MAX2678 GPS/GNSS Front-End Amplifier
EVALUATION KIT AVAILABLE
MAX2678
GPS/GNSS Front-End Amplifier
General Description
The MAX2678 GPS/GNSS front-end amplifier IC is
designed for automotive and marine GPS/GNSS satellite
navigation antenna modules, or for any application that
needs to compensate for cable losses from the antenna
to receiver. Two unconditionally stable low-noise amplifier
stages provide the high gain and integrated I/O matching
to minimize the need for external matching components
and eliminate the need for additional gain stages. The
IC features the option to place a bandpass ceramic or
surface acoustic wave (SAW) filter between the two amplifier stages for improved immunity to out-of-band interferers.
Additionally, a 3.4dB-gain step is provided to compensate
for cable loss variation between different applications.
The device is designed to operate across all GNSS
frequency standards with a 35dB typical cascaded gain
and a 25mA supply current. The two LNA stages allow
the use of a wide range of GNSS filter types for maximum
flexibility in system design. The final RF output pin, which
drives the cable to the GNSS receiver, is also the powersupply connection that accepts a DC supply in the 3.0V to
5.25V range. Alternatively, the DC supply can be applied
to pin 4.
This GPS/GNSS front-end amplifier is available in a leadfree, 10-pin TDFN surface-mount package (3mm x 3mm).
Electrical performance is guaranteed over the extended
-40°C to +105°C temperature range.
Features
●● First Amplifier Noise Figure: 0.9dB
●● High Gain:* 35dB
●● 3.4dB Gain Step
●● Shared VCC and RFOUT2 Pin
●● Integrated 50Ω Output Matching
●● AMP 2 includes 50Ω Input Matching
●● 3.0V to 5.25V Supply Voltage Range
●● Small (3mm x 3mm) Low-Cost Package
●● AEC-Q100 Qualified
●● ESD Protected to ±2kV Human Body Model
●● -40°C to +105°C Ambient Temperature Range
Applications
●● Integrated Automotive and Marine GPS Receivers
●● Active Antennas
*First amplifier input is impedance matched (S11 = -10dB).
Second amplifier is set to high gain. Amplifiers are cascaded
without interstage filter.
Ordering Information and Typical Operating Circuit appear
at end of data sheet.
Functional Diagram
TOP VIEW
+
RFIN2
1
GND
2
GND
3
EXTCAP/ALT_VCC
4
RFOUT2/VCC
5
AMP 2
AMP 1
DC
GENERATION
TDFN
19-8660; Rev 0; 10/16
10 RFOUT1
MAX2678
9
GND
8
GND
7
GAIN_SELECT
6
RFIN1
MAX2678
GPS/GNSS Front-End Amplifier
Absolute Maximum Ratings
RFOUT2/VCC, EXTCAP/ALT_VCC,
VCC to GND.......................................................-0.3V to +5.5V
GAIN_SELECT,
RFOUT1 to GND...............-0.3V to (VCC + 0.25V, but ≤ 5.5V)
RFIN1, RFIN2 Input Power (50Ω source).......................+15dBm
RFIN1, RFIN2 to GND.............................................-0.3V to +1V
Continuous Power Dissipation (TA = +70°C)
12-Pin TDFN (derate 18.5mW/°C above +70°C).......1481mW
Operating Ambient Temperature Range............ -40°C to +105°C
Maximum Junction Temperature......................................+150°C
Storage Temperature Range............................. -65°C to +150°C
Lead Temperature (soldering, 10s).................................. +300°C
Soldering Temperature (reflow)........................................+260°C
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
(VIN = 3.0V to 5.25V, TA = -40°C to +105°C. Typical values are at +5.0V and at TA = +25°C. Pin 7 is open, unless otherwise noted.)
