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19-3425; Rev 0; 10/04
KIT ATION EVALU E AILABL AV
Single-Chip Global Positioning System Receiver Front-End
General Description Features
o Complete Single-Chip GPS Radio for 16.368MHz and 32.736MHz Floorplans o Single-Ended or Differential Outputs at 4.092MHz o Low 3.5dB Typical Noise Figure o No External IF SAW or Discrete Filters Required o On-Chip Temperature Sensor o 2.4V to 3.6V Operational Supply Voltage Range o Power Consumption as Low as 41mW at 2.4V o Wide -40C to +85C Operational Temperature Range
MAX2745
The MAX2745 complete single-chip global positioning system (GPS) RF front-end downconverter utilizes many innovative and leading-edge RF CMOS design techniques. This high-performance, state-of-the-art device consumes extremely low power and eliminates the need for costly SAW and bulky discrete IF filters. The MAX2745 incorporates a fully integrated low-noise amplifier (LNA) and mixer, IF section, digital sampler, and local oscillator synthesizer. The MAX2745 also provides a voltage supply for an external LNA. In addition, the MAX2745 features a voltage booster, which can extend the power-supply voltage to as low as 1.6V. The MAX2745 supports both 3rd overtone crystal designs in 32MHz and fundamental frequency crystal designs in 16MHz, as well as a TCXO implementation. In addition, the MAX2745 incorporates an on-chip temperature sensor and crystal oscillator with trimmed capacitors, resulting in a very accurate frequency and additional system cost savings. The MAX2745 is available in a space-saving 48-pin TQFP package and is specified for the extended (-40C to +85C) temperature range. The power consumption of this device is as low as 41mW at 2.4V.
Ordering Information
PART MAX2745ECM TEMP RANGE -40C to +85C PIN-PACKAGE 48 TQFP-EP*
*EP = Exposed paddle. Typical Operating Circuit appears at end of data sheet
Applications
In-Vehicle Navigation Systems (IVNSs)
XTALOUT
CP_OUT
XTALIN
VTUNE
Telematics (Vehicle/Asset Tracking and Inventory Management) Recreational Handheld/Walkie Talkies Geographical Information Systems (GISs) Emergency Roadside Assistance Emergency Response Systems Digital Cameras/Camcorders Consumer Electronics
48 RBIAS 1 CBIAS 2 VDD 3 VDD 4 GND 5 GND 6
47
46
45
44
43
42
41
40
39
38
SDATA
37 36 BPF_CTRL 35 ODS 34 CFS 33 COE 32 VDD 31 SCLK 30 GND 29 VOUT+ 28 VOUT27 VDD 26 GND 25 VDD 24
SHDN
Location-Based Services (PDAs and Accessories)
Block Diagram/ Pin Configuration
GND GND VDD VDD VDD
VSPORT LNA/MIXER RFIN 7 GND 8 VDD 9 BANDPASS FILTER IEXT_LNA 10 VDD 11 AGC_FIL 12 13 14 15 16 17 18 19 20 21 22 23 FILTER AUTOMATIC TUNING VOLTAGE BOOSTER AGC QUANTIZER VCO
VCXO
MAX2745
TEMPERATURE SENSOR
BIAS PFD DIVIDER CHG PUMP
XTAL_SSEL
XTAL_CSEL
BST_CTRL
TEST_EN
VDD_VB
VB_CS+
VB_CS-
CKOUT
DOUT
GND
VDD
VTO
________________________________________________________________ Maxim Integrated Products
VOUT
1
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.
Single-Chip Global Positioning System Receiver Front-End MAX2745
ABSOLUTE MAXIMUM RATINGS
VDD to GND ...........................................................-0.3V to +3.7V Other Pins to GND......................................-0.3V to (VDD + 0.3V) RF LNA Input Power .......................................................+10dBm Continuous Power Dissipation (TA = +70C) 48-Pin TQFP-EP (derate 12.5mW/C above +70C) ............1W Operating Temperature Range ...........................-40C to +85C
CAUTION! ESD SENSITIVE DEVICE 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.
Junction Temperature ......................................................+150C Storage Temperature Range .............................-65C to +150C Soldering Temperature (10s) ...........................................+300C
DC ELECTRICAL CHARACTERISTICS
(MAX2745 EV kit, VDD = +2.4V to +3.6V, SHDN = GND, TA = -40C to +85C. Typical values are at VDD = +3.0V and TA = +25C, unless otherwise noted.)
