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Teilenummer | MAX12000 |
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Beschreibung | 1575MHz GPS Front-End Amplifier | |
Hersteller | Maxim Integrated Products | |
Logo | ||
Gesamt 9 Seiten 19-4021; Rev 0; 3/06
EVAALVUAAILTAIOBNLEKIT
1575MHz GPS Front-End Amplifierwww.DataSheet4U.com
General Description
The MAX12000 GPS front-end amplifier IC is designed
for automotive and marine GPS satellite navigation
antenna modules or for any application that needs to
compensate for cable losses from the GPS antenna to
receiver. Two unconditionally stable low-noise amplifier
stages provide the high gain and integrated I/O match-
ing to minimize the need for external matching compo-
nents and eliminate the need for additional gain stages.
The MAX12000 features the option to place a bandpass
ceramic or SAW filter between the two amplifier stages
to provide a narrow-band output to further improve the
noise performance of the GPS receiver. Additionally, a
3.4dB gain step is provided to compensate for cable
loss variation between different applications.
The MAX12000 is designed to operate at the GPS fre-
quency of 1575MHz with a 34.8dB typical cascaded
gain and a 25mA supply current. The two LNA stages
allow the use of a wide range of GPS filter types for
maximum flexibility in system design. The final RF out-
put pin, which drives the cable to the GPS receiver, is
also the power-supply connection that accepts a DC
supply in the +3.0V to +5.5V range. Alternatively, the
DC supply can be applied to pin 4.
The GPS front-end amplifier is designed on a low-noise,
advanced SiGe process and is available in a lead-free,
10-pin TDFN surface-mount package (3mm x 3mm).
Applications
Integrated Automotive and Marine GPS
Receivers
Features
♦ First Amp Noise Figure*: 1.0dB
♦ High Gain**: 34.8dB
♦ 3.4dB Gain Step
♦ Integrated 50Ω Output Matching
♦ 3.0V to 5.5V Supply Voltage Range
♦ Small, Low-Cost Package (3mm x 3mm)
♦ ESD Protected to ±1kV Human Body Model
*Without external input impedance match.
**First amplifier input is impedance matched (S11 = -10dB).
Second amplifier set to high gain. Amplifiers cascaded without
interstage filter.
Ordering Information
PART
TEMP RANGE
MAX12000ETB+ -40°C to +85°C
+Denotes lead-free package.
PIN-
PACKAGE
10 TDFN
PKG
CODE
T1033-2
Typical Operating Circuit appears at end of data sheet.
Pin Configuration/Functional Diagram
TOP VIEW
+
RFIN2 1
GND 2
GND 3
EXTCAP/ALT_VCC 4
RFOUT2/VCC 5
MAX12000
AMP 2
AMP 1
DC
GENERATION
10 RFOUT1
9 GND
8 GND
7 GAIN_SELECT
6 RFIN1
TDFN
________________________________________________________________ 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.
1575MHz GPS Front-End Amplifier
www.DataSheet4U.com
Detailed Description
The MAX12000 IC contains two LNA stages tuned for
use at 1575MHz.
AMP 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 sup-
presses gain variation with changes in temperature and
supply voltage. At the input, an integrated DC-blocking
capacitor and matching network are intentionally omit-
ted to allow selection of external components to opti-
mize for noise or gain.
AMP 2 with Gain Step
The output of 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. The gain-select pin is
connected to an inverter with an internal pullup resistor.
Hence, the gain-select pin is set by default to high-gain
mode. 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.
Supply
The IC power can be supplied from the navigation sys-
tem through the RF cable (pin 5). An integrated filter
circuit is connected to the output of LNA 2 to separate
the supply voltage from the GPS signal. Alternatively,
the supply voltage can be applied to the external
capacitor pin (pin 4).
Layout Considerations
For best performance, carefully lay out the printed cir-
cuit board using high-frequency techniques. Use con-
trolled-impedance transmission lines to interface with
the MAX12000 high-speed inputs and outputs and iso-
late the input signals from the output signals as much
as possible. For improved noise figure, keep the con-
nection 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, con-
nect pin 7 directly to the ground plane with a very short
printed circuit board trace. Good grounding is critical
for this device. The backside ground plane should be
as close as possible. See Figure 1 for printed circuit
board layout.
Typical Operating Circuit
PINNING:
1 = LNA 2 INPUT
2 = GND
3 = GND
4 = EXTCAP/ALT_VCC
5 = LNA 2 OUTPUT/VCC
6 = LNA 1 INPUT
7 = GAIN SETTING
8 = GND
9 = GND
10 = LNA 1 OUTPUT
VCC
REG
SAW
10 1
VCC
REG
4
MATCHING
NETWORK/
DC BLOCK
6
LNA 1
8/9 EXPOSED PADDLE
MAX12000
LNA 2
2/3
5 OUTPUT
7 GAIN SETTING
OPEN = 31.4dB GAIN
SHORT TO GROUND = 28dB GAIN
6 _______________________________________________________________________________________
6 Page | ||
Seiten | Gesamt 9 Seiten | |
PDF Download | [ MAX12000 Schematic.PDF ] |
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