19-3559; Rev 0; 1/05 KIT ATION EVALU LE B A IL A AV Integrated L1-Band GPS Receiver Supports All Popular Handset Reference Frequencies Up to 26MHz 4.7dB Cascaded Noise Figure 80dB Cascaded Gain Tolerates -90dBm In-Band Jammer Tolerates +13dBm CDMA Out-of-Band Jammer at Device Input Integrated Synthesizer and VCO Integrated 2- or 3-Bit ADC 50dB IF AGC Range Small 28-Pin Thin QFN Package SPITM Control Interface Clock Output for Baseband Processor SPI is a trademark of Motorola, Inc. Ordering Information THIN Q PIN FN 28- The MAX2741 L1-band GPS receiver IC offers a highperformance, compact solution for mobile handsets, PDAs, and automotive applications. Total voltage gain of 80dB and a 4.7dB cascaded noise figure can provide receiver sensitivity for applications requiring -185dBW for indoor tracking solutions. This dual-conversion receiver downconverts the 1575.42MHz GPS signal to a 37.38MHz first IF, and then a 3.78MHz second IF. An integrated 2- or 3-bit ADC (1bit SIGN, 1- or 2-bit MAG selectable) samples the second IF and outputs the digitized signals to the baseband processor. The integrated synthesizer offers the flexibility in frequency planning to allow a single board design to be employed for reference frequencies from 2MHz to 26MHz. The integrated reference oscillator allows either TCXO or crystal operation. The receiver runs from a 2.7V to 3.0V supply, and draws only 30mA when active. It is offered in a 28-pin thin QFN package, and is specified for -40C to +85C at 3V. Features PART MAX2741ETI PIN-PACKAGE -40C to +85C 28 Thin QFN m 5. 0m TEMP RANGE mx5 .0 m Pin Configuration/ Functional Diagram Automotive Security VCC1 1 N.C. 2 IFOUT- IFIN+ IFIN- N.C. N.C. Telematics (Vehicle and Asset Tracking, Inventory Management) IFOUT+ In-Vehicle Navigation Systems (IVNS) VCC6 Applications 28 27 26 25 24 23 22 MAX2741 21 SDO 20 N.C. 19 VCC5 18 GPSIF0 17 GPSIF1 16.8MHz 16 GPSIF2 REF OSC 15 GPSCLK Emergency Response Systems RFIN 3 Digital Cameras/Camcorders /96 4 /16128 ADC P.D. 6 GND 7 /R /192 MUX SPI INTERFACE 8 9 10 11 12 13 14 REFCLK VCC4 200kHz VCO 3225.6MHz XTAL 5 SHDN VCC3 Consumer Electronics (Location-Based Games) Precision Timing 0 /2 SDI Geographical Information Systems (GIS) VCC2 90 CS Recreational Handhelds/Walkie-Talkies LNA 1612.8MHz SCLK Location-Based Services/Internet (PDAs) 33.6MHz FILT Emergency Road-Side Assistance ________________________________________________________________ Maxim Integrated Products For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at 1-888-629-4642, or visit Maxim's website at www.maxim-ic.com. 1 MAX2741 General Description MAX2741 Integrated L1-Band GPS Receiver ABSOLUTE MAXIMUM RATINGS VCC Pins to GND ...................................................-0.3V to +3.3V VCC Pins to Each Other .........................................-0.3V to +0.3V FILT to GND................................................-0.3V to (VCC + 0.3V) CMOS Inputs to GND (SHDN, SCLK, CS, SDI).................................................+0.3V to (VCC + 0.3V) CMOS Outputs to GND (CLKOUT, GPSIF_, SDO).........................................-0.3V to (VCC + 0.3V) RFIN to GND...............................................-0.3V to (VCC + 0.3V) First IF Filter I/O to GND (IFOUT, IFIN).....-0.3V to (VCC + 0.3V) Crystal Inputs to GND (XTAL, REFCLK).....-0.3V to (VCC + 0.3V) Maximum RF Input Power...................................................0dBm Continuous Power Dissipation (TA = +85C) 28-Pin Thin QFN (derate 20.8mW/C above +70C) .1000mW Operating Temperature Range ...........................-40C to +85C Junction Temperature ......................................................+150C Storage Temperature Range .............................