General Description
The MAX2741 L1-band GPS receiver IC offers a high-
performance, compact solution for mobile handsets,
PDAs, and automotive applications. Total voltage gain
of 80dB and a 4.7dB cascaded noise figure can pro-
vide receiver sensitivity for applications requiring
-185dBW for indoor tracking solutions.
This dual-conversion receiver downconverts the
1575.42MHz GPS signal to a 37.38MHz first IF, and then
a 3.78MHz second IF. An integrated 2- or 3-bit ADC (1-
bit SIGN, 1- or 2-bit MAG selectable) samples the sec-
ond IF and outputs the digitized signals to the baseband
processor.
The integrated synthesizer offers the flexibility in fre-
quency planning to allow a single board design to be
employed for reference frequencies from 2MHz to
26MHz. The integrated reference oscillator allows either
TCXO or crystal operation.
The receiver runs from a 2.7V to 3.0V supply, and draws
only 30mA when active. It is offered in a 28-pin thin QFN
package, and is specified for -40°C to +85°C at 3V.
Applications
In-Vehicle Navigation Systems (IVNS)
Telematics (Vehicle and Asset Tracking,
Inventory Management)
Automotive Security
Emergency Response Systems
Emergency Road-Side Assistance
Location-Based Services/Internet (PDAs)
Digital Cameras/Camcorders
Recreational Handhelds/Walkie-Talkies
Geographical Information Systems (GIS)
Consumer Electronics (Location-Based Games)
Precision Timing
Features
♦Supports All Popular Handset Reference
Frequencies Up to 26MHz
♦4.7dB Cascaded Noise Figure
♦80dB Cascaded Gain
♦Tolerates -90dBm In-Band Jammer
♦Tolerates +13dBm CDMA Out-of-Band Jammer at
Device Input
♦Integrated Synthesizer and VCO
♦Integrated 2- or 3-Bit ADC
♦50dB IF AGC Range
♦Small 28-Pin Thin QFN Package
♦SPI™ Control Interface
♦Clock Output for Baseband Processor
MAX2741
Integrated L1-Band GPS Receiver
________________________________________________________________ Maxim Integrated Products 1
28 27 26 25 24 23 22
VCC6
IFOUT+
IFOUT-
IFIN+
IFIN-
N.C.
N.C.
891011 12 13 14
FILT
SCLK
CS
SDI
SHDN
XTAL
REFCLK
15
16
17
18
19
20
21
GPSCLK
GPSIF2
GPSIF1
GPSIF0
VCC5
N.C.
SDO
7
6
5
4
3
2
1
GND
VCC4
VCC3VCO
3225.6MHz
VCC2
RFIN
N.C.
VCC1Σ
LNA
1612.8MHz
33.6MHz
16.8MHz
200kHz
90 0 /96
/192
/2
/16128
P.D.
/R
REF
OSC
ADC
SPI INTERFACE
MAX2741
MUX
Pin Configuration/
Functional Diagram
Ordering Information
19-3559; Rev 0; 1/05
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.
SPI is a trademark of Motorola, Inc.
PART TEMP RANGE PIN-PACKAGE
MAX2741ETI -40°C to +85°C 28 Thin QFN
5
.
0
m
m
x
5
.
0
m
m
2
8
-
P
I
N
T
H
I
N
Q
F
N
EVALUATION KIT
AVAILABLE
MAX2741
Integrated L1-Band GPS Receiver
2_______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
DC ELECTRICAL CHARACTERISTICS
(Operating conditions (unless otherwise specified): VCC = 2.7V to 3.0V; REFCLK driven with 10MHz sinusoid, 1.2VP-P; registers set
according to mode; no RF input signal; digital baseband outputs left open; TA= -40°C to +85°C. Typical values are measured at VCC =
2.75V, TA= +25°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.
