5 0 -5 -10 -15 -20 -25 -30 -35 -40 -45 -50 -55 -60 -65 UPCONVERTER IM3 LEVELS vs. GC VOLTAGE (POWERS ARE PER TONE) TRANSMITTER DIFFERENTIAL OUTPUT IMPEDANCE vs. FREQUENCY REAL AND IMAGINARY IMPEDANCE Ω Tx POUT (dBm) TRANSMITTER OUTPUT POWER vs. GC VOLTAGE (FREQUENCY) 60 85 5 -40 -20 0 20 40 TEMPERATURE (°C) 60 85 0 10.7 20 30 40 50 IF FREQUENCY (MHz) _______________________________________________________________________________________ 7 MAX2511 ____________________________Typical Operating Characteristics (continued) (MAX2511 test fixture, VCC = +3.0V, 0.01µF across CZ and CZ, MIXOUT tied to VREF through 165Ω resistor, TXIN, TXIN tied to VREF through 50Ω resistor, TXOUT and TXOUT loaded with 100Ω differential, GC open, LIMOUT, LIMOUT loaded with 2kΩ differential, TANK and TANK driven with -2.5dBm from a 100Ω source; OSCOUT AC-terminated with 50Ω, 100pF at RSSI pin, 0.1µF at VREF pin, Rx inputs and Tx outputs differentially coupled, PRXIN, RXIN = -28dBm (200Ω system), fRXIN, RXIN = 425MHz, fLO = 435.7MHz, fTXIN, TXIN = 10.7MHz, TA = +25°C, unless otherwise noted.) ____________________________Typical Operating Characteristics (continued) (MAX2511 test fixture, VCC = +3.0V, 0.01µF across CZ and CZ, MIXOUT tied to VREF through 165Ω resistor, TXIN, TXIN tied to VREF through 50Ω resistor, TXOUT and TXOUT loaded with 100Ω differential, GC open, LIMOUT, LIMOUT loaded with 2kΩ differential, TANK and TANK driven with -2.5dBm from a 100Ω source; OSCOUT AC-terminated with 50Ω, 100pF at RSSI pin, 0.1µF at VREF pin, Rx inputs and Tx outputs differentially coupled, PRXIN, RXIN = -28dBm (200Ω system), fRXIN, RXIN = 425MHz, fLO = 435.7MHz, fTXIN, TXIN = 10.7MHz, TA = +25°C, unless otherwise noted.) RSSI RELATIVE ERROR vs. LIMIN INPUT AND TEMPERATURE RSSI OUTPUT VOLTAGE vs. LIMIN INPUT POWER AND TEMPERATURE 1 .9 4 RSSI ERROR (dB) .5 TA = +85°C .4 .3 2 1 0 -1 -2 TA = +25°C TA = +25°C TA = -40°C -3 .2 -4 TA = -40°C .1 -5 0 -120 -100 -80 -60 -40 -20 0 -90 -80 -70 -60 -50 -40 -30 -20 -10 0 10 20 20 PLIMIN (dBm, 50Ω) PLIMIN (dBm, 50Ω) TRANSMITTER IMAGE REJECTION vs. TEMPERATURE AND SUPPLY VOLTAGE MIXER INPUT-REFERRED RSSI VOLTAGE vs. RXIN INPUT POWER 1.1 MAX2511TOCE 40 38 VCC = 5.5V 1.0 0.9 RSSI VOLTAGE (V) VCC = 3.3V 36 34 32 VCC = 2.7V MAX2511-TOC15 RSSI OUTPUT (V) .6 TA = +85°C 3 .8 .7 MAX2511 TOC2514 5 MAX2511 TOC13 1.1 Tx IMAGE REJECTION (dBc) MAX2511 Low-Voltage IF Transceiver with Limiter and RSSI 0.8 0.7 0.6 0.5 0.4 30 0.3 28 0.2 26 -40 -20 0 20 40 TEMPERATURE (°C) 8 60 85 0.1 -120 -100 -80 -60 -40 -20 0 10 PRXIN (dBm, 50Ω) _______________________________________________________________________________________ Low-Voltage IF Transceiver with Limiter and RSSI PIN NAME FUNCTION 1 LIMIN Limiter Input. Connect a 330Ω (typ) resistor to VREF for DC bias, as shown in the Typical Operating Circuit. 2, 3 CZ, CZ Offset-Correction Capacitor pins. Connect a 0.01µF capacitor between CZ and CZ. 4 RSSI 5 GC Gain-Control pin in transmit mode. Applying a DC voltage to GC between 0V and 2.0V adjusts the transmitter gain by 40dB. In receive mode, GC adjusts the limiter output level from 0Vp-p to about 1Vp-p. This pin’s input impedance is typically 80kΩ terminated to 1.35V. 6, 9 TANK, TANK Tank pins. Connect the resonant tank across these pins, as shown in the Typical Operating Circuit. 7, 10 GND Ground. Connect GND to the PC board ground plane with minimal inductance. 