-65C to +160C Lead Temperature (soldering, 10s) .................................+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. CAUTION! ESD SENSITIVE DEVICE DC ELECTRICAL CHARACTERISTICS (Operating conditions (unless otherwise specified): VCC = 2.7V to 3.0V; REFCLK driven with 10MHz sinusoid, 1.2VP-P; registers set according to mode; no RF input signal; digital baseband outputs left open; TA = -40C to +85C. Typical values are measured at VCC = 2.75V, TA = +25C.) PARAMETER CONDITIONS Supply Voltage Supply Current MIN TYP 2.7 Normal operation (TA = +25C) 30 Standby (V SHDN = VIL, SYNTH:D8 = 0) 0.7 MAX UNITS 3.0 V 42 VCC 0.1 Input-Logic High Threshold V Input-Logic Low Threshold Input-Logic High/Low Current -10 Output-Logic High ILOAD = 100A Output-Logic Low ILOAD = 100A mA 0.1 V +10 A VCC 0.3 V 0.3 V AC ELECTRICAL CHARACTERISTICS (Operating conditions (unless otherwise specified): VCC = 2.7V to 3.0V for TA = -40C to +85C; REFCLK driven at 10MHz sinusoid, 1.2VP-P; registers set according to mode; using the Typical Application Circuit; CW RF signal at 1575.42MHz. Typical values are measured at VCC = 2.75V, TA = +25C.) PARAMETER CONDITIONS MIN TYP MAX UNITS 1st CONVERSION STAGE (RF TO 1st IF) RF Frequency L1-band RF Conversion Gain (Note 1) 1575.42 15 21 MHz 32 dB Noise Figure Mid-gain (CONFIG1:D4-D0 = 10000) 4.7 dB Input IP3 (Note 2) -30 dBm RF Image Rejection (Notes 3, 4) 35 dB LO Leakage at RF LO to RFIN pin -90 dBm 2 20 _______________________________________________________________________________________ Integrated L1-Band GPS Receiver (Operating conditions (unless otherwise specified): VCC = 2.7V to 3.0V for TA = -40C to +85C; REFCLK driven at 10MHz sinusoid, 1.2VP-P; registers set according to mode; using the Typical Application Circuit; CW RF signal at 1575.42MHz. Typical values are measured at VCC = 2.75V, TA = +25C.) PARAMETER CONDITIONS MIN TYP MAX UNITS 2nd CONVERSION STAGE (1st IF TO ADC INPUT) 1st IF Frequency At IFOUT Max gain (CONFIG1:D4-D0 = 11111) (Note 1) Conversion Gain 37.38 48 61 MHz 74 dB Min gain (CONFIG1:D4-D0 = 00000) (Note 1) 10 dB Input IP3 1st conversion (Note 5) -36 dBm Noise Figure Max gain (CONFIG1:D4-D0 = 11111) 12 dB Real 0.40 mS Imaginary 1.5 pF Real 0.40 mS Imaginary 0.15 pF (SYNTH:D13-D10 = 1111) 2.9 (SYNTH:D13-D10 = 0000) 7.7 ICP_OH PLL charge-pump source current 75 ICP_OL PLL charge-pump sink current -100 A Closed-Loop Phase Noise At 1kHz offset -55 dBc/Hz Comparison Spurs At 200kHz offset -44 dBc/Hz Reference Oscillator Frequency Sinusoid (Note 1) 2 REF Input Voltage Level Sinusoid (Note 1) 0.6 VCO Coarse Tune Range Programmable (CONFIG1:D7 to D5 = 000 to 111) (Note 1) IF Output Port Admittance IF Input Port Admittance LPF -3dB Corner Frequency MHz SYNTHESIZER 10 A 26 MHz 2.2 VP-P 240 MHz 1 MHz DIGITAL I/O SPI Clock Frequency Note 1: Note 2: Note 3: Note 4: Note 5: Production tested for +25C and +85C, guaranteed by design and characterization for -40C. Test tones at 1575.8MHz and 1576.8MHz at -60dBm/tone. Guaranteed by design and characterization. Image frequency is 1575.42MHz + 2(fIF) = 1650.18MHz Test tones at 37.38MHz and 36.88MHz at -50dBm/tone. _______________________________________________________________________________________ 3 MAX2741 AC ELECTRICAL CHARACTERISTICS (continued) MAX2741 Integrated L1-Band GPS Receiver Pin Description PIN NAME FUNCTION 1 VCC1 LNA Supply Connection. External RF bypass capacitor to ground required. 2, 20, 22, 23 N.C. Reserved. Make no connections to this pin. 3 RFIN LNA Input. Connect to GPS antenna through a bandpass filter. This input requires an external matching network to match to 50. AC-couple to this pin. 4 VCC2 VCO Supply Connection. External RF bypass capacitor to ground required. 