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19-1209; Rev 0; 10/97
KIT ATION EVALU LE B AVAILA
Low-Voltage IF Transceiver with Limiter and RSSI
____________________________Features
o Single +2.7V to +5.5V Supply o Complete Receive Path: 200MHz to 440MHz (first IF) to 8MHz to 13MHz (second IF) o Limiter with Differential Outputs (adjustable level) o RSSI Function with 90dB Monotonic Dynamic Range o Complete Transmit Path: 8MHz to 13MHz (second IF) to 200MHz to 440MHz (first IF) o On-Chip Oscillator with Voltage Regulator and Buffer o Advanced System Power Management (four modes) o 0.1A Shutdown Supply Current
_______________General Description
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 0.1A 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.
MAX2511
______________Ordering Information
PART MAX2511EEI TEMP. RANGE -40C to +85C PIN-PACKAGE 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
LIMIN CZ CZ RSSI GC TANK GND VCC TANK
1 2 3 4 5 6 7 8 9
28 VREF 27 MIXOUT 26 GND 25 RXIN TXOUT TXOUT
MAX2511
24 23
22 RXIN 21 VCC 20 GND 19 18 17 16 15 VCC TXEN RXEN TXIN TXIN
GND 10 VCC 11 OSCOUT 12 LIMOUT 13
Typical Operating Circuit appears at end of data sheet.
LIMOUT 14
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.
Low-Voltage IF Transceiver with Limiter and RSSI MAX2511
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 = +70C) QSOP (derate 11mW/C above 70C) ...........................909mW Operating Temperature Range MAX2511EEI ......................................................-40C to +85C Junction Temperature ......................................................+150C Storage Temperature Range .............................-65C to +165C Lead Temperature (soldering, 10sec) .............................+300C
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, 0.01F across CZ and CZ; TANK = TANK; MIXOUT tied to VREF through a 165 resistor; GC open, RXIN = RXIN; TXOUT = TXOUT = VCC; TA = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C.) PARAMETER Operating Voltage Range Digital Input Voltage High Digital Input Voltage Low Digital Input Current High Digital Input Current Low Rx mode, RXEN = high, TXEN = low VCC = 3.0V TA = +25C Tx mode, RXEN = low, TXEN = high, VGC = 0.5V Standby mode, RXEN = high, TXEN = high Shutdown mode, RXEN = low, TXEN = low Rx mode, RXEN = high, TXEN = low VCC = 2.7V to 5.5V, TA = -40C to +85C Tx mode, RXEN = low, TXEN = high, VGC = 0.5V Standby mode, RXEN = high, TXEN = high Shutdown mode, RXEN = low, TXEN = low VREF Voltage LIMOUT, LIMOUT Differential Output Impedance GC Input Resistance Internally terminated to 1.35V 60 (Note 1) -5 RXEN, TXEN RXEN, TXEN 23 -1 24 26 9.5 0.1 38.5 45 14.5 5 VCC / 2 - VCC / 2 VCC / 2 + 100mV 100mV 2 80 125 A V k k mA A mA CONDITIONS MIN 2.7 2.0 0.4 32 TYP 3.0 MAX 5.5 UNITS V V V A A
Typical Supply Current
Worst-Case Supply Current
2
_______________________________________________________________________________________
Low-Voltage IF Transceiver with Limiter and RSSI MAX2511
AC ELECTRICAL CHARACTERISTICS
(MAX2511 test fixture, VCC = +3.0V, RXEN = TXEN = low, 0.01F across CZ and CZ, MIXOUT tied to VREF through 165 resistor, TXIN, TXIN tied to VREF through 50 resistor, TXOUT and TXOUT loaded with 100 differential, GC open, LIMOUT, LIMOUT loaded with 2k differential, TANK and TANK driven with -2.5dBm from a 100 source; OSCOUT AC-terminated with 50, 330pF at RSSI pin, 0.1F at VREF pin, Rx inputs and Tx outputs differentially coupled, PRXIN, RXIN = -28dBm (200 system), fRXIN, RXIN = 425MHz, fLO = 435.7MHz, fTXIN, TXIN = 10.7MHz, TA = +25C, unless otherwise