8, 11 VCC Supply Voltage. Bypass VCC directly to GND. See the Layout Issues section. Receive-Signal-Strength-Indicator Output. The voltage on RSSI is proportional to the signal power at LIMIN. The RSSI output sources current pulses into an external capacitor (100pF typ). The output is internally terminated with 6kΩ, and this RC time constant sets the decay time. 12 OSCOUT Oscillator-Buffer Output. OSCOUT provides a buffered oscillator signal (at the oscillator frequency) for driving an external prescaler. This pin is a current output and must be AC-coupled to a resistive load. The output power is typically -9dBm into a 50Ω load. If a larger output swing is required, a larger load resistance (up to 100Ω) can be used. 13, 14 LIMOUT, LIMOUT Differential Outputs of the Limiting Amplifier. LIMOUT and LIMOUT are open-collector outputs that are internally pulled up to VCC through 1kΩ resistors. 15, 16 TXIN, TXIN Differential Inputs of the Image-Reject Upconverter Mixer. TXIN and TXIN are high impedance and must be pulled up to VCC through two external resistors whose value is equal to the desired terminating impedance (50Ω to 50kΩ). 17 RXEN Receiver-Enable pin. When high, RXEN enables the receiver if TXEN is low. If both RXEN and TXEN are high, the part is in standby mode; if both are low, the part is in shutdown. See the Power Management section for more details. 18 TXEN Transmitter-Enable pin. When high, TXEN enables the transmitter, if RXEN is low. If both TXEN and RXEN are high, the part is in standby mode; if both are low, the part is in shutdown. See the Power Management section for more details. 19, 21 VCC Bias VCC Supply pins. Decouple these pins to GND. See the Layout Issues section. 20 GND Receiver/Transmitter Ground pin. Connect to the PC board ground plane with minimal inductance. 22, 25 RXIN, RXIN 23, 24 TXOUT, TXOUT Differential Outputs of the Image-Reject Upconverter. TXOUT and TXOUT must be pulled up to VCC with two external inductors and AC coupled to the load. 26 GND Receiver Front-End Ground. Connect GND to the PC board ground plane with minimal inductance. 27 MIXOUT Single-Ended Output of the Image-Reject Downconverter. MIXOUT is high impedance and must be biased to the VREF pin through an external terminating resistor whose value depends on the interstage filter characteristics. See the Applications Information section for more details. 28 VREF Reference Voltage pin. VREF is used to provide an external bias voltage for the MIXOUT and LIMIN pins. Bypass this pin with a 0.1µF capacitor to ground. VREF voltage is equal to VCC / 2. See the Typical Operating Circuit for more information. Differential Inputs of the Image-Reject Downconverter Mixer. In most applications, an impedance matching network is required. See the Applications Information section for more details. _______________________________________________________________________________________ 9 MAX2511 ______________________________________________________________Pin Description MAX2511 Low-Voltage IF Transceiver with Limiter and RSSI IF BPF LIMIN VREF MIXOUT CZ CZ OFFSET CORRECTION RECEIVE IMAGE-REJECT MIXER 90° RXIN Σ RXIN LIMITER GM LIMOUT 0° LIMOUT VGA TANK RSSI 0° 90° TANK RSSI VREF = VCC / 2 LO PHASE SHIFTER OSCOUT RXEN BIAS TXEN TXIN PA TXOUT 0° VGA Σ TXIN TXOUT 90° TRANSMIT IMAGE-REJECT MIXER AND VGA/PA MAX2511 VOLTAGE GAIN AND BIAS CONTROL GC Figure 1. Functional Diagram _______________Detailed Description The following sections describe each of the blocks shown in Figure 1. Receiver The receiver consists of two basic blocks: the imagereject downconverter mixer and the limiter/RSSI section. The receiver inputs are the RXIN, RXIN pins, which should be AC coupled and may require a matching network, as shown in the Typical Operating Circuit. To design a matching network for a particular application, refer to the Applications Information section and the receiver input impedance plots in the Typical Operating Characteristics. 