19-3425; Rev 0; 10/04
IT
TION K
VALUA
E
BLE
AVAILA
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 -40°C to +85°C 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 tech-
niques. 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 pro-
vides 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 tem-
perature 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.
Ordering Information
PART
MAX2745ECM
TEMP RANGE
-40°C to +85°C
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
V
DD
3
V
DD
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 V
DD
31 SCLK
30 GND
29 VOUT+
28 VOUT-
27 V
DD
26 GND
25 V
DD
24
SHDN
Location-Based Services (PDAs and
Accessories)
Block Diagram/
Pin Configuration
GND
GND
V
DD
V
DD
V
DD
VSPORT
LNA/MIXER
RFIN 7
GND 8
V
DD
9
BANDPASS FILTER
IEXT_LNA 10
V
DD
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
V
TO
________________________________________________________________
Maxim Integrated Products
V
OUT
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
V
DD
to 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
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 ......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Soldering Temperature (10s) ...........................................+300°C
DC ELECTRICAL CHARACTERISTICS
(MAX2745 EV kit, V
DD
= +2.4V to +3.6V, SHDN = GND, T
A
= -40°C
to +85°C. Typical values are at V
DD
= +3.0V and T
A
= +25°C,
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
V
DD
= +3.0V, T
A
= +25°C (Note 1)
Shutdown mode
V
DD
= +3.0V
2.0
0.5
+10
CONDITIONS
MIN
2.4
20.5
11
10
TYP
MAX
3.6
27
UNITS
V
mA
µA
mA
V
V
µA
AC ELECTRICAL CHARACTERISTICS
(MAX2745 EV kit, V
DD
= +2.4V to +3.6V, SHDN = GND, T
A
= -40°C to +85°C. Typical values are at V
DD
= +3.0V and T
A
= +25°C,
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
f
1
= 5.09MHz and f
2
= 7.09MHz above carrier frequency
MIN
TYP
105
1575.42
3.5
-14
-25
4.092
16
6
V
DD
- 0.9
0
V
DD
MAX
120
UNITS
dB
MHz
dB
dB
dBm
MHz
ns
V
V
Differential (VOUT+, VOUT-), C
L
< 20pF
Single ended (DOUT), C
L
<20pF
Differential
Single ended
Differential
Single ended
2
_______________________________________________________________________________________
Single-Chip Global Positioning System
Receiver Front-End
AC ELECTRICAL CHARACTERISTICS (continued)
(MAX2745 EV kit, V
DD
= +2.4V to +3.6V, SHDN = GND, T
A
= -40°C to +85°C. Typical values are at V
DD
= +3.0V and T
A
= +25°C,
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
f
OFFSET
= 10kHz offset,
BW
LOOP
= 70kHz
f
OFFSET
= 1MHz offset,
BW
LOOP
= 70kHz
BW
LOOP
= 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 T
A
= +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.
Typical Operating Characteristics
(MAX2745 EV kit, V
DD
= +3.0V, SHDN = GND, f
RF
= 1575.42MHz, and T
A
= +25°C, 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
V
CC
= 2.4V
V
CC
= 2.7V
V
CC
= 3V
MAX2745 toc02
IF STAGE GAIN vs. TEMPERATURE
95
90
IF STAGE GAIN (dB)
V
CC
= 2.4V
85
80
75
70
65
60
V
CC
= 3V
V
CC
= 2.7V
MAX2745 toc03
30
40
100
26
SUPPLY CURRENT (mA)
V
CC
= 2.7V
22
V
CC
= 3V
18
V
CC
= 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)
_______________________________________________________________________________________
3
Single-Chip Global Positioning System
Receiver Front-End
MAX2745
Typical Operating Characteristics (continued)
(MAX2745 EV kit, V
DD
= +3.0V, SHDN = GND, f
RF
= 1575.42MHz, and T
A
= +25°C, unless otherwise noted.)
TOTAL GAIN vs. TEMPERATURE
TEMPERATURE-SENSOR OUTPUT VOLTAGE, V
TO
(V)
MAX2745 toc04
TEMPERATURE-SENSOR OUTPUT VOLTAGE
vs. TEMPERATURE
MAX4725 toc05
VOLTAGE-BOOSTER
OUTPUT vs. VDD_VB
VOLTAGE-BOOSTER OUTPUT, V
OUT
(V)
BST_CTRL = HIGH
V
OUT
= V
DD
T
A
= -40°C
2.8
2.6
2.4
T
A
= +85°C
2.2
2.0
T
A
= +25°C
MAX2745 toc06
110
V
CC
= 3V
108
TOTAL GAIN (dB)
V
CC
= 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)
V
DD
= 2.4V
V
DD
= 3.6V
3.2
3.0
106
V
CC
= 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
V
DD
FUNCTION
External BIAS Resistor. For normal bias, connect a 100kΩ (1%) resistor to ground.
BIAS Bypass Capacitor. Connect a 0.1µF capacitor to ground.
Power-Supply Voltage. Bypass with a 0.1µF 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_CS-
V
OUT
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 V
DD
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 1µF capacitor as close to the pin as possible.
4
_______________________________________________________________________________________
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
VOUT-
VOUT+
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 limited-
swing 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
_______________________________________________________________________________________
5
京公网安备 11010802033920号
Copyright © 2005-2026 EEWORLD.com.cn, Inc. All rights reserved
电子工程世界
