MAX1472_05 [MAXIM]
300MHz-to-450MHz Low-Power, Crystal-Based ASK Transmitter; 300MHz的至450MHz，低功耗，基于晶振的ASK发送器
| 型号： | MAX1472_05 |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | 300MHz-to-450MHz Low-Power, Crystal-Based ASK Transmitter |
| 文件： | 总9页 (文件大小：240K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-2872; Rev 1; 4/05
300MHz-to-450MHz Low-Power, Crystal-Based
ASK Transmitter
General Description
Features
The MAX1472 is a crystal-referenced phase-locked
loop (PLL) VHF/UHF transmitter designed to transmit
OOK/ASK data in the 300MHz to 450MHz frequency
range. The MAX1472 supports data rates up to
100kbps, and adjustable output power to more than
+10dBm into a 50Ω load. The crystal-based architec-
ture of the MAX1472 eliminates many of the common
problems with SAW transmitters by providing greater
modulation depth, faster frequency settling, higher
tolerance of the transmit frequency, and reduced
temperature dependence. Combined, these improve-
ments enable better overall receiver performance when
using a superheterodyne receiver such as the MAX1470
or MAX1473.
♦ 2.1V to 3.6V Single-Supply Operation
♦ Low 5.3mA Operating Supply Current*
♦ Supports ASK with 90dB Modulation Depth
♦ Output Power Adjustable to More than +10dBm
♦ Uses Small Low-Cost Crystal
♦ Small 3mm ✕ 3mm 8-Pin SOT23 Package
♦ Fast-On Oscillator 220µs Startup Time
The MAX1472 is available in a 3mm x 3mm 8-pin
SOT23 package and is specified for the automotive
(-40°C to +125°C) temperature range. An evaluation kit
is available. Contact Maxim Integrated Products for
more information.
*At 50% duty cycle (315MHz, 2.7V supply, +10dBm output
power)
Applications
Ordering Information
Remote Keyless Entry
RF Remote Controls
TEMP
RANGE
PIN-
PACKAGE
TOP
MARK
PART
Tire Pressure Monitoring
Security Systems
MAX1472AKA-T
-40°C to +125°C
8 SOT23-8
AEKS
Radio-Controlled Toys
Wireless Game Consoles
Wireless Computer Peripherals
Wireless Sensors
Typical Application Circuit
Pin Configuration
TOP VIEW
*
XTAL1
GND
1
2
XTAL2
8
7
3.0V
XTAL1
GND
1
2
3
4
8
7
6
5
XTAL2
MAX1472
V
DD
V
DD
50Ω
ANTENNA
MAX1472
220pF 680pF
DATA
3
4
PAGND
6
5
PAGND
PAOUT
DATA
DATA INPUT
ENABLE
PAOUT
ENABLE
STANDBY OR
POWER-UP
SOT23
*Optional power adjust resistor.
________________________________________________________________ Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
300MHz-to-450MHz Low-Power, Crystal-Based
ASK Transmitter
ABSOLUTE MAXIMUM RATINGS
DD
All Other Pins to GND ................................-0.3V to (V
V
to GND ..........................................................-0.3V to +4.0V
Operating Temperature Range .........................-40°C to +125°C
Storage Temperature Range.............................-60°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
+ 0.3V)
DD
Continuous Power Dissipation (T = +70°C)
A
8-Pin SOT23 (derate 8.9mW/°C above +70°C)............714mW
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.