10 Image-Reject Mixer The downconverter is implemented using an imagereject mixer consisting of an input buffer with dual outputs, each of which is fed to a double-balanced mixer. The LO signal is generated by an on-chip oscillator and an external tank circuit. The buffered oscillator signal drives a quadrature phase generator that provides two outputs with 90° of phase shift between them. This pair of LO signals is fed to the two receive mixers. The mixer’s outputs are then passed through a pair of phase shifters, which provide 90° of phase shift across their outputs. The resulting two signals are then summed together. The final phase relationship is such that the desired signal is reinforced, and the image signal is largely canceled. The downconverter mixer’s ______________________________________________________________________________________ Low-Voltage IF Transceiver with Limiter and RSSI Limiter The signal passes through an external IF bandpass filter into the limiter input (LIMIN). LIMIN is a singleended input that is centered around the VREF pin voltage. Open-circuit input impedance is typically greater than 10kΩ terminated to VREF. For proper operation, LIMIN must be tied to VREF through the filter terminating impedance (not more than 1kΩ). The limiter provides a constant output level, which is largely independent of the limiter input-signal level over an 80dB input range. The adjustable output level allows easy interfacing of the limiter output to the downstream circuitry. The limiter’s output drives a variable-gain amplifier that adjusts the limited output level from 0Vp-p to typically 1Vp-p as the GC pin voltage is adjusted from 0.5V to 2.0V. Using this feature allows the downstream circuitry, such as an analog-to-digital converter (ADC), to run at optimum performance by steering the limiter’s output level to match the desired ADC input level. GC is also used for transmit (Tx) gain adjustment in Tx mode, so be sure to keep the voltage at an appropriate value for each mode. to less than -40dBm by controlling the GC pin. For output levels between -10dBm and -40dBm, -40dBc IM3 levels are maintained. The resulting signal appears as a differential output on TXOUT and TXOUT, which expect a 100Ω differential load impedance. TXOUT and TXOUT are open-collector outputs and need external pull-up inductors to VCC for proper operation. They also need a DC block so the load does not affect DC biasing. A shunt resistor across TXOUT, TXOUT can be used to back-terminate an external filter, as shown in the Typical Operating Circuit. It is possible to use the receiver inputs RXIN and RXIN to provide this termination, as described in the Filter Sharing section. For single-ended operation, tie the unused input to VCC. Local Oscillator and Oscillator Buffer The on-chip LO requires only an external LC tank circuit for operation. The tank circuit is connected across TANK and TANK. A dual varactor diode is typically used to adjust the frequency in a phase-locked loop (PLL). See the Applications Information section for the tank circuit design equations. Keep the resonator’s Q as high VCC Received-Signal-Strength Indicator The RSSI output provides a linear indication of the received power level on the LIMIN input. The RSSI monotonic dynamic range exceeds 90dB while providing better than 80dB linear range. The RSSI output pulses current into an external filter capacitor (typically 100pF). The output is internally terminated with 6kΩ to GND, and this R-C time constant sets the decay time. Transmitter The image-reject upconverter mixer operates in a fashion similar to the downconverter mixer. The transmit mixer consists of an input buffer amplifier that drives on-chip IF phase shifters. The shifted signals are then input to a pair of double-balanced mixers, which are driven with the same quadrature (Q) LO source used by the receiver. The mixer