Maxim MAX7032 Low-cost, crystal-based, programmable, ask/fsk transceiver with fractional-n pll Datasheet

19-3685; Rev 2; 11/10
KIT
ATION
EVALU
E
L
B
A
AVAIL
Low-Cost, Crystal-Based, Programmable,
ASK/FSK Transceiver with Fractional-N PLL
The MAX7032 crystal-based, fractional-N transceiver is
designed to transmit and receive ASK/OOK or FSK
data in the 300MHz to 450MHz frequency range with
data rates up to 33kbps (Manchester encoded) or
66kbps (NRZ encoded). This device generates a typical output power of +10dBm into a 50Ω load, and
exhibits typical sensitivities of -114dBm for ASK data
and -110dBm for FSK data. The MAX7032 features separate transmit and receive pins (PAOUT and LNAIN)
and provides an internal RF switch that can be used to
connect the transmit and receive pins to a common
antenna.
The MAX7032 transmit frequency is generated by a 16bit, fractional-N, phase-locked loop (PLL), while the
receiver’s local oscillator (LO) is generated by an integer-N PLL. This hybrid architecture eliminates the need
for separate transmit and receive crystal reference
oscillators because the fractional-N PLL allows the
transmit frequency to be set within 2kHz of the receive
frequency. The 12-bit resolution of the fractional-N PLL
allows frequency multiplication of the crystal frequency
in steps of fXTAL/4096. Retaining the fixed-N PLL for the
receiver avoids the higher current drain requirements of
a fractional-N PLL and keeps the receiver current drain
as low as possible.
Features
♦ +2.1V to +3.6V or +4.5V to +5.5V Single-Supply
Operation
♦ Single Crystal Transceiver
♦ User-Adjustable 300MHz to 450MHz Carrier
Frequency
♦ ASK/OOK and FSK Modulation
♦ User-Adjustable FSK Frequency Deviation
Through Fractional-N PLL Register
♦ Agile Transmitter Frequency Synthesizer with
fXTAL/4096 Carrier-Frequency Spacing
♦ +10dBm Output Power into 50Ω Load
♦ Integrated TX/RX Switch
♦ Integrated Transmit and Receive PLL, VCO, and
Loop Filter
♦ > 45dB Image Rejection
♦ Typical RF Sensitivity*
ASK: -114dBm
FSK: -110dBm
♦ Selectable IF Bandwidth with External Filter
The fractional-N architecture of the MAX7032 transmit
PLL allows the transmit FSK signal to be programmed for
exact frequency deviations, and completely eliminates
the problems associated with oscillator-pulling FSK signal generation. All frequency-generation components are
integrated on-chip, and only a crystal, a 10.7MHz IF filter,
and a few discrete components are required to implement a complete antenna/digital data solution.
♦ RSSI Output with High Dynamic Range
The MAX7032 is available in a small 5mm x 5mm, 32-pin,
thin QFN package, and is specified to operate in the
automotive -40°C to +125°C temperature range.
♦ < 800nA Shutdown Current
Applications
2-Way Remote Keyless Entry
Security Systems
♦ Autopolling Low-Power Management
♦ < 12.5mA Transmit-Mode Current
♦ < 6.7mA Receive-Mode Current
♦ < 23.5µA Polling-Mode Current
♦ Fast-On Startup Feature, < 250µs
♦ Small 32-Pin, Thin QFN Package
*0.2% BER, 4kbps Manchester-encoded data, 280kHz IF BW,
average RF power
Home Automation
Remote Controls
Remote Sensing
Smoke Alarms
Garage Door Openers
Ordering Information
PART
MAX7032ATJ+
TEMP RANGE
-40°C to +125°C
PIN-PACKAGE
32 Thin QFN-EP**
+Denotes a lead(Pb)-free/RoHS-compliant package.
**EP = Exposed pad.
Local Telemetry Systems
Pin Configuration, Typical Application Circuit, and
Functional Diagram appear at end of data sheet.
________________________________________________________________ Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
MAX7032
General Description
MAX7032
Low-Cost, Crystal-Based, Programmable,
ASK/FSK Transceiver with Fractional-N PLL
ABSOLUTE MAXIMUM RATINGS
HVIN to GND .........................................................-0.3V to +6.0V
PAVDD, AVDD, DVDD to GND..............................-0.3V to +4.0V
ENABLE, T/R, DATA, CS, DIO, SCLK, CLKOUT to
GND......................................................-0.3V to (HVIN + 0.3V)
All Other Pins to GND ...............................-0.3V to (_VDD + 0.3V)
Continuous Power Dissipation (TA = +70°C)
32-Pin Thin QFN (derate 21.3mW/°C above +70°C)....1702mW
Operating Temperature Range .........................-40°C to +125°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
(Typical Application Circuit, 50Ω system impedance, VAVDD = VDVDD = VPAVDD = VHVIN = +2.1V to +3.6V, fRF = 300MHz to 450MHz,
TA = -40°C to +125°C, unless otherwise noted. Typical values are at VAVDD = VDVDD = VPAVDD = VHVIN = +2.7V, TA = +25°C, unless
otherwise noted.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Supply Voltage (3V Mode)
VDD
HVIN, PAVDD, AVDD, and DVDD connected to
power supply
2.1
2.7
3.6
V
Supply Voltage (5V Mode)
HVIN
PAVDD, AVDD, and DVDD unconnected from
HVIN, but connected together
4.5
5.0
5.5
V
Supply Current
IDD
Transmit mode, PA off,
VDATA at 0% duty cycle
(ASK) (Note 2)
fRF = 315MHz
3.5
5.4
fRF = 434MHz
4.3
6.7
Transmit mode, VDATA
at 50% duty cycle
(ASK) (Notes 3, 4)
fRF = 315MHz
7.6
12.3
fRF = 434MHz
8.4
13.6
Transmit mode, VDATA
at 100% duty cycle
(FSK)
fRF = 315MHz (Note 4)
11.6
19.1
fRF = 434MHz (Note 2)
12.4
20.4
Receiver (ASK 315MHz)
6.1
7.9
Receiver (ASK 434MHz)
6.4
8.3
Receiver (FSK 315MHz)
6.4
8.4
TA < +85°C,
typ at +25°C
(Note 4)
TA < +125°C,
typ at +125°C
(Note 2)
Voltage Regulator
2
VREG
mA
Receiver (FSK 434MHz)
6.7
8.7
DRX (3V mode)
23.4
77.3
DRX (5V mode)
67.2
94.4
Deep-sleep (3V mode)
0.8
8.8
Deep-sleep (5V mode)
Receiver (ASK 315MHz)
2.4
6.4
10.9
8.2
Receiver (ASK 434MHz)
6.7
8.4
Receiver (FSK 315MHz)
6.8
8.7
Receiver (FSK 434MHz)
7.0
8.8
DRX (3V mode)
33.5
103.0
DRX (5V mode)
82.3
116.1
Deep-sleep (3V mode)
8.0
34.2
Deep-sleep (5V mode)
14.9
39.3
VHVIN = 5V, ILOAD = 15mA
3.0
_______________________________________________________________________________________
mA
µA
mA
µA
V
Low-Cost, Crystal-Based, Programmable,
ASK/FSK Transceiver with Fractional-N PLL
(Typical Application Circuit, 50Ω system impedance, VAVDD = VDVDD = VPAVDD = VHVIN = +2.1V to +3.6V, fRF = 300MHz to 450MHz,
TA = -40°C to +125°C, unless otherwise noted. Typical values are at VAVDD = VDVDD = VPAVDD = VHVIN = +2.7V, TA = +25°C, unless
otherwise noted.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
DIGITAL I/O
Input High Threshold
VIH
(Note 2)
Input Low Threshold
VIL
(Note 2)
0.1 x VHVIN
V
SCLK, ENABLE, T/R, DATA (VHVIN = 5.5V)
20
µA
Pulldown Sink Current
0.9 x VHVIN
DIO, CS (VHVIN = 5.5V)
Pullup Source Current
Output-Low Voltage
VOL
ISINK = 500µA
Output-High Voltage
VOH
ISOURCE = 500µA
V
20
µA
0.15
V
VHVIN 0.26
V
AC ELECTRICAL CHARACTERISTICS
(Typical Application Circuit, 50Ω system impedance, VAVDD = VDVDD = VPAVDD = VHVIN = +2.1V to +3.6V, fRF = 300MHz to 450MHz,
TA = -40°C to +125°C, unless otherwise noted. Typical values are at VPAVDD = VAVDD = VDVDD = VHVIN = +2.7V, TA = +25°C, unless
otherwise noted.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
450
MHz
GENERAL CHARACTERISTICS
Frequency Range
300
Maximum Input Level
PRFIN
Transmit Efficiency 100% Duty
Cycle
Transmit Efficiency 50% Duty
Cycle
Power-On Time
tON
0
fRF = 315MHz (Note 6)
32
fRF = 434MHz (Note 6)
30
fRF = 315MHz (Note 6)
24
fRF = 434MHz (Note 6)
22
ENABLE or T/R transition low to high,
transmitter frequency settled to within
50kHz of the desired carrier
200
ENABLE or T/R transition low to high,
transmitter frequency settled to within 5kHz
of the desired carrier
350
ENABLE transition low to high, or T/R
transition high to low receiver startup time
(Note 5)
250
dBm
%
%
µs
RECEIVER
Sensitivity
0.2% BER, 4kbps
Manchester data rate,
280kHz IF BW, ±50kHz
FSK deviation,
average power
Image Rejection
(Note 8)
ASK (315MHz)
-114
ASK (434MHz)
-113
FSK (315MHz)
-110
FSK (434MHz)
-107
46
dBm
dB
_______________________________________________________________________________________
3
MAX7032
DC ELECTRICAL CHARACTERISTICS (continued)
MAX7032
Low-Cost, Crystal-Based, Programmable,
ASK/FSK Transceiver with Fractional-N PLL
AC ELECTRICAL CHARACTERISTICS (continued)