ELECTRICAL CHARACTERISTICS
(Typical Application Circuit, output power is referenced to 50Ω, V
= 2.1V to 3.6V, V
= V , T = -40°C to +125°C, unless
DD
ENABLE
DD
A
otherwise noted. Typical values are at V
= 2.7V, T = +25°C, unless otherwise noted.) (Note 1)
DD
A
PARAMETER
SYSTEM PERFORMANCE
Supply Voltage
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
V
2.1
3.6
9.2
V
DD
V
= V
= V
ENABLE
DD
DD
5.3
9.1
1.5
5.7
9.6
(Note 2)
V
V
,
,
ENABLE
DATA
f
f
= 315MHz
= 433MHz
16.4
2.1
RF
= V
DD
V
V
= V
= V
= V
ENABLE
DD
DD
DD
= 0V
DATA
Supply Current
I
mA
DD
V
ENABLE
(Note 2)
V
V
,
,
ENABLE
DATA
RF
= V
DD
V
V
= V
DD
= 0V
ENABLE
1.7
5
2.5
DATA
V
V
< V , T < +85°C (Note 3)
350
1.7
nA
µA
ENABLE
ENABLE
IL
A
Standby Current
I
STDBY
< V
T < +125°C (Note 3)
A
IL
Frequency Range
Data Rate
f
(Note 1)
(Note 3)
300
0
450
100
MHz
kbps
dB
RF
Modulation Depth
ON to OFF P
ratio (Note 4)
90
OUT
T
T
T
= +25°C, V
= 2.7V (Notes 8, 9)
DD
7.3
3.3
10.3
6.0
12.8
16.2
A
A
A
Output Power
P
dBm
= +125°C, V = 2.1V (Notes 8, 9)
OUT
DD
= -40°C, V
= 3.6V (Notes 8, 9)
13.7
220
450
43.6
41.3
37.6
35.1
DD
To f
To f
< 50kHz (Note 5)
< 5kHz (Note 5)
OFFSET
OFFSET
Turn-On Time
t
µs
%
%
ON
f
RF
f
RF
f
RF
f
RF
= 315MHz (Note 6)
= 433MHz (Note 6)
= 315MHz (Note 7)
= 433MHz (Note 7)
Transmit Efficiency with CW
Transmit Efficiency at 50%
Duty Cycle
2
_______________________________________________________________________________________
300MHz-to-450MHz Low-Power, Crystal-Based
ASK Transmitter
ELECTRICAL CHARACTERISTICS (continued)
(Typical Application Circuit, output power is referenced to 50Ω, V
= 2.1V to 3.6V, V
= V , T = -40°C to +125°C, unless
DD
ENABLE
DD
A
otherwise noted. Typical values are at V
= 2.7V, T = +25°C, unless otherwise noted.) (Note 1)
DD
A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
PHASE-LOCKED LOOP PERFORMANCE
VCO Gain
330
-84
-91
-82
-89
-50
-50
-75
-81
1.6
MHz/V
f
f
f
f
=100kHz
= 1MHz
=100kHz
= 1MHz
OFFSET
OFFSET
OFFSET
OFFSET
f
f
= 315MHz
= 433MHz
RF
Phase Noise
dBc/Hz
RF
f
RF
f
RF
f
RF
f
RF
= 315MHz
= 433MHz
= 315MHz
= 433MHz
Maximum Carrier Harmonics
dBc
dBc
Reference Spur
Loop Bandwidth
MHz
MHz
pF
Crystal Frequency
f
f
/ 32
XTAL
RF
Oscillator Input Impedance
From each XTAL pin to GND
6.2
3
Frequency Pushing by V
ppm/V
nH
DD
Maximum Crystal Inductance
DIGITAL INPUTS
50
Data Input High
V
V
DD
- 0.25
V
V
IH
Data Input Low
V
0.25
IL
Maximum Input Current
Pulldown Current
2
nA
µA
25
Note 1: 100% tested at T = +25°C. Guaranteed by design and characterization over temperature.
A
Note 2: 50% duty cycle at 10kHz data.
Note 3: Guaranteed by design and characterization, not production tested.
Note 4: Generally limited by PC board layout.
Note 5: V
Note 6: V
Note 7: V
< V to V
> V . f
is defined as the frequency deviation from the desired carrier frequency.
ENABLE
ENABLE
ENABLE
IL
ENABLE
IH OFFSET
> V , V
> V , Efficiency = P
/(V
x I ).
IH DATA
IH
OUT DD DD
> V , DATA toggled from V to V , 10kHz, 50% duty cycle, Efficiency = P
/(V
x I ).
IH
IL
IH
OUT DD DD
Note 8: Output power can be adjusted with external resistor.
Note 9: Guaranteed by design and characterization at f = 315MHz.
RF
_______________________________________________________________________________________
3
300MHz-to-450MHz Low-Power, Crystal-Based
ASK Transmitter
Typical Operating Characteristics
(Typical Application Circuit, V
= 2.7V, T = +25°C, unless otherwise noted.)