5 VCC3 CML Supply Connection. External RF bypass capacitor to ground required. 6 VCC4 Digital Logic and PLL Supply Connection. External RF bypass capacitor to digital ground required. 7 GND Ground. Connect to PC board digital ground plane. 8 FILT PLL Loop Filter Connection. This is the output of the phase detector's charge pump. Use the recommended filter on EV kit for optimal phase noise and lock time. 4 9 SCLK 10 CS SPI Chip-Select Input (CMOS, Active Low) SPI Clock Input (CMOS) 11 SDI SPI Data Input (CMOS) 12 SHDN Full IC Power-Down. This shutdown pin disables the on-chip oscillator and the rest of the IC. To keep the oscillator running, use the software shutdown (SYNTH:D8); (CMOS, active high). 13 XTAL Crystal Oscillator Feedback Capacitor Connection 14 REFCLK Reference Clock Input for PLL. Drive with 1.2VP-P when using TCXO module. 15 GPSCLK GPS Clock Output to Baseband. This is the clock used by the ADC to sample the GPS data (CMOS). 16 GPSIF2 Sampled IF Output, Bit 2 (CMOS). See Table 5. 17 GPSIF1 Sampled IF Output, Bit 1 (CMOS). See Table 5. 18 GPSIF0 19 VCC5 IF Supply Connection. External RF bypass capacitor to ground required. 21 SDO SPI Data Output (CMOS) 24 IFIN- 1st IF Input (Inverting). Connect this 2.5k differentially terminated input to the 1st IF filter's (-) output. 25 IFIN+ 1st IF Input (Noninverting). Connect this 2.5k differentially terminated input to the 1st IF filter's (+) output. Sampled IF Output, Bit 0 (CMOS). See Table 5. 26 IFOUT- 27 IFOUT+ 1st IF Output (Inverting). Connect this 2.4k differential output to the 1st IF filter's (-) input. 28 VCC6 RF Image-Reject Mixer Supply. External RF bypass capacitor to ground required. Exposed GND RF Ground. Ultra-low inductance connection to ground. Place several vias to PC board ground plane. 1st IF Output (Noninverting). Connect this 2.4k differential output to the 1st IF filter's (+) input. _______________________________________________________________________________________ Integrated L1-Band GPS Receiver The MAX2741 GPS offers a high-performance superheterodyne receiver solution for low-power mobile devices, with the benefit of using the system's existing clock reference. This receiver is ideal for integration into mobile phone handsets using common reference frequencies such as 10.0, 13.0, 14.4, 19.2, 20.0, and 26.0MHz. The only external components required are the GPS RF filter, an IF filter (typically designed from inexpensive discretes), a three-component PLL loop filter, and a few other resistors and capacitors. The MAX2741 integrates the reference oscillator core, the VCO and its tank, the synthesizer, a 1- to 3-bit ADC, and all signal path blocks except for the 1st IF filter. The typical application area for the receiver is less than 2cm2. RF/1st Conversion Stage (Front-End) The MAX2741 RF front-end LNA and mixer are the most important in the signal path. This stage sets the noise figure for the receiver, defining the sensitivity, and mixes the 1575.42MHz L1-band GPS signal down to a 1st IF of 37.38MHz. The LNA itself has an NF of approximately 1.5dB; the cascaded NF of the front-end (including the mixer) is approximately 4.7dB, and the cascaded gain is typically 21dB. The image-reject mixer is set up for a high-side injected RFLO (1612.80MHz), and offers typically better than 30dB rejection of the image noise (1650.18MHz). The -30dBm input 3rd-order intercept (IIP3) of the RF strip, in conjunction with the GPS IF filter, provides excellent out-of-band interferer immunity. The 1st IF outputs (IFOUT) are internally biased to approximately 2V, and have a differential source impedance of approximately 2.5k. The IF filter can be