MAX2745 [MAXIM]
Single-Chip Global Positioning System Receiver Front-End; 单芯片，全球定位系统接收前端
| 型号： | MAX2745 |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | Single-Chip Global Positioning System Receiver Front-End |
| 文件： | 总9页 (文件大小：411K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-3425; Rev 0; 10/04
Single-Chip Global Positioning System
Receiver Front-End
General Description
Features
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.
ꢀ 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
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.
Range
Ordering Information
PART
TEMP RANGE
PIN-PACKAGE
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.
MAX2745ECM
-40°C to +85°C
48 TQFP-EP*
*EP = Exposed paddle.
Typical Operating Circuit appears at end of data sheet
Applications
In-Vehicle Navigation Systems (IVNSs)
Block Diagram/
Pin Configuration
Location-Based Services (PDAs and
Accessories)
Telematics (Vehicle/Asset Tracking and
Inventory Management)
48
47
46
45
44
43
42
41
40
39
38
37
BPF_CTRL
ODS
36
35
34
33
32
31
30
29
28
27
RBIAS
CBIAS
1
2
3
4
5
6
7
8
9
TEMPERATURE
SENSOR
VCXO
Recreational Handheld/Walkie Talkies
Geographical Information Systems (GISs)
Emergency Roadside Assistance
Emergency Response Systems
Digital Cameras/Camcorders
MAX2745
CFS
V
V
DD
DD
BIAS
COE
PFD
DIVIDER
CHG
PUMP
V
GND
GND
RFIN
GND
DD
SCLK
GND
VSPORT
LNA/MIXER
VCO
Consumer Electronics
VOUT+
VOUT-
V
DD
BANDPASS FILTER
AGC
QUANTIZER
IEXT_LNA 10
V
DD
VOLTAGE
BOOSTER
V
11
12
26 GND
DD
FILTER AUTOMATIC TUNING
AGC_FIL
V
DD
25
13
14
15
16
17
18
19
20
21
22
23
24
________________________________________________________________ Maxim Integrated Products
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
ABSOLUTE MAXIMUM RATINGS
DD
Other Pins to GND......................................-0.3V to (V
RF LNA Input Power.......................................................+10dBm
V
to GND...........................................................-0.3V to +3.7V
Junction Temperature......................................................+150°C
Storage Temperature Range.............................-65°C to +150°C
Soldering Temperature (10s)...........................................+300°C
+ 0.3V)
DD
Continuous Power Dissipation (T = +70°C)
A
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.
DC ELECTRICAL CHARACTERISTICS
(MAX2745 EV kit, V
= +2.4V to +3.6V, SHDN = GND, T = -40°C to +85°C. Typical values are at V
= +3.0V and T = +25°C,
DD A
DD
A
unless otherwise noted.)
PARAMETER
CONDITIONS
MIN
TYP
MAX
3.6
UNITS
V
Supply Voltage
2.4
V
= +3.0V, T = +25°C (Note 1)
20.5
11
27
mA
µA
DD
A
Supply Current
Shutdown mode
Optional External LNA Supply
Current
V
= +3.0V
10
mA
DD
Logic-Input High Voltage
Logic-Input Low Voltage
Logic-Input Bias Current
2.0
-10
V
V
0.5
+10
µA
AC ELECTRICAL CHARACTERISTICS
(MAX2745 EV kit, V
= +2.4V to +3.6V, SHDN = GND, T = -40°C to +85°C. Typical values are at V
= +3.0V and T = +25°C,
DD A
DD
A
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
CONDITIONS
MIN
TYP
MAX
UNITS
(Notes 2, 3)
Measured at quantizer output
f = 5.09MHz and f = 7.09MHz above carrier frequency
105
1575.42
3.5
-14
-25
120
dB
MHz
dB
dB
dBm
MHz
1
2
4.092
Differential (VOUT+, VOUT-), C < 20pF
Single ended (DOUT), C <20pF
L
Differential
Single ended
Differential
16
6
- 0.9
DD
L
Output Rise/Fall Time
ns
V
V
Output-Voltage-Level Low
Output-Voltage-Level High
0
V
V
DD
Single ended
2
_______________________________________________________________________________________
Single-Chip Global Positioning System
Receiver Front-End
AC ELECTRICAL CHARACTERISTICS (continued)
(MAX2745 EV kit, V
= +2.4V to +3.6V, SHDN = GND, T = -40°C to +85°C. Typical values are at V
= +3.0V and T = +25°C,
DD A
DD
A
unless otherwise noted.)