VCC Pins to GND ...................................................-0.3V to +3.3V
VCC Pins to Each Other.........................................-0.3V to +0.3V
FILT to GND................................................-0.3V to (VCC + 0.3V)
CMOS Inputs to GND (SHDN, SCLK,
CS, SDI).................................................+0.3V to (VCC + 0.3V)
CMOS Outputs to GND (CLKOUT,
GPSIF_, SDO).........................................-0.3V to (VCC + 0.3V)
RFIN to GND...............................................-0.3V to (VCC + 0.3V)
First IF Filter I/O to GND (IFOUT±, IFIN±).....-0.3V to (VCC + 0.3V)
Crystal Inputs to GND (XTAL, REFCLK).....-0.3V to (VCC + 0.3V)
Maximum RF Input Power...................................................0dBm
Continuous Power Dissipation (TA= +85°C)
28-Pin Thin QFN (derate 20.8mW/°C above +70°C) .1000mW
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature......................................................+150°C
Storage Temperature Range .............................-65°C to +160°C
Lead Temperature (soldering, 10s) .................................+300°C
PARAMETER CONDITIONS
MIN
TYP
MAX
UNITS
Supply Voltage 2.7 3.0 V
Normal operation (TA = +25°C) 30 42
Supply Current Standby (V SHDN = VIL, SYNTH:D8 = 0) 0.7 mA
Input-Logic High Threshold VCC -
0.1 V
Input-Logic Low Threshold 0.1 V
Input-Logic High/Low Current -10
+10
µA
Output-Logic High ILOAD = 100µA VCC -
0.3 V
Output-Logic Low ILOAD = 100µA 0.3 V
AC ELECTRICAL CHARACTERISTICS
(Operating conditions (unless otherwise specified): VCC = 2.7V to 3.0V for TA= -40°C to +85°C; REFCLK driven at 10MHz sinusoid,
1.2VP-P; registers set according to mode; using the Typical Application Circuit; CW RF signal at 1575.42MHz. Typical values are mea-
sured at VCC = 2.75V, TA= +25°C.)
PARAMETER CONDITIONS
MIN
TYP
MAX
UNITS
1st CONVERSION STAGE (RF TO 1st IF)
RF Frequency L1-band
1575.42
MHz
RF Conversion Gain (Note 1) 15 21 32 dB
Noise Figure Mid-gain (CONFIG1:D4–D0 = 10000) 4.7 dB
Input IP3 (Note 2) -30
dBm
RF Image Rejection (Notes 3, 4) 20 35 dB
LO Leakage at RF LO to RFIN pin -90
dBm
CAUTION! ESD SENSITIVE DEVICE
MAX2741
Integrated L1-Band GPS Receiver
_______________________________________________________________________________________ 3
AC ELECTRICAL CHARACTERISTICS (continued)
(Operating conditions (unless otherwise specified): VCC = 2.7V to 3.0V for TA= -40°C to +85°C; REFCLK driven at 10MHz sinusoid,
1.2VP-P; registers set according to mode; using the Typical Application Circuit; CW RF signal at 1575.42MHz. Typical values are mea-
sured at VCC = 2.75V, TA= +25°C.)
PARAMETER CONDITIONS
MIN TYP MAX
UNITS
2nd CONVERSION STAGE (1st IF TO ADC INPUT)
1st IF Frequency At IFOUT
37.38
MHz
Max gain (CONFIG1:D4–D0 = 11111) (Note 1) 48 61 74 dB
Conversion Gain Min gain (CONFIG1:D4–D0 = 00000) (Note 1) 10 dB
Input IP3 1st conversion (Note 5) -36
dBm
Noise Figure Max gain (CONFIG1:D4–D0 = 11111) 12 dB
Real
0.40
mS
IF Output Port Admittance Imaginary 1.5 pF
Real
0.40
mS
IF Input Port Admittance Imaginary
0.15
pF
(SYNTH:D13–D10 = 1111) 2.9
LPF -3dB Corner Frequency (SYNTH:D13–D10 = 0000) 7.7 MHz
SYNTHESIZER
ICP_OH PLL charge-pump source current 75 µA
ICP_OL PLL charge-pump sink current
-100
µA
Closed-Loop Phase Noise At 1kHz offset -55
dBc/Hz
Comparison Spurs At ±200kHz offset -44
dBc/Hz
Reference Oscillator Frequency Sinusoid (Note 1) 2 10 26 MHz
REF Input Voltage Level Sinusoid (Note 1) 0.6 2.2 VP-P
VCO Coarse Tune Range Programmable (CONFIG1:D7 to D5 = 000 to 111)
(Note 1)
240
MHz
DIGITAL I/O
SPI Clock Frequency 1MHz
Note 1: Production tested for +25°C and +85°C, guaranteed by design and characterization for -40°C.
Note 2: Test tones at 1575.8MHz and 1576.8MHz at -60dBm/tone.
Note 3: Guaranteed by design and characterization.
Note 4: Image frequency is 1575.42MHz + 2(fIF) = 1650.18MHz
Note 5: Test tones at 37.38MHz and 36.88MHz at -50dBm/tone.
MAX2741
Integrated L1-Band GPS Receiver
4_______________________________________________________________________________________
Pin Description
PIN NAME FUNCTION
1V
CC1LNA Supply Connection. External RF bypass capacitor to ground required.
2, 20, 22, 23
N.C. Reserved. Make no connections to this pin.
3RFIN LNA Input. Connect to GPS antenna through a bandpass filter. This input requires an external
matching network to match to 50Ω. AC-couple to this pin.
4V
CC2VCO Supply Connection. External RF bypass capacitor to ground required.
5V
CC3CML Supply Connection. External RF bypass capacitor to ground required.