implemented as a discrete L/C filter, or as a monolithic SAW or ceramic if one is available. IF/2nd Conversion Stage The 2nd conversion stage consists of an active mixer, a variable-gain amplifier (VGA), and a tunable lowpass filter. The IF mixer is configured for low-side LO injection for a 2nd IF of 3.78MHz. Total gain in this stage is 62dB, and the VGA offers 51dB of gain adjustment. The VGA is typically controlled by the baseband IC through the SPI interface to optimize the signal swing for digitization by the ADC. The on-chip lowpass filter has an adjustable cutoff frequency, programmable from 2.9MHz to 7.7MHz in 16 steps. This LPF further reduces out-of-band noise and band-limits the signal to the ADC, ensuring that the sampling process does not generate alias components. DC offset compensation at the ADC input is performed by an on-chip 4-bit DAC. This compensates for any DC error introduced by transistor mismatch in the differential stage driving the ADC input, allowing the downconverted GPS signal's DC level to be centered within the threshold voltages of the ADC. ADC The on-chip ADC samples the down-converted GPS signal at the 2nd IF (3.78MHz). Sampled output is provided in either 2-bit (1-bit magnitude, 1-bit sign) or 3-bit (2-bit magnitude, 1-bit sign) formats, as determined by the ADC mode configuration bit (CONFIG1:D15); see Table 5 for details. The ADC sample clock (system GPS clock) is derived either directly from the reference clock (SYNTH:D9 = 1), or from an RFLO divide-by-96 block to provide a 16.8MHz sample clock (SYNTH:D9 = 0). The clock is available to the baseband processor at GPSCLK (pin 15). The sampled ADC data bits are available on pins 16, 17, and 18 (GPSIF2, GPSIF1, and GPSIF0). The functionality of the pins is different in each mode (2-bit vs. 3-bit)--see Table 5 in determining the interface connection for the application circuit. Synthesizer The MAX2741 integrates an integer-N synthesizer; all blocks except the loop filter are on-chip. The reference can be either a crystal (driven by the internal oscillator), or a TCXO module. The oscillator provides a 5pF load to the crystal. A TCXO module should provide a swing in the 0.6VP-P to 2.2VP-P range. The reference divider (/R) is programmable (SYNTH: D7-D0), and can accommodate reference frequencies up to 26MHz. The reference divider needs to be set so the comparison frequency (fCOMP) at the frequency/ phase detector is 200kHz. The VCO runs at twice the frequency of the RFLO; the RFLO is therefore generated from the VCO using a quadrature divide-by-2 block. The RF LO is fCOMP x 8064 (typically 1612.80MHz), and the 1st IF LO is fCOMP x 168 (typically 33.6MHz); the RF and IF LO division ratios are not adjustable. This configuration allows for the use of reference frequencies common to GSM, CDMA, TDMA, TD-SCDMA, and UMTS handsets: 9.6MHz (R = 48), 13.0MHz (R = 65), 14.4MHz (R = 72), 19.2MHz (R = 96), 26.0MHz (R = 130), etc. _______________________________________________________________________________________ 5 MAX2741 Detailed Description Integrated L1-Band GPS Receiver VCC4 GND MAX2741 6 7 FILT 8 9 SCLK MAX2741 SPI Bus, Address and Bit Assignments 22nF 100pF 36k Figure 1. Recommended 3rd-Order PLL Filter The VCO offers a bank of tuning capacitors that can be latched in/out to adjust the center frequency. Because the system does not require any RF LO frequency change (i.e., changing channels), the VCO varactor tuning gain is very low by design, which means the tuning range of the VCO is narrow. The coarse-tune capacitors in the tank circuit allow the system to adjust the VCO center frequency as needed to guarantee that the synthesizer can lock. In practice, process and