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
SYNTHESIZER
Fundamental frequency crystal
3rd overtone crystal
16.368
32.736
0.4
Crystal Input Frequency
Charge-Pump Current
MHz
mA
f
= 10kHz offset,
OFFSET
-81
BW
= 70kHz
LOOP
Phase Noise
dBc/Hz
f
= 1MHz offset,
OFFSET
-104
BW
BW
(Notes 2, 3)
(Notes 2, 3)
= 70kHz
LOOP
Maximum PLL Spur
VCO Tuning Frequency Range
VCO Tuning Gain
= 70kHz
-39
210
210
dBc
MHz
MHz/V
LOOP
150
150
270
310
IF STAGE
IF Stage Gain
VGA set at maximum gain
80
56
3.1
5.1
2.0
dB
dB
Dynamic Range IF Stage Gain
Bandpass Filter 1dB Corner
Frequency
Bandpass Filter 3dB Bandwidth
Bandpass Filter 60dB High-Side
Rejection
Low-frequency corner
High-frequency corner
MHz
MHz
MHz
6.6
1.6
Bandpass Filter 60dB Low-Side
Rejection
MHz
Image Rejection
In-Band Ripple
AGC Loop Lock Time
17
1
1
dB
dB
ms
Note 1: At T = +25°C, min/max limits are guaranteed by production test.
A
Note 2: At T = -40°C, min/max limits are guaranteed by design and characterization.
A
Note 3: At T = +25°C and +85°C, min/max limits are guaranteed by production test.
A
Typical Operating Characteristics
(MAX2745 EV kit, V
= +3.0V, SHDN = GND, f = 1575.42MHz, and T = +25°C, unless otherwise noted.)
DD
RF
A
SUPPLY CURRENT vs. TEMPERATURE
LNA/MIXER GAIN vs. TEMPERATURE
IF STAGE GAIN vs. TEMPERATURE
30
26
22
18
14
10
40
100
95
90
85
80
75
70
65
60
35
30
25
20
15
10
5
V
= 3V
CC
V
= 2.4V
CC
V
= 2.7V
CC
V
= 3V
CC
V
= 3V
CC
V
= 2.4V
CC
0
V
= 2.7V
60
V
= 2.7V
40
V
= 2.4V
CC
CC
CC
0
-40
-20
0
20
40
60
80
-40
-20
20
40
80
-40
-20
0
20
60
80
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
_______________________________________________________________________________________
3
Single-Chip Global Positioning System
Receiver Front-End
Typical Operating Characteristics (continued)
(MAX2745 EV kit, V
= +3.0V, SHDN = GND, f = 1575.42MHz, and T = +25°C, unless otherwise noted.)
DD
RF
A
TEMPERATURE-SENSOR OUTPUT VOLTAGE
vs. TEMPERATURE
VOLTAGE-BOOSTER
OUTPUT vs. VDD_VB
TOTAL GAIN vs. TEMPERATURE
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
110
108
106
104
102
100
3.2
3.0
2.8
2.6
2.4
2.2
2.0
BST_CTRL = HIGH
V
= 3V
V
= V
CC
OUT
DD
V
= 2.7V
CC
T
= -40°C
A
V
= 3.6V
DD
T
= +25°C
A
V
= 2.4V
CC
T
= +85°C
V
= 2.4V
A
DD
-40 -20
0
20
40
60
80
1.6 1.7 1.8 1.9 2.0 2.1 2.2 2.3
VDD_VB (V)
-40
-20
0
20
40
60
80
TEMPERATURE (°C)
TEMPERATURE (°C)
Pin Description
PIN
1
NAME
RBIAS
CBIAS
FUNCTION
External BIAS Resistor. For normal bias, connect a 100kΩ (1%) resistor to ground.
2
BIAS Bypass Capacitor. Connect a 0.1µF capacitor to ground.