6V
CC4Digital Logic and PLL Supply Connection. External RF bypass capacitor to digital ground required.
7GND Ground. Connect to PC board digital ground plane.
8FILT PLL Loop Filter Connection. This is the output of the phase detector’s charge pump. Use the
recommended filter on EV kit for optimal phase noise and lock time.
9SCLK SPI Clock Input (CMOS)
10 CS SPI Chip-Select Input (CMOS, Active Low)
11 SDI SPI Data Input (CMOS)
12 SHDN Full IC Power-Down. This shutdown pin disables the on-chip oscillator and the rest of the IC. To keep
the oscillator running, use the software shutdown (SYNTH:D8); (CMOS, active high).
13 XTAL Crystal Oscillator Feedback Capacitor Connection
14 REFCLK Reference Clock Input for PLL. Drive with 1.2VP-P when using TCXO module.
15 GPSCLK
GPS Clock Output to Baseband. This is the clock used by the ADC to sample the GPS data (CMOS).
16 GPSIF2 Sampled IF Output, Bit 2 (CMOS). See Table 5.
17 GPSIF1 Sampled IF Output, Bit 1 (CMOS). See Table 5.
18 GPSIF0 Sampled IF Output, Bit 0 (CMOS). See Table 5.
19 VCC5IF Supply Connection. External RF bypass capacitor to ground required.
21 SDO SPI Data Output (CMOS)
24 IFIN-
1st IF Input (Inverting). Connect this 2.5kΩ differentially terminated input to the 1st IF filter’s (-) output.
25 IFIN+ 1st IF Input (Noninverting). Connect this 2.5kΩ differentially terminated input to the 1st IF filter’s (+)
output.
26 IFOUT- 1st IF Output (Inverting). Connect this 2.4kΩ differential output to the 1st IF filter’s (-) input.
27 IFOUT+ 1st IF Output (Noninverting). Connect this 2.4kΩ differential output to the 1st IF filter’s (+) input.
28 VCC6RF Image-Reject Mixer Supply. External RF bypass capacitor to ground required.
Exposed GND
RF Ground. Ultra-low inductance connection to ground. Place several vias to PC board ground plane.
MAX2741
Integrated L1-Band GPS Receiver
_______________________________________________________________________________________ 5
Detailed Description
The MAX2741 GPS offers a high-performance super-
heterodyne receiver solution for low-power mobile
devices, with the benefit of using the system’s existing
clock reference. This receiver is ideal for integration into
mobile phone handsets using common reference fre-
quencies such as 10.0, 13.0, 14.4, 19.2, 20.0, and
26.0MHz. The only external components required are the
GPS RF filter, an IF filter (typically designed from inexpen-
sive discretes), a three-component PLL loop filter, and a
few other resistors and capacitors. The MAX2741 inte-
grates the reference oscillator core, the VCO and its tank,
the synthesizer, a 1- to 3-bit ADC, and all signal path
blocks except for the 1st IF filter. The typical application
area for the receiver is less than 2cm2.
RF/1st Conversion Stage (Front-End)
The MAX2741 RF front-end LNA and mixer are the most
important in the signal path. This stage sets the noise
figure for the receiver, defining the sensitivity, and mixes
the 1575.42MHz L1-band GPS signal down to a 1st IF of
37.38MHz. The LNA itself has an NF of approximately
1.5dB; the cascaded NF of the front-end (including the
mixer) is approximately 4.7dB, and the cascaded gain
is typically 21dB.
The image-reject mixer is set up for a high-side injected
RFLO (1612.80MHz), and offers typically better than 30dB
rejection of the image noise (1650.18MHz). The -30dBm
input 3rd-order intercept (IIP3) of the RF strip, in conjunc-
tion with the GPS IF filter, provides excellent out-of-band
interferer immunity.
The 1st IF outputs (IFOUT±) are internally biased to
approximately 2V, and have a differential source
impedance of approximately 2.5kΩ. The IF filter can be
implemented as a discrete L/C filter, or as a monolithic
SAW or ceramic if one is available.
IF/2nd Conversion Stage
The 2nd conversion stage consists of an active mixer, a
variable-gain amplifier (VGA), and a tunable lowpass
filter. The IF mixer is configured for low-side LO injec-
tion for a 2nd IF of 3.78MHz. Total gain in this stage is
62dB, and the VGA offers 51dB of gain adjustment. The
VGA is typically controlled by the baseband IC through
the SPI interface to optimize the signal swing for digiti-
zation by the ADC.
The on-chip lowpass filter has an adjustable cutoff fre-
quency, programmable from 2.9MHz to 7.7MHz in 16
steps. This LPF further reduces out-of-band noise and
band-limits the signal to the ADC, ensuring that the
sampling process does not generate alias components.