temperature effects on VCO centering are negligible, and a coarsetune setting of 110 (CONFIG:D7 to D5) will center the VCO tuning range correctly in virtually all cases. To aid in bench and prototype testing, the PFD offers out-of-lockhigh and out-of-lock-low indicators, available in the SPI STATUS register (STATUS:D9 to D8). Use these flags to determine if the VCO tuning range needs to be adjusted higher or lower in the case where the PLL cannot lock. The PLL filter is the only external block of the synthesizer. The typical filter is a classic C-R-C two-pole shunt network on the tune line. Low phase noise is preferred at the expense of longer PLL settling times, so a low 10kHz to 20kHz loop bandwidth is used. The recommended PLL 10kHz filter implementation, with charge pump set to 200A (CONFIG1:D10 = 1), is shown in Figure 1. The system/GPS clock is derived either directly from the reference oscillator, or synthesized from the RFLO (see the ADC section). This clock is used as the sampling clock for the on-chip ADC, and is seen at pin 15, GPSCLK. 6 An SPI-compatible serial interface is used to program the MAX2741 for configuring the different operating modes. In addition, data can be read out of the MAX2741 for status and diagnostic use. The serial interface is controlled by four signals: SCLK (serial clock), CS (chip-select), SDI (data input), and SDO (data output). The control of the PLL, AGC, test, offset management, and block selection is performed through the SPI bus from the baseband controller. A 20-bit word, with the MSB (D15) being sent first, is clocked into a serial shift register when the chip-select signal is asserted low. The SPI bus has four control lines: serial clock (SCLK), chip-select (CS), data in (SDI), and data out (SDO). Enable SDO functionality by setting the digital test bus bits: CONFIG1:D9 to D8 = 01. The timing of the interface signals is shown in Figure 2 and Table 1 along with typical values for setup and hold time requirements. For best performance, the SPI bus should be configured during the startup initialization and then left with the optimum values in the registers. Any changes to the ADC and VGA bits during GPS signal processing may cause glitches and corrupt the analog signal path. Reading from the SPI bus does not interrupt GPS operation. tSETUPSS CS tEND tSETUPD SCLK tHDATA SDI LSB tPERIOD MSB Figure 2. SPI Timing Diagram Table 1. SPI Timing Requirements SYMBOL PARAMETER TYP VALUE UNITS ns tSETUPD Data to SCLK setup 20 tPERIOD SCLK period 100 ns tHDATA Data hold to SCLK 20 ns tSETUPSS CS to SCLK disable 20 ns tEND Falling SCLK to CS inactive 20 ns _______________________________________________________________________________________ D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0 Out-of-Lock (High) Out-of-Lock (Low) XTAL Clock Selected Parity Reserved LPF Autocalibrate End LPF Autotune (MSB) LPF Autotune LPF Autotune LPF Autotune (LSB) D12 D11 Reserved Reserved D14 D13 Reserved D15 Reserved REGISTER NAME LPF Tuning Word LPF Tuning Word LPF Tuning Word (LSB) XTAL Clock Select Standby PLL Ref Div Ratio (MSB) PLL Ref Div Ratio PLL Ref Div Ratio PLL Ref Div Ratio PLL Ref Div Ratio PLL Ref Div Ratio PLL Ref Div Ratio ADC Offset Control (MSB) ADC Offset Control (SIGN) Double ChargePump Current Digital Test Bus Mode Select (MSB) Digital Test Bus Mode Select (LSB) VCO Coarse Tuning Range (MSB) VCO Coarse Tuning Range VCO Coarse Tuning Range (LSB) AGC Gain (MSB) AGC Gain AGC Gain AGC Gain Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved Analog Test Mode Select Analog Test Mode Select Analog Test Mode Select Analog Test Mode Select PLL Ref Div Ratio (LSB) LPF Tuning Word (MSB) Drive VCO High ADC Offset