noted.) PARAMETER DOWNCONVERTER (RXEN = high) Downconverter Mixer Voltage Gain Downconverter Mixer Noise Figure Downconverter Mixer Input 1dB Compression Level Input Third-Order Intercept Image Rejection MIXOUT Maximum Voltage Swing Power-Up Time Standby to RX or TX (Note 3) 120 475 950 1100 3.6 80 90 10.6 -82 1 -75 2 2.5 6.4 50 850 200 -88 36 -65 -12 -13 220 -9 90 940 135 1025 440 degrees dB dB mV/dB dBm dB s mV mV MHz dBc/Hz kHz dBm dBm s LIMITING AMPLIFIER AND RSSI (RXEN = high) VGC = 0.8V (Note 4) Limiter Output Level Phase Variation Minimum Linear RSSI Range Minimum Monotonic RSSI Range RSSI Slope RSSI Maximum Intercept RSSI Relative Error RSSI Rise Time Minimum-Scale RSSI Voltage Maximum-Scale RSSI Voltage OSCILLATOR (TXEN = RXEN = high) Frequency Range Phase Noise Maximum LO Frequency Pulling LO Leakage Oscillator Buffer Output Power Maximum Power-Up Time VGC = open VGC = 2.0V (PLIMIN = +5dBm) -75dBm to 5dBm from 50 -75dBm to 5dBm from 50 -80dBm to 10dBm from 50 -75dBm to 5dBm from 50 (Note 5) TA = +25C TA = -40C to +85C (Note 1) Rise time to within 1dB accuracy; using a 100pF capacitor from RSSI to GND At LIMIN input of -75dBm At LIMIN input of 5dBm (Note 7) At 10kHz offset Standby mode to TX or RX mode At RXIN port TA = +25C (Note 8) TA = -40C to +85C (Notes 1 and 8) Shutdown to standby mode (Note 9) (Note 2) Two tones at 424MHz and 425MHz, -30dBm per tone fIMAGE = fLO + fIF = 446.4MHz 25 TA = +25C TA = -40C to +85C (Note 1) 21.5 20 14 -16 -11 34 2 5 160 625 mVp-p 23.6 25.5 27 dB dB dBm dBm dB Vp-p s CONDITIONS MIN TYP MAX UNITS
_______________________________________________________________________________________
3
Low-Voltage IF Transceiver with Limiter and RSSI MAX2511
AC ELECTRICAL CHARACTERISTICS (continued)
(MAX2511 test fixture, VCC = +3.0V, RXEN = TXEN = low, 0.01F across CZ and CZ, MIXOUT tied to VREF through 165 resistor, TXIN, TXIN tied to VREF through 50 resistor, TXOUT and TXOUT loaded with 100 differential, GC open, LIMOUT, LIMOUT loaded with 2k differential, TANK and TANK driven with -2.5dBm from a 100 source; OSCOUT AC-terminated with 50, 330pF at RSSI pin, 0.1F at VREF pin, Rx inputs and Tx outputs differentially coupled, PRXIN, RXIN = -28dBm (200 system), fRXIN, RXIN = 425MHz, fLO = 435.7MHz, fTXIN, TXIN = 10.7MHz, TA = +25C, unless otherwise noted.) PARAMETER CONDITIONS MIN TYP -44 -19 -5 -6 34 40 VGC = 2.0V 0.5V < VGC < 1.87V -40dBm < POUT < -10dBm (Note 10) VGC = 2.0V 2 -40 -35 25 30 dBc dBc dBm dBc -2 dBm MAX UNITS
TRANSMITTER (TXEN = high, VTXIN and VTXIN = 100mVp-p differential) VGC = 0.5V, TA = +25C Output Power VGC = open, TA = +25C VGC = 2.0V, TA = +25C VGC = 2.0V, TA = -40C to +85C (Note 1) Image Rejection LO Rejection Output 1dB Compression Point Output IM3 Level
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 2k 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 50. 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 100) 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
__________________________________________Typical Operating Characteristics
(MAX2511 test fixture, VCC = +3.0V, 0.01F across CZ and CZ, MIXOUT tied to VREF through 165 resistor, TXIN, TXIN tied to VREF through 50 resistor, TXOUT and TXOUT loaded with 100 differential, GC open, LIMOUT, LIMOUT loaded with 2k differential, TANK and TANK driven with -2.5dBm from a 100 source; OSCOUT AC-terminated with 50, 100pF at RSSI pin, 0.1F at VREF pin, Rx inputs and Tx outputs differentially coupled, PRXIN, RXIN = -28dBm (200 system), fRXIN, RXIN = 425MHz, fLO = 435.7MHz, fTXIN, TXIN = 10.7MHz, TA = +25C, unless otherwise noted.)