outputs are summed together, largely canceling the image signal component. The image-canceled signal from the mixer outputs is fed through a variable-gain amplifier (VGA) with 40dB of gain-adjust range. The VGA output is connected to a driver amplifier with an output 1dB compression point of 2dBm. The output power can be adjusted from approximately 2dBm VBIAS Figure 2. Simplified Oscillator Equivalent Circuit ______________________________________________________________________________________ 11 MAX2511 output is buffered and converted to a single-ended current output at the MIXOUT pin, which can drive a shuntterminated bandpass filter over a large dynamic range. MIXOUT can drive a shunt-terminated 330Ω filter (165Ω load) to more than 2Vp-p over the entire supply range. MAX2511 Low-Voltage IF Transceiver with Limiter and RSSI as possible for lowest phase noise. The tank’s PC board layout is also critical to good performance (consult the Layout Issues section for more information). The OSCOUT pin buffers the internal oscillator signal for driving an external PLL. This output should be AC coupled and terminated at the far end (typically the input to a prescaler) with a 50Ω load. If a larger output level is desired, you can use a resistive termination up to 100Ω. When a controlled-impedance PC board is used, this trace’s impedance should match the termination impedance. Power Management The MAX2511 features four power-supply modes to preserve battery life. These modes are selected via the RXEN and TXEN pins, according to Table 1. In shutdown mode, all part functions are off. In standby mode, the LO and the LO buffer are active. This allows a PLL (implemented externally to the MAX2511) to remain up and running, avoiding any delay resulting from PLL loop settling. Transmit (Tx) mode enables the LO circuitry, upconverter mixer, transmit VGA, and output driver amplifier. Receive (Rx) mode enables the LO circuitry, downconverter mixer, limiting amplifier, and adjustable output level amplifier. Table 1. Power-Supply Mode Selection RXEN STATE TXEN STATE MODE Low Low Shutdown Transmit Low High High Low Receive High High Standby __________Applications Information 400MHz ISM Applications The MAX2511 can be used in applications where the 200MHz to 440MHz signal is an RF (rather than an IF) signal, such as in 400MHz ISM applications. In this case, we recommend preceding the MAX2511 receiver section with a low-noise amplifier (LNA) that can operate over the same supply-voltage range. The MAX2630–MAX2633 family of amplifiers meets this requirement. But since these parts have single-ended inputs and outputs, it is necessary to AC terminate the unused MAX2511 input (RXIN) to ground with 47nF. 12 Oscillator Tank The on-chip oscillator circuit requires a parallel resonant tank circuit connected across TANK and TANK. Figure 3 shows an example of an oscillator tank circuit. Inductor L1 is resonated with the effective total capacitance of C1 in parallel with the series combination of C2, C3, and (CD1) / 2. CD1 is the capacitance of one of the varactor diodes. Typically, C2 = C3 to maintain symmetry. The effective parasitic capacitance, CP (including PCB parasitics), is approximately 3.5pF. The total capacitance is given by the following equation: CEFF = 1 + C1 + CP 2 2 + C2 CD1 Using this value for the resonant tank circuit, the oscillation frequency is as follows: 1 FOSC = L1CEFF 2πEquation.2 EMBED Starting with the inductor recommended in Table 2, choose the component values according to your application needs, such as phase noise, tuning range, and VCO gain. Keep the tank’s Q as high as possible to reduce phase noise. For most of the MAX2511’s applications (such as a first IF to second IF transceiver), the