Control 0 1 0 0 AGC Gain (LSB) LPF Autotune Initiate ADC Offset Control (LSB) CONFIG 2 Drive VCO Low REGISTER NAME 0 1 0 1 Analog Test Mode Select Reserved CONFIG 1 ADC Mode D15 Reserved SYNTH Reset CMOS Table 2. Register Address and Data Bit Assigments (Write) DATA ADDRESS D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0 A3 A2 A1 A0 0 1 1 0 Table 3. Register Address and Data Bit Assigments (Read) DATA ADDRESS A3 A2 A1 A0 0 1 1 _______________________________________________________________________________________ 1 7 MAX2741 STATUS Reserved Integrated L1-Band GPS Receiver MAX2741 Integrated L1-Band GPS Receiver Detailed Register Definitions Table 4. Detailed Register Definition for Write Address 0100: SYNTH DATA BIT DEFAULT DESCRIPTION D15 1 D14 1 D13-D10 0100 D9 1 XTAL Clock Select: 1 = External reference, 0 = Synthesized 16.8MHz. D8 0 Standby: 0 = Normal operating mode, 1 = Standby (oscillator remains active), but only if D9 = 1. D7-D0 01100000 Reserved LPF Autotune Initiate: I = Initiate autotune, 0 = Manual tuning. LPF Tuning Word: 0000 ~ 7.7MHz, 1111 ~ 2.9MHz. Reference Division Ratio. Default 19.2MHz external reference (R = 96dec). R = fREF / 200kHz. Table 5. Detailed Register Definition for Write Address 0101: CONFIG 1 DATA BIT DEFAULT D15 1 D14-D11 0000 D10 0 Double Charge-Pump Current: 0 = 100A, 1 = 200A. D9 to D8 00 Digital Test Bus Mode Select. See Table 9 for test-mode descriptions. D7 to D5 001 D4-D0 11111 DESCRIPTION ADC Mode. Select 1 for 1-bit magnitude and sign, select 0 for 2-bit magnitude and sign. 1: GPSIF2 = sign, GPSIF1 = magnitude, GPSIF0 = X 0: GPSIF2 = MSB magnitude, GPSIF1 = LSB magnitude, GPSIF0 = sign ADC Offset Control (approx 4mV/step): D14 = LSB, D12 = MSB, D11 = sign. VCO Coarse Tuning Range. 000 = Lowest frequency, 111 = Highest frequency. AGC Gain. Digital control of the AGC amplifier in the 2nd IF section. 00000 => min gain, 11111 => max gain (linear gain ~2.5dB per unit SPI word). Table 6. Detailed Register Definition for Write Address 0110: CONFIG 2 8 DATA BIT DEFAULT D15 1 Reset CMOS: 0 = Hold CMOS dividers in reset and PFD is tri-stated, 1 = Inactive. D14 1 Drive VCO Low: 0 = Active, forces VCO to lowest frequency. N.B. do not activate both D14 and D13 at the same time. D13 1 Drive VCO High: <forces LCP low FET on, driving VTUNE low, forcing VCO to highest extreme> 0 = Active, forces VCO to highest frequency. N.B. do not activate both D14 and D13 at the same time. D12-D7 100000 D6 to D5 11 D4-D0 11111 DESCRIPTION Reserved Must be programmed to 11 Analog Test Mode Select: Reserved _______________________________________________________________________________________ Integrated L1-Band GPS Receiver MAX2741 Table 7. Detailed Register Definition for Read Address 0111: STATUS DATA BIT DEFAULT D15-D10 XXXXXX DESCRIPTION D9 X Out-of-Lock (High Frequency): 1 = PLL is out of lock, VCO free-running at its highest frequency, 0 = Locked. D8 X Out-of-Lock (Low Frequency): 1 = PLL is out of lock, VCO free-running at its lowest frequency, 0 = Locked high. D7 1 XTAL Clock Selected: 1 = Synthesized 16.8MHz reference, 0 = External clock. D6 X Parity: 1 = Even, 0 = Odd. D5 X Reserved D4 X LPF Autotune End: 0 = Autotune run ended; 1 = Calibrating or manual tuning. D3-D0 XXXX Reserved LPF Autotune: 0000 ~ 7.7MHz; 1111 = 2.9MHz. Applications Information Fundamentally, the only application areas that require careful consideration are the LNA input match and the 1st IF filter. Of course, proper supply bypassing, grounding, and layout is required for reliable performance from any RF circuit. Table 8. MAX2741 S11 FREQ (MHz) S11 (MAG) S11 () 1100 0.874 -50.9 1200 0.867 -56.1 1300 0.859 -61.5 LNA Input Matching 1400 0.842 -66.9 Input matching is critical for optimum noise figure and system sensitivity. Optimum source impedance (as seen from the LNA input) for lowest noise figure is 29 + j47. Remember that optimum noise match and optimum gain match (return loss) do not occur simultaneously, so a good application circuit will sacrifice gain slightly in favor of reduced noise figure. Gain and noise circles are provided in Figure 3; S11 tabular data is provided in Table 8. 