MAX2511
SUPPLY CURRENT vs. TEMPERATURE
MAX2511 TOC01
SUPPLY CURRENT vs. SUPPLY VOLTAGE
MAX2511 TOC02
SUPPLY CURRENT vs. GC VOLTAGE
MAX2511 TOC03
40 35 Tx MODE 30
40 35 30
ICC (mA)
50 45 40 ICC (mA) Tx MODE
Tx MODE
ICC (mA)
25 Rx MODE 20 15 10 STANDBY MODE 5 0 -40 25 TEMPERATURE (C) 85
25 20 15 10 STANDBY MODE 5 0 2.7 3.0 3.5
Rx MODE
35 30 25 20
Rx MODE 0 0.4 0.8 1.2 1.6 2.0 2.4 2.8 3.2
4.0 VCC (V)
4.5
5.0
5.5
GC VOLTAGE (V)
SHUTDOWN CURRENT vs. SUPPLY VOLTAGE
MAX2511 TOC04
2.0 TA = +85C
24 23 GAIN (dB)
24.5 VOLTAGE GAIN (dB) 24.0 23.5 23.0 22.5
RXEN = HIGH TXEN = LOW
TA = -40C
ICC (A)
1.5
TA = +25C 22 TA = +85C 21
1.0 TA = +25C
0.5 TA = -40C 0 2.7 3.0 3.5 4.0 4.5
20 19 2.7 3.0 3.5 4.0 4.5 VCC (V)
RXEN = HIGH TXEN = LOW 5.0 5.5
22.0 200 275 350 425 RXIN FREQUENCY (MHz)
5.0
5.5
SUPPLY VOLTAGE (V)
_______________________________________________________________________________________
MAX2511/TOC07A
MAX2511-TOC05
2.5
DOWNCONVERTER MIXER CONVERSION GAIN vs. SUPPLY VOLTAGE
25
DOWNCONVERTER GAIN vs. RXIN FREQUENCY
25.0
5
Low-Voltage IF Transceiver with Limiter and RSSI MAX2511
____________________________Typical Operating Characteristics (continued)
(MAX2511 test fixture, VCC = +3.0V, 0.01F across CZ and CZ, MIXOUT tied to VREF through 165 resistor, TXIN, TXIN tied to VREF through 50 resistor, TXOUT and TXOUT loaded with 100 differential, GC open, LIMOUT, LIMOUT loaded with 2k differential, TANK and TANK driven with -2.5dBm from a 100 source; OSCOUT AC-terminated with 50, 100pF at RSSI pin, 0.1F at VREF pin, Rx inputs and Tx outputs differentially coupled, PRXIN, RXIN = -28dBm (200 system), fRXIN, RXIN = 425MHz, fLO = 435.7MHz, fTXIN, TXIN = 10.7MHz, TA = +25C, unless otherwise noted.)
DOWNCONVERTER IMAGE REJECTION vs. RXIN FREQUENCY
MAX2511/TOC0A1
DOWNCONVERTER-MIXER IMAGE REJECTION vs. TEMPERATURE AND SUPPLY VOLTAGE
MAX2511 TOC0A2
DOWNCONVERTER IMAGE REJECTION vs. IF FREQUENCY
35 IMAGE REJECTION (dB) 30 25 20 15 10 5 0 TXEN = LOW RXEN = HIGH
MAX2511-TOC08
45
40 38 Rx IMAGE REJECTION (dBc) 36 34 32 30 28 VCC = 3.0V VCC = 5.5V VCC = 2.7V
40
IMAGE REJECTION (dB)
40
35
30
25 200 250 300 350 400 425 FREQUENCY (MHz)
26 -40 -20 0 20 40 60 85 TEMPERATURE (C)
0
10
20
30
40
50
IF FREQUENCY (MHz)
DOWNCONVERTER INPUT 1dB COMPRESSION LEVEL
MAX2511-TOC09
RXIN DIFFERENTIAL INPUT IMPEDANCE vs. FREQUENCY
MAX2511/TOC10
LIMITER OUTPUT LEVEL vs. GC VOLTAGE
TA = -40C TA = +25C TA = +85C
MAX2511-TOC11
70 TA = +85C 1dB COMPRESSION LEVEL (mVrms) 60 50 40 TA = -40C 30 20 10 0 2.7 3.0 3.5 4.0 4.5 VCC (V) 5.0 5.5 TXEN = LOW RXEN = HIGH TA = +25C
250 REAL AND IMAGINARY IMPEDANCE () 200 150 100 50 0 -50 -100 -150 -200 -250 200 300 RX OFF IMAGINARY 400 RX MODE IMAGINARY RX MODE REAL RX OFF REAL
1.2 1.0 OUTPUT LEVEL (Vp-p) .8 .6 .4 .2 0
TXEN = LOW RXEN = HIGH 0 0.4 0.8 1.2 1.6 2.0 2.4 2.8 3.0
500