(Note 1)
PARAMETER
Supply Voltage
SYMBOL
CONDITIONS
VCC
Supply Current
ICC
Gain-Select Input Current
IIL
MIN
TYP
3.0
TA = +25°C
15.0
25
TA = -40°C to +105°C
MAX
UNITS
5.25
V
32
35
VIL = 0V
20
100
mA
µA
AC Electrical Characteristics
(VCC = 3.0V to 5.25V, PIN = -40dBm, fIN = 1575MHz, TA = -40°C to +105°C. Typical values are at 5.0V and at TA = +25°C. AMP 1
input matched to 50Ω. All ports terminated in 50Ω. Pin 7 is open, unless otherwise noted.) (Note 1)
PARAMETER
Operating Frequency
AMP 1 Gain
SYMBOL
CONDITIONS
MIN
fRF
|S21|1
14
AMP 1 Gain Variation Over
Temperature
AMP 1 Noise Figure
NF1
AMP 1 Input Third-Order
Intercept Point
IIP3
TYP
MAX
1575
Two tones at 1574.5MHz and 1575.5MHz,
-35dBm per tone
AMP 1 Input 1dB
Compression Point
17
UNITS
MHz
20
dB
0.3
dB
0.9
dB
-12
dBm
-18
dBm
AMP 1 Input Return Loss
|S11|1
-9
dB
AMP 1 Output Return Loss
|S22|1
-15
dB
AMP 1 Reverse Isolation
|S12|1
-33
dB
AMP 2 Gain
|S21|2
AMP 2 Gain Step
Gain change when pin 7 is shorted to GND
AMP 2 Gain Variation Over
Temperature
AMP 2 Noise Figure
NF2
AMP 2 Output Third-Order
Intercept Point
OIP3
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Two tones at 1574.5MHz and 1575.5MHz,
-30dBm per tone
14.5
18
22
dB
-2
-3.4
-6
dB
1
dB
1.8
dB
20
dBm
Maxim Integrated │ 2
MAX2678
GPS/GNSS Front-End Amplifier
AC Electrical Characteristics (continued)
(VCC = 3.0V to 5.25V, PIN = -40dBm, fIN = 1575MHz, TA = -40°C to +105°C. Typical values are at 5.0V and at TA = +25°C. Input
matched to 50Ω, load = 50Ω, pin 7 is open, unless otherwise noted.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
AMP 2 Output 1dB
Compression Point
MAX
UNITS
6
dBm
-18
dB
AMP 2 Input Return Loss
|S11|2
AMP 2 Output Return Loss
|S22|2
-11
dB
AMP 2 Reverse Isolation
|S12|2
-27
dB
Note 1: TA = +25°C and TA = +105°C are guaranteed by production test. At TA = -40°C, the minimum and maximum values are
guaranteed by design and characterization, unless otherwise noted.
Typical Operating Characteristics
(MAX2678 EV kit, all measurements are calibrated to SMA connectors, PIN = -40dBm, fIN = 1575MHz, inputs and outputs are terminated
to 50Ω, VCC = 5.0V, TA = +25°C, unless otherwise noted.)
AMP 1 NOISE FIGURE
vs. TEMPERATURE (NF1)
AMP 2 NOISE FIGURE
vs. TEMPERATURE (NF2)
toc01
5.5
NOISE FIGURE (dB)
1.2
1.0
0.8
27
4.5
26
4.0
3.5
HIGH-GAIN
MODE
3.0
LOW-GAIN
MODE
2.5
2.0
0.6
-20
0
20
40
60
80
100
24
23
22
TA = -40°C
TA = +25°C
21
18
-40
-20
0
20
40
60
80
3.0
100
3.5
4.0
4.5
5.0
TEMPERATURE (°C)
TEMPERATURE (°C)
SUPPLY VOLTAGE (V)
AMP 1 GAIN
vs. SUPPLY VOLTAGE
AMP 2 GAIN vs. SUPPLY VOLTAGE
(PIN 7 OPEN, HIGH-GAIN MODE)
AMP 2 GAIN vs. SUPPLY VOLTAGE