PARAMETER Supply Voltage Supply Current Optional External LNA Supply Current Logic-Input High Voltage Logic-Input Low Voltage Logic-Input Bias Current -10 VDD = +3.0V, TA = +25C (Note 1) Shutdown mode VDD = +3.0V 2.0 0.5 +10 CONDITIONS MIN 2.4 20.5 11 10 TYP MAX 3.6 27 UNITS V mA A mA V V A
AC ELECTRICAL CHARACTERISTICS
(MAX2745 EV kit, VDD = +2.4V to +3.6V, SHDN = GND, TA = -40C to +85C. Typical values are at VDD = +3.0V and TA = +25C, unless otherwise noted.)
PARAMETER GENERAL PERFORMANCE Maximum Conversion Gain Input Frequency Noise Figure Return Loss (S11) LNA/Mixer Input IP3 Output IF Frequency OUTPUT STAGE Output Rise/Fall Time Output-Voltage-Level Low Output-Voltage-Level High CONDITIONS (Notes 2, 3) Measured at quantizer output f1 = 5.09MHz and f2 = 7.09MHz above carrier frequency MIN TYP 105 1575.42 3.5 -14 -25 4.092 16 6 VDD - 0.9 0 VDD MAX 120 UNITS dB MHz dB dB dBm MHz ns V V
Differential (VOUT+, VOUT-), CL < 20pF Single ended (DOUT), CL<20pF Differential Single ended Differential Single ended
2
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Single-Chip Global Positioning System Receiver Front-End
AC ELECTRICAL CHARACTERISTICS (continued)
(MAX2745 EV kit, VDD = +2.4V to +3.6V, SHDN = GND, TA = -40C to +85C. Typical values are at VDD = +3.0V and TA = +25C, unless otherwise noted.)
PARAMETER SYNTHESIZER Crystal Input Frequency Charge-Pump Current Phase Noise Maximum PLL Spur VCO Tuning Frequency Range VCO Tuning Gain IF STAGE IF Stage Gain Dynamic Range IF Stage Gain Bandpass Filter 1dB Corner Frequency Bandpass Filter 3dB Bandwidth Bandpass Filter 60dB High-Side Rejection Bandpass Filter 60dB Low-Side Rejection Image Rejection In-Band Ripple AGC Loop Lock Time fOFFSET = 10kHz offset, BWLOOP = 70kHz fOFFSET = 1MHz offset, BWLOOP = 70kHz BWLOOP = 70kHz (Notes 2, 3) (Notes 2, 3) VGA set at maximum gain Low-frequency corner High-frequency corner CONDITIONS Fundamental frequency crystal 3rd overtone crystal MIN TYP 16.368 32.736 0.4 -81 dBc/Hz -104 150 150 -39 210 210 80 56 3.1 5.1 2.0 6.6 1.6 17 1 1 270 310 dBc MHz MHz/V dB dB MHz MHz MHz MHz dB dB ms MAX UNITS MHz mA
MAX2745
Note 1: At TA = +25C, min/max limits are guaranteed by production test. Note 2: At TA = -40C, min/max limits are guaranteed by design and characterization. Note 3: At TA = +25C and +85C, min/max limits are guaranteed by production test.
Typical Operating Characteristics
(MAX2745 EV kit, VDD = +3.0V, SHDN = GND, fRF = 1575.42MHz, and TA = +25C, unless otherwise noted.)
SUPPLY CURRENT vs. TEMPERATURE
MAX2745 toc01
LNA/MIXER GAIN vs. TEMPERATURE
35 LNA MIXER GAIN (dB) 30 25 20 15 10 5 VCC = 2.4V VCC = 2.7V VCC = 3V
MAX2745 toc02
IF STAGE GAIN vs. TEMPERATURE
95 90 IF STAGE GAIN (dB) VCC = 2.4V 85 80 75 70 65 60 VCC = 3V VCC = 2.7V
MAX2745 toc03
30
40
100
26 SUPPLY CURRENT (mA) VCC = 2.7V
22
VCC = 3V
18 VCC = 2.4V
14
10 -40 -20 0 20 40 60 80 TEMPERATURE (C)
0 -40 -20 0 20 40 60 80 TEMPERATURE (C)
-40
-20
0
20
40
60
80
TEMPERATURE (C)
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3
Single-Chip Global Positioning System Receiver Front-End MAX2745
Typical Operating Characteristics (continued)
(MAX2745 EV kit, VDD = +3.0V, SHDN = GND, fRF = 1575.42MHz, and TA = +25C, unless otherwise noted.)