FREQUENCY (MHz)
GC VOLTAGE (V)
6
_______________________________________________________________________________________
Low-Voltage IF Transceiver with Limiter and RSSI
____________________________Typical Operating Characteristics (continued)
(MAX2511 test fixture, VCC = +3.0V, 0.01F across CZ and CZ, MIXOUT tied to VREF through 165 resistor, TXIN, TXIN tied to VREF through 50 resistor, TXOUT and TXOUT loaded with 100 differential, GC open, LIMOUT, LIMOUT loaded with 2k differential, TANK and TANK driven with -2.5dBm from a 100 source; OSCOUT AC-terminated with 50, 100pF at RSSI pin, 0.1F at VREF pin, Rx inputs and Tx outputs differentially coupled, PRXIN, RXIN = -28dBm (200 system), fRXIN, RXIN = 425MHz, fLO = 435.7MHz, fTXIN, TXIN = 10.7MHz, TA = +25C, unless otherwise noted.)
TRANSMITTER OUTPUT POWER vs. GC VOLTAGE (FREQUENCY)
5 0 -5 -10 -15 -20 -25 -30 -35 -40 -45 -50 -55 -60 -65 0 0.4 0.8 1.2
MAX2511TOCB
MAX2511
TRANSMITTER DIFFERENTIAL OUTPUT IMPEDANCE vs. FREQUENCY
REAL AND IMAGINARY IMPEDANCE 0 -100 -200 -300 -400 -500 -600 -700 -800 -900 -1000
-100
UPCONVERTER IM3 LEVELS vs. GC VOLTAGE (POWERS ARE PER TONE)
MAX2511 TOC21
Tx MODE REAL Tx OFF REAL
INTERMODULATION POWER (dBm)
-30 -40 -50 -60 -70 -80 -90 0 0.4 0.8 1.2 1.6 2.0 2.4 2.8
Tx POUT (dBm)
205MHz 260MHz 350MHz 430MHz
Tx OFF IMAGINARY Tx MODE IMAGINARY
1.6
2.0
2.4
2.7
200
300
400
500
GC VOLTAGE (V)
FREQUENCY (MHz)
GC VOLTAGE (V)
TRANSMITTER OUTPUT POWER vs. TEMPERATURE, SUPPLY, AND GC VOLTAGE
MAX2511tocC
TRANSMITTER OUTPUT POWER vs. TEMPERATURE AND SUPPLY GC VOLTAGE (GC = 2V)
-1.0 -1.5 Tx POUT (dBm) -2.0 -2.5 -3.0 -3.5 VCC = 5.5V VCC = 2.7V
MAX2511TOCD
UPCONVERTER IMAGE REJECTION vs. IF FREQUENCY
MAX2511 TOC20
0 -5 -10 TX PORT (dBm) -15 -20 -25 -30 -35 -40 -45 -50 -40 -20 0 20 40 60 VGC = 0.5V VCC = 5.5V VCC = 2.7V VGC = OPEN VCC = 2.7V VCC = 5.5V VGC = 2V VCC = 2.7V VCC = 5.5V
-0.5
35 30 IMAGE REJECTION (dB) 25 20 15 10 5
-4.0 -4.5 -5.0 85 -40 -20 0 20 40 60 85
0
10.7
20
30
40
50
TEMPERATURE (C)
TEMPERATURE (C)
IF FREQUENCY (MHz)
_______________________________________________________________________________________
MAX2511-TOC16a
100
-20
7
Low-Voltage IF Transceiver with Limiter and RSSI MAX2511
____________________________Typical Operating Characteristics (continued)
(MAX2511 test fixture, VCC = +3.0V, 0.01F across CZ and CZ, MIXOUT tied to VREF through 165 resistor, TXIN, TXIN tied to VREF through 50 resistor, TXOUT and TXOUT loaded with 100 differential, GC open, LIMOUT, LIMOUT loaded with 2k differential, TANK and TANK driven with -2.5dBm from a 100 source; OSCOUT AC-terminated with 50, 100pF at RSSI pin, 0.1F at VREF pin, Rx inputs and Tx outputs differentially coupled, PRXIN, RXIN = -28dBm (200 system), fRXIN, RXIN = 425MHz, fLO = 435.7MHz, fTXIN, TXIN = 10.7MHz, TA = +25C, unless otherwise noted.)