(Typical Application Circuit, 50Ω system impedance, VAVDD = VDVDD = VPAVDD = VHVIN = +2.1V to +3.6V, fRF = 300MHz to 450MHz,
TA = -40°C to +125°C, unless otherwise noted. Typical values are at VPAVDD = VAVDD = VDVDD = VHVIN = +2.7V, TA = +25°C, unless
otherwise noted.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
TA = +25°C (Note 4)
4.6
10.0
15.5
TA = +125°C, VAVDD = VDVDD = VHVIN =
VPAVDD = +2.1V (Note 2)
3.9
6.7
UNITS
POWER AMPLIFIER
Output Power
POUT
13.1
82
dB
With output-matching network
-40
dBc
-50
dBc
340
MHz/V
Modulation Depth
Maximum Carrier Harmonics
dBm
TA = -40°C, VAVDD = VDVDD = VHVIN =
VPAVDD = +3.6V (Note 4)
Reference Spur
15.8
PHASE-LOCKED LOOP
Transmit VCO Gain
KVCO
Transmit PLL Phase Noise
10kHz offset, 200kHz loop BW
-68
1MHz offset, 200kHz loop BW
-98
Receive VCO Gain
dBc/Hz
340
Receive PLL Phase Noise
Loop Bandwidth
10kHz offset, 500kHz loop BW
-80
1MHz offset, 500kHz loop BW
-90
Transmit PLL
200
Receive PLL
500
Minimum Transmit Frequency
Step
Reference Frequency Input Level
Programmable Divider Range
In transmit mode (Note 4)
MHz/V
dBc/Hz
kHz
fXTAL/
4096
kHz
0.5
VP-P
20
27
LOW-NOISE AMPLIFIER/MIXER (Note 9)
LNA Input Impedance
ZINLNA
Normalized to
50Ω
High-gain state
Voltage-Conversion Gain
Low-gain state
Input-Referred 3rd-Order
Intercept Point
IIP3
fRF = 315MHz
1 - j4.7
fRF = 434MHz
1 - j3.3
fRF = 315MHz
50
fRF = 434MHz
45
fRF = 315MHz
13
fRF = 434MHz
9
High-gain state
-42
Low-gain state
-6
dB
dBm
Mixer Output Impedance
330
Ω
LO Signal Feedthrough to
Antenna
-100
dBm
RSSI
Input Impedance
Operating Frequency
3dB Bandwidth
4
fIF
330
Ω
10.7
MHz
10
MHz
_______________________________________________________________________________________
Low-Cost, Crystal-Based, Programmable,
ASK/FSK Transceiver with Fractional-N PLL
(Typical Application Circuit, 50Ω system impedance, VAVDD = VDVDD = VPAVDD = VHVIN = +2.1V to +3.6V, fRF = 300MHz to 450MHz,
TA = -40°C to +125°C, unless otherwise noted. Typical values are at VPAVDD = VAVDD = VDVDD = VHVIN = +2.7V, TA = +25°C, unless
otherwise noted.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
Gain
MIN
TYP
MAX
UNITS
15
mV/dB
2.0
mV/kHz
Maximum Data Filter Bandwidth
50
kHz
Maximum Data Slicer Bandwidth
100
kHz
Maximum Peak Detector
Bandwidth
50
kHz
FSK DEMODULATOR
Conversion Gain
ANALOG BASEBAND
Maximum Data Rate
Manchester coded
33
NRZ
66
kbps
CRYSTAL OSCILLATOR
Crystal Frequency
fXTAL
Frequency Pulling by VDD
Crystal Load Capacitance
(Note 7)
(fRF - 10.7)/24
MHz
2
ppm/V
4.5
pF
SERIAL INTERFACE TIMING CHARACTERISTICS (see Figure 7)
Minimum SCLK Setup to Falling
Edge of CS
tSC
30
ns
Minimum CS Falling Edge to
SCLK Rising-Edge Setup Time
tCSS
30
ns
Minimum CS Idle Time
tCSI
125
ns
Minimum CS Period
tCS
2.125
µs
Maximum SCLK Falling Edge to
Data Valid Delay
tDO
80
ns
Minimum Data Valid to SCLK
Rising-Edge Setup Time
tDS
30
ns
Minimum Data Valid to SCLK
Rising-Edge Hold Time
tDH
30
ns
Minimum SCLK High Pulse Width
tCH
100
ns
Minimum SCLK Low Pulse Width
tCL
100
ns
Minimum CS Rising Edge to
SCLK Rising-Edge Hold Time
tCSH
30
ns
Maximum CS Falling Edge to
Output Enable Time
tDV
25
ns
Maximum CS Rising Edge to
Output Disable Time
tTR
25
ns
_______________________________________________________________________________________
5
MAX7032
AC ELECTRICAL CHARACTERISTICS (continued)
AC ELECTRICAL CHARACTERISTICS (continued)
(Typical Application Circuit, 50Ω system impedance, VAVDD = VDVDD = VPAVDD = VHVIN = +2.1V to +3.6V, fRF = 300MHz to 450MHz,
TA = -40°C to +125°C, unless otherwise noted. Typical values are at VPAVDD = VAVDD = VDVDD = VHVIN = +2.7V, TA = +25°C, unless
otherwise noted.) (Note 1)
Supply current, output power, and efficiency are greatly dependent on board layout and PAOUT match.
100% tested at TA = +125°C. Guaranteed by design and characterization overtemperature.
50% duty cycle at 10kHz ASK data (Manchester coded).
Guaranteed by design and characterization. Not production tested.
Time for final signal detection; does not include baseband filter settling.
Efficiency = POUT/(VDD x IDD).
Dependent on PCB trace capacitance.
The oscillator register (0x05) is set to the nearest integer result of fXTAL/100kHz (see the Oscillator Frequency Register
(Address 0x05) section).
Note 9: Input impedance is measured at the LNAIN pin. Note that the impedance at 315MHz includes the 12nH inductive degeneration from the LNA source to ground. The impedance at 434MHz includes a 10nH inductive degeneration connected from the
LNA source to ground. The equivalent input circuit is approximately 50Ω in series with ~ 2.2pF. The voltage conversion is
measured with the LNA input matching inductor, the degeneration inductor, and the LNA/mixer tank in place, and does not
include the IF filter insertion loss.
Note 1:
Note 2:
Note 3:
Note 4:
Note 5:
Note 6:
Note 7:
Note 8:
Typical Operating Characteristics
(Typical Application Circuit, VPAVDD = VAVDD = VDVDD = VHVIN = +3.0V, fRF = 433.92MHz, TA = +25°C, IF BW = 280kHz, data rate
= 4kbps Manchester encoded, frequency deviation = ±50kHz, BER = 0.2% average RF power, unless otherwise noted.)
RECEIVER
SUPPLY CURRENT vs. RF FREQUENCY
(ASK MODE)
TA = +85°C
6.4
6.2
TA = +25°C
6.0
MAX7032 toc02a
6.5
TA = +85°C
6.4
TA = +25°C
6.2
TA = -40°C
5.8
6.0
2.1
2.4
2.7
3.0
SUPPLY VOLTAGE (V)
3.3
3.6
TA = +125°C
6.9
6.8
TA = +85°C
6.7
TA = +25°C
6.6
TA = -40°C
6.5
TA = -40°C
6.1
5.6
6
TA = +125°C
6.6
6.3
7.0
SUPPLY CURRENT (mA)
6.6
6.7
SUPPLY CURRENT (mA)
TA = +125°C
6.8
6.8
MAX7032 toc01
7.0
SUPPLY CURRENT vs. RF FREQUENCY
(FSK MODE)
MAX7032 toc02b
SUPPLY CURRENT vs. SUPPLY VOLTAGE
(ASK MODE)
SUPPLY CURRENT (mA)
MAX7032
Low-Cost, Crystal-Based, Programmable,
ASK/FSK Transceiver with Fractional-N PLL
6.4
300
325
350
375
400
RF FREQUENCY (MHz)
425
450
300
325
350
375
400
RF FREQUENCY (MHz)
_______________________________________________________________________________________
425
450
Low-Cost, Crystal-Based, Programmable,
ASK/FSK Transceiver with Fractional-N PLL
RECEIVER
VCC = +3.0V
10
VCC = +2.1V
8
10
BIT-ERROR RATE (%)
VCC = +3.6V
12
6
fRF = 434MHz
1
0.2% BER
MAX7032 toc05
fRF = 434MHz
1
0.2% BER
0.1
0.1
4
fRF = 315MHz
2
0
fRF = 315MHz
0.01
0.01
-15
-10
35
60
85
110
-121
-119
-117
-115
-113
-116
-111
-114
-112
-110
-108
-106
-104
TEMPERATURE (°C)
AVERAGE INPUT POWER (dBm)
AVERAGE INPUT POWER (dBm)
SENSITIVITY vs. TEMPERATURE
(ASK DATA)
SENSITIVITY vs. TEMPERATURE
(FSK DATA)
SENSITIVITY vs. FREQUENCY DEVIATION
(FSK DATA)
-108
fRF = 434MHz
-111
-114
fRF = 315MHz
-117
-96
SENSITIVITY (dBm)
-102
SENSITIVITY (dBm)
-105
-94
-104
fRF = 434MHz
-106
MAX7032 toc08
-100
MAX7032 toc06
-102
MAX7032 toc07
-40
-108
-98
-100
-102
-104
-110
-106
fRF = 315MHz
-108
-112
10
35
60
85
110
-40
-15
TEMPERATURE (°C)
10
35
60
85
RSSI vs. RF INPUT POWER
1.8
1.6
1.4
1.2
1
110
RSSI AND DELTA vs. IF INPUT POWER
0.8
AGC SWITCH
POINT
1.5
RSSI
1.2
0.5
0.9
-0.5
0.6
LOW-GAIN MODE
-1.5
DELTA
-2.5
0.3
0.2
AGC HYSTERESIS: 3dB
0
-3.5
0
-130 -110
-90
-70
-50
-30
RF INPUT POWER (dBm)
-10
10
3.5
2.5
1.8
1.5
1.0
0.4
MAX7032 toc10
2.1
HIGH-GAIN MODE
0.6
100
10
FREQUENCY DEVIATION (kHz)
TEMPERATURE (°C)
RSSI (V)
-15
MAX7032 toc09
-40
DELTA (%)
-120
RSSI (V)
SENSITIVITY (dBm)
10
BIT-ERROR RATE (%)
14
100
MAX7030 toc04
16
DEEP-SLEEP CURRENT (μA)
100
MAX7032 toc03
18
BIT-ERROR RATE
vs. AVERAGE INPUT POWER (FSK DATA)
BIT-ERROR RATE
vs. AVERAGE INPUT POWER (ASK DATA)
DEEP-SLEEP CURRENT vs. TEMPERATURE
-90
-70
-50
-30
-10
10
IF INPUT POWER (dBm)
_______________________________________________________________________________________
7
MAX7032
Typical Operating Characteristics (continued)
(Typical Application Circuit, VPAVDD = VAVDD = VDVDD = VHVIN = +3.0V, fRF = 433.92MHz, TA = +25°C, IF BW = 280kHz, data rate
= 4kbps Manchester encoded, frequency deviation = ±50kHz, BER = 0.2% average RF power, unless otherwise noted.)
Typical Operating Characteristics (continued)
(Typical Application Circuit, VPAVDD = VAVDD = VDVDD = VHVIN = +3.0V, fRF = 433.92MHz, TA = +25°C, IF BW = 280kHz, data rate
= 4kbps Manchester encoded, frequency deviation = ±50kHz, BER = 0.2% average RF power, unless otherwise noted.)