TOTAL GAIN vs. TEMPERATURE
TEMPERATURE-SENSOR OUTPUT VOLTAGE, VTO (V)
MAX2745 toc04
TEMPERATURE-SENSOR OUTPUT VOLTAGE vs. TEMPERATURE
MAX4725 toc05
VOLTAGE-BOOSTER OUTPUT vs. VDD_VB
VOLTAGE-BOOSTER OUTPUT, VOUT (V) BST_CTRL = HIGH VOUT = VDD TA = -40C 2.8 2.6 2.4 TA = +85C 2.2 2.0 TA = +25C
MAX2745 toc06
110 VCC = 3V 108 TOTAL GAIN (dB) VCC = 2.7V
1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 -40 -20 0 20 40 60 80 TEMPERATURE (C) VDD = 2.4V VDD = 3.6V
3.2 3.0
106 VCC = 2.4V
104
102
100 -40 -20 0 20 40 60 80 TEMPERATURE (C)
1.6
1.7
1.8
1.9
2.0
2.1
2.2
2.3
VDD_VB (V)
Pin Description
PIN 1 2 3, 4, 9, 11, 13, 25, 27, 32, 39, 43, 46 5, 6, 8, 14, 26, 30, 41, 44 7 10 12 15 16 17 18 19 20 21 22 23 24 NAME RBIAS CBIAS VDD FUNCTION External BIAS Resistor. For normal bias, connect a 100k (1%) resistor to ground. BIAS Bypass Capacitor. Connect a 0.1F capacitor to ground. Power-Supply Voltage. Bypass with a 0.1F capacitor to ground as close to the pins as possible.
GND RFIN IEXT_LNA AGC_FIL XTAL_SSEL XTAL_CSEL BST_CTRL TEST_EN VDD_VB CKOUT DOUT VB_CS+ VB_CSVOUT
Ground RF Input Signal. Requires external matching network. External LNA Voltage Supply AGC External Filter. Requires external RC lowpass filter. Crystal Swing Select. Drive logic high for full swing. Drive logic low for limited swing. Crystal Clock Select. Drive logic high for fundamental mode of 16.368MHz. Drive logic low for third overtone mode of 32.736MHz. Active-High Boost Control Input. Drive logic high to activate the voltage booster (crystal oscillator is biased from BIAS). Drive logic low to deactivate the voltage booster (crystal oscillator is self-biased). Connect to Ground for Normal Operation Power Supply for Voltage Booster. Connect to VDD if voltage booster is not used. Full-Swing Clock Output Single-Ended Full-Swing Digital Output Positive Voltage Booster External Floating CAP. Connect a 6nF capacitor to GND. Negative Voltage Booster External Floating CAP. Connect a 6nF capacitor to GND. Voltage Booster Output. Bypass to GND with a 1F capacitor as close to the pin as possible.
4
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Single-Chip Global Positioning System Receiver Front-End MAX2745
Pin Description (continued)
PIN 28 29 31 33 34 35 36 37 38 40 42 45 47 48 NAME VOUTVOUT+ SCLK COE CFS ODS BPF_CTRL SDATA TEMPOUT VTUNE CP_OUT SHDN XTALOUT XTALIN FUNCTION Quantizer Analog Negative Limited-Swing Output Quantizer Analog Positive Limited-Swing Output Serial Port Clock Input (Bidirectional PAD) Clock Output Enable. Drive logic high to enable the clock output. Drive logic low to disable the clock output. Clock Frequency Select. Drive logic high to select 16MHz. Drive logic low to select 32MHz. Output Data Select. Drive logic high to select full-swing output. Drive logic low to select limitedswing output. Bandpass Filter (BPF) Control. Drive logic high to activate the tuning block control BPF. Drive logic low to let BPF be controlled by fuses. Serial Port Data (Bidirectional PAD) Temperature Sense DC Voltage Output VCO Tuning Input PLL Charge-Pump Output. Analog high-impedance output. Current source. Connect directly to the PLL loop filter input. Active-High Shutdown Input. Drive logic low to disable all device functions. Drive logic high for normal operation. Crystal Output. Connect directly to the external crystal. Crystal Input. Connect directly to the external crystal or TCXO.