RSSI OUTPUT VOLTAGE vs. LIMIN INPUT POWER AND TEMPERATURE
1 .9 .8 RSSI OUTPUT (V) .7 .6 .5 .4 .3 .2 .1 0 -120 -100 -80 -60 -40 -20 0 20 PLIMIN (dBm, 50) TA = -40C TA = +85C TA = +25C RSSI ERROR (dB)
MAX2511 TOC13
RSSI RELATIVE ERROR vs. LIMIN INPUT AND TEMPERATURE
4 3 2 1 0 -1 -2 -3 -4 -5 -90 -80 -70 -60 -50 -40 -30 -20 -10 0 10 20 PLIMIN (dBm, 50) TA = +25C TA = -40C
MAX2511 TOC2514
1.1
5 TA = +85C
TRANSMITTER IMAGE REJECTION vs. TEMPERATURE AND SUPPLY VOLTAGE
MAX2511TOCE
MIXER INPUT-REFERRED RSSI VOLTAGE vs. RXIN INPUT POWER
1.0 0.9 RSSI VOLTAGE (V) 0.8 0.7 0.6 0.5 0.4 0.3
MAX2511-TOC15
40 38 Tx IMAGE REJECTION (dBc) VCC = 5.5V 36 34 32 30 28 26 -40 -20 0 20 40 60 VCC = 2.7V VCC = 3.3V
1.1
0.2 85 0.1 -120 -100 -80 -60 -40 -20 0 10
TEMPERATURE (C)
PRXIN (dBm, 50)
8
_______________________________________________________________________________________
Low-Voltage IF Transceiver with Limiter and RSSI
______________________________________________________________Pin Description
PIN 1 2, 3 4 NAME LIMIN CZ, CZ RSSI FUNCTION Limiter Input. Connect a 330 (typ) resistor to VREF for DC bias, as shown in the Typical Operating Circuit. Offset-Correction Capacitor pins. Connect a 0.01F capacitor between CZ and CZ. 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 6k, and this RC time constant sets the decay time. 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 80k terminated to 1.35V. Tank pins. Connect the resonant tank across these pins, as shown in the Typical Operating Circuit. Ground. Connect GND to the PC board ground plane with minimal inductance. Supply Voltage. Bypass VCC directly to GND. See the Layout Issues section. 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 50 load. If a larger output swing is required, a larger load resistance (up to 100) can be used. Differential Outputs of the Limiting Amplifier. LIMOUT and LIMOUT are open-collector outputs that are internally pulled up to VCC through 1k resistors. 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 (50 to 50k). 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. 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. Bias VCC Supply pins. Decouple these pins to GND. See the Layout Issues section. Receiver/Transmitter Ground pin. Connect to the PC board ground plane with minimal inductance. 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. 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. Receiver Front-End Ground. Connect GND to the PC board ground plane with minimal inductance. 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. Reference Voltage pin. VREF is used to provide an external bias voltage for the MIXOUT and LIMIN pins. Bypass this pin with a 0.1F capacitor to ground. VREF voltage is equal to VCC / 2. See the Typical Operating Circuit for more information.
MAX2511
5 6, 9 7, 10 8, 11
GC TANK, TANK GND VCC
12
OSCOUT
13, 14
LIMOUT, LIMOUT TXIN, TXIN
15, 16
17
RXEN
18 19, 21 20 22, 25 23, 24 26 27
TXEN VCC GND RXIN, RXIN TXOUT, TXOUT GND MIXOUT
28
VREF
_______________________________________________________________________________________
9
Low-Voltage IF Transceiver with Limiter and RSSI MAX2511
IF BPF LIMIN MIXOUT RECEIVE IMAGE-REJECT MIXER RXIN 90 VREF CZ OFFSET CORRECTION CZ
0
GM
LIMITER LIMOUT LIMOUT VGA
RXIN
TANK
0 90 VREF = VCC / 2
RSSI
RSSI
TANK OSCOUT
LO PHASE SHIFTER BIAS
RXEN
TXEN TXIN PA TXOUT VGA 0
90 TRANSMIT IMAGE-REJECT MIXER AND VGA/PA
TXIN
TXOUT
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.