1500 0.821 -72.3 1550 0.809 -74.9 1560 0.806 -75.4 G = Gmax - 1dB NF = NFmin + 0.2dB 1570 0.804 -75.9 1575 0.803 -76.2 1580 0.801 -76.4 1590 0.799 -77.0 1600 0.796 -77.5 1650 0.783 -80.0 1700 0.768 -82.5 1800 0.739 -87.4 1900 0.708 -92.3 2000 0.677 -96.8 1st IF Interface and Filtering The typical application uses a 37.38MHz 1st IF, and employs an IF filter. The order of the filter should be tailored to suit the application--stand-alone GPS receivers will not require the channel-selection and stopband attenuation of GPS receivers that are integrated into other wireless handsets. Be sure that the filter topology provides DC-blocking for the IF I/O ports. Figure 3. Gain and Noise Circles for MAX2741 LNA Input _______________________________________________________________________________________ 9 MAX2741 Integrated L1-Band GPS Receiver VCC1 N.C. RFIN VCC2 VCC3 VCC4 GND 27 26 25 24 23 N.C. N.C. IFIN- IFIN+ IFOUT- VCC6 28 IFOUT+ Typical Interface Diagram 22 1 21 2 20 3 19 MAX2741 4 18 5 17 6 16 7 15 SDO N.C. BASEBAND IC SDO SD1 VCC5 CS GPSIF0 SCLK GPSIF1 GPSIF0 GPSIF2 GPSCLK GPSIF1 GPSIF2 GPSCLK REFCLK 13 14 REFCLK 12 XTAL 11 SHDN CS 10 SDI FILT 9 SCLK 8 Interface Summary All I/O connections are DC-coupled. Supply voltages as specified in the electrical specifications. RF I/O CONNECTION RFIN RECEIVER LNA Input RF BPF RF BPF Output IF I/O CONNECTION RECEIVER IF FILTER IFOUT+ 1st IF Output from Mixer (+) IF BPF Input, 2.5k Differential IFOUT- 1st IF Output from Mixer (-) IF BPF Input, 2.5k Differential IFIN+ 1st IF Input (+) IF BPF Input, 2.5k Differential IFIN- 1st IF Input (-) IF BPF Input, 2.5k Differential BASEBAND I/O CONNECTION RECEIVER BB IC/MAC SCLK CMOS Input CMOS Output CS CMOS Input CMOS Output SDI CMOS Input CMOS Output SDO CMOS Output CMOS Input CMOS Input CMOS Output SHDN GPSCLK CMOS Output CMOS Input GPSIF0 CMOS Output CMOS Input GPSIF1 CMOS Output CMOS Input GPSIF2 CMOS Output CMOS Input SYNTHESIZER I/O CONNECTION FILT RECEIVER PLL Phase-Detector Charge-Pump PLL Loop Filter XTAL Crystal Oscillator Feedback Feedback Capacitors External TCXO or Crystal Analog (also connected to REFCLK input to MAC) REFCLK 10 EXTERNAL COMPONENTS ______________________________________________________________________________________ Integrated L1-Band GPS Receiver 680pF 5.6pF 470H 470H 680pF 5.6pF 28 VCC1 VCC 100pF 27 26 IFIN- IFIN+ IFOUT- IFOUT+ 22pF VCC6 100pF 25 24 680pF 23 1 39pF N.C. 39pF 680pF N.C. VCC 22 MAX2741 21 SDO SPI DATA OUT TO BASEBAND PROCESSOR 22pF N.C. 2 20 N.C. 33.6MHz 100pF 6.2nH RFIN 19 1612.8MHz VCC2 VCC 90 0 /2 VCC3 VCC 4 P.D. 100pF VCC4 VCC 100nF 18 ADC 200kHz VCO 3225.6MHz 17 /R /192 MUX 6 VCC 100pF /16128 5 VCC5 /96 22pF 100pF 16.8MHz 16 REF OSC 15 1nF GPSIF0 GPSIF1 GPSIF2 GPS DATA AND CLOCK TO BASEBAND PROCESSOR 100pF 10 11 12 13 GPSCLK 14 REFCLK 9 SCLK FILT 8 XTAL SPI INTERFACE 7 SHDN GND SDI 1nF LNA 3 2.2pF CS GPS RF INPUT FROM GPS BPF 22nF 220pF 100pF 36k SPI CLOCK AND DATA INTO BASEBAND PROCESSOR H/W SHUTDOWN LINE FROM BASEBAND PROCESSOR SYSTEM TCXO (2MHz TO 26MHz) Table 9. Digital Test-Mode-Select Description DIGITAL OUTPUT FUNCTION MODE REGISTER SETTING CONFIG1:D9 to D8 GPSIF2 GPSIF1 GPSIF0 3 11 SIGN LSB MSB 2 10 M COUNTER R COUNTER HANDSHAKE STATUS 1 01 CHARGE PUMP UP CHARGE