Functional Diagram
1.57542GHz BPF LNA IMAGE REJECTION BPF VGA QUANTIZER
4.092MHz IF OUTPUT: FULL SWING DIFFERENTIAL LIMITED SWING
AGC SHUTDOWN POWER SWITCH /96 /48 PFD
OUTPUT CONTROL
VDD1V6
VOLTAGE BOOSTER
16.368MHz 32.768MHz
MAX2745
DIGITAL CONTROL TEMP SENSOR CP MUX CLOCK OUTPUT: 16.368MHz 32.768MHz
VSPORT
TEMP SENSOR DC OUTPUT
PLL LOOP FILTER
CLOCK FREQ CONTROL
CLOCK OUTPUT CONTROL
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5
Single-Chip Global Positioning System Receiver Front-End MAX2745
Detailed Description
The MAX2745 complete single-chip GPS front-end downconverter utilizes many innovative and leadingedge RF CMOS design techniques. This high-performance, state-of-the-art device consumes extremely low power and eliminates the need for costly SAW and bulky discrete IF filters. The MAX2745 incorporates a fully integrated LNA/mixer, IF section, digital sampler, and local oscillator synthesizer. The MAX2745 also provides voltage supply for an external LNA. In addition, the MAX2745 features a voltage booster that can extend the power-supply voltage to as low as 1.6V. The MAX2745 supports both 3rd overtone crystal designs in 32MHz and fundamental frequency crystal design in 16MHz, as well as a TCXO implementation. In addition, the MAX2745 incorporates an on-chip temperature sensor and crystal oscillator with trimmed capacitors, resulting in a very accurate frequency and additional system cost savings. The MAX2745 also incorporates a 2MHz bandwidth bandpass filter to reduce off-band noise. The bandwidth and the center frequency of the bandpass filter are guaranteed by an advanced tuning scheme. The MAX2745 is offered in a space-saving 48-pin TQFP package. The operational temperature range is specified from -40C to +85C. The power consumption of this device is as low as 41mW at 2.4V. oscillator driver generates the reference frequency. The integrated synthesizer includes the VCO, crystal oscillator driver, main frequency divider, phase-frequency detector, and charge pump. It uses an off-chip PLL loop filter and crystal. If a TCXO is used, connect the output of the TCXO to XTALIN. The main division ratio for the synthesizer is 96 or 48. With this division ratio, a low-side injection LO can be used with a 16.368MHz or 32.736MHz crystal. Note that if a 3rd overtone crystal is used for the 32.736MHz, an off-chip notch filter to reject the fundamental frequency is required. The notch filter can be built with one inductor and one capacitor.
Control Block
This block is used mainly for testing purposes and to set the internal trimmed capacitor. This block is programmed through the VSport.
VSport Serial Data Interface
The serial interface within the MAX2745 is used by the baseband to communicate control signals and is also used for internal testing of the device. (This serial port is described in a separate document, which is available upon request.)
Trimmed VCXO Frequency
An on-chip, trimmed capacitor with a temperature coefficient of better than 30ppm/C is used to compensate for the component variation of the reference frequency associated circuitry. The value of the capacitor is programmed in 512 binary steps and ranges from a minimum of 80fF to a maximum of 40pF, 20%. Programming is accomplished with the VSport serial interface. The no load capacitance on the crystal out follows the equation: C(no load) = ([Register Value] x 40/512) pF Upon power-up, the capacitor value is set to the minimum value. This enables the MAX2745 to work with an off-chip, trimmed capacitor. If the baseband has the capability of programming the radio, the off-chip, trimmed capacitor can be omitted by setting the internal trimmed capacitor through the VSPORT.
LNA/Mixer
The RF input signal from the GPS antenna is fed through an LNA with a gain of 20dB. The amplified signal is then fed to a mixer that downconverts the signal (1575.42MHz) to a quadrature differential IF of 4.092MHz.
IF Stage
The quadrature IF signals pass through the IF filter, which rejects the out-of-band spurs by more than 60dB and the image noise by 17dB (typ). After the image reject filter, the signal is converted from quadrature to differential. The filtered IF signal is then amplified by the AGC block, which sets the VGA output signal level to a predetermined value through the application using 56dB of dynamic range.
IF Output Selection
The sampled outputs of the GPS signal are available in a single-ended or limited-differential format. The ODS pin controls the output format.
