The ATR0601 is a single IF GPS front-end IC, designed to meet the requirements of
mobile and automotive applications. Excellent RF performance combined with low
noise figure enables high quality GPS solutions and it's very low power consumption
fits perfectly to portable devices. Featuring a balanced XTO and a fully integrated balanced frequency synthesizer, only few external components are required. The
ATR0601 offers a complete autonomous mode, utilizing the on chip AGC in closed
loop operation, to set the gain of the IF VGA. Alternatively, in combination with the
baseband processor ATR0621 the optimum gain of the IF VGA can be computed and
set by software, using the digital SDI interface.
Figure 1-1.Block Diagram
GPS Front-end
IC
ATR0601
Preliminary
PUXTO
PURF
RF
NRF
XTO
NXTO
NX
MO
AGCO
EGC
SDI
1
A
D
A
D
SL
SH
SC
Rev. 4866A–GPS–08/05
VCC
VCC
VDIG
PMSS
Logic
X
GND
BP
NBP
VCO
XTO
PLL
BPI
NBPI
EST
2.Pin Configuration
Figure 2-1.Pinning QFN24
SDI
NRF
EGC
RF
19
12
VCC
NC
18
17
16
15
14
13
PURF
PUXTO
NBPI
BPI
NBP
BP
VDIG
AGCO
NXTO
NX
XTO
SCSHSL
24
222120
23
1
2
3
4
X
5
6
7
VCC
Paddle
GND
91011
8
MO
TEST
Table 2-1.Pin Description
PinSymbolType
PaddleGNDSCommon ground
1VDIGSDigital supply
2AGCOA_I/OAGC: gain control voltage output/corner frequency determination
3NXTOA_IXTO interface (optional: TCXO input)
4NXA_OXTO interface
5XA_OXTO interface
6XTOA_IXTO interface (optional: TCXO input)
7VCCSAnalog supply
8MOA_OTestbuffer output (f
9TESTA_IEnable testbuffer
10NRFA_IRF input complementary
11RFA_IRF input
12NC–Not connected
13BPA_OIF-Filter interface (mixer output, open collector)
14NBPA_OIF-Filter interface (mixer output complementary, open collector)
15BPIA_IIF-Filter interface (IF-input)
16NBPIA_IIF-Filter interface (IF-input complementary)
17PUXTOD_IPower-up XTO
18PURFD_IPower-up RF
19VCCSAnalog supply
20EGCD_IEnable external gain control (high = external; low = internal)
21SDID_IInput for external gain control signal (Σ∆ modulation)
22SLD_OData output: “low”
23SHD_OData output: “high”
24SCD_OSample clock
Note:1. Type: A_I Analog input, A_O Analog output, D_I Digital input, D_O Digital output, S Supply
(1)
Function
)
IF
2
ATR0601 [Preliminary]
4866A–GPS–08/05
3.Functional Description
3.1General Description
The ATR0601 GPS receiver IC has been especially designed for GPS applications in both
mobile phone and automotive applications. From this system point of view, it incorporates highest isolation between GPS and cellular bands, as well as very low power consumption.
ATR0601 [Preliminary]
3.2PMSS Logic
3.3XTO
3.4VCO/PLL
The L1 input signal (f
quency of: f
= 1575.42 MHz. The digital modulation scheme is Bi-Phase-Shift-Keying (BPSK)
RF
) is a Direct Sequence Spread Spectrum (DSSS) signal with a centre fre-
RF
with a chip rate of 1.023 Mbps. As the input signal power at the antenna is approximately
–140 dBm, the desired signal is below the thermal noise floor.
The Power Management, Startup and Shutdown Logic ensures reliable operation within the recommended operating conditions. The external power control signals PUrf and PUxto are passed
thru Schmitt-trigger inputs to eliminate voltage ripple and prevent undesired behaviour during
startup and shutdown. Digital and analog supply voltages are analyzed by a monitoring circuit,
enabling the startup of the IC only within a secure operating area.
The XTO is designed for minimum phase noise and frequency perturbations. The balanced
topology gives maximum isolation from external and ground coupled noise. The built-in jump
start circuitry ensures reliable start-up behaviour of any specified crystal. For use with an external TCXO, the XTO circuitry can be used as a single-ended or balanced input buffer.
The recommended reference frequency is: f
= 23.104 MHz.
XTO
The frequency synthesizer features a balanced VCO and a fully integrated loop filter, thus no
external components are required. The VCO combines very good phase noise behaviour and
excellent spurious suppression. The relation between the reference frequency (f
VCO centre frequency (f
) is given by: f
VCO
VCO
= f
× 64 = 23.104 MHz × 64 = 1478.656 MHz.
XTO
) and the
XTO
3.5RF-Mixer/Image-filter
Combined with the antenna an external LNA provides a first band path filtering of the signal. For
the LNA, Atmel’s ATR0610 is recommended, due to it’s low Noise Figure, high linearity an low
power consumption. The output of the LNA drives an SAW filter, which provides image rejection
for the mixer and the required isolation of all GSM bands. The output of the SAW filter is fed into
a highly linear mixer with high conversion gain and excellent noise performance.
The IF frequency (f
3.6IF-filter
The mixer directly drives an external LC-Bandpath filter via open collector outputs. In order to
provide highest selectivity and conversion gain, it is recommended to design the external filter,
according to the application proposal, as a 2-pole filter with a quality factor Q > 25.
4866A–GPS–08/05
) is given by: fIF = fRF – f
IF
= 1575.42 MHz – 1478.656 MHz = 96.764 MHz.
VCO
3
3.7VGA/AGC
The output of the IF-Filter drives an on-chip Variable Gain Amplifier (VGA) which is combined
with additional low-pass filtering. The on-chip Automatic Gain Control (AGC) stage sets the gain
of the VGA in order to optimally charge the input of the following analog-to-digital converter. The
AGC control loop can be selected for on-chip closed loop operation or for external gain control
mode. For external gain control mode, the loop needs to be closed by the baseband IC
ATR0621.
3.8A/D Converter
The analog-to-digital converter stage has a total resolution of 1.5 bit. It comprises balanced comparators and a sub sampling unit, clocked by the reference frequency (f
spectrum of the digital output signal (f
by: f
= ⏐ fIF – f
OUT
digital output signal, with a centre frequency given by:
f
= fIF – f
OUT
3.9Clock and Data Driver
CMOS output drivers are providing sign and magnitude bits as well as the system clock to the
baseband IC ATR0621. The rail-to-rail output signal level is determined by the digital supply voltage (VDIG).
), present at the data outputs SL and SH, is then given
OUT
× n⏐ . The selected sub sampling factor (n = 4) leads to the designated
XTO
× 4 = 96.764 MHz – 23.104 MHz – 4 = 4.348 MHz.
XTO
). The frequency
XTO
4
ATR0601 [Preliminary]
4866A–GPS–08/05
ATR0601 [Preliminary]
4.Absolute Maximum Ratings
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress rating
only and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of this
specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
ParametersSymbolValueUnit
Analog supply voltageV
Digital supply voltageV
Input voltageV
Operating temperatureT
Storage temperature T
CC
DIG
in
op
stg
5.Thermal Resistance
ParametersSymbolValueUnit
Junction ambientR
th
6.Operating Range
ParametersSymbolValueUnit
Analog supply voltageV
Digital supply voltageV
= V
– V
Supply voltage difference (V
∆
CC
)V
DIG
Temperature rangeTemp–40 to +85°C
Input frequencyf
Reference frequencyf
Figure 8-5.Synchronous Shut-down Behaviour of SC with Respect to PUxto
VCC
VDIG
PUxto
SC
T = 1/23.104 MHz
tmin = 0s
tmax = 25ns
tmax = 0s
Figure 8-6.Data Outputs SL and SH are Valid with Rising Edge of Sample Clock SC
SL
SH
SC
T = 1/23.104 MHz
8
ATR0601 [Preliminary]
4866A–GPS–08/05
9.Application Circuit
ATR0601 [Preliminary]
Figure 9-1.Application Example Using a GPS Crystal with ESR
220nH
5pF
13
BP
220nH
14
NBP
VCO
PLL
XTO
VCC
220nH
15
BPI
5pF
220nH
16
NBPI
10nF
47pF
4.7nH
1.5pF
LNA section (opt.)
PU XTO
27
SAW
B4060
X1
PU RF
1.3pF
1.3pF
47pF
82pF
47pF
VCC
PU RF
ATR0610
Reference frequency: Application #1
17
18
11
5.6nH
10
6
3
5
4
100nF
100nF
100nF
PUxto
PUrf
RF
NRF
XTO
NXTO
X
NX
VDIG
VCC
VCC
7
19
1
VCC
VCC
VDIG
PMSS
Logic
GND
= 12Ω (Please see Table 9-1 on page 11)
typ
100pF
TEST
9
2
AGCO
NC12
MO8
20
EGC
SDI
1
A
D
A
D
SL
SH
SC
21
22
23
24
Data out "low"
Data out "high"
Sample clock
Note:Please consider the recommended IF-filter layout, shown in Figure 9-5 on page 11.
Figure 9-2.Application Example Using a GPS Crystal with ESR
≠ 12Ω
typ
(Please see Table 9-2 on page 11)
6
XTO
3
47pF
R1
82pF
X1
47pF
Reference frequency: Application #2
Note:The external series resistor R1 has to be selected depending on the typical value of the crystal
ESR. Please refer to Application Note “ATR0601: Crystal and TXCO selection”.
NXTO
5
X
4
NX
4866A–GPS–08/05
9
Figure 9-3.Equivalent Application Examples Using a GPS TCXO (Please see Table 9-3 on
page 12)
TCXO
10 pF
22 pF
Do not
connect
Reference frequency: Application #4a
10 pF
TCXO
22 pF
Do not
connect
Reference frequency: Application #4b
33 pF
33 pF
6
XTO
3
NXTO
5
X
4
NX
6
XTO
3
NXTO
5
X
4
NX
Figure 9-4.Application Example Using an External Reference and Balanced Inputs
(Please see Table 9-4 on page 12)
1:1
Vin
Do not
connect
Reference frequency: Application #5
6
XTO
3
NXTO
5
X
4
NX
10
ATR0601 [Preliminary]
4866A–GPS–08/05
ATR0601 [Preliminary]
Figure 9-5.Recommended IF-filter: Layout versus Schematic
13 14 15 16
Ca
Cb
Lc
LeLf
A
BP
NBP
BPI
NBPI
131415
Ld
B
Ca
Lc LdLe
16
Cb
Lf
VCC
Note:Mutual inductance between the four inductors Lc - Lf plays an important role in the IF-filter charac-
teristics. In any design, the layout arrangement shown in Figure 9-5 on page 11 should be
resembled as close as possible. Measures: A = 2.8 mm; B = 1.4 mm; Lc - Lf: Wirewound SMD
inductors, 0603 size. (Please see Table 10-1).
Table 9-1.Specification of GPS Crystals Appropriate for the Application Example Shown in
Figure 9-1 on page 9
ParameterCommentMin.Typ.Max. Units
Frequency Characteristics
Fundamental Frequency
Calibration toleranceFrequency at 23°C ±2°C7.0±ppm
Frequency deviationOver operating temperature range15.0±ppm
Temperature rangeOperating temperature range–40.0+85.0°C
Electrical
Load capacitance (CL)18.519.5pF
Equivalent Series Resistance (ESR)
FundamentalSpecification71223Ω
Nominal frequency referenced to
25°C
23.104MHz
4866A–GPS–08/05
Table 9-2.Specification of GPS Crystals Appropriate for the Application Example Shown in
Figure 9-2 on page 9
ParameterCommentMin.Typ.Max. Units
Equivalent Series Resistance (ESR)
FundamentalSpecification740Ω
Note:All other parameters as specified in Table 9-1.
11
Table 9-3.Specification of GPS TCXOs Appropriate for the Application Example Shown in
Figure 9-3 on page 10
ParameterCommentMin.Typ.Max. Units
Frequency Characteristics
Nominal Frequency
Frequency deviationOver operating temperature range2.0±ppm
Temperature rangeOperating temperature range–40.0+85.0°C
Electrical
Output waveformDC coupled clipped sinewave
Output voltage
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