DC offset compensation at the ADC input is performed by
an on-chip 4-bit DAC. This compensates for any DC error
introduced by transistor mismatch in the differential stage
driving the ADC input, allowing the downconverted GPS
signal’s DC level to be centered within the threshold volt-
ages of the ADC.
ADC
The on-chip ADC samples the down-converted GPS
signal at the 2nd IF (3.78MHz). Sampled output is pro-
vided in either 2-bit (1-bit magnitude, 1-bit sign) or 3-bit
(2-bit magnitude, 1-bit sign) formats, as determined by
the ADC mode configuration bit (CONFIG1:D15); see
Table 5 for details. The ADC sample clock (system GPS
clock) is derived either directly from the reference clock
(SYNTH:D9 = 1), or from an RFLO divide-by-96 block to
provide a 16.8MHz sample clock (SYNTH:D9 = 0). The
clock is available to the baseband processor at
GPSCLK (pin 15). The sampled ADC data bits are
available on pins 16, 17, and 18 (GPSIF2, GPSIF1, and
GPSIF0). The functionality of the pins is different in
each mode (2-bit vs. 3-bit)—see Table 5 in determining
the interface connection for the application circuit.
Synthesizer
The MAX2741 integrates an integer-N synthesizer; all
blocks except the loop filter are on-chip. The reference
can be either a crystal (driven by the internal oscillator),
or a TCXO module. The oscillator provides a 5pF load
to the crystal. A TCXO module should provide a swing
in the 0.6VP-P to 2.2VP-P range.
The reference divider (/R) is programmable (SYNTH:
D7–D0), and can accommodate reference frequencies
up to 26MHz. The reference divider needs to be set so
the comparison frequency (fCOMP) at the frequency/
phase detector is 200kHz. The VCO runs at twice the fre-
quency of the RFLO; the RFLO is therefore generated
from the VCO using a quadrature divide-by-2 block. The
RF LO is fCOMP x 8064 (typically 1612.80MHz), and the
1st IF LO is fCOMP x 168 (typically 33.6MHz); the RF and
IF LO division ratios are not adjustable. This configuration
allows for the use of reference frequencies common to
GSM, CDMA, TDMA, TD-SCDMA, and UMTS handsets:
9.6MHz (R = 48), 13.0MHz (R = 65), 14.4MHz (R = 72),
19.2MHz (R = 96), 26.0MHz (R = 130), etc.
MAX2741
Integrated L1-Band GPS Receiver
6_______________________________________________________________________________________
The VCO offers a bank of tuning capacitors that can be
latched in/out to adjust the center frequency. Because
the system does not require any RF LO frequency
change (i.e., changing channels), the VCO varactor tun-
ing gain is very low by design, which means the tuning
range of the VCO is narrow. The coarse-tune capacitors
in the tank circuit allow the system to adjust the VCO
center frequency as needed to guarantee that the syn-
thesizer can lock. In practice, process and temperature
effects on VCO centering are negligible, and a coarse-
tune setting of 110 (CONFIG:D7 to D5) will center the
VCO tuning range correctly in virtually all cases. To aid in
bench and prototype testing, the PFD offers out-of-lock-
high and out-of-lock-low indicators, available in the SPI
STATUS register (STATUS:D9 to D8). Use these flags to
determine if the VCO tuning range needs to be adjusted
higher or lower in the case where the PLL cannot lock.
The PLL filter is the only external block of the synthesizer.
The typical filter is a classic C-R-C two-pole shunt network
on the tune line. Low phase noise is preferred at the
expense of longer PLL settling times, so a low 10kHz to
20kHz loop bandwidth is used. The recommended PLL
10kHz filter implementation, with charge pump set to
200µA (CONFIG1:D10 = 1), is shown in Figure 1.
The system/GPS clock is derived either directly from
the reference oscillator, or synthesized from the RFLO
(see the ADC section). This clock is used as the sam-
pling clock for the on-chip ADC, and is seen at pin 15,
GPSCLK.
SPI Bus, Address and Bit Assignments
An SPI-compatible serial interface is used to program the
MAX2741 for configuring the different operating modes.
In addition, data can be read out of the MAX2741 for sta-
tus and diagnostic use. The serial interface is controlled
by four signals: SCLK (serial clock), CS (chip-select), SDI
(data input), and SDO (data output).
The control of the PLL, AGC, test, offset management,
and block selection is performed through the SPI bus
from the baseband controller. A 20-bit word, with the MSB
(D15) being sent first, is clocked into a serial shift register
when the chip-select signal is asserted low.
The SPI bus has four control lines: serial clock (SCLK),
chip-select (CS), data in (SDI), and data out (SDO).
Enable SDO functionality by setting the digital test bus
bits: CONFIG1:D9 to D8 = 01. The timing of the inter-
face signals is shown in Figure 2 and Table 1 along
with typical values for setup and hold time require-
ments.