(PIN 7 SHORT TO GND, LOW-GAIN MODE)
toc04
17.4
toc05
19.5
TA = -40°C
19.3
15.8
19.1
15.6
17.1
18.9
TA = +25°C
17.0
16.9
16.8
TA = +85°C
16.7
16.6
TA = +105°C
18.3
17.9
17.7
17.5
4.0
4.5
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5.0
TA = +85°C
18.1
16.4
SUPPLY VOLTAGE (V)
TA = +25°C
18.5
16.5
3.5
TA = -40°C
18.7
TA = +105°C
toc06
16.0
17.2
GAIN (dB)
17.3
3.0
TA = +85°C
19
1.0
-40
TA = +105°C
25
20
1.5
0.4
GAIN (dB)
5.0
15.4
GAIN (dB)
NOISE FIGURE (dB)
1.4
toc03
28
SUPPLY CURRENT (mA)
1.6
SUPPLY CURRENT vs. SUPPLY VOLTAGE
(PIN 7 OPEN, HIGH-GAIN MODE)
toc02
TA = -40°C
15.2
15.0
TA = +25°C
14.8
14.6
TA = +85°C
14.4
14.2
TA = +105°C
14.0
3.0
3.5
4.0
4.5
SUPPLY VOLTAGE (V)
5.0
3.0
3.5
4.0
4.5
5.0
SUPPLY VOLTAGE (V)
Maxim Integrated │ 3
MAX2678
GPS/GNSS Front-End Amplifier
Typical Operating Characteristics (continued)
(MAX2678 EV kit, all measurements are calibrated to SMA connectors, PIN = -40dBm, fIN = 1575MHz, inputs and outputs are terminated
to 50Ω, VCC = 5.0V, TA = +25°C, unless otherwise noted.)
AMP 1 GAIN
vs. FREQUENCY (WIDE BAND)
AMP 1 GAIN
vs. FREQUENCY (NARROW BAND)
toc07
18
AMP 2 GAIN
vs. FREQUENCY (WIDE BAND)
toc08
19
18
17
14
14
GAIN (dB)
GAIN (dB)
GAIN (dB)
15
17
12
10
LOW-GAIN
MODE
8
13
6
16
4
12
2
11
800
1000
1200
1400
1600
1800
0
15
1545 1555 1565 1575 1585 1595 1605 1615
2000
FREQUENCY (MHz)
800
toc11
1600
1800
2000
toc12
7.00
6.75
-16.5
HIGH-GAIN
MODE
1400
AMP 2 OUTPUT P1dB vs. TEMPERATURE
(PIN 7 OPEN, HIGH-GAIN MODE)
-16.0
19
16
15
LOW-GAIN
MODE
-17.0
OUTPUT P1dB (dBm)
INPUT P1dB (dBm)
6.50
17
14
1200
FREQUENCY (MHz)
AMP 1 INPUT P1dB
vs. TEMPERATURE
toc10
20
18
1000
FREQUENCY (MHz)
AMP 2 GAIN
vs. FREQUENCY (NARROW BAND)
GAIN (dB)
HIGH-GAIN
MODE
16
18
16
-17.5
-18.0
6.25
6.00
5.75
5.50
-18.5
13
12
1545 1555 1565 1575 1585 1595 1605 1615
5.25
-19.0
5.00
-40
-20
FREQUENCY (MHz)
AMP 1 S11 vs.
FREQUENCY (|S11|1)
toc13
0
0
20
40
60
80
100
-40
0
20
40
60
80
TEMPERATURE (°C)
AMP 1 S22
vs. FREQUENCY (|S22|1)
AMP 1 S12
vs. FREQUENCY (|S12|1)
toc14
0
100
toc15
-34
-36
-5
-2
-20
TEMPERATURE (°C)
-1
-38
-3
-4
-5
-6
|S12| (dB)
-10
|S22| (dB)
|S11| (dB)
toc09
20
-15
-42
-44
-20
-7
-40
-46
-8
-25
-48
-9
-10
-30
800
1000
1200
1400
1600
FREQUENCY (MHz)
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1800
2000
-50
800
1000
1200
1400
1600
FREQUENCY (MHz)
1800
2000
800
1000
1200
1400
1600
1800
2000
FREQUENCY (MHz)
Maxim Integrated │ 4
MAX2678
GPS/GNSS Front-End Amplifier
Typical Operating Characteristics (continued)
(MAX2678 EV kit, all measurements are calibrated to SMA connectors, PIN = -40dBm, fIN = 1575MHz, inputs and outputs are terminated
to 50Ω, VCC = 5.0V, TA = +25°C, unless otherwise noted.)