A
DD
SUPPLY CURRENT vs. SUPPLY VOLTAGE
SUPPLY CURRENT vs. SUPPLY VOLTAGE
SUPPLY CURRENT vs. SUPPLY VOLTAGE
13
12
11
10
9
13
12
11
10
9
1.9
1.8
1.7
1.6
1.5
1.4
1.3
1.2
1.1
V
V
f
= V ,
IH
V
V
f
= V ,
IH
+125°C
ENABLE
DATA
RF
ENABLE
DATA
RF
V
V
= V ,
IH
ENABLE
= V ,
DATA IH
= V
IH
,
= V ,
IL
+25°C
= 315MHz
= 315MHz
f
RF
= 433MHz
+85°C
-40°C
+25°C
-40°C
+125°C
+85°C
+85°C
8
8
+125°C
-40°C
7
7
6
5
+25°C
6
5
2.0
2.4
2.8
3.2
3.6
2.0
2.4
2.8
3.2
3.6
2.0
2.4
2.8
3.2
3.6
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
SUPPLY CURRENT vs. SUPPLY VOLTAGE
OUTPUT POWER vs. SUPPLY VOLTAGE
OUTPUT POWER vs. SUPPLY VOLTAGE
14
13
2.2
2.0
1.8
1.6
1.4
1.2
14
13
+125°C
V
V
f
= V
,
V
V
f
= V ,
IH
V
V
f
= V ,
IH
ENABLE
DATA
RF
IH
ENABLE
= V ,
DATA IH
RF
ENABLE
DATA
RF
= V
IH
,
= V ,
IL
-25°C
+85°C
= 315MHz
= 433MHz
= 433MHz
+25°C
12
11
10
9
12
11
-40°C
-40°C
+125°C
10
9
+125°C
+85°C
-40°C
8
7
+85°C
+25°C
8
7
6
5
6
2.0
2.4
2.8
3.2
3.6
2.0
2.4
2.8
3.2
3.6
2.0
2.4
2.8
3.2
3.6
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
REFERENCE SPUR MAGNITUDE
vs. SUPPLY VOLTAGE
FREQUENCY STABILITY
vs. SUPPLY VOLTAGE
TRANSMIT POWER EFFICIENCY
vs. SUPPLY VOLTAGE
-65
-67
-69
-71
-73
-75
-77
-79
-81
-83
-85
2
1
55
50
45
40
35
30
25
-40°C
+25°C
+85°C
0
315MHz
315MHz
-1
-2
-3
-4
433MHz
433MHz
+125°C
CW OUTPUT
= 315MHz
f
RF
2.0
2.4
2.8
3.2
3.6
2.0
2.4
2.8
3.2
3.6
2.0
2.4
2.8
3.2
3.6
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
4
_______________________________________________________________________________________
300MHz-to-450MHz Low-Power, Crystal-Based
ASK Transmitter
Typical Operating Characteristics (continued)
(Typical Application Circuit, V
= 2.7V, T = +25°C, unless otherwise noted.)
A
DD
TRANSMIT POWER EFFICIENCY
vs. SUPPLY VOLTAGE
TRANSMIT POWER EFFICIENCY
vs. SUPPLY VOLTAGE
TRANSMIT POWER EFFICIENCY
vs. SUPPLY VOLTAGE
50
45
40
35
30
25
50
45
40
35
30
25
20
45
40
35
30
25
20
+25°C
-40°C
-40°C
+25°C
+25°C
-40°C
+125°C
+125°C
+85°C
+85°C
+125°C
+85°C
OOK OUTPUT AT
50% DUTY CYCLE
OOK OUTPUT AT
CW OUTPUT
50% DUTY CYCLE
f
= 433MHz
RF
f
= 433MHz
f
= 315MHz
RF
RF
2.0
2.4
2.8
3.2
3.6
2.0
2.4
2.8
3.2
3.6
2.0
2.4
2.8
3.2
3.6
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
SUPPLY CURRENT AND OUTPUT POWER
vs. EXTERNAL RESISTOR
PHASE NOISE vs. OFFSET FREQUENCY
SUPPLY CURRENT vs. OUTPUT POWER
MAX1472 toc14
12
12
10
8
-40
-50
10
9
f
= 315MHz
RF
f
= 315MHz
RF
POWER
10
8
-60
8
-70
CURRENT
7
-80
CW
6
6
-90
6
-100
-110
-120
-130
-140
5
4
4
4
50% DUTY CYCLE
2
2
3
0
0
1000
2
0.1
1
10
100
10
100
1k
10k
100k
1M
10M
0
2
4
6
8
10
EXTERNAL RESISTOR (Ω)
f
(Hz)
OUTPUT POWER (dBm)
OFFSET
AM DEMODULATION OF PA OUTPUT
FREQUENCY SETTLING TIME
MAX1472 toc17
MAX1472 toc16
DATA RATE
= 100kHz
ENABLE
25kHz/div
TRANSITION
FROM LOW
TO HIGH
15%/div
START: 0s
1ms
1ms
ENABLE
2.5kHz/div
TRANSITION
FROM LOW
TO HIGH
START: 0s
START: 0s
STOP: 20µs
_______________________________________________________________________________________
5
300MHz-to-450MHz Low-Power, Crystal-Based
ASK Transmitter
Pin Description
PIN
1
NAME
XTAL1
GND
FUNCTION
1st Crystal Input. f = 32 x f
.