For best performance, the SPI bus should be configured
during the startup initialization and then left with the opti-
mum values in the registers. Any changes to the ADC
and VGA bits during GPS signal processing may cause
glitches and corrupt the analog signal path. Reading
from the SPI bus does not interrupt GPS operation.
6
VCC4
7
GND
89
FILT
SCLK
MAX2741
22nF
36kΩ
100pF
Figure 1. Recommended 3rd-Order PLL Filter
LSB MSB
CS
SCLK
SDI
tSETUPD
tHDATA tPERIOD
tEND
tSETUPSS
Figure 2. SPI Timing Diagram
Table 1. SPI Timing Requirements
SYMBOL
PARAMETER TYP
VALUE
UNITS
tSETUPD Data to SCLK setup 20 ns
tPERIOD SCLK period 100 ns
tHDATA Data hold to SCLK 20 ns
tSETUPSS CS to SCLK disable 20 ns
tEND
Falling SCLK to CS inactive
20 ns
MAX2741
Integrated L1-Band GPS Receiver
_______________________________________________________________________________________ 7
Table 2. Register Address and Data Bit Assigments (Write)
DATA ADDRESS
REGISTER
NAME
D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0 A3 A2 A1
A0
SYNTH
Reserved
LPF Autotune
Initiate
LPF Tuning
Word (MSB)
LPF Tuning
Word
LPF Tuning
Word
LPF Tuning
Word (LSB)
XTAL Clock
Select
Standby
PLL Ref Div
Ratio (MSB)
PLL Ref Div
Ratio
PLL Ref Div
Ratio
PLL Ref Div
Ratio
PLL Ref Div
Ratio
PLL Ref Div
Ratio
PLL Ref Div
Ratio
PLL Ref Div
Ratio (LSB)
010
0
CONFIG 1
ADC Mode
ADC Offset Control
(LSB)
ADC Offset Control
ADC Offset Control
(MSB)
ADC Offset Control
(SIGN)
Double Charge-
Pump Current
Digital Test Bus
Mode Select (MSB)
Digital Test Bus
Mode Select (LSB)
VCO Coarse Tuning
Range (MSB)
VCO Coarse Tuning
Range
VCO Coarse Tuning
Range (LSB)
AGC Gain (MSB)
AGC Gain
AGC Gain
AGC Gain
AGC Gain (LSB)
010
1
CONFIG 2
Reset CMOS
Drive VCO Low
Drive VCO High
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Analog Test
Mode Select
Analog Test
Mode Select
Analog Test
Mode Select
Analog Test
Mode Select
Analog Test
Mode Select
011
0
Table 3. Register Address and Data Bit Assigments (Read)
DATA ADDRESS
REGISTER
NAME
D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0 A3 A2 A1
A0
STATUS
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Out-of-Lock
(High)
Out-of-Lock
(Low)
XTAL Clock
Selected
Parity
Reserved
LPF Auto-
calibrate End
LPF Autotune
(MSB)
LPF Autotune
LPF Autotune
LPF Autotune
(LSB)
011
1
MAX2741
Integrated L1-Band GPS Receiver
8_______________________________________________________________________________________
Detailed Register Definitions
Table 4. Detailed Register Definition for Write Address 0100: SYNTH
DATA BIT
DEFAULT
DESCRIPTION
D15 1 Reserved
D14 1 LPF Autotune Initiate: I = Initiate autotune, 0 = Manual tuning.
D13–D10
0100 LPF Tuning Word: 0000 ~ 7.7MHz, 1111 ~ 2.9MHz.
D9 1 XTAL Clock Select: 1 = External reference, 0 = Synthesized 16.8MHz.
D8 0 Standby: 0 = Normal operating mode, 1 = Standby (oscillator remains active), but only if D9 = 1.
D7–D0
01100000
Reference Division Ratio. Default 19.2MHz external reference (R = 96dec). R = fREF / 200kHz.
Table 5. Detailed Register Definition for Write Address 0101: CONFIG 1
DATA BIT
DEFAULT
DESCRIPTION
D15 1
ADC Mode. Select 1 for 1-bit magnitude and sign, select 0 for 2-bit magnitude and sign.
1: GPSIF2 = sign, GPSIF1 = magnitude, GPSIF0 = X
0: GPSIF2 = MSB magnitude, GPSIF1 = LSB magnitude, GPSIF0 = sign
D14–D11
0000 ADC Offset Control (approx 4mV/step): D14 = LSB, D12 = MSB, D11 = sign.
D10 0 Double Charge-Pump Current: 0 = 100µA, 1 = 200µA.