oscillator’s tuning range can be quite small, since the IF frequencies are not tuned for channel selection. This allows a narrowband oscillator tank to be used, which typically provides better phase noise and stability performance than wideband tank circuits. Careful PC board layout of the oscillator tank is essential. See the Layout Issues section for more information. To overdrive the oscillator from an external 50Ω source, see Figure 4. Rx Input Impedance Matching The RXIN, RXIN port typically needs an impedancematching network for proper connection to external circuitry such as a filter. See the Typical Operating Circuit for an example circuit topology. A shunt resistor across RXIN, RXIN can be used to set terminating impedance, with a slight degradation of the Noise Figure. The component values used in the matching network depend on the desired operating frequency as well as the filter impedance. Table 3 indicates the RXIN, RXIN differential input impedance in both series and parallel form. This data is also plotted in the Typical Operating Characteristics. ______________________________________________________________________________________ Low-Voltage IF Transceiver with Limiter and RSSI Receive IF Filter The interstage 10.7MHz filter, located between the MIXOUT pin and the LIMIN pin, is not shared. This filter prevents the limiter from acting on any undesired signals that are present at the mixer’s output, such as LO feedthrough, out-of-band channel leakage, and other mixer products. This filter is also set up to pass DC bias voltage from the the V REF pin into the LIMIN and MIXOUT pins through two filter-termination resistors (330Ω—see the Typical Operating Circuit for more information). If the filter can provide a DC shunt path, such as a transformer-capacitor based filter or some L-C filters, the two resistors can be combined into one parallel, equivalent resistor (165Ω) to reduce component count (Figure 5—inset). ______________________Layout Issues A well-designed PC board is an essential part of an RF circuit. For best performance, pay attention to powersupply issues, as well as the layout of the matching networks and tank circuit. Power-Supply Layout For minimizing coupling between different sections of the chip, the ideal power-supply layout is a star configuration, which has a heavily decoupled central VCC node. The VCC traces branch out from this node, each going to one VCC node on the MAX2511. At the end of each of these traces is a bypass capacitor that is good at the RF frequency of interest. This arrangement provides local decoupling at each VCC pin. At high frequency, any signal leaking from a supply pin sees a relatively high impedance (formed by the VCC trace impedance) to the central VCC node, and an even higher impedance to any other supply pin. Place the VREF decoupling capacitor (0.1µF typ) as close to the MAX2511 as possible for best interstage filter performance. Use a high-quality, low-ESR capacitor for best results. Matching Network Layout The TXOUT, TXOUT port requires a bias network that consists of two inductors to VCC (for differential drive) and optionally a back-termination resistor for matching to an external filter. The RXIN, RXIN port also needs an impedance-matching network. Both networks should be symmetrical and as close to the chip as possible. See the Typical Operating Circuit for more details. If you use a ground-plane PC board, cut out the ground plane under the matching network components to reduce parasitic capacitance. Local-Oscillator Tank Layout Oscillator-tank circuit layout is critical. Parasitic PC board capacitance, as well as trace inductance, can affect oscillation frequency. Keep the tank layout symmetrical, tightly packed, and as close