RECEIVER
0.8
0.4
30
FROM RFIN
TO MIXOUT
fRF = 434MHz
48dB IMAGE
REJECTION
20
10
fRF = 434MHz
IMAGE REJECTION (dB)
SYSTEM GAIN (dBm)
1.2
UPPER SIDEBAND
40
48
MAX7032 toc12
MAX7032 toc11
0
46
44
LOWER SIDEBAND
42
-20
0
10.5
10.6
10.7
10.8
10.9
5
0
11.0
10
15
20
25
-40
30
-15
10
NORMALIZED IF GAIN vs. IF FREQUENCY
S11 vs. RF FREQUENCY
85
MAX7032 toc15
-4
60
-6
S11 (dB)
-8
434MHz
-12
433.92MHz
-12
-18
-16
-20
400MHz
500MHz
-24
1
100
10
200
250
IF FREQUENCY (MHz)
300
350
400
450
INPUT IMPEDANCE
vs. INDUCTIVE DEGENERATION
INPUT IMPEDANCE
vs. INDUCTIVE DEGENERATION
MAX7032 toc17
-220
90
-230
80
MAX7032 toc18
fRF = 434MHz
IMAGINARY
IMPEDANCE
-240
60
-250
50
-260
40
-270
REAL IMPEDANCE
30
20
1
10
INDUCTIVE DEGENERATION (nH)
100
REAL IMPEDANCE (Ω)
REAL IMPEDANCE (Ω)
80
IMAGINARY IMPEDANCE (Ω)
fRF = 315MHz
70
500
RF FREQUENCY (MHz)
90
110
S11 SMITH PLOT OF RFIN
0
MAX7032 toc14
0
35
TEMPERATURE (°C)
IF FREQUENCY (MHz)
IF FREQUENCY (MHz)
MAX7032 toc16
10.4
fRF = 315MHz
-150
-160
IMAGINARY
IMPEDANCE
70
-170
60
-180
50
-190
40
-200
-280
30
-290
20
REAL IMPEDANCE
-210
-220
1
10
INDUCTIVE DEGENERATION (nH)
_______________________________________________________________________________________
100
IMAGINARY IMPEDANCE (Ω)
FSK DEMODULATOR OUTPUT (V)
50
-10
8
IMAGE REJECTION vs. TEMPERATURE
SYSTEM GAIN vs. IF FREQUENCY
1.6
MAX7032 toc13
FSK DEMODULATOR OUTPUT
vs. IF FREQUENCY
NORMALIZED IF GAIN (dB)
MAX7032
Low-Cost, Crystal-Based, Programmable,
ASK/FSK Transceiver with Fractional-N PLL
Low-Cost, Crystal-Based, Programmable,
ASK/FSK Transceiver with Fractional-N PLL
RECEIVER
fRF = 434MHz
-60
PHASE NOISE (dBc/Hz)
PHASE NOISE (dBc/Hz)
MAX7032 toc19
fRF = 315MHz
-60
PHASE NOISE vs. OFFSET FREQUENCY
-50
-70
-80
-90
-100
-110
MAX7032 toc20
PHASE NOISE vs. OFFSET FREQUENCY
-50
-70
-80
-90
-100
-110
-120
-120
100
1k
10k
100k
1M
10M
100
1k
OFFSET FREQUENCY (Hz)
10k
100k
10M
1M
OFFSET FREQUENCY (Hz)
TRANSMITTER
SUPPLY CURRENT
vs. SUPPLY VOLTAGE
TA = +125°C
12
TA = -40°C
TA = +25°C
10
5.0
TA = +125°C
4.5
TA = +85°C
4.0
3.5
TA = +25°C
2.5
8
3.0
3.3
3.6
2.4
SUPPLY VOLTAGE (V)
TA = +85°C
4.5
4.0
3.0
3.3
TA = +25°C
TA = -40°C
9
8
PA ON
7
2.7
3.0
SUPPLY VOLTAGE (V)
3.3
3.6
2.7
3.0
3.3
3.6
14
fRF = 434MHz
ENVELOPE SHAPING ENABLED
13
12
11
10
9
PA ON
8
7
6
50% DUTY CYCLE
4
2.4
2.4
SUPPLY CURRENT vs. OUTPUT POWER
10
5
3.0
2.1
TA = +25°C
2.1
3.6
6
3.5
TA = -40°C
SUPPLY VOLTAGE (V)
fRF = 315MHz
ENVELOPE SHAPING ENABLED
11
SUPPLY CURRENT (mA)
SUPPLY CURRENT (mA)
TA = +125°C
5.0
2.7
SUPPLY CURRENT vs. OUTPUT POWER
12
MAX7032 toc24
fRF = 434MHz
PA OFF
5.5
TA = +125°C
13
SUPPLY VOLTAGE (V)
SUPPLY CURRENT
vs. SUPPLY VOLTAGE
6.0
TA = +85°C
9
2.1
SUPPLY CURRENT (mA)
2.7
MAX7032 toc25
2.4
15
TA = -40°C
2.0
2.1
fRF = 434MHz
PA ON
WITHOUT ENVELOPE SHAPING
11
3.0
MAX7032 toc23
5.5
17
MAX7032 toc26
TA = +85°C
SUPPLY CURRENT vs. SUPPLY VOLTAGE
fRF = 315MHz
PA OFF
SUPPLY CURRENT (mA)
14
6.0
MAX7032 toc21
fRF = 315MHz
PA ON
WITHOUT ENVELOPE SHAPING
SUPPLY CURRENT (mA)
SUPPLY CURRENT (mA)
16
MAX7032 toc22
SUPPLY CURRENT vs. SUPPLY VOLTAGE
50% DUTY CYCLE
5
-14
-10
-6
-2
2
6
AVERAGE OUTPUT POWER (dBm)
10
-14
-10
-6
-2
2
6
10
AVERAGE OUTPUT POWER (dBm)
_______________________________________________________________________________________
9
MAX7032
Typical Operating Characteristics (continued)
(Typical Application Circuit, VPAVDD = VAVDD = VDVDD = VHVIN = +3.0V, fRF = 433.92MHz, TA = +25°C, IF BW = 280kHz, data rate
= 4kbps Manchester encoded, frequency deviation = ±50kHz, BER = 0.2% average RF power, unless otherwise noted.)
Typical Operating Characteristics (continued)
(Typical Application Circuit, VPAVDD = VAVDD = VDVDD = VHVIN = +3.0V, fRF = 433.92MHz, TA = +25°C, IF BW = 280kHz, data rate
= 4kbps Manchester encoded, frequency deviation = ±50kHz, BER = 0.2% average RF power, unless otherwise noted.)
TRANSMITTER
SUPPLY CURRENT AND OUTPUT POWER
vs. EXTERNAL RESISTOR
12
16
14
8
14
12
4
0
CURRENT
8
-4
6
-8
-8
4
-12
4
-16
2
10
100
10k
1k
-16
0.1
1
EXTERNAL RESISTOR (Ω)
8
TA = +125°C
6
TA = +85°C
MAX7032 28-2
TA = +25°C
10
8
TA = +125°C
6
14
TA = +85°C
3.0
3.3
2.4
OUTPUT POWER vs. SUPPLY VOLTAGE
2.7
3.0
3.3
2.1
3.6
2.4
12
fRF = 315MHz
PA ON
TA = -40°C
35
EFFICIENCY (%)
TA = -40°C
TA = +25°C
10
3.3
3.6
fRF = 434MHz
PA ON
TA = -40°C
35
TA = +85°C
25
TA = +125°C
3.0
EFFICIENCY vs. SUPPLY VOLTAGE
40
TA = +25°C
30
2.7
SUPPLY VOLTAGE (V)
EFFICIENCY vs. SUPPLY VOLTAGE
40
MAX7032 29-2
fRF = 434MHz
PA ON
ENVELOPE SHAPING ENABLED
8
TA = +125°C
TA = +85°C
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
14
8
4
2.1
3.6
EFFICIENCY (%)
2.7
MAX7032 toc30
2.4
10k
10
6
4
4
2.1
1k
fRF = 434MHz
PA ON
ENVELOPE SHAPING DISABLED
TA = -40°C
TA = +25°C
12
OUTPUT POWER (dBm)
TA = +25°C
10
fRF = 315MHz
PA ON
ENVELOPE SHAPING ENABLED
TA = -40°C
12
OUTPUT POWER (dBm)
OUTPUT POWER (dBm)
12
100
OUTPUT POWER vs. SUPPLY VOLTAGE
OUTPUT POWER vs. SUPPLY VOLTAGE
14
MAX7032 28-1
fRF = 315MHz
PA ON
ENVELOPE SHAPING DISABLED
TA = -40°C
10
EXTERNAL RESISTOR (Ω)
OUTPUT POWER vs. SUPPLY VOLTAGE
14
-12
fRF = 434MHz
PA ON
MAX7032 29-1
1
4
CURRENT
0
6
0.1
12
10
-4
fRF = 315MHz
PA ON
16
8
12
8
2
POWER
MAX7032 toc31
10
OUTPUT POWER (dBm)
POWER
MAX7032 toc27-2
OUTPUT POWER (dBm)
18
SUPPLY CURRENT (mA)
16
16
SUPPLY CURRENT (mA)
SUPPLY CURRENT AND OUTPUT POWER
vs. EXTERNAL RESISTOR
MAX7032 toc27-1
18
OUTPUT POWER (dBm)
MAX7032
Low-Cost, Crystal-Based, Programmable,
ASK/FSK Transceiver with Fractional-N PLL
TA = +25°C
30
TA = +85°C
25
TA = +125°C
TA = +125°C
TA = +85°C
6
2.4
2.7
3.0
SUPPLY VOLTAGE (V)
10
20
20
2.1
3.3
3.6
2.1
2.4
2.7
3.0
SUPPLY VOLTAGE (V)
3.3
3.6
2.1
2.4
2.7
3.0
SUPPLY VOLTAGE (V)
______________________________________________________________________________________
3.3
3.6
Low-Cost, Crystal-Based, Programmable,
ASK/FSK Transceiver with Fractional-N PLL
TRANSMITTER
TA = +125°C
TA = +25°C
20
TA = +85°C
15
-60
2.7
3.0
3.3
3.6
2.1
SUPPLY VOLTAGE (V)
-100
-110
2.4
2.7
3.0
100
3.6
3.3
1k
10k
-70
-80
-90
-100
-110
-120
-40
REFERENCE SPUR MAGNITUDE (dBc)
-60
1M
10M
REFERENCE SPUR MAGNITUDE
vs. SUPPLY VOLTAGE
MAX7032 toc35
fRF = 434MHz
100k
OFFSET FREQUENCY (Hz)
SUPPLY VOLTAGE (V)
-40
PHASE NOISE (dBc/Hz)
-90
-130
PHASE NOISE
vs. OFFSET FREQUENCY
-50
-80
-140
15
2.4
-70
-120
TA = +125°C
-45
433.92MHz
-50
-55
315MHz
-60
-65
-130
-140
-70
1k
10k
100k
1M
10M
2.1
2.4
OFFSET FREQUENCY (Hz)
8
fRF = 315MHz
2
0
fRF = 434MHz
-2
3.3
3.6
-4
-6
-56
CLKOUT SPUR MAGNITUDE (dBc)
10
4
3.0
CLKOUT SPUR MAGNITUDE
vs. SUPPLY VOLTAGE
FREQUENCY STABILITY
vs. SUPPLY VOLTAGE
6
2.7
SUPPLY VOLTAGE (V)
MAX7032 toc38
100
MAX7032 toc37
2.1
fRF = 315MHz
-50
TA = +85°C
10
MAX7032 toc34
TA = -40°C
25
-40
MAX7032 toc36
20
fRF = 434MHz
50% DUTY CYCLE
PHASE NOISE (dBc/Hz)
EFFICIENCY (%)
TA = +25°C
FREQUENCY STABILITY (ppm)
EFFICIENCY (%)
30
MAX7032 toc32
TA = -40°C
25
PHASE NOISE vs. OFFSET FREQUENCY
EFFICIENCY vs. SUPPLY VOLTAGE
fRF = 315MHz
50% DUTY CYCLE
MAX7032 toc33
EFFICIENCY vs. SUPPLY VOLTAGE
30
fRF = 434MHz
CLKOUT SPUR = fRF ± fCLKOUT
10pF LOAD CAPACITANCE
-58
fCLKOUT = fXTAL/8
-60
-62
fCLKOUT = fXTAL/2
-64
fCLKOUT = fXTAL/4
-8
-66
-10
2.1
2.4
2.7
3.0
SUPPLY VOLTAGE (V)
3.3
3.6
2.1
2.4
2.7
3.0
3.3
3.6
SUPPLY VOLTAGE (V)
______________________________________________________________________________________
11
MAX7032
Typical Operating Characteristics (continued)
(Typical Application Circuit, VPAVDD = VAVDD = VDVDD = VHVIN = +3.0V, fRF = 433.92MHz, TA = +25°C, IF BW = 280kHz, data rate
= 4kbps Manchester encoded, frequency deviation = ±50kHz, BER = 0.2% average RF power, unless otherwise noted.)