D9 to D8
00 Digital Test Bus Mode Select. See Table 9 for test-mode descriptions.
D7 to D5
001 VCO Coarse Tuning Range. 000 = Lowest frequency, 111 = Highest frequency.
D4–D0 11111 AGC Gain. Digital control of the AGC amplifier in the 2nd IF section. 00000 => min gain, 11111 =>
max gain (linear gain ~2.5dB per unit SPI word).
Table 6. Detailed Register Definition for Write Address 0110: CONFIG 2
DATA BIT
DEFAULT
DESCRIPTION
D15 1 Reset CMOS: 0 = Hold CMOS dividers in reset and PFD is tri-stated, 1 = Inactive.
D14 1 Drive VCO Low: 0 = Active, forces VCO to lowest frequency.
N.B. do not activate both D14 and D13 at the same time.
D13 1 Drive VCO High: <forces LCP low FET on, driving VTUNE low, forcing VCO to highest extreme> 0 =
Active, forces VCO to highest frequency. N.B. do not activate both D14 and D13 at the same time.
D12–D7 100000 Reserved
D6 to D5
11 Must be programmed to 11
D4–D0 11111 Analog Test Mode Select: Reserved
MAX2741
Integrated L1-Band GPS Receiver
_______________________________________________________________________________________ 9
Applications Information
Fundamentally, the only application areas that require
careful consideration are the LNA input match and the
1st IF filter. Of course, proper supply bypassing,
grounding, and layout is required for reliable perfor-
mance from any RF circuit.
LNA Input Matching
Input matching is critical for optimum noise figure and
system sensitivity. Optimum source impedance (as seen
from the LNA input) for lowest noise figure is 29Ω+ j47Ω.
Remember that optimum noise match and optimum gain
match (return loss) do not occur simultaneously, so a
good application circuit will sacrifice gain slightly in favor
of reduced noise figure. Gain and noise circles are pro-
vided in Figure 3; S11 tabular data is provided in Table 8.
1st IF Interface and Filtering
The typical application uses a 37.38MHz 1st IF, and
employs an IF filter. The order of the filter should be tai-
lored to suit the application—stand-alone GPS
receivers will not require the channel-selection and
stopband attenuation of GPS receivers that are inte-
grated into other wireless handsets. Be sure that the fil-
ter topology provides DC-blocking for the IF I/O ports.
Table 7. Detailed Register Definition for Read Address 0111: STATUS
DATA BIT
DEFAULT
DESCRIPTION
D15–D10
XXXXXX Reserved
D9 X Out-of-Lock (High Frequency): 1 = PLL is out of lock, VCO free-running at its highest frequency,
0 = Locked.
D8 X Out-of-Lock (Low Frequency): 1 = PLL is out of lock, VCO free-running at its lowest frequency,
0 = Locked high.
D7 1 XTAL Clock Selected: 1 = Synthesized 16.8MHz reference, 0 = External clock.
D6 X Parity: 1 = Even, 0 = Odd.
D5 X Reserved
D4 X LPF Autotune End: 0 = Autotune run ended; 1 = Calibrating or manual tuning.
D3–D0 XXXX LPF Autotune: 0000 ~ 7.7MHz; 1111 = 2.9MHz.
Table 8. MAX2741 S11
G = Gmax - 1dB NF = NFmin + 0.2dB
Figure 3. Gain and Noise Circles for MAX2741 LNA Input
FREQ (MHz) S11 (MAG) S11 (°)
1100 0.874 -50.9
1200 0.867 -56.1
1300 0.859 -61.5
1400 0.842 -66.9
1500 0.821 -72.3
1550 0.809 -74.9
1560 0.806 -75.4
1570 0.804 -75.9
1575 0.803 -76.2
1580 0.801 -76.4
1590 0.799 -77.0
1600 0.796 -77.5
1650 0.783 -80.0
1700 0.768 -82.5
1800 0.739 -87.4
1900 0.708 -92.3
2000 0.677 -96.8
MAX2741
Integrated L1-Band GPS Receiver
10 ______________________________________________________________________________________
28 27 26 25 24 23 22
VCC6
IFOUT+
IFOUT-
IFIN+
IFIN-
N.C.
N.C.
891011 12 13 14
FILT
SCLK
CS
SDI
SHDN
XTAL
REFCLK
15
16
17
18
19
20
21
GPSCLK
GPSIF2
GPSIF1
GPSIF0
VCC5
N.C.
SDO
7
6
5
4
3
2
1
GND
VCC4
VCC3
VCC2
RFIN
N.C.