PUMP DOWN SDO 0 00 CML CLOCK CALIBRATE LPF END XTL CLOCK SELECTED Digital Test Bus The digital test bus (DTB) is provided to allow for easy bench analysis of the digital workings of the receiver. ______________________________________________________________________________________ 11 MAX2741 Typical Application Circuit Package Information (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.) QFN THIN.EPS MAX2741 Integrated L1-Band GPS Receiver D2 D MARKING b C L 0.10 M C A B D2/2 D/2 k L XXXXX E/2 E2/2 C L (NE-1) X e E DETAIL A PIN # 1 I.D. E2 PIN # 1 I.D. 0.35x45 e (ND-1) X e DETAIL B e L L1 C L C L L L e e 0.10 C A C 0.08 C A1 A3 PACKAGE OUTLINE, 16, 20, 28, 32L THIN QFN, 5x5x0.8mm 21-0140 -DRAWING NOT TO SCALE- COMMON DIMENSIONS A1 0.70 0.75 0.80 0.70 0.75 0.80 0.70 0.75 0.80 0.70 0.75 0.80 0 A3 b D E L1 0 0.02 0.05 0 0.20 REF. 0.20 REF. 0.02 0.05 0 0.20 REF. 0.02 0.05 0.20 REF. 0.25 0.30 0.35 0.25 0.30 0.35 0.20 0.25 0.30 0.20 0.25 0.30 4.90 5.00 5.10 4.90 5.00 5.10 4.90 5.00 5.10 4.90 5.00 5.10 4.90 5.00 5.10 4.90 5.00 5.10 4.90 5.00 5.10 4.90 5.00 5.10 e k L 0.02 0.05 0.65 BSC. 0.80 BSC. 0.50 BSC. 0.50 BSC. 0.25 - 0.25 - 0.25 - 0.25 0.30 0.40 0.50 0.45 0.55 0.65 0.45 0.55 0.65 0.30 0.40 0.50 - - - - - N ND NE 16 4 4 20 5 5 JEDEC WHHB WHHC - - 1 2 EXPOSED PAD VARIATIONS PKG. 20L 5x5 28L 5x5 32L 5x5 16L 5x5 SYMBOL MIN. NOM. MAX. MIN. NOM. MAX. MIN. NOM. MAX. MIN. NOM. MAX. A G - - - 28 7 7 WHHD-1 - - 32 8 8 WHHD-2 NOTES: 1. DIMENSIONING & TOLERANCING CONFORM TO ASME Y14.5M-1994. 2. ALL DIMENSIONS ARE IN MILLIMETERS. ANGLES ARE IN DEGREES. 3. N IS THE TOTAL NUMBER OF TERMINALS. D2 L E2 PKG. CODES MIN. NOM. MAX. MIN. NOM. MAX. 0.15 T1655-1 T1655-2 T1655N-1 3.00 3.00 3.00 3.10 3.20 3.00 3.10 3.20 3.00 3.10 3.20 3.00 3.10 3.20 3.10 3.20 3.10 3.20 T2055-2 T2055-3 T2055-4 3.00 3.00 3.00 3.10 3.20 3.00 3.10 3.20 3.00 3.10 3.20 3.00 3.10 3.20 3.10 3.20 3.10 3.20 ** ** ** ** T2055-5 T2855-1 T2855-2 T2855-3 T2855-4 T2855-5 T2855-6 T2855-7 T2855-8 T2855N-1 T3255-2 T3255-3 T3255-4 T3255N-1 3.15 3.15 2.60 3.15 2.60 2.60 3.15 2.60 3.15 3.15 3.00 3.00 3.00 3.00 3.25 3.25 2.70 3.25 2.70 2.70 3.25 2.70 3.25 3.25 3.10 3.10 3.10 3.10 3.25 3.25 2.70 3.25 2.70 2.70 3.25 2.70 3.25 3.25 3.10 3.10 3.10 3.10 4. THE TERMINAL #1 IDENTIFIER AND TERMINAL NUMBERING CONVENTION SHALL CONFORM TO JESD 95-1 SPP-012. DETAILS OF TERMINAL #1 IDENTIFIER ARE OPTIONAL, BUT MUST BE LOCATED WITHIN THE ZONE INDICATED. THE TERMINAL #1 IDENTIFIER MAY BE EITHER A MOLD OR MARKED FEATURE. 3.35 3.35 2.80 3.35 2.80 2.80 3.35 2.80 3.35 3.35 3.20 3.20 3.20 3.20 3.15 3.15 2.60 3.15 2.60 2.60 3.15 2.60 3.15 3.15 3.00 3.00 3.00 3.00 3.35 3.35 2.80 3.35 2.80 2.80 3.35 2.80 3.35 3.35 3.20 3.20 3.20 3.20 ** ** 0.40 DOWN BONDS ALLOWED NO YES NO NO YES NO Y ** NO NO YES YES NO ** ** 0.40 ** ** ** ** ** NO YES Y N NO YES NO NO ** ** ** ** ** SEE COMMON DIMENSIONS TABLE 5. DIMENSION b APPLIES TO METALLIZED TERMINAL AND IS MEASURED BETWEEN 0.25 mm AND 0.30 mm FROM TERMINAL TIP. 6. ND AND NE REFER TO THE NUMBER OF TERMINALS ON EACH D AND E SIDE RESPECTIVELY. 7. DEPOPULATION IS POSSIBLE IN A SYMMETRICAL FASHION. 8. COPLANARITY APPLIES TO THE EXPOSED HEAT SINK SLUG AS WELL AS THE TERMINALS. 9. DRAWING CONFORMS TO JEDEC MO220, EXCEPT EXPOSED PAD DIMENSION FOR T2855-1, T2855-3 AND T2855-6. 10. WARPAGE SHALL NOT EXCEED 0.10 mm. 11. MARKING IS FOR PACKAGE ORIENTATION REFERENCE ONLY. 12. NUMBER OF LEADS SHOWN ARE FOR REFERENCE ONLY. PACKAGE OUTLINE, 16, 20, 28, 32L THIN QFN, 5x5x0.8mm 21-0140 -DRAWING NOT TO SCALE- G 2 2 Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. 12 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 (c) 2005 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products, Inc.