RF
XTAL
2
Ground. Connect to system ground.
3
PAGND
Ground for the Power Amplifier (PA). Connect to system ground.
Power-Amplifier Output. This output requires a pullup inductor to the supply voltage, which may be part
of the output-matching network to a 50Ω antenna.
4
PAOUT
5
6
7
8
ENABLE
DATA
Standby/Power-Up Input. A logic low on ENABLE places the device in standby mode.
OOK Data Input. Power amplifier is ON when DATA is high.
V
Supply Voltage. Bypass to GND with capacitor as close to the pin as possible.
DD
XTAL2
2nd Crystal Input. f = 32 x f
.
RF
XTAL
Power Amplifier
The PA of the MAX1472 is a high-efficiency, open-drain,
class-C amplifier. With proper output matching network,
the PA can drive a wide range of impedances, including
the small-loop PC board trace antenna and any 50Ω
antenna. The output-matching network for a 50Ω anten-
na is shown in the Typical Application Circuit. The out-
put-matching network suppresses the carrier harmonics
and transforms the antenna impedance to an optimal
impedance at PAOUT (pin 4), which is about 250Ω .
When the output matching network is properly tuned,
the PA transmits power with high efficiency. The Typical
Application Circuit delivers 10.3dBm at 2.7V supply with
9.1mA of supply current. Thus, the overall efficiency is
44%. The efficiency of the PA itself is more than 52%.
Detailed Description
The MAX1472 is a highly integrated OOK/ASK transmit-
ter operating over the 300MHz to 450MHz frequency
range. The IC includes a complete PLL and a highly
efficient PA. The device can also be easily placed into
a 5nA low-power shutdown mode.
Shutdown Mode
The ENABLE pin is internally pulled down with a 15µA
current source. If the pin is left floating or pulled low,
the MAX1472 goes into shutdown mode, where the
supply current drops to less than 5nA. When ENABLE
is high, the IC is enabled and is ready for transmission
after 220µs (frequency settles to within 50kHz).
The 220µs turn-on time of the MAX1472 is mostly domi-
nated by the crystal oscillator startup time. Once the
oscillator is running, the 1.6MHz PLL loop bandwidth
allows fast-frequency recovery during power-amplifier
toggling.
Applications Information
Output Power Adjustment
It is possible to adjust the output power down to
-10dBm with the addition of a resistor. The addition of
the power-adjust resistor also reduces power con-
sumption. See the Supply Current and Output Power
vs. External Resistor and Supply Current vs. Output
Power graphs in the Typical Operating Characteristics
section. It is imperative to add both a low-frequency
and a high-frequency decoupling capacitor as shown
in the Typical Application Circuit.
Phase-Locked Loop
The PLL block contains a phase detector, charge
pump, integrated loop filter, VCO, 32X clock divider,
and crystal oscillator. This PLL requires no external
components, other than a crystal. The relationship
between the carrier and crystal frequency is given by:
f
= f / 32
RF
XTAL
The lock-detect circuit prevents the PA from transmit-
ting until the PLL is locked. In addition, the device shuts
down the PA if the reference frequency is lost.
6
_______________________________________________________________________________________
300MHz-to-450MHz Low-Power, Crystal-Based
ASK Transmitter
Crystal Oscillator
The crystal oscillator in the MAX1472 is designed to
present a capacitance of approximately 3.1pF between
the XTAL1 and XTAL2 pins. If a crystal designed to
oscillate with a different load capacitance is used, the
crystal is pulled away from its intended operating fre-
quency, thus introducing an error in the reference fre-
quency. Crystals designed to operate with higher
differential load capacitance always pull the reference
frequency higher. For example, a 9.84375MHz crystal
designed to operate with a 10pF load capacitance
oscillates at 9.84688MHz with the MAX1472, causing
the transmitter to be transmitting at 315.1MHz rather
than 315.0MHz, an error of about 100kHz, or 320ppm.