to the device as possible. If a ground-plane PC board is used, the ground plane should be cut out under the oscillator components to reduce parasitic capacitance. ______________________________________________________________________________________ 13 MAX2511 Filter Sharing In half-duplex or TDD applications, the number of external filters can be minimized by combining transmit and receive filter paths (Figure 5). The 10.7MHz filter that is usually connected to the TXIN, TXIN ports can be the same filter that is connected at LIMOUT and LIMOUT. To use the same filter, connect TXIN to LIMOUT, and TXIN to LIMOUT. The 425MHz SAW filter needed at the RXIN, RXIN ports and the filter needed at TXOUT and TXOUT can be shared in a similar manner. The RXIN, RXIN ports must be DC blocked to prevent the bias voltage needed by the TXOUT and TXOUT pins from entering the receiver. When sharing filters in this manner, the transmitter output port (TXOUT, TXOUT) and receiver input port (RXIN, RXIN) matching networks must be modified. The receiver port’s input impedance must be the parallel combination of the receiver and transmitter ports in Rx mode. In this case, the receiver port is active, but the transmitter port adds an additional parasitic impedance. See the transmitter and receiver-port impedance graphs in the Typical Operating Characteristics. When the part is in transmit mode, the RXIN and RXIN inputs provide back termination for the TXOUT and TXOUT outputs so that a single IF filter can be connected (Figure 5). With this technique, the matching network can be adjusted so the input VSWR is less than 1.5:1 in Rx mode, and the output VSWR is less than 2:1 in Tx mode. MAX2511 Low-Voltage IF Transceiver with Limiter and RSSI 10k TANK C2 10k CP L1 VCO VOLTAGE FROM PLL C1 C3 TANK 10k C2 = C3 Figure 3. Oscillator Tank Schematic TANK MINI CIRCUITS TC4-1Ω 50Ω SIGNAL SOURCE R = 200Ω CP TANK ADJUST R FOR BEST RETURN LOSS AT SIGNAL SOURCE Figure 4. Overdriving the On-Chip Oscillator Table 2. Recommended Values for L1 14 fLO (MHz) L1 (µH) 200 to 300 18 300 to 400 12 400 to 500 8.2 Table 3. Rx Input Impedance FREQUENCY (MHz) SERIES IMPEDANCE (Ω) EQUIVALENT PARALLEL IMPEDANCE R (Ω) C (pF) 100 274-j226 460 2.85 200 131-j186 395 2.86 300 79-j138 320 2.9 400 58-j105 248 2.9 500 48-j82 188 2.9 600 43-j62 132 2.9 ______________________________________________________________________________________ Low-Voltage IF Transceiver with Limiter and RSSI MAX2511 ONE PORT FILTER (LC OR TRANSFORMER-C) TWO-PORT FILTER 10.7 MHz BPF 165Ω 0.1µF 330Ω MIXOUT VREF 330Ω LIMIN 0.1µF MIXOUT LIMIN RXIN ROPT VCC LIMOUT RX MIXER VREF LIMITER LIMOUT VCC RXIN LMATCH LMATCH CBLOCK CBLOCK MAX2511 TXOUT TXIN CMATCH TXOUT 10.7MHz BPF TX MIXER TXIN 425MHz BPF CMATCH CONTROL GC Figure 5. Filter Sharing ______________________________________________________________________________________ 15 MAX2511 Low-Voltage IF Transceiver with Limiter and RSSI ___________________________________________________Typical Operating Circuit VCC VCC 47nF LCHOKE 47nF LCHOKE 24 1k TXOUT TXIN CBLOCK Tx OUTPUT TXIN R* 23 LIMOUT TXOUT LIMOUT CBLOCK 25 RXIN RXEN CMATCH Rx INPUT LMATCH TXEN CMATCH MAX2511 22 1k 10.7MHz Tx 0.1µF 15 INPUT 0.1µF 13 10.7MHz Rx 0.1µF 14 IF OUTPUT 18 CONTROL LOGIC 17 VCC VCC 8 GND 7 TANK 6 RXIN VCC 47nF VCC 20 21 47nF VCC 6.8pF 10kΩ D1 8.2nH 20 GND TANK 4 5 FOSC = 435.7MHz VCC 47nF 100pF 0.1µF 16 10kΩ 12pF VCO ADJUST FROM PLL 10kΩ 9 6.8 pF RSSI 470pF OSCOUT GC 12 TO PRESCALER VCC 26 0.01µF* 27 VCC GND GND MIXOUT LIMIN 10.7MHz BPF, Z0 = 330Ω 1 330Ω 330Ω 0.1µF CZ VREF CZ 28 11 10 D1 = ALPHA SMV1204-199 47nF 3 2 0.01µF GAIN CONTROL VOLTAGE RSSI OUTPUT *OPTIONAL 16 ______________________________________________________________________________________