Low-Cost, Crystal-Based, Programmable,
ASK/FSK Transceiver with Fractional-N PLL
MAX7032
Pin Description
PIN
1
12
NAME
PAVDD
FUNCTION
Power-Amplifier Supply Voltage. Bypass to GND with 0.01µF and 220pF capacitors placed as close
as possible to the pin.
2
ROUT
Envelope-Shaping Output. ROUT controls the power-amplifier envelope’s rise and fall times. Connect
ROUT to the PA pullup inductor or optional power-adjust resistor. Bypass the inductor to GND as
close as possible to the inductor with 680pF and 220pF capacitors as shown in the Typical
Application Circuit.
3
TX/RX1
Transmit/Receive Switch Throw. Drive T/R high to short TX/RX1 to TX/RX2. Drive T/R low to disconnect
TX/RX1 from TX/RX2. Functionally identical to TX/RX2.
4
TX/RX2
Transmit/Receive Switch Pole. Typically connected to ground. See the Typical Application Circuit.
5
PAOUT
Power-Amplifier Output. Requires a pullup inductor to the supply voltage (or ROUT if envelope
shaping is desired), which may be part of the output-matching network to an antenna.
6
AVDD
Analog Power-Supply Voltage. AVDD is connected to an on-chip +3.0V regulator in 5V operation.
Bypass AVDD to GND with 0.1µF and 220pF capacitors placed as close as possible to the pin.
7
LNAIN
Low-Noise Amplifier Input. Must be AC-coupled.
8
LNASRC
Low-Noise Amplifier Source for External Inductive Degeneration. Connect an inductor to GND to set
the LNA input impedance.
9
LNAOUT
Low-Noise Amplifier Output. Must be connected to AVDD through a parallel LC tank filter. AC-couple
to MIXIN+.
10
MIXIN+
11
MIXIN-
12
MIXOUT
Noninverting Mixer Input. Must be AC-coupled to the LNA output.
Inverting Mixer Input. Bypass to AVDD with a capacitor as close as possible to LNA LC tank filter.
330Ω Mixer Output. Connect to the input of the 10.7MHz filter.
13
IFIN-
Inverting 330Ω IF Limiter Amplifier Input. Bypass to GND with a capacitor.
14
IFIN+
Noninverting 330Ω IF Limiter Amplifier Input. Connect to the output of the 10.7MHz IF filter.
15
PDMIN
16
PDMAX
17
DS-
Inverting Data Slicer Input
18
DS+
Noninverting Data Slicer Input
19
OP+
20
DF
21
RSSI
22
T/R
23
ENABLE
24
DATA
25
CLKOUT
26
DVDD
Minimum-Level Peak Detector for Demodulator Output
Maximum-Level Peak Detector for Demodulator Output
Noninverting Op Amp Input for the Sallen-Key Data Filter
Data Filter Feedback Node. Input for the feedback of the Sallen-Key data filter.
Buffered Received-Signal-Strength Indicator Output
Transmit/ Receive. Drive high to put the device in transmit mode. Drive low or leave unconnected to
put the device in receive mode. It is internally pulled down. This function is also controlled by a
configuration register.
Enable. Drive high for normal operation. Drive low or leave unconnected to put the device into
shutdown mode.
Receiver Data Output/Transmitter Data Input
Divided Crystal Clock Buffered Output
Digital Power-Supply Voltage. Bypass to GND with 0.01µF and 220pF capacitors placed as close as
possible to the pin.
______________________________________________________________________________________
Low-Cost, Crystal-Based, Programmable,
ASK/FSK Transceiver with Fractional-N PLL
PIN
NAME
FUNCTION
27
HVIN
28
CS
Serial Interface Active-Low Chip Select
29
DIO
Serial Interface Serial Data Input/Output
30
SCLK
Serial Interface Clock Input
31
XTAL1
Crystal Input 1. Bypass to GND if XTAL2 is driven by an AC-coupled external reference.
32
XTAL2
Crystal Input 2. XTAL2 can be driven from an AC-coupled external reference.
—
EP
Exposed Pad. Solder evenly to the board’s ground plane for proper operation.
High-Voltage Supply Input. For 3V operation, connect HVIN to PAVDD, AVDD, and DVDD. For 5V
operation, connect only HVIN to 5V. Bypass HVIN to GND with 0.01µF and 220pF capacitors placed
as close as possible to the pin.
Detailed Description
The MAX7032 300MHz to 450MHz CMOS transceiver
and a few external components provide a complete
transmit and receive chain from the antenna to the digital data interface. This device is designed for transmitting and receiving ASK and FSK data. All transmit
frequencies are generated by a fractional-N-based synthesizer, allowing for very fine frequency steps in increments of fXTAL/4096. The receive LO is generated by a
traditional integer-N-based synthesizer. Depending on
component selection, data rates as high as 33kbps
(Manchester encoded) or 66kbps (NRZ encoded) can
be achieved.
Receiver
Low-Noise Amplifier (LNA)
The LNA is a cascode amplifier with off-chip inductive
degeneration that achieves approximately 30dB of voltage gain that is dependent on both the antenna matching network at the LNA input and the LC tank network
between the LNA output and the mixer inputs.
The off-chip inductive degeneration is achieved by
connecting an inductor from LNASRC to GND. This
inductor sets the real part of the input impedance at
LNAIN, allowing for a more flexible match for low-input
impedance such as a PCB trace antenna. A nominal
value for this inductor with a 50Ω input impedance is
12nH at 315MHz and 10nH at 434MHz, but the inductance is affected by PCB trace length. LNASRC can be
shorted to ground to increase sensitivity by approximately 1dB, but the input match must then be reoptimized.
The LC tank filter connected to LNAOUT consists of L5
and C9 (see the Typical Application Circuit). Select L5
and C9 to resonate at the desired RF input frequency.
The resonant frequency is given by:
f=
1
2π L TOTAL × CTOTAL
where LTOTAL = L5 + LPARASITICS and CTOTAL = C9 +
CPARASITICS.
LPARASITICS and CPARASITICS include inductance and
capacitance of the PCB traces, package pins, mixer
input impedance, LNA output impedance, etc. These
parasitics at high frequencies cannot be ignored and
can have a dramatic effect on the tank filter center frequency. Lab experimentation must be done to optimize
the center frequency of the tank. The total parasitic
capacitance is generally between 5pF and 7pF.
Automatic Gain Control (AGC)
When the AGC is enabled, it monitors the RSSI output.
When the RSSI output reaches 1.28V, which corresponds to an RF input level of approximately -55dBm,
the AGC switches on the LNA gain-reduction attenuator. The attenuator reduces the LNA gain by 36dB,
thereby reducing the RSSI output by about 540mV to
740mV. The LNA resumes high-gain mode when the
RSSI output level drops back below 680mV (approximately -59dBm at the RF input) for a programmable
interval called the AGC dwell time. The AGC has a hysteresis of approximately 4dB. With the AGC function,
the RSSI dynamic range is increased, allowing the
MAX7032 to reliably produce an ASK output for RF
input levels up to 0dBm with a modulation depth of
18dB. AGC is not required and can be disabled in
either ASK or FSK mode. AGC is not necessary for FSK
mode because large received signal levels do not
affect FSK performance.
______________________________________________________________________________________
13
MAX7032
Pin Description (continued)
MAX7032
Low-Cost, Crystal-Based, Programmable,
ASK/FSK Transceiver with Fractional-N PLL
Mixer
A unique feature of the MAX7032 is the integrated
image rejection of the mixer. This eliminates the need
for a costly front-end SAW filter for many applications.
The advantage of not using a SAW filter is increased
sensitivity, simplified antenna matching, less board
space, and lower cost.
The mixer cell is a pair of double-balanced mixers that
perform an IQ downconversion of the RF input to the
10.7MHz intermediate frequency (IF) with low-side
injection (i.e., fLO = fRF - fIF). The image-rejection circuit
then combines these signals to achieve a typical 46dB
of image rejection over the full temperature range. Lowside injection is required as high-side injection is not
possible due to the on-chip image rejection. The IF output is driven by a source follower, biased to create a
driving impedance of 330Ω to interface with an off-chip
330Ω ceramic IF filter. The voltage-conversion gain driving a 330Ω load is approximately 20dB. Note that the
MIXIN+ and MIXIN- inputs are functionally identical.
Integer-N Phase-Locked Loop (PLL)
The MAX7032 utilizes a fixed integer-N PLL to generate
the receive LO. All PLL components, including the loop filter, VCO, charge pump, asynchronous 24x divider, and
phase-frequency detector are integrated on-chip. The
loop bandwidth is approximately 500kHz. The relationship
between RF, IF, and reference frequencies is given by:
fREF = (fRF – fIF)/24
Intermediate Frequency (IF)
The IF section presents a differential 330Ω load to provide matching for the off-chip ceramic filter. The internal six AC-coupled limiting amplifiers produce an
overall gain of approximately 65dB, with a bandpass filter type response centered near the 10.7MHz IF frequency with a 3dB bandwidth of approximately 10MHz.
For ASK data, the RSSI circuit demodulates the IF to
baseband by producing a DC output proportional to
the log of the IF signal level with a slope of approximately 15mV/dB. For FSK, the limiter output is fed into a
PLL to demodulate the IF. The FSK demodulation slope
is approximately 2.0mV/kHz.
FSK Demodulator
The FSK demodulator uses an integrated 10.7MHz PLL
that tracks the input RF modulation and converts the frequency deviation into a voltage difference. The PLL is
illustrated in Figure 1. The input to the PLL comes from
the output of the IF limiting amplifiers. The PLL control
voltage responds to changes in the frequency of the
input signal with a nominal gain of 2.0mV/kHz. For example, an FSK peak-to-peak deviation of 50kHz generates
14
TO FSK BASEBAND FILTER
AND DATA SLICER
PHASE
DETECTOR
IF
LIMITING
AMPS
CHARGE
PUMP
LOOP
FILTER
10.7MHz VCO
2.0mV/kHz
Figure 1. FSK Demodulator PLL Block Diagram
a 100mVP-P signal on the control line. This control voltage is then filtered and sliced by the baseband circuitry.
The FSK demodulator PLL requires calibration to overcome variations in process, voltage, and temperature.
For more information on calibrating the FSK demodulator, see the Calibration section. The maximum calibration time is 150µs. In discontinuous receive (DRX)
mode, the FSK demodulator calibration occurs automatically just after the IC exits sleep mode, as long as
the ACAL bit is set to 1.
Data Filter
The data filter for the demodulated data is implemented
as a 2nd-order lowpass Sallen-Key filter. The pole locations are set by the combination of two on-chip resistors
and two external capacitors. Adjusting the value of the
external capacitors changes the corner frequency to
optimize for different data rates. The corner frequency in
kHz should be set to approximately 3 times the fastest
expected Manchester data rate in kbps from the transmitter (1.5 times the fastest expected NRZ data rate) for
ASK. For FSK, the corner frequency should be set to
approximately 2 times the fastest expected Manchester
data rate in kbps from the transmitter (1 times the fastest
expected NRZ data rate). Keeping the corner frequency
near the data rate rejects any noise at higher frequencies, resulting in an increase in receiver sensitivity.