Synthesizer
An on-chip VCO provides quadrature differential LO signals to the downconverting mixer. An on-chip crystal
6 _______________________________________________________________________________________
Single-Chip Global Positioning System Receiver Front-End
Temperature Sensor
The MAX2745 features an on-chip temperature sensor to facilitate system temperature compensations in conjunction with the trimmed capacitor. This circuit generates an output voltage at TEMPOUT, which is used to approximate the temperature by the following equation: T = TO + (VOUT - VOUT,TO)/SG where SG is the sensor gain, TO is factory-trimmed temperature, which can be any value (normally +27C), and VOUT is the temperature output voltage at TO. The coefficient SG in the above equation is targeted to be between 6mV/C and 8mV/C, depending on the temperature. VB_CS, pins 22 and 23, and 1F bypass capacitor to VOUT, pin 24. Connect VOUT (pin 24) to all the powersupply (VDD) pins and pull BST_CTRL, pin 17, high to activate the booster. Then the MAX2745 can be powered from supply voltages ranging from 1.6V to 2.3V at VDD_VB, pin 19, and the voltage booster output can source up to 25mA current. It is recommended that the voltage booster be used as a backup supply. To do this, additional circuits including a voltage monitor and a switch are needed. These components are inexpensive and can be found in the Maxim product family.
MAX2745
Layout Issues
A properly designed PC board is an essential part of any RF/microwave circuit. Use the MAX2745 EV kit as a guide. Use controlled-impedance lines on all frequency inputs and outputs. Use low inductance connections to ground on all ground pins and wherever the components are connected to ground. Place decoupling capacitors close to all V CC connections. For proper operation, connect the metal exposed paddle at the back of the IC to the PC board ground plane with multiple vias.
Voltage Booster
The MAX2745 integrates an internal voltage booster to allow proper operation with supply voltages as low as 1.6V. The circuit includes two 6nF floating external capacitors connected to VB_CS (pins 22 and 23) and a 1F capacitance to VOUT (boosted voltage output, pin 24). To reduce the output voltage ripple, use an external LC lowpass filter, which can be built with two inductors and one capacitor.
Applications Information
Operation with Voltage Booster
Under normal operating conditions, the recommended power-supply voltage ranges from 2.4V to 3.6V. But with the integrated voltage booster on-chip, the MAX2745 can be powered from power-supply voltages as low as 1.6V, and only requires a minimal number of external components. This is not the most efficient operating mode, since the power efficiency will be lowered to less than 50%. As described in the Detailed Description section, to use the voltage booster, connect 6nF floating capacitors to
Chip Information
TRANSISTOR COUNT: 9205 PROCESS: CMOS
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7
Single-Chip Global Positioning System Receiver Front-End MAX2745
Typical Application Circuit
TCXO OPTIONAL XTAL INPUT
PIN 47 PIN 48
XTALOUT
CP_OUT
XTALIN
VTUNE
TEMPOUT
38
VDD
GND
VDD
48
47
46
45
44
43
42
41
40
39
RBIAS CBIAS
1 2 VCXO
MAX2745
TEMPERATURE SENSOR PFD DIVIDER BIAS CHG PUMP
SDATA
37
SHDN
GND
VDD
36 BPF_CTRL 35 34 33 ODS CFS COE
VDD 3 VDD 4 GND 5 GND 6 fIN 1575.42MHz GND 8 VDD 9 RFIN 7
32 VDD VSPORT LNA/MIXER VCO 30 GND 29 VOUT+ 28 VOUTBANDPASS FILTER AGC QUANTIZER 27 VDD VOLTAGE BOOSTER 26 GND 25 VDD 31 SCLK
IEXT_LNA 10 VDD 11 FILTER AUTOMATIC TUNING AGC_FIL 12
13
14
15
16
17
18
19
20
21
22
23
24
XTAL_SSEL
XTAL_CSEL
BST_CTRL
TEST_EN
VDD_VB
VB_CS+
VB_CS-
CKOUT
DOUT
GND
VDD
8
_______________________________________________________________________________________
VOUT
SSingle-Chip Global Positioning System Receiver Front-End
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.)
48L,TQFP.EPS
MAX2745
PACKAGE OUTLINE, 32/48L TQFP, 7x7x1.0mm EP OPTION
21-0065
F
1 2
PACKAGE OUTLINE, 32/48L TQFP, 7x7x1.0mm EP OPTION
21-0065
F
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.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 _____________________ 9 (c) 2004 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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