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
10
______________________________________________________________________________________
Low-Voltage IF Transceiver with Limiter and RSSI
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 330 filter (165 load) to more than 2Vp-p over the entire supply range. 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 100 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.
MAX2511
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 10k terminated to VREF. For proper operation, LIMIN must be tied to VREF through the filter terminating impedance (not more than 1k). 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.
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 6k 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
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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 50 load. If a larger output level is desired, you can use a resistive termination up to 100. When a controlled-impedance PC board is used, this trace's impedance should match the termination impedance.
MAX2511
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:
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.
CEFF =
1 + C1 + CP 2 2 + C2 CD1
Using this value for the resonant tank circuit, the oscillation frequency is as follows: 1 FOSC = 2 L1CEFF EMBED Equation.2 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 50 source, see Figure 4.
Table 1. Power-Supply Mode Selection
RXEN STATE Low Low High High TXEN STATE Low High Low High MODE Shutdown Transmit Receive 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.
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.
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Low-Voltage IF Transceiver with Limiter and RSSI
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.
______________________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.
MAX2511
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 (0.1F 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.
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 (330--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 (165) to reduce component count (Figure 5--inset).
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.
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Low-Voltage IF Transceiver with Limiter and RSSI MAX2511
TANK C2 10k
10k CP L1 C1 VCO VOLTAGE FROM PLL
TANK
C3
10k
C2 = C3
Figure 3. Oscillator Tank Schematic
TANK
MINI CIRCUITS TC4-1 R = 200
50 SIGNAL SOURCE
CP
TANK ADJUST R FOR BEST RETURN LOSS AT SIGNAL SOURCE
Figure 4. Overdriving the On-Chip Oscillator
Table 2. Recommended Values for L1
fLO (MHz) 200 to 300 300 to 400 400 to 500 L1 (H) 18 12 8.2
Table 3. Rx Input Impedance
FREQUENCY (MHz) 100 200 300 400 500 600 SERIES IMPEDANCE () 274-j226 131-j186 79-j138 58-j105 48-j82 43-j62 EQUIVALENT PARALLEL IMPEDANCE R () 460 395 320 248 188 132 C (pF) 2.85 2.86 2.9 2.9 2.9 2.9
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Low-Voltage IF Transceiver with Limiter and RSSI MAX2511
ONE PORT FILTER (LC OR TRANSFORMER-C) TWO-PORT FILTER 10.7 MHz BPF
165
0.1F 330 MIXOUT VREF LIMIN 0.1F MIXOUT RXIN ROPT VCC VCC RXIN RX MIXER VREF LIMITER LIMOUT LIMIN LIMOUT 330
LMATCH
LMATCH
CBLOCK CBLOCK TXOUT
MAX2511
10.7MHz BPF
TXIN CMATCH TXOUT 425MHz BPF CMATCH CONTROL TX MIXER TXIN
GC
Figure 5. Filter Sharing
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Low-Voltage IF Transceiver with Limiter and RSSI MAX2511
___________________________________________________Typical Operating Circuit
VCC 47nF LCHOKE LCHOKE 24 CBLOCK Tx OUTPUT R* 23 CBLOCK 25 Rx INPUT CMATCH LMATCH CMATCH 22 RXIN VCC VCC 20 21 47nF 47nF 8.2nH 20 4 100pF 0.01F* 5 26 27 GND TANK RSSI GC GND MIXOUT LIMIN 10.7MHz BPF, Z0 = 330 1 VREF CZ 28 2 OSCOUT VCC GND CZ 12 VCC 11 10 3 47nF D1 = ALPHA SMV1204-199 9 6.8 pF 470pF TO PRESCALER 12pF 10k VCC VCC TANK 6.8pF 6 D1 10k 10k GND 7 TXEN RXIN TXIN LIMOUT TXOUT LIMOUT RXEN TXOUT TXIN 16 15 13 14 18 17 VCC 8 47nF FOSC = 435.7MHz CONTROL LOGIC 1k 1k VCC 47nF 0.1F 10.7MHz Tx 0.1F INPUT 0.1F 10.7MHz Rx 0.1F IF OUTPUT
MAX2511
VCC
VCO ADJUST FROM PLL
330 0.1F
330
0.01F
GAIN CONTROL VOLTAGE RSSI OUTPUT
*OPTIONAL
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