VCC1
MAX2741
SDO
SD1
CS
SCLK
GPSIF0
GPSIF1
GPSIF2
GPSCLK
REFCLK
BASEBAND IC
RF
I/O CONNECTION RECEIVER RF BPF
RFIN LNA Input RF BPF Output
IF
I/O CONNECTION RECEIVER IF FILTER
IFOUT+ 1st IF Output from Mixer (+) IF BPF Input, 2.5kΩ Differential
IFOUT- 1st IF Output from Mixer (-) IF BPF Input, 2.5kΩ Differential
IFIN+ 1st IF Input (+) IF BPF Input, 2.5kΩ Differential
IFIN- 1st IF Input (-) IF BPF Input, 2.5kΩ Differential
BASEBAND
I/O CONNECTION RECEIVER BB IC/MAC
SCLK CMOS Input CMOS Output
CS CMOS Input CMOS Output
SDI CMOS Input CMOS Output
SDO CMOS Output CMOS Input
SHDN CMOS Input CMOS Output
GPSCLK CMOS Output CMOS Input
GPSIF0 CMOS Output CMOS Input
GPSIF1 CMOS Output CMOS Input
GPSIF2 CMOS Output CMOS Input
SYNTHESIZER
I/O CONNECTION RECEIVER EXTERNAL COMPONENTS
FILT PLL Phase-Detector Charge-Pump PLL Loop Filter
XTAL Crystal Oscillator Feedback Feedback Capacitors
REFCLK External TCXO or Crystal Analog (also connected to REFCLK input to MAC)
Typical Interface Diagram
Interface Summary
All I/O connections are DC-coupled. Supply voltages as specified in the electrical specifications.
MAX2741
Integrated L1-Band GPS Receiver
______________________________________________________________________________________ 11
Digital Test Bus
The digital test bus (DTB) is provided to allow for easy
bench analysis of the digital workings of the receiver.
Typical Application Circuit
VCC6
IFOUT+
IFOUT-
IFIN+
IFIN-
N.C.
N.C.
FILT
SCLK
CS
SDI
SHDN
XTAL
REFCLK
GPSCLK
GPSIF2
GPSIF1
GPSIF0
VCC5
N.C.
SDO
GND
VCC4
VCC3
VCC2
RFIN
N.C.
VCC1
VCC
GPS RF INPUT
FROM GPS BPF
VCC
VCC
VCC
2.2pF
100pF 22pF
100pF 22pF
VCC
1nF100pF
220pF
100nF 100pF
1nF 100pF
6.2nH
SPI DATA OUT
TO BASEBAND PROCESSOR
GPS DATA AND CLOCK
TO BASEBAND PROCESSOR
22nF
36kΩ
100pF
H/W SHUTDOWN LINE
FROM BASEBAND PROCESSOR
SPI CLOCK AND DATA INTO
BASEBAND PROCESSOR SYSTEM TCXO
(2MHz TO 26MHz)
VCC
100pF 22pF
39pF 470µH 470µH 39pF
680pF 5.6pF 680pF
680pF 5.6pF 680pF
100pF
28 27 26 25 24 23 22
891011 12 13 14
15
16
17
18
19
20
21
7
6
5
4
3
2
1
VCO
3225.6MHz
Σ
LNA
1612.8MHz
33.6MHz
16.8MHz
200kHz
90 0 /96
/192
/2
/16128
P.D.
/R
REF
OSC
ADC
SPI INTERFACE
MAX2741
MUX
Table 9. Digital Test-Mode-Select Description
DIGITAL OUTPUT FUNCTION
MODE
REGISTER SETTING
CONFIG1:D9 to D8
GPSIF2 GPSIF1 GPSIF0
311 SIGN LSB MSB
210M COUNTER R COUNTER HANDSHAKE STATUS
101CHARGE PUMP UP CHARGE PUMP DOWN SDO
000CML CLOCK CALIBRATE LPF END XTL CLOCK SELECTED
MAX2741
Integrated L1-Band GPS Receiver
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.
12 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
©2005 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products, Inc.
QFN THIN.EPS
D2
(ND-1) X e
e
D
C
PIN # 1
I.D.
(NE-1) X e
E/2
E
0.08 C
0.10 C
A
A1 A3
DETAIL A
E2/2
E2
0.10 M C A B
PIN # 1 I.D.
b
0.35x45∞
D/2 D2/2
L
C
L
C
e e
L
CC
L
k
LL
DETAIL B
L
L1
e
XXXXX
MARKING
G1
2
21-0140
PACKAGE OUTLINE,
16, 20, 28, 32L THIN QFN, 5x5x0.8mm
-DRAWING NOT TO SCALE-
L
COMMON DIMENSIONS
3.353.15
T2855-1 3.25 3.353.15 3.25
MAX.
3.20
EXPOSED PAD VARIATIONS
3.00T2055-2 3.10
D2
NOM.MIN.
3.203.00 3.10
MIN.
E2
NOM. MAX.
NE
ND
PKG.
