General Description
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 (-40°C
to +85°C) temperature range. The power consumption
of this device is as low as 41mW at 2.4V.
Applications
In-Vehicle Navigation Systems (IVNSs)
Location-Based Services (PDAs and
Accessories)
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
Features
♦ Complete Single-Chip GPS Radio for 16.368MHz
and 32.736MHz Floorplans
♦ Single-Ended or Differential Outputs at 4.092MHz
♦ Low 3.5dB Typical Noise Figure
♦ No External IF SAW or Discrete Filters Required
♦ On-Chip Temperature Sensor
♦ 2.4V to 3.6V Operational Supply Voltage Range
♦ Power Consumption as Low as 41mW at 2.4V
♦ Wide -40°C to +85°C Operational Temperature
Range
MAX2745
Single-Chip Global Positioning System
Receiver Front-End
________________________________________________________________ Maxim Integrated Products 1
Ordering Information
19-3425; Rev 0; 10/04
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.
EVALUATION KIT
AVAILABLE
PART TEMP RANGE PIN-PACKAGE
MAX2745ECM -40°C to +85°C 48 TQFP-EP*
*EP = Exposed paddle.
Block Diagram/
Pin Configuration
VCXO
BIAS
LNA/MIXER
PFD
DIVIDER
CHG
PUMP
VCO
TEMPERATURE
SENSOR
VSPORT
BANDPASS FILTER
FILTER AUTOMATIC TUNING
AGC
QUANTIZER
VOLTAGE
BOOSTER
48
XTALIN
11
V
DD
12
AGC_FIL
25
V
DD
10
IEXT_LNA
7
RFIN
9
V
DD
47
XTALOUT
2
CBIAS
4
30
GND
27
V
DD
20
CKOUT
19
VDD_VB
1
RBIAS
3
V
DD
V
DD
5
GND
13
V
DD
14
GND
15
XTAL_SSEL
16
XTAL_CSEL
17
BST_CTRL
18
TEST_EN
21
DOUT
23
VB_CS-
24
V
OUT
22
VB_CS+
28
VOUT-
29
VOUT+
31
SCLK
32
V
DD
33
COE
34
CFS
35
ODS
36
BPF_CTRL
37
SDATA
38
V
TO
39
V
DD
40
VTUNE
41
GND
42
CP_OUT
43
V
DD
44
GND
46
V
DD
6
GND
8
GND
GND
26
45
SHDN
MAX2745
Typical Operating Circuit appears at end of data sheet
MAX2745
Single-Chip Global Positioning System
Receiver Front-End
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
DC ELECTRICAL CHARACTERISTICS
(MAX2745 EV kit, VDD= +2.4V to +3.6V, SHDN = GND, TA= -40°C to +85°C. Typical values are at VDD= +3.0V and TA= +25°C,
unless otherwise noted.)
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.
VDDto GND...........................................................-0.3V to +3.7V
Other Pins to GND......................................-0.3V to (V
DD
+ 0.3V)
RF LNA Input Power .......................................................+10dBm
Continuous Power Dissipation (T
A
= +70°C)
48-Pin TQFP-EP (derate 12.5mW/°C above +70°C) ............1W
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Soldering Temperature (10s) ...........................................+300°C
3.6 V
VDD = +3.0V, TA = +25°C (Note 1)
27 mA
Supply Current
Shutdown mode 11 µA
Optional External LNA Supply
Current
V
DD
= +3.0V
mA
Logic-Input High Voltage
V
Logic-Input Low Voltage
V
Logic-Input Bias Current
CAUTION! ESD SENSITIVE DEVICE
AC ELECTRICAL CHARACTERISTICS
(MAX2745 EV kit, VDD= +2.4V to +3.6V, SHDN = GND, TA= -40°C to +85°C. Typical values are at VDD= +3.0V and TA= +25°C,
unless otherwise noted.)
GENERAL PERFORMANCE
Maximum Conversion Gain (Notes 2, 3) 105
Noise Figure Measured at quantizer output 3.5 dB
Return Loss (S11) -14 dB
LNA/Mixer Input IP3
OUTPUT STAGE
Differential (VOUT+, VOUT-), CL < 20pF 16
Output Rise/Fall Time
Single ended (DOUT), C
L
<20pF 6
ns
Differential
Output-Voltage-Level Low
Single ended 0
V
Differential
Output-Voltage-Level High
Single ended
V
DD
V
2.4
20.5
10
2.0
-10 +10
f1 = 5.09MHz and f2 = 7.09MHz above carrier frequency
MIN
1575.42
4.092
VDD - 0.9
0.5
MAX
120
MAX2745
Single-Chip Global Positioning System
Receiver Front-End
_______________________________________________________________________________________ 3
Note 1: At TA= +25°C, min/max limits are guaranteed by production test.
Note 2: At T
A
= -40°C, min/max limits are guaranteed by design and characterization.
Note 3: At T
A
= +25°C and +85°C, min/max limits are guaranteed by production test.
AC ELECTRICAL CHARACTERISTICS (continued)
(MAX2745 EV kit, VDD= +2.4V to +3.6V, SHDN = GND, TA= -40°C to +85°C. Typical values are at VDD= +3.0V and TA= +25°C,
unless otherwise noted.)
SYNTHESIZER
Fundamental frequency crystal
Crystal Input Frequency
3rd overtone crystal
Charge-Pump Current 0.4 mA
f
OFFSET
= 10kHz offset,
BW
LOOP
= 70kHz
-81
Phase Noise
f
OFFSET
= 1MHz offset,
BW
LOOP
= 70kHz
Maximum PLL Spur BW
LOOP
= 70kHz -39 dBc
VCO Tuning Frequency Range (Notes 2, 3)
VCO Tuning Gain (Notes 2, 3)
IF STAGE
IF Stage Gain VGA set at maximum gain 80 dB
Dynamic Range IF Stage Gain 56 dB
Low-frequency corner 3.1
Bandpass Filter 1dB Corner
Frequency
High-frequency corner 5.1
Bandpass Filter 3dB Bandwidth 2.0
Bandpass Filter 60dB High-Side
Rejection
6.6
Bandpass Filter 60dB Low-Side
Rejection
1.6
Image Rejection 17 dB
In-Band Ripple 1dB
AGC Loop Lock Time 1ms
Typical Operating Characteristics
(MAX2745 EV kit, VDD= +3.0V, SHDN = GND, fRF= 1575.42MHz, and TA= +25°C, unless otherwise noted.)
SUPPLY CURRENT vs. TEMPERATURE
MAX2745 toc01
TEMPERATURE (°C)
SUPPLY CURRENT (mA)
6040200-20
14
18
22
26
30
10
-40 80
VCC = 2.4V
VCC = 2.7V
VCC = 3V
LNA/MIXER GAIN vs. TEMPERATURE
MAX2745 toc02
TEMPERATURE (°C)
LNA MIXER GAIN (dB)
6040200-20
10
5
15
20
25
30
35
40
0
-40 80
VCC = 2.4V
VCC = 2.7V
VCC = 3V
IF STAGE GAIN vs. TEMPERATURE
MAX2745 toc03
TEMPERATURE (°C)
IF STAGE GAIN (dB)
6040200-20
70
65
75
80
85
90
95
100
60
-40 80
VCC = 2.4V
VCC = 2.7V
VCC = 3V
MIN
150
150
MAX
16.368
32.736
-104