Output Matching to 50Ω
When matched to a 50Ω system, the MAX1472 PA is
capable of delivering more than +10dBm of output
power at V
= 2.7V. The output of the PA is an open-
DD
drain transistor that requires external impedance
matching and pullup inductance for proper biasing.
The pullup inductance from PA to V
serves three
DD
main purposes: It resonates the capacitance of the PA
output, provides biasing for the PA, and becomes a
high-frequency choke to reduce the RF energy cou-
pling into V . The recommended output-matching net-
DD
work topology is shown in the Typical Application
Circuit. The matching network transforms the 50Ω load
to a higher impedance at the output of the PA in addi-
tion to forming a bandpass filter that provides attenua-
tion for the higher order harmonics.
In actuality, the oscillator pulls every crystal. The crys-
tal’s natural frequency is really below its specified fre-
quency, 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:
Output Matching to PC Board Loop
Antenna
In most applications, the MAX1472 PA output has to be
impedance matched to a small-loop antenna. The
antenna is usually fabricated out of a copper trace on a
PC board 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.
⎛
⎞
C
2
1
+ C
1
6
m
f
=
−
× 10
⎜
⎟
p
C
C
+ C
spec
case
load
case
⎝
⎠
where:
f is the amount the crystal frequency is pulled in ppm.
p
C
C
C
C
is the motional capacitance of the crystal.
m
is the case capacitance.
case
spec
load
The objective of the matching network is to match the
PA output to the small loop antenna. The matching
components thus transform the low radiative and resis-
tive parts of the antenna into the much higher value of
the PA output, which gives higher efficiency. The low
radiative and lossy components of the small loop anten-
na result in a higher Q matching network than the 50Ω
network; thus, the harmonics are lower.
is the specified load capacitance.
is the actual load capacitance.
When the crystal is loaded as specified, i.e., C
spec
=
load
C
, the frequency pulling equals zero.
_______________________________________________________________________________________
7
300MHz-to-450MHz Low-Power, Crystal-Based
ASK Transmitter
Layout Considerations
Functional Diagram
A properly designed PC board is an essential part of
any RF/microwave circuit. On the PA output, use con-
trolled-impedance lines and keep them as short as
DATA
ENABLE
AND
GATE
possible to minimize losses and radiation. At high fre-
quencies, trace lengths that are on the order of λ/10 or
V
DD
longer can act as antennas.
MAX1472
Keeping the traces short also reduces parasitic induc-
tance. Generally, 1in of PC board trace adds about
20nH of parasitic inductance. The parasitic inductance
can have a dramatic effect on the effective inductance.
For example, a 0.5in trace connecting a 100nH induc-
tor adds an extra 10nH of inductance, or 10%.
PAOUT
PAGND
GND
PA
LOCK DETECT
32 x PLL
To reduce the parasitic inductance, use wider traces
and a solid ground or power plane below the signal
traces. Using a solid ground plane can reduce the par-
asitic inductance from approximately 20nH/in to 7nH/in.
Also, use low-inductance connections to ground on all
GND pins, and place decoupling capacitors close to all
CRYSTAL-
OSCILLATOR
DRIVER
XTAL1
XTAL2
V
connections.
DD
Chip Information
TRANSISTOR COUNT: 1430
PROCESS: CMOS
8
_______________________________________________________________________________________
300MHz-to-450MHz Low-Power, Crystal-Based
ASK Transmitter
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.)
SEE DETAIL "A"
SYMBOL
MIN
MAX
e
b
A
0.90
0.00
0.90
0.28
0.09
2.80
2.60
1.50
0.30
1.45
0.15
1.30
0.45
0.20
3.00
3.00
1.75
0.60
C
L
A1
A2
b
C
D
E
C
C
L
E1
L
E
E1
L
0.25 BSC.
L2
e
PIN 1
I.D. DOT
(SEE NOTE 6)
0.65 BSC.
1.95 REF.
0∞
e1
0
8∞
e1
D
C
C
L
L2
A2
A
GAUGE PLANE
A1
SEATING PLANE
C
0
L
NOTE:
1. ALL DIMENSIONS ARE IN MILLIMETERS.
2. FOOT LENGTH MEASURED FROM LEAD TIP