CODES
1. DIMENSIONING & TOLERANCING CONFORM TO ASME Y14.5M-1994.
2. ALL DIMENSIONS ARE IN MILLIMETERS. ANGLES ARE IN DEGREES.
3. N IS THE TOTAL NUMBER OF TERMINALS.
4. THE TERMINAL #1 IDENTIFIER AND TERMINAL NUMBERING CONVENTION SHALL
CONFORM TO JESD 95-1 SPP-012. DETAILS OF TERMINAL #1 IDENTIFIER ARE
OPTIONAL, BUT MUST BE LOCATED WITHIN THE ZONE INDICATED. THE TERMINAL #1
IDENTIFIER MAY BE EITHER A MOLD OR MARKED FEATURE.
5. DIMENSION b APPLIES TO METALLIZED TERMINAL AND IS MEASURED BETWEEN 0.25 mm AND 0.30 mm
FROM TERMINAL TIP.
6. ND AND NE REFER TO THE NUMBER OF TERMINALS ON EACH D AND E SIDE RESPECTIVELY.
7. DEPOPULATION IS POSSIBLE IN A SYMMETRICAL FASHION.
8. COPLANARITY APPLIES TO THE EXPOSED HEAT SINK SLUG AS WELL AS THE TERMINALS.
9. DRAWING CONFORMS TO JEDEC MO220, EXCEPT EXPOSED PAD DIMENSION FOR T2855-1,
T2855-3 AND T2855-6.
NOTES:
SYMBOL
PKG.
N
L1
e
E
D
b
A3
A
A1
k
10. WARPAGE SHALL NOT EXCEED 0.10 mm.
JEDEC
T1655-1 3.203.00 3.10 3.00 3.10 3.20
0.70 0.800.75
4.90
4.90
0.25
0.25
0
--
4
WHHB
4
16
0.350.30
5.10
5.105.00
0.80 BSC.
5.00
0.05
0.20 REF.
0.02
MIN. MAX.NOM.
16L 5x5
3.10
T3255-2 3.00 3.20 3.00 3.10 3.20
2.70
T2855-2 2.60 2.602.80 2.70 2.80
L0.30 0.500.40
------
WHHC
20
5
5
5.00
5.00
0.30
0.55
0.65 BSC.
0.45
0.25
4.90
4.90
0.25
0.65
--
5.10
5.10
0.35
20L 5x5
0.20 REF.
0.75
0.02
NOM.
0
0.70
MIN.
0.05
0.80
MAX.
---
WHHD-1
28
7
7
5.00
5.00
0.25
0.55
0.50 BSC.
0.45
0.25
4.90
4.90
0.20
0.65
--
5.10
5.10
0.30
28L 5x5
0.20 REF.
0.75
0.02
NOM.
0
0.70
MIN.
0.05
0.80
MAX.
---
WHHD-2
32
8
8
5.00
5.00
0.40
0.50 BSC.
0.30
0.25
4.90
4.90
0.50
--
5.10
5.10
32L 5x5
0.20 REF.
0.75
0.02
NOM.
0
0.70
MIN.
0.05
0.80
MAX.
0.20 0.25 0.30
DOWN
BONDS
ALLOWED
NO
YES3.103.00 3.203.103.00 3.20T2055-3
3.103.00 3.203.103.00 3.20T2055-4
T2855-3 3.15 3.25 3.35 3.15 3.25 3.35
T2855-6 3.15 3.25 3.35 3.15 3.25 3.35
T2855-4 2.60 2.70 2.80 2.60 2.70 2.80
T2855-5 2.60 2.70 2.80 2.60 2.70 2.80
T2855-7 2.60 2.70 2.80 2.60 2.70 2.80
3.203.00 3.10T3255-3 3.203.00 3.10
3.203.00 3.10T3255-4 3.203.00 3.10
NO
NO
NO
NO
NO
NO
NO
NO
YES
YES
YES
YES
3.203.00T1655-2 3.10 3.00 3.10 3.20 YES
NO3.203.103.003.10T1655N-1 3.00 3.20
3.353.15T2055-5 3.25 3.15 3.25 3.35 Y
3.35
3.15T2855N-1 3.25 3.15 3.25 3.35 N
3.35
3.15T2855-8 3.25 3.15 3.25 3.35 Y
3.203.10T3255N-1 3.00 NO
3.203.103.00
L
0.40
0.40
**
**
**
**
**
**
**
**
**
**
**
**
**
**
**
**
**
**
**
SEE COMMON DIMENSIONS TABLE
±0.15
11. MARKING IS FOR PACKAGE ORIENTATION REFERENCE ONLY.
G
2
2
21-0140
PACKAGE OUTLINE,
16, 20, 28, 32L THIN QFN, 5x5x0.8mm
-DRAWING NOT TO SCALE-
12. NUMBER OF LEADS SHOWN ARE FOR REFERENCE ONLY.
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.)