3, 4, 9, 11, 13,
25, 27, 32, 39,
43, 46
V
Power-Supply Voltage. Bypass with a 0.1µF capacitor to ground as close to the pins as possible.
DD
5, 6, 8, 14, 26,
30, 41, 44
GND
Ground
7
RFIN
RF Input Signal. Requires external matching network.
External LNA Voltage Supply
10
12
15
IEXT_LNA
AGC_FIL
AGC External Filter. Requires external RC lowpass filter.
XTAL_SSEL 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.
16
17
XTAL_CSEL
Active-High Boost Control Input. Drive logic high to activate the voltage booster (crystal oscillator is
BST_CTRL
biased from BIAS). Drive logic low to deactivate the voltage booster (crystal oscillator is self-biased).
18
19
20
21
22
23
24
TEST_EN
VDD_VB
CKOUT
DOUT
Connect to Ground for Normal Operation
Power Supply for Voltage Booster. Connect to V
Full-Swing Clock Output
if voltage booster is not used.
DD
Single-Ended Full-Swing Digital Output
VB_CS+
VB_CS-
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.
V
OUT
4
_______________________________________________________________________________________
Single-Chip Global Positioning System
Receiver Front-End
Pin Description (continued)
PIN
28
NAME
FUNCTION
Quantizer Analog Negative Limited-Swing Output
VOUT-
VOUT+
SCLK
29
Quantizer Analog Positive Limited-Swing Output
Serial Port Clock Input (Bidirectional PAD)
31
Clock Output Enable. Drive logic high to enable the clock output. Drive logic low to disable the clock
output.
33
34
35
COE
CFS
ODS
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.
36
BPF_CTRL
SDATA
37
38
40
Serial Port Data (Bidirectional PAD)
TEMPOUT Temperature Sense DC Voltage Output
VTUNE
VCO Tuning Input
PLL Charge-Pump Output. Analog high-impedance output. Current source. Connect directly to the
PLL loop filter input.
42
45
CP_OUT
Active-High Shutdown Input. Drive logic low to disable all device functions. Drive logic high for
normal operation.
SHDN
47
48
XTALOUT
XTALIN
Crystal Output. Connect directly to the external crystal.
Crystal Input. Connect directly to the external crystal or TCXO.
Functional Diagram
4.092MHz IF OUTPUT:
1.57542GHz
BPF
FULL SWING
DIFFERENTIAL
LIMITED SWING
IMAGE
REJECTION
BPF
VGA
AGC
QUANTIZER
LNA
OUTPUT
CONTROL
POWER
SWITCH
SHUTDOWN
/96
/48
PFD
CP
VOLTAGE
BOOSTER
16.368MHz
32.768MHz
VDD1V6
MAX2745
DIGITAL
CONTROL
TEMP
SENSOR
CLOCK OUTPUT:
16.368MHz
MUX
32.768MHz
VSPORT
TEMP
SENSOR DC
OUTPUT
CLOCK
FREQ
CONTROL
CLOCK
OUTPUT
CONTROL
PLL LOOP
FILTER
_______________________________________________________________________________________
5
Single-Chip Global Positioning System
Receiver Front-End
oscillator driver generates the reference frequency. The
Detailed Description
integrated synthesizer includes the VCO, crystal oscil-
lator 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 MAX2745 complete single-chip GPS front-end
downconverter utilizes many innovative and leading-
edge RF CMOS design techniques. This high-perfor-
mance, 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 pro-
vides 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 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 induc-
tor and one capacitor.
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 tempera-
ture sensor and crystal oscillator with trimmed capaci-
tors, resulting in a very accurate frequency and
additional system cost savings.
Control Block
This block is used mainly for testing purposes and to
set the internal trimmed capacitor. This block is pro-
grammed 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.)
The MAX2745 also incorporates a 2MHz bandwidth
bandpass filter to reduce off-band noise. The band-
width 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 speci-
fied from -40°C to +85°C. The power consumption of
this device is as low as 41mW at 2.4V.