toc16
0
-15
-20
-25
-28
-29
-10
-15
-30
-31
-32
HIGH-GAIN
MODE
-20
HIGH-GAIN
MODE
-27
|S12| (dB)
-10
toc18
-26
LOW-GAIN
MODE
-5
|S22| (dB)
|S11| (dB)
toc17
0
LOW-GAIN
MODE
-5
AMP 2 S12
vs. FREQUENCY (|S12|2)
AMP 2 S22
vs. FREQUENCY (|S22|2)
AMP 2 S11
vs. FREQUENCY (|S11|2)
-33
-34
-25
-35
-30
-36
-30
800
1000
1200
1400
1600
1800
2000
800
FREQUENCY (MHz)
1000
1200
1400
1600
1800
800
2000
1000
1400
1600
1800
2000
AMP 1 OUTPUT STABILITY FACTOR (µ)
AMP 1 INPUT STABILITY FACTOR (µ')
toc19
2.50
1200
FREQUENCY (MHz)
FREQUENCY (MHz)
toc20
6.0
5.5
2.25
5.0
4.5
2.00
µ
µ'
4.0
1.75
3.5
3.0
1.50
2.5
2.0
1.25
1.5
1.00
1.0
800
1000
1200
1400
1600
1800
2000
800
1000
FREQUENCY (MHz)
1400
1600
1800
2000
FREQUENCY (MHz)
AMP 2 INPUT STABILITY FACTOR (µ')
AMP 2 OUTPUT STABILITY FACTOR (µ)
toc21
2.3
toc22
5.5
HIGH-GAIN
MODE
2.0
1200
5.0
LOW-GAIN
MODE
4.5
4.0
1.8
µ
µ'
3.5
LOW-GAIN
MODE
1.5
3.0
2.5
2.0
1.3
HIGH-GAIN
MODE
1.5
1.0
1.0
800
1000
1200
1400
1600
FREQUENCY (MHz)
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1800
2000
800
1000
1200
1400
1600
1800
2000
FREQUENCY (MHz)
Maxim Integrated │ 5
MAX2678
GPS/GNSS Front-End Amplifier
Pin Configuration
TOP VIEW
+
RFIN2
1
10 RFOUT1
GND
2
9
GND
GND
3
8
GND
EXTCAP/ALT_VCC
4
7
GAIN_SELECT
RFOUT2/VCC
5
6
RFIN1
MAX2678
EP
TDFN
Pin Description
PIN
NAME
1
RFIN2
2, 3, 8, 9
GND
4
EXTCAP/
ALT_VCC
5
RFOUT2/VCC
6
RFIN1
7
GAIN_SELECT
10
RFOUT1
EP
—
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FUNCTION
Amplifier 2 Input. Incorporates an internal DC-blocking capacitor and is internally matched to 50Ω.
This input is designed to be connected to a bandpass filter.
Electrical Ground
External Smoothing Capacitor for Internal Supply Voltage. Can be used as the external DC supply
pin to eliminate the need for a Bias-T on RFOUT2/VCC.
Amplifier 2 Output. Incorporates an internal DC-blocking capacitor and is internally matched to 50Ω.
DC bias on this pin serves as the power supply through a bias-T.
Amplifier 1 Input. Requires an external DC-blocking capacitor and matching components.
Amplifier 2 Gain Select. Open is high-gain mode. Short to ground is low-gain mode.
Amplifier 1 Output. Incorporates an internal DC-blocking capacitor and is internally matched to 50Ω.
This output is designed to drive a bandpass filter.
Exposed Pad Ground. The exposed pad must be soldered to the circuit board for proper thermal
and electrical performance.
Maxim Integrated │ 6
MAX2678
GPS/GNSS Front-End Amplifier
Detailed Description
Alternate Supply (ALT_VCC)
The IC power can be supplied from the navigation system
through RFOUT2/VCC (pin 5). An integrated filter is connected to the output of AMP 2 to separate the supply voltage from the GPS signal. Alternatively, the supply voltage
can be applied to the EXTCAP/ALT_VCC pin (external
capacitor pin 4).
The MAX2678 IC contains two LNA stages tuned for use
at 1575MHz.
Amplifier 1
Amplifier 1 (AMP 1) has an internal load that limits the
bandwidth and provides a 50Ω output impedance through
a DC-blocking capacitor. The internal biasing for AMP 1
suppresses gain variation with changes in temperature
and supply voltage. At the input, an integrated DC-blocking
capacitor and matching network are intentionally omitted
to allow selection of external components to optimize for
noise or gain.
Layout Considerations
For best performance, carefully lay out the PCB using
high-frequency techniques. Use controlled-impedance
transmission lines to interface with the MAX2678 highspeed inputs and outputs and isolate the input signals from the output signals as much as possible. For
improved noise figure, keep the connection to the input
of LNA 1 as short as possible. A power-supply decoupling
capacitor should be placed very close to pin 4 and connected directly to a ground plane. If low-gain selection for
LNA 2 is required, connect pin 7 directly to the ground
plane with a very short PCB trace. Good grounding is
critical for this device. The backside ground plane should
be as close as possible.
Amplifier 2 with Gain Step
The output of Amplifier 2 (AMP 2) has the dual role of
providing both the RF output drive and receiving the DC
power supply through a single cable. Both the input and
output ports of AMP 2 are internally matched to 50Ω
impedance at 1575MHz. A 3.4dB gain switch can be used
to adjust the gain for different applications. For maximum
gain, the GAIN_SELECT pin should be left open. Shorting
the GAIN_SELECT pin to ground sets the gain stage to a
3.4dB lower gain. As with AMP 1, AMP 2 has an internal
load that limits the bandwidth, and the amplifier’s internal
biasing suppresses gain variation with changes in temperature and supply voltage.
Visit www.maximintegrated.com/evkitsoftware to
download the latest MAX2678 EV kit BOM, schematic
and PCB layout diagrams, including Gerber data.
Typical Operating Circuit
SAW
RFOUT1
RFIN2
10
VCC
REG
RFIN1
6
MAX2678
www.maximintegrated.com
1
4
EXTCAP/ALT_VCC
VCC
REG
AMP 1
2, 3, 8, 9
ALT_VCC
AMP 2
5
7
RFOUT2/VCC
GAIN_SELECT
EXPOSED PAD
Maxim Integrated │ 7
MAX2678
GPS/GNSS Front-End Amplifier
Ordering Information
PART
TEMP RANGE
Package Information
PIN-PACKAGE
MAX2678GTB/V+
-40°C to +105°C
10 TDFN-EP*
MAX2678GTB/V+T
-40°C to +105°C
10 TDFN-EP*
/V denotes an automotive qualified part.
+Denotes a lead(Pb)-free/RoHS-compliant package.
T = Tape and reel.
*EP = Exposed pad.
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For the latest package outline information and land patterns
(footprints), go to www.maximintegrated.com/packages. Note
that a “+”, “#”, or “-” in the package code indicates RoHS status
only. Package drawings may show a different suffix character, but
the drawing pertains to the package regardless of RoHS status.
PACKAGE
TYPE
PACKAGE
CODE
OUTLINE
NO.
LAND
PATTERN NO.
10 TDFN-EP
T1033+4
21-0137
90-0061
Maxim Integrated │ 8
MAX2678
GPS/GNSS Front-End Amplifier
Revision History
REVISION
NUMBER
REVISION
DATE
0
10/16
DESCRIPTION
Initial release
PAGES
CHANGED
—
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim Integrated’s website at www.maximintegrated.com.
Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses
are implied. Maxim Integrated reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and max limits)
shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.
Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc.
© 2016 Maxim Integrated Products, Inc. │ 9
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