Table 1 lists coefficients to calculate CF1 and CF2.
Table 1. Coefficients to Calculate CF1 and
CF2
FILTER TYPE
a
b
Butterworth
(Q = 0.707)
1.414
1.000
Bessel
(Q = 0.577)
1.3617
0.618
______________________________________________________________________________________
Low-Cost, Crystal-Based, Programmable,
ASK/FSK Transceiver with Fractional-N PLL
b
CF1 =
a(100kΩ)(π)(fC )
a
CF2 =
4(100kΩ)(π)(fC )
RSSI OR
FSK DEMOD
MAX7032
100kΩ
100kΩ
DS+
MAX7032
The configuration shown in Figure 2 can create a
Butterworth or Bessel response. The Butterworth filter
offers a very flat amplitude response in the passband
and a rolloff rate of 40dB/decade for the two-pole filter.
The Bessel filter has a linear phase response, which
works well for filtering digital data. To calculate the
value of the capacitors, use the following equations,
along with the coefficients in Table 1:
OP+
DF
CF1
CF2
Figure 2. Sallen-Key Lowpass Data Filter
where fC is the desired 3dB corner frequency.
For example, choose a Butterworth filter response with
a corner frequency of 5kHz:
MAX7032
1.000
CF1 =
≈ 450pF
(1.414)(100kΩ)(3.14)(5kHz)
1.414
CF2 =
≈ 225pF
(4)(100kΩ)(3.14)(5kHz)
Choosing standard capacitor values changes CF1 to
470pF and CF2 to 220pF. In the Typical Application Circuit,
CF1 and CF2 are named C16 and C17, respectively.
Data Slicer
The data slicer takes the analog output of the data filter
and converts it to a digital signal. This is achieved by
using a comparator and comparing the analog input to
a threshold voltage. The threshold voltage is set by the
voltage on the DS- pin, which is connected to the negative input of the data-slicer comparator.
Numerous configurations can be used to generate the
data-slicer threshold. For example, the circuit in Figure
3 shows a simple method using only one resistor and
one capacitor. This configuration averages the analog
output of the filter and sets the threshold to approximately 50% of that amplitude. With this configuration,
the threshold automatically adjusts as the analog signal
varies, minimizing the possibility for errors in the digital
data. The values of R and C affect how fast the threshold tracks the analog amplitude. Be sure to keep the
corner frequency of the RC circuit much lower (about
10 times) than the lowest expected data rate.
With this configuration, a long string of NRZ zeros or ones
can cause the threshold to drift. This configuration works
DATA
SLICER
DS-
DATA
DS+
R
C
Figure 3. Generating Data Slicer Threshold Using a Lowpass
Filter
best if a coding scheme, such as Manchester coding,
which has an equal number of zeros and ones, is used.
Figure 4 shows a configuration that uses the positive and
negative peak detectors to generate the threshold. This
configuration sets the threshold to the midpoint between
a high output and a low output of the data filter.
Peak Detectors
The maximum peak detector (PDMAX) and minimum
peak detector (PDMIN), with resistors and capacitors
shown in Figure 4, create DC output voltages equal to
the high and low peak values of the filtered ASK or FSK
demodulated signals. The resistors provide a path for
the capacitors to discharge, allowing the peak detectors to dynamically follow peak changes of the data filter output voltages.
______________________________________________________________________________________
15
MAX7032
Low-Cost, Crystal-Based, Programmable,
ASK/FSK Transceiver with Fractional-N PLL
MAX7032
MINIMUM PEAK
DETECTOR
MAX7032
PDMIN
PEAK
DET
PEAK
DET
DATA
SLICER
BASEBAND
FILTER
PDMAX
R
DATA
TO SLICER
INPUT
TRK_EN = 1
MAXIMUM PEAK
DETECTOR
PDMIN
R
PDMAX
C
C
TRK_EN = 1
Figure 4. Generating Data Slicer Threshold Using the Peak
Detectors
Figure 5. Peak-Detector Track Enable
The maximum and minimum peak detectors can be
used together to form a data slicer threshold voltage at
a value midway between the maximum and minimum
voltage levels of the data stream (see the Data Slicer
section and Figure 4). The RC time constant of the
peak-detector combining network should be set to at
least 5 times the data period.
If there is an event that causes a significant change in
the magnitude of the baseband signal, such as an AGC
gain switch or a power-up transient, the peak detectors
may “catch” a false level. If a false peak is detected,
the slicing level is incorrect. The MAX7032 has a feature called peak-detector track enable (TRK_EN),
where the peak-detector outputs can be reset (see
Figure 5). If TRK_EN is set (logic 1), both the maximum
and minimum peak detectors follow the input signal.
When TRK_EN is cleared (logic 0), the peak detectors
revert to their normal operating mode. The TRK_EN
function is automatically enabled for a short time whenever the IC is first powered up, or transitions from transmit to receive mode, or recovers from the sleep portion
of DRX mode, or when an AGC gain switch occurs
regardless of the bit setting. Since the peak detectors
exhibit a fast-attack/slow-decay response, this feature
allows for an extremely fast startup or AGC recovery.
See Figure 6 for an illustration of a fast-recovery
sequence. In addition to the automatic control of this
function, the TRK_EN bits can be controlled through the
serial interface (see the Serial Control Interface section).
Transmitter
Power Amplifier (PA)
The PA of the MAX7032 is a high-efficiency, opendrain, switch-mode amplifier. The PA with proper
16
RECEIVER ENABLED, TRK_EN SET
TRK_EN CLEARED
MAX PEAK DETECTOR
200mV/div
FILTER OUTPUT
MIN PEAK DETECTOR
DATA OUTPUT
DATA OUTPUT
2V/div
100μs/div
Figure 6. Fast Receiver Recovery in FSK Mode Utilizing Peak
Detectors
output-matching network can drive a wide range of
antenna impedances, which includes a small-loop PCB
trace and a 50Ω antenna. The output-matching network
for a 50Ω antenna is shown in the Typical Application
Circuit. The output-matching network suppresses the
carrier harmonics and transforms the antenna impedance to an optimal impedance at PAOUT (pin 5). The
optimal impedance at PAOUT is 250Ω.
When the output-matching network is properly tuned,
the PA transmits power with a high overall efficiency of
up to 32%. The efficiency of the PA itself is more than
46%. The output power is set by an external resistor at
PAOUT and is also dependent on the external antenna
and antenna-matching network at the PA output.
______________________________________________________________________________________
Low-Cost, Crystal-Based, Programmable,
ASK/FSK Transceiver with Fractional-N PLL
Fractional-N PLL
The MAX7032 utilizes a fully integrated fractional-N PLL
for its transmit frequency synthesizer. All PLL components, including the loop filter, are included on chip.
The loop bandwidth is approximately 200kHz. The 16bit fractional-N topology allows the transmit frequency
to be adjusted in increments of fXTAL/4096. The finefrequency-adjustment capability enables the use of a
single crystal, as the transmit frequency can be set
within 2kHz of the receive frequency.
The fractional-N topology also allows exact FSK frequency deviations to be programmed, completely eliminating the problems associated with generating
frequency deviations by crystal oscillator pulling.
The integer and fractional portions of the PLL divider
ratio set the transmit frequency. The example below
shows how to calculate fXTAL and how to determine the
correct values to be loaded to register TxLOW (register
0x0D and 0x0E) and TxHIGH (registers 0x0F and
0x10):
Assume the receiver/ASK transmit frequency = 315MHz
and IF = 10.7MHz:
(f − 10.7)
fXTAL = RF
= 12.67917MHz
24
and
fRF
fXTAL
= 24.8439 = transmit PLL divider ratio
Due to the nature of the transmit PLL frequency divider,
a fixed offset of 16 must be subtracted from the transmit PLL divider ratio for programming the MAX7032’s
transmit frequency registers. To determine the value to
program the MAX7032’s transmit frequency registers,
convert the decimal value of the following equation to
the nearest hexadecimal value:
⎛ fRF
⎞
− 16⎟ × 4096 = decimal value to program
⎜ f
⎝ XTAL
⎠
transmit frequency registers
In this example, the rounded decimal value is 36,225,
or 8D81 hexadecimal. The upper byte (8D) is loaded
into register 0x0D, and the low byte (81) is loaded into
register 0x0E.
In FSK mode, the transmit frequencies equal the upper
and lower frequencies that are programmed into the
MAX7032’s transmit frequency registers. Calculate the
upper frequency in the same way as shown above. In
ASK mode, the transmit frequency equals the lower frequency that is programmed into the MAX7032’s transmit frequency registers.
Power-Supply Connections
The MAX7032 can be powered from a 2.1V to 3.6V
supply or a 4.5V to 5.5V supply. If a 4.5V to 5.5V supply
is used, then the on-chip linear regulator reduces the
5V supply to the 3V needed to operate the chip.
To operate the MAX7032 from a 3V supply, connect
PAVDD, AVDD, DVDD, and HVIN to the 3V supply.
When using a 5V supply, connect the supply to HVIN
only and connect AVDD, PAVDD, and DVDD together.
In both cases, bypass DVDD, PAVDD and HVIN to
GND with a 0.01µF and 220pF capacitor and bypass
AVDD to GND with a 0.1µF and 220pF capacitor.
Bypass T/R, ENABLE, DATA, CS, DIO, and SCLK with
10pF capacitors to GND. Place all bypass capacitors
as close as possible to the respective pins.
Transmit/Receive Antenna Switch
The MAX7032 features an internal SPST RF switch,
which, when combined with a few external components, allows the transmit and receive pins to share a
common antenna (see the Typical Application Circuit).
In receive mode, the switch is open and the power
amplifier is shut down, presenting a high impedance to
minimize the loading of the LNA. In transmit mode, the
switch closes to complete a resonant tank circuit at the
PA output and forms an RF short at the input to the
LNA. In this mode, the external passive components
couple the output of the PA to the antenna to protect
the LNA input from strong transmitted signals.
The switch state is controlled either by an external digital input or by the T/R bit, which is bit 6 in the configuration 0 register, T/R. Drive the T/R pin high to put the
device in transmit mode; drive the T/R pin low to put the
device in receive mode.
______________________________________________________________________________________
17
MAX7032
Envelope Shaping
The MAX7032 features an internal envelope-shaping
resistor, which connects between the open-drain output
of the PA and the power supply (see the Typical
Application Circuit ). The envelope-shaping resistor
slows the turn-on/turn-off of the PA in ASK mode and
results in a smaller spectral width of the modulated PA
output signal.
MAX7032
Low-Cost, Crystal-Based, Programmable,
ASK/FSK Transceiver with Fractional-N PLL
Crystal Oscillator (XTAL)
The XTAL oscillator in the MAX7032 is designed to present a capacitance of approximately 3pF between the
XTAL1 and XTAL2 pins. In most cases, this corresponds to a 4.5pF load capacitance applied to the
external crystal when typical PCB parasitics are added.
It is very important to use a crystal with a load
capacitance that is equal to the capacitance of the
MAX7032 crystal oscillator plus PCB parasitics. If a
crystal designed to oscillate with a different load
capacitance is used, the crystal is pulled away from its
stated operating frequency, introducing an error in the
reference frequency. Crystals designed to operate with
higher differential load capacitance always pull the reference frequency higher.
In actuality, the oscillator pulls every crystal. The crystal’s natural frequency is really below its specified frequency, but when loaded with the specified load
capacitance, the crystal is pulled and oscillates at its
specified frequency. This pulling is already accounted
for in the specification of the load capacitance.
Additional pulling can be calculated if the electrical
parameters of the crystal are known. The frequency
pulling is given by:
⎞
C ⎛
1
1
fP = m ⎜
−
× 106
2 ⎝ CCASE + CLOAD CCASE + CSPEC ⎟⎠
where:
fp is the amount the crystal frequency is pulled in ppm.
Cm is the motional capacitance of the crystal.
CCASE is the case capacitance.
CSPEC is the specified load capacitance.
CLOAD is the actual load capacitance.
When the crystal is loaded as specified, i.e., CLOAD =
CSPEC, the frequency pulling equals zero.
Serial Control Interface
Communication Protocol
The MAX7032 programs through a 3-wire interface. The
data input must follow the timing diagrams shown in
Figures 7, 8, and 9.
Note that the DIO line must be held LOW while CS is
high. This is to prevent the MAX7032 from entering discontinuous receive mode if the DRX bit is high. The
data is latched on the rising edge of SCLK, and therefore must be stable before that edge. The data
sequencing is MSB first, the command (C[1:0] see
Table 2), the register address (A[5:0] see Table 3), and
the data (D[7:0] see Table 4).
Table 2. Command Bits
C[1:0]
DESCRIPTION
0x0
No operation
0x1
Write data
0x2
Read data
0x3
Master reset
tCS
CS
tCH
tCSS
tSC
tCSH
tCL
SCLK
tDH
tTH
tDS
DIO
HI-Z
HI-Z
DATA IN
D7
D0
DATA OUT
Figure 7. Serial Interface Timing Diagram
18
tTR
tDO
tDV
______________________________________________________________________________________
HI-Z
Low-Cost, Crystal-Based, Programmable,
ASK/FSK Transceiver with Fractional-N PLL
MAX7032
Table 3. Register Summary
REGISTER A[5:0]
REGISTER NAME
DESCRIPTION
0x00
Power configuration
Enables/disables the LNA, AGC, mixer, baseband, peak
detectors, PA, and RSSI output (see Table 5).
0x01
Control
Controls AGC lock, gain state, peak-detector tracking, polling
timer and FSK calibration, clock signal output, and sleep mode
(see Table 6).
0x02
Configuration0
Sets options for modulation, TX/RX mode, manual-gain mode,
discontinuous receive mode, off-timer and on-timer prescalers
(see Table 7).
0x03
Configuration1
Sets options for automatic FSK calibration, clock output, output
clock divider ratio, AGC dwell timer (see Tables 8, 10, 11, and 12).
0x05
Oscillator frequency
Sets the internal clock frequency divisor. This register must be set
to the integer result of fXTAL/100kHz (see the Oscillator Frequency
Register (Address 0x05) section).
0x06
Off timer—tOFF (upper byte)
0x07
Off timer—tOFF (lower byte)
0x08
CPU recovery timer—tCPU
0x09
RF settling timer—tRF (upper
byte)
0x0A
RF settling timer—tRF (lower
byte)
0x0B
On timer—tON (upper byte)
0x0C
On timer—tON (lower byte)
0x0D
Transmitter low-frequency
setting—TxLOW (upper byte)
0x0E
Transmitter low-frequency
setting—TxLOW (lower byte)
0x0F
Transmitter high-frequency
setting—TxHIGH (upper byte)
0x10
Transmitter high-frequency
setting—TxHIGH (lower byte)
0x1A
Status register (read only)
Sets the duration that the MAX7032 remains in low-power mode
when DRX is active (see Table 12).
Increases maximum time the MAX7032 stays in lower power mode
while CPU wakes up when DRX is active (see Table 13).
During the time set by the RF settling timer, the MAX7032 is
powered on with the peak detectors and the data outputs disabled
to allow time for the RF section to settle. DIO must be driven low at
any time during tLOW = tCPU + tRF + tON or the timer sequence
restarts (see Table 14).
Sets the duration that the MAX7032 remains in active mode when
DRX is active (see Table 15).
Sets the low frequency (FSK) of the transmitter or the carrier
frequency of ASK for the fractional-N synthesizer.
Sets the high frequency (FSK) of the transmitter for the fractional-N
synthesizer.
Provides status for PLL lock, AGC state, crystal operation, polling
timer, and FSK calibration (see Table 9).
______________________________________________________________________________________
19
MAX7032
Low-Cost, Crystal-Based, Programmable,
ASK/FSK Transceiver with Fractional-N PLL
CS
SCLK
DIO
C1
C0
A5
A4
A3
COMMAND
A2
A1
A0
D7
D6
D5
D4
D3
D2
D1
D0
DATA
ADDRESS
Figure 8. Data Input Diagram
CS
SCLK
DIO
1
0
A5
A4
A3
A2
A1
A0
0
0
0
0
0
0
0
R7
R6
R5
DATA
ADDRESS
READ
COMMAND
0
R4
R3
R2
R1
R0
R7
R0
REGISTER
DATA
REGISTER DATA
16 BITS OF DATA
CS
SCLK
DIO
1
0
READ
COMMAND
A5
A4
A3
A2
A1
A0
0
0
ADDRESS
0
0
0
DATA
0
0
0
R7
R6
R5
R4
R3
R2
R1
A3
REGISTER DATA
8 BITS OF DATA
Figure 9. Read Command on a 3-Wire Serial Interface
DIO is selected as an output of the MAX7032 for the following CS cycle whenever a READ command is
received. The CPU must tri-state the DIO line on the
cycle of CS that follows a read command, so the
MAX7032 can drive the data output line. Figure 9
shows the diagram of the 3-wire interface. Note that the
user can choose to send either 16 cycles of SLCK or
just eight cycles as all the registers are 8-bits wide. The
20
user must drive DIO low at the end of the read
sequence.
The MASTER RESET command (0x3) (see Table 2)
sends a reset signal to all the internal registers of the
MAX7032 just like a power-off and power-on sequence
would do. The reset signal remains active for as long as
CS is high after the command is sent.
______________________________________________________________________________________
Low-Cost, Crystal-Based, Programmable,
ASK/FSK Transceiver with Fractional-N PLL
MAX7032
Table 4. Register Configuration
DATA
NAME (ADDRESS)
D7
D6
D5
D4
D3
D2
D1
D0
POWER[7:0] (0x00)
LNA
AGC
MIXER
BaseB
PkDet
PA
RSSIO
X
CONTRL[7:0] (0x01)
AGCLK
GAIN
TRK_EN
X
PCAL
FCAL
CKOUT
SLEEP
CONF0[7:0] (0x02)
MODE
T/R
MGAIN
DRX
OFPS1
OFPS0
ONPS1
ONPS0
CONF1[7:0] (0x03)
X
ACAL
CLKOF
CDIV1
CDIV0
DT2
DT1
DT0
OSC[7:0] (0x05)
OSC7
OSC6
OSC5
OSC4
OSC3
OSC2
OSC1
OSC0
tOFF[15:8] (0x06)
tOFF 15
tOFF 14
tOFF 13
tOFF 12
tOFF 11
tOFF 10
tOFF 9
tOFF 8
tOFF[7:0] (0x07)
tOFF 7
tOFF 6
tOFF 5
tOFF 4
tOFF 3
tOFF 2
tOFF 1
tOFF 0
tCPU[7:0] (0x08)
tCPU 7
tCPU 6
tCPU 5
tCPU 4
tCPU 3
tCPU 2
tCPU 1
tCPU 0
tRF[15:8] (0x09)
tRF 15
tRF 14
tRF 13
tRF 12
tRF 11
tRF 10
tRF 9
tRF 8
tRF[7:0] (0x0A)
tRF 7
tRF 6
tRF 5
tRF 4
tRF 3
tRF 2
tRF 1
tRF 0
tON[15:8] (0x0B)
tON 15
tON 14
tON 13
tON 12
tON 11
tON 10
tON 9
tON 8
tON[7:0] (0x0C)
tON 7
tON 6
tON 5
tON 4
tON 3
tON 2
tON 1
tON 0
TxLOW[15:8] (0x0D)
TxL15
TxL14
TxL13
TxL12
TxL11
TxL10
TxL9
TxL8
TxLOW[7:0] (0x0E)
TxL7
TxL6
TxL5
TxL4
TxL3
TxL2
TxL1
TxL0
TxHIGH[15:8] (0x0F)
TxH15
TxH14
TxH13
TxH12
TxH11
TxH10
TxH9
TxH8
TxHIGH[7:0] (0x10)
TxH7
TxH6
TxH5
TxH4
TxH3
TxH2
TxH1
TxH0
STATUS[7:0] (0x1A)
LCKD
GAINS
CLKON
0
0
0
PCALD
FCALD
Continuous Receive Mode (DRX = 0)
In continuous receive mode, individual analog modules
can be powered on directly through the power configuration register (register 0x00). The SLEEP bit (bit 0 in
register 0x01) overrides the power configuration registers and puts the device into deep-sleep mode when
set. It is also necessary to write the frequency divisor of
the external crystal in the oscillator frequency register
(register 0x05) to optimize image rejection and to
enable accurate calibration sequences for the polling
timer and the FSK demodulator. This number is the
integer result of fXTAL/100kHz.
If the FSK receive function is selected, it is necessary to
perform an FSK calibration to allow operation; otherwise, the demodulator is saturated. Polling timer calibration is not necessary. See the Calibration section for
more information.
Discontinuous Receive Mode (DRX = 1)
In the discontinuous receive mode (DRX = 1), the
receiver modules set to logic 1 by the power register
(0x00) of the MAX7032 toggle between OFF and ON,
according to internal timers tOFF, tCPU, tRF, and tON. It
is also necessary to write the frequency divisor of the
external crystal in the oscillator frequency register (register 0x05). This number is the integer result of
f XTAL /100kHz. Before entering the discontinuous
receive mode for the first time, it is also necessary to
calibrate the timers (see the Calibration section).
The MAX7032 uses a series of internal timers (tOFF,
tCPU, tRF, and tON) to control its power-up sequence.
The timer sequence begins when both CS and DIO are
one. The MAX7032 has an internal pullup on the DIO
pin, so the user must tri-state the DIO line when CS
goes high.
The external CPU can then go to a sleep mode during
tOFF. A high-to-low transition on DIO or a low level on
DIO serves as the wake-up signal for the CPU, which
must then start its wake-up procedure and drive DIO
low before tLOW expires (tCPU + tRF + tON). Once tRF
expires and tON is active, the MAX7032 enables the
data output. The CPU must then keep DIO low for as
long as it may need to analyze any received data.
Releasing DIO after tON expires causes the MAX7032
to pull up DIO, reinitiating the tOFF timer.
______________________________________________________________________________________
21
MAX7032
Low-Cost, Crystal-Based, Programmable,
ASK/FSK Transceiver with Fractional-N PLL
Table 5. Power-Configuration Register (Address: 0x00)
BIT ID
BIT NAME
BIT LOCATION (0 = LSB)
FUNCTION
LNA
LNA enable
7
1 = Enable LNA
0 = Disable LNA
AGC
AGC enable
6
1 = Enable AGC
0 = Disable AGC
MIXER
Mixer enable
5
1 = Enable mixer
0 = Disable mixer
BaseB
Baseband enable
4
1 = Enable baseband
0 = Disable baseband
PkDet
Peak-detector enable
3
1 = Enable peak detector
0 = Disable peak detector
PA
Transmitter PA enable
2
1 = Enable PA
0 = Disable PA
RSSIO
RSSI amplifier enable
1
1 = Enable buffer
0 = Disable buffer
None
0
Not used
X
Table 6. Control Register (Address: 0x01)
BIT ID
BIT NAME
AGCLK
AGC locking feature
7
1 = Enable AGC lock
0 = Disable AGC lock
Gain state
6
1 = Force manual high-gain state if MGAIN = 1
0 = Force manual low-gain state if MGAIN = 1
Manual peak-detector
tracking
5
1 = Force manual peak-detector tracking
0 = Release peak-detector tracking
None
4
Not used
PCAL
Polling timer calibration
3
1 = Perform polling timer calibration
Automatically reset to zero once calibration is completed
FCAL
FSK calibration
2
1 = Perform FSK calibration
Automatically reset to zero once calibration is completed
CKOUT
Crystal clock output enable
1
1 = Enable crystal clock output
0 = Disable crystal clock output
SLEEP
Sleep mode
0
1 = Deep-sleep mode, regardless the state of
ENABLE pin
0 = Normal operation
GAIN
TRK_EN
X
22
BIT LOCATION (0 = LSB)
FUNCTION
______________________________________________________________________________________
Low-Cost, Crystal-Based, Programmable,
ASK/FSK Transceiver with Fractional-N PLL
BIT ID
MODE
BIT NAME
BIT LOCATION (0 = LSB)
FSK or ASK modulation
FUNCTION
7
1 = Enable FSK for both receive and
transmit
0 = Enable ASK for both receive and
transmit
T/R
Transmit or receive
6
1 = Enable transmit mode of the
transceiver, regardless the state of pin
T/R
0 = Enable receive mode of the transceiver
when pin T/R = 0
MGAIN
Manual gain mode
5
1 = Enable manual-gain mode
0 = Disable manual-gain mode
Discontinuous receive
mode
4
1 = Enable DRX
0 = Disable DRX
OFPS1
Off-timer prescaler
3
OFPS0
Off-timer prescaler
2
ONPS1
On-timer prescaler
1
ONPS0
On-timer prescaler
0
DRX
Sets the time base for the off timer (see the
Off Timer (tOFF) section)
Sets the time base for the on timer (see the
On Timer (tON) section)
Table 8. Configuration 1 Register (Address: 0x03)
BIT ID
X
BIT NAME
BIT LOCATION (0 = LSB)
FUNCTION
None
7
Not used
ACAL
Automatic FSK calibration
6
1 = Enable automatic FSK calibration when
coming out of the sleep state in DRX mode
0 = Disable automatic FSK calibration
CLKOF
Continuous clock output
(even during tOFF or when
ENABLE pin is low)
5
1 = Enable continuous clock output when CKOUT
=1
0 = Continuous clock output; if CKOUT = 1, clock
output is active during tON (DRX mode) or when
ENABLE pin is high (continuous receive mode)
CDIV1
Crystal divider
4
CLKOUT crystal-divider MSB
CDIV0
Crystal divider
3
CLKOUT crystal-divider LSB
DT2
AGC dwell timer
2
AGC dwell timer MSB
DT1
AGC dwell timer
1
AGC dwell timer
DT0
AGC dwell timer
0
AGC dwell timer LSB
______________________________________________________________________________________
23
MAX7032
Table 7. Configuration 0 Register (Address: 0x02)
MAX7032
Low-Cost, Crystal-Based, Programmable,
ASK/FSK Transceiver with Fractional-N PLL
Table 9. Status Register (Read Only) (Address: 0x1A)
BIT ID
BIT LOCATION
(0 = LSB)
BIT NAME
LCKD
Lock detect
7
1 = Internal PLL is locked
0 = Internal PLL is not locked so the
MAX7032 does not receive or transmit data
GAINS
AGC gain state
6
1 = LNA in high-gain state
0 = LNA in low-gain state
CLKON
Clock/crystal alive
5
1 = Valid clock at crystal inputs
0 = No valid clock signal seen at the crystal
inputs
X
None
4
Zero
X
None
3
Zero
X
None
2
Zero
PCALD
Polling timer calibration
done
1
1 = Polling timer calibration is completed
0 = Polling timer calibration is in progress or
not completed
FCALD
FSK calibration done
0
1 = FSK calibration is completed
0 = FSK calibration is in progress or not
completed
Table 10. Clock Output Divider Ratio
Configuration
CLOCKOUT
FREQUENCY
CKOUT
CDIV1
CDIV0
0
X
X
Disabled at logic 0
1
0
0
fXTAL
1
0
1
fXTAL/2
1
1
0
fXTAL/4
1
1
1
fXTAL/8
Oscillator Frequency Register (Address 0x05)
The MAX7032 has an internal frequency divider that
divides down the crystal frequency to 100kHz. The
MAX7032 uses the 100kHz clock signal when calibrating itself and also to set image-rejection frequency. The
24
FUNCTION
hexadecimal value written to the oscillator frequency
register is the nearest integer result of fXTAL/100kHz.
For example, if data is being received at 315MHz, the
crystal frequency is 12.67917MHz. Dividing the crystal
frequency by 100kHz and rounding to the nearest integer gives 127, or 0x7F hex. So for 315MHz, 0x7F would
be written to the oscillator frequency register.
AGC Dwell Timer (Address 0x03)
The AGC dwell timer holds the AGC in low-gain state
for a set amount of time after the power level drops
below the AGC switching threshold. After that set
amount of time, if the power level is still below the AGC
threshold, the LNA goes into high-gain state. This is
important for ASK since the modulated data may have
a high level above the threshold and a low level below
the threshold, which without the dwell timer would
cause the AGC to switch on every bit.
______________________________________________________________________________________
Low-Cost, Crystal-Based, Programmable,
ASK/FSK Transceiver with Fractional-N PLL
Dwell Time =
2K
fXTAL
where K is an odd integer in decimal from 9 to 23; see
Table 11.
To calculate the value of K, use the following equation
and use the next odd integer higher than the calculated
result:
K ≥ 3.3 x log10 (Dwell Time x fXTAL)
For Manchester Code (50% duty cycle), set the dwell
time to at least twice the bit period. For NRZ data, set
the dwell to greater than the period of the longest string
of zeros or ones. For example, using Manchester Code
at 315MHz (fXTAL = 12.679MHz) with a data rate of
4kbps (bit period = 125µs), the dwell time needs to be
greater than 250µs:
K ≥ 3.3 x log10 (250µs x 12.679MHz) ≈ 11.553
Choose the register value to be the next odd integer value
higher than 11.553, which is K = 13. The default value of
the AGC dwell timer on power-up or rest is zero (K = 9).
Table 11. AGC Dwell Timer Configuration
(Address 0x03)
DT2
DT1
DT0
0
0
0
K=9
DESCRIPTION
0
0
1
K = 11
0
1
0
K = 13
0
1
1
K = 15
1
0
0
K = 17
1
0
1
K = 19
1
1
0
K = 21
1
1
1
K = 23
Calibration
The MAX7032 must be calibrated to ensure accurate
timing of the off timer in discontinuous receive mode or
when receiving FSK signals. The first step in calibration
is ensuring that the oscillator frequency register (register: 0x05) has been programmed with the correct divisor value (see the Oscillator Frequency Register
(Address 0x05) section). Next, enable the mixer to turn
the crystal driver on.
Calibrate the polling timer by setting PCAL = 1 in the
control register (register 0x01, bit 3). Upon completion,
the PCALD bit in the status register (register 0x1A,
bit 1) is 1 and the PCAL bit is reset to zero. If using the
MAX7032 in continuous receive mode, polling timer
calibration is not needed.
To calibrate the FSK receiver, set FCAL = 1. Upon
completion, the FCALD bit in the status register (register 0x1A) is one, and the FCAL bit is reset to zero.
When in continuous receive mode and receiving FSK
data, recalibrate the FSK receiver after a significant
change in temperature or supply voltage. When in discontinuous receive mode, the polling timer and FSK
receiver (if enabled) are automatically calibrated every
wake-up cycle.
Off Timer (tOFF)
The off timer, tOFF (see Figure 10), is a 16-bit timer that
is configured using register 0x06 for the upper byte,
register 0x07 for the lower byte, and bits OFPS1 and
OFPS0 in the configuration 0 register (register 0x02, bit
3 and bit 2, respectively). Table 12 summarizes the
configuration of the tOFF timer. The OFPS1 and OFPS0
bits set the size of the shortest time possible (tOFF time
base). The data written to the tOFF registers (register
0x06 and register 0x07) are multiplied by the time base
to give the total tOFF time. See the example below. On
power-up, the off-timer registers are reset to zero and
must be written before using DRX mode.
Table 12. Off-Timer (tOFF) Configuration
OFPS1
OFPS0
tOFF
TIME BASE
MIN tOFF
REG 0x06 = 0x00
REG 0x07 = 0x01
MAX tOFF
REG 0x06 = 0xFF
REG 0x07 = 0xFF
0
0
120µs
120µs
7.86s
0
1
480µs
480µs
31.46s
1
0
1920µs
1.92ms
2min 6s
1
1
7680µs
7.68ms
8min 23s
______________________________________________________________________________________
25
MAX7032
The AGC dwell time is dependent on the crystal frequency and the bit settings of the AGC dwell timer. To
calculate the dwell time, use the following equation:
MAX7032
Low-Cost, Crystal-Based, Programmable,
ASK/FSK Transceiver with Fractional-N PLL
CS
DIO
tOFF
tCPU
tOFF
tCPU
tLOW
tRF
tRF
tON
tON
ASK_DATA OR
FSK_DATA
Figure 10. DRX Mode Sequence of the MAX7032
Set OFPS1 to be 1 and OFPS0 to be 1. That sets the
tOFF time base (1 LSB) to be 7680µs. Set REG 0x06
and REG 0x07 to be FFFF, which is 65535 in decimal.
Therefore, the total tOFF is:
tOFF = 7680µs x 65535 = 8min 23s
During tOFF, the MAX7032 is operating with very low
supply current (23.4µA typ), where all its modules are
turned off, except for the tOFF timer itself. Upon completion of the tOFF time, the MAX7032 signals the user
by asserting DIO low.
CPU Recovery Timer (tCPU)
The CPU recovery timer, tCPU (see Figure 10), is used
to delay power up of the MAX7032, thereby providing
extra power savings and giving the CPU time to complete its own power-on sequence. The CPU is signaled
to begin powering up when the DIO line is pulled low
by the MAX7032 at the end of tOFF. Then, tCPU begins
counting, while DIO is held low by the MAX7032. At the
end of tCPU, the tRF counter begins.
tCPU is an 8-bit timer, configured through register 0x08.
The possible tCPU settings are summarized in Table 13.
The data written to the tCPU register (register 0x08) is
multiplied by 120µs to give the total tCPU time. See the
example below. On power-up, the CPU timer register is
reset to zero and must be written before using DRX
mode.
Set REG 0x08 to be FF in hex, which is 255 in decimal.
Therefore, the total tCPU is:
tCPU = 120µs x 255 = 30.6ms
26
RF Settling Timer (tRF)
The RF settling timer, tRF (see Figure 10), allows the RF
sections of the MAX7032 to power up and stabilize
before ASK or FSK data is received. tRF begins counting once tCPU has expired. At the beginning of tRF, the
modules selected in the power control register (register
0x00) are all powered up and the peak detectors are in
the track mode and have the tRF period to settle.
tRF is a 16-bit timer, configured through register 0x09
(upper byte) and register 0x0A (lower byte). The possible tRF settings are listed in Table 14. The data written
to the tRF register (register 0x09 and register 0x0A) are
multiplied by 120µs to give the total tRF time. See the
example in the CPU Recovery Timer (tCPU) section. On
power-up, the RF timer registers are reset to zero and
must be written before using DRX mode.
Table 13. CPU Recovery Timer (tCPU)
Configuration
TIME BASE
(µs)
MIN tCPU
REG 0x08 = 0x01
(µs)
MAX tCPU
REG 0x08 = 0xFF
(ms)
120
120
30.6
Table 14. RF Settling Timer (tRF)
Configuration
tRF TIME BASE
(µs)
MIN tRF
REG 0x09 = 0x00
REG 0x0A = 0x01
(µs)
MAX tRF
REG 0x09 = 0xFF
REG 0x0A = 0xFF
(s)
120
120
7.86
______________________________________________________________________________________
Low-Cost, Crystal-Based, Programmable,
ASK/FSK Transceiver with Fractional-N PLL
MAX7032
Table 15. On-Timer (tON) Configuration
ONPS1
ONPS0
tON TIME BASE
MIN tON
REG 0x0B = 0x00
REG 0x0C = 0x01
MAX tON
REG 0x0B = 0xFF
REG 0x0C = 0xFF
0
0
120µs
120µs
7.86s
0
1
480µs
480µs
31.46s
1
0
1920µs
1.92ms
2min 6s
1
1
7680µs
7.68ms
8min 23s
On Timer (tON)
The on timer, tON (see Figure 10), is a 16-bit timer that
is configured through register 0x0B for the upper byte,
register 0x0C for the lower byte (Table 15). The information stored in this timer provides an additional way to
control the duration of the on time of the receiver.
The CPU must begin driving DIO low any time during
tLOW = tCPU + tRF + tON. If the CPU fails to drive DIO
low at the end of tON, DIO is pulled high through the
internal pullup resistor and the time sequence is restarted, leaving the MAX7032 powered down. Any time the
DIO line is driven high while the DRX = 1, the DRX
sequence is initiated, as defined in Figure 10. In the
event that the CPU is processing data, after t ON
expires, the CPU should keep the MAX7032 awake by
holding the DIO line low.
The data written to the tON register (register 0x0B and
register 0x0C) are multiplied by the t ON time base
(Table 15) to give the total tON time. See the example in
the Off Timer (tOFF) section. On power-up, the on-timer
register is reset to zero and must be written before
using DRX mode.
Transmitter Low-Frequency Register (TxLOW)
The TxLOW register sets the divider information of the
fractional-N synthesizer for the lower transmit frequency
in FSK mode. See the example given in the Fractional-N
PLL section. In ASK mode, TxLOW determines the carrier frequency.
Transmitter High-Frequency Register (TxHIGH)
The TxHIGH register sets the divider information of the
fractional-N synthesizer for the upper transmit frequency
in the FSK mode. In ASK mode, the content of TxHIGH
is not used. The 16-bit register contains the binary representation of the TX PLL divider ratio, which is shown in
the example in the Fractional-N PLL section.
Applications Information
Output Matching to 50Ω
When matched to a 50Ω system, the MAX7032’s PA is
capable of delivering +10dBm of output power at VDD
= +2.7V. The output of the PA is an open-drain transistor that requires external impedance matching and
pullup inductance for proper biasing. The pullup inductance from the PA to PAVDD serves three main purposes: it resonates the capacitive PA output, provides
biasing for the PA, and becomes a high-frequency
choke to prevent RF energy from coupling into VDD.
The network also forms a bandpass filter that provides
attention for the higher order harmonics.
Output Matching to PCB Loop Antenna
In most applications, the MAX7032 must be impedance
matched to a small-loop antenna. The antenna is usually fabricated out of a copper trace on a PCB in a rectangular, circular, or square pattern. The antenna has
an impedance that consists of a lossy component and
a radiative component. To achieve high radiating efficiency, the radiative component should be as high as
possible, while minimizing the lossy component. In
addition, the loop antenna has an inherent loop inductance associated with it (assuming the antenna is terminated to ground). For example, in a typical application,
the radiative impedance is less than 0.5Ω, the lossy
impedance is less than 0.7Ω, and the inductance is
approximately 50nH to 100nH.
Layout Considerations
A properly designed PCB is an essential part of any
RF/microwave circuit. On high-frequency inputs and
outputs, use controlled-impedance lines and keep
them as short as possible to minimize losses and radiation. At high frequencies, trace lengths that are on the
order of λ/10 or longer act as antennas, where λ is the
wavelength.
______________________________________________________________________________________
27
Keeping the traces short also reduces parasitic inductance. Generally, 1in of PCB trace adds about 20nH of
parasitic inductance. The parasitic inductance can
have a dramatic effect on the effective inductance of a
passive component. For example, a 0.5in trace connecting to a 100nH inductor adds an extra 10nH of
inductance, or 10%.
To reduce parasitic inductance, use wider traces and a
solid ground or power plane below the signal traces.
Also, use low-inductance connections to the ground
plane and place decoupling capacitors as close as
possible to all VDD pins and HVIN.
Typical Application Circuit
SCLK
DIO
CS
VDD
Y1
VDD
C20
27
26
C22
2
CLOCK
OUTPUT
25
CLKOUT
28
DVDD
29
HVIN
PAVDD
30
XTAL1
1
31
CS
32
SCLK
VDD
DIO
C21
C23
C24
C19
C18
XTAL2
3.0V
ROUT
24
DATA
R3*
C1
4
L1
5
VDD
6
C5
OP+
19
C17
C6
8
L4
LNAIN
LNASRC
9
11
10
C10
12
C12
13
C13
14
15
PDMAX
DS+
7
PDMIN
L6
IFIN+
L3
EXPOSED
PAD
AVDD
IFIN-
C7
C8
20
DF
PAOUT
MIXOUT
C4
C3
21
RSSI
MAX7032
TX/RX2
MIXIN-
L2
TRANSMIT/
RECEIVE
TX/RX1
MIXIN+
C2
ENABLE
22
T/R
3
DATA
23
ENABLE
LNAOUT
MAX7032
Low-Cost, Crystal-Based, Programmable,
ASK/FSK Transceiver with Fractional-N PLL
16
DS-
18
17
R1
C15
C9
L5
C11
VDD
IN
GND
Y2
R2
OUT
C14
*OPTIONAL POWER-ADJUST RESISTOR
28
______________________________________________________________________________________
C16
Low-Cost, Crystal-Based, Programmable,
ASK/FSK Transceiver with Fractional-N PLL
MAX7032
Table 16. Component Values for Typical Application Circuit
COMPONENT
VALUE FOR
433.92MHz RF
VALUE FOR
315MHz RF
DESCRIPTION
C1
220pF
220pF
10%
C2
680pF
680pF
10%
C3
6.8pF
12pF
5%
C4
6.8pF
10pF
5%
C5
10pF
22pF
5%
C6
220pF
220pF
10%
C7
0.1µF
0.1µF
10%
C8
100pF
100pF
5%
±0.1pF
C9
1.8pF
2.7pF
C10
100pF
100pF
5%
C11
220pF
220pF
10%
C12
100pF
100pF
5%
C13
1500pF
1500pF
10%
C14
0.047µF
0.047µF
10%
C15
0.047µF
0.047µF
10%
C16
470pF
470pF
10%
C17
220pF
220pF
10%
C18
220pF
220pF
10%
C19
0.01µF
0.01µF
10%
C20
100pF
100pF
5%
C21
100pF
100pF
5%
C22
220pF
220pF
10%
C23
0.01µF
0.01µF
10%
C24
0.01µF
0.01µF
10%
L1
22nH
27nH
Coilcraft 0603CS
L2
22nH
30nH
Coilcraft 0603CS
L3
22nH
30nH
Coilcraft 0603CS
L4
10nH
12nH
Coilcraft 0603CS
L5
16nH
30nH
Murata LQW18A
L6
68nH
100nH
Coilcraft 0603CS
R1
100kΩ
100kΩ
5%
R2
100kΩ
100kΩ
5%
R3
0Ω
0Ω
—
Y1
17.63416MHz
12.67917MHz
Crystal, 4.5pF load
capacitance
Y2
10.7MHz ceramic filter
10.7MHz ceramic filter
Murata SFECV10.7 series
Note: Component values vary depending on PC board layout.
______________________________________________________________________________________
29
Low-Cost, Crystal-Based, Programmable,
ASK/FSK Transceiver with Fractional-N PLL
MAX7032
Functional Diagram
LNAOUT MIXIN+ MIXIN9
10
MIXOUT
IFIN+
IFIN-
12
14
13
11
IF LIMITING
AMPS
0°
LNAIN
7
LNA
FSK
DEMODULATOR
Σ
LNASRC
8
ASK
90°
I
Q
20 DF
RSSI
100kΩ
19 OP+
21 RSSI
DATA FILTER
18 DS+
31
CRYSTAL
OSCILLATOR
XTAL2
100kΩ
RX VCO
RX
FREQUENCY
DIVIDER
XTAL1
FSK
PHASE
DETECTOR
32
CLKOUT 25
TX
FREQUENCY
DIVIDER
15 PDMIN
CHARGE
PUMP
1/K
16 PDMAX
TX VCO
HVIN 27
3.0V
REGULATOR
ΔΣ
MODULATOR
LOOP FILTER
17 DSRX
DATA
AVDD
6
EXPOSED
PAD
MAX7032
30 SCLK
PA
SERIAL
INTERFACE AND
DIGITAL LOGIC
28 CS
29 DIO
24 DATA
2
ROUT
30
1
5
3
4
PAVDD
PAOUT
TX/RX1
TX/RX2
22
T/R
26
23
DVDD ENABLE
______________________________________________________________________________________
Low-Cost, Crystal-Based, Programmable,
ASK/FSK Transceiver with Fractional-N PLL
Chip Information
DATA
ENABLE
T/R
RSSI
DF
OP+
DS+
DS-
PROCESS: CMOS
TOP VIEW
24
23
22
21
20
19
18
17
25
16
PDMAX
DVDD
26
15
PDMIN
HVIN
27
14
IFIN+
CS
28
13
IFIN-
DIO
29
12
MIXOUT
SCLK
30
11
MIXIN-
XTAL1
31
10
MIXIN+
XTAL2
32
9
LNAOUT
5
6
7
8
LNAIN
LNASRC
TX/RX1
4
AVDD
3
PAOUT
2
TX/RX2
1
ROUT
+
MAX7032
PAVDD
CLKOUT
Package Information
For the latest package outline information and land patterns, go
to www.maxim-ic.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.
32 Thin QFN-EP
T3255+3
21-0140
90-0001
THIN QFN
______________________________________________________________________________________
31
MAX7032
Pin Configuration
MAX7032
Low-Cost, Crystal-Based, Programmable,
ASK/FSK Transceiver with Fractional-N PLL
Revision History
REVISION
NUMBER
REVISION
DATE
0
5/05
Initial release
—
1
6/09
Made correction in Power Amplifier (PA) section
16
2
11/10
Updated Ordering Information, Absolute Maximum Ratings, AC Electrical
Characteristics, FSK Demodulator, and Calibration sections, Table 8, and
Package Information
DESCRIPTION
PAGES
CHANGED
1, 2, 5, 14,
23, 25, 31
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.
32 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2010 Maxim Integrated Products
Maxim is a registered trademark of Maxim Integrated Products, Inc.