Trimmed VCXO Frequency
An on-chip, trimmed capacitor with a temperature coeffi-
cient 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 pro-
grammed in 512 binary steps and ranges from a mini-
mum of 80fF to a maximum of 40pF, 20%. Pro-
gramming is accomplished with the VSport serial inter-
face. The no load capacitance on the crystal out follows
the equation:
LNA/Mixer
The RF input signal from the GPS antenna is fed
through an LNA with a gain of 20dB. The amplified sig-
nal is then fed to a mixer that downconverts the signal
(1575.42MHz) to a quadrature differential IF of
4.092MHz.
C(no load) = ([Register Value] x 40/512) pF
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.
Upon power-up, the capacitor value is set to the mini-
mum 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 inter-
nal trimmed capacitor through the VSPORT.
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
VB_CS , pins 22 and 23, and 1µF bypass capacitor to
OUT
Temperature Sensor
The MAX2745 features an on-chip temperature sensor to
facilitate system temperature compensations in conjunc-
tion with the trimmed capacitor. This circuit generates an
output voltage at TEMPOUT, which is used to approxi-
mate the temperature by the following equation:
V
, pin 24. Connect V
(pin 24) to all the power-
OUT
supply (V ) pins and pull BST_CTRL, pin 17, high to
DD
activate the booster. Then the MAX2745 can be pow-
ered 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 inexpen-
sive and can be found in the Maxim product family.
T = T + (V
- V
)/SG
OUT,TO
O
OUT
where SG is the sensor gain, T is factory-trimmed tem-
O
perature, which can be any value (normally +27°C), and
V
is the temperature output voltage at T . The coeffi-
O
OUT
cient SG in the above equation is targeted to be between
6mV/°C and 8mV/°C, depending on the temperature.
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 compo-
nents are connected to ground. Place decoupling
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 1µF capacitance to V
(boosted voltage output,
OUT
capacitors close to all V
connections. For proper
CC
pin 24). To reduce the output voltage ripple, use an
external LC lowpass filter, which can be built with two
inductors and one capacitor.
operation, connect the metal exposed paddle at the
back of the IC to the PC board ground plane with multi-
ple vias.
Applications Information
Chip Information
TRANSISTOR COUNT: 9205
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 low-
ered to less than 50%.
PROCESS: CMOS
As described in the Detailed Description section, to use
the voltage booster, connect 6nF floating capacitors to
_______________________________________________________________________________________
7
Single-Chip Global Positioning System
Receiver Front-End
Typical Application Circuit
PIN 47
PIN 48
TCXO
OPTIONAL XTAL INPUT
48
47
46
45
44
43
42
41
40
39
38
37
RBIAS
BPF_CTRL
ODS
MAX2745
1
2
36
35
34
33
32
31
30
29
VCXO
CBIAS
TEMPERATURE
SENSOR
CFS
COE
PFD
DIVIDER
V
V
DD
3
CHG
PUMP
4
DD
BIAS
GND
V
5
DD
VSPORT
GND
RFIN
SCLK
GND
6
LNA/MIXER
VCO
f
IN
7
1575.42MHz
GND
VOUT+
8
V
9
28 VOUT-
DD
BANDPASS FILTER
AGC
QUANTIZER
IEXT_LNA
10
11
12
27
V
DD
V
VOLTAGE
BOOSTER
26 GND
DD
FILTER AUTOMATIC TUNING
AGC_FIL
25
V
DD
13
14
15
16
17
18
19
20
21
22
23
24
8
_______________________________________________________________________________________
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.)
PACKAGE OUTLINE,
32/48L TQFP, 7x7x1.0mm EP OPTION
1
21-0065
F
2
PACKAGE OUTLINE,
32/48L TQFP, 7x7x1.0mm EP OPTION
2
21-0065
F
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
© 2004 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.
相关型号：
MAX2745ECM+T
Consumer Circuit, CMOS, PQFP48, 7 X 7 MM, 1 MM HEIGHT, ROHS COMPLIANT, MS-026ABC-HD, TQFP-48
MAXIM
MAX274ACNG+
Continuous Time Filter, 1 Func, Butterworth/bessel/chebyshev, Lowpass/Bandpass, PDIP24, ROHS COMPLIANT, PLASTIC, DIP-24
MAXIM
©2020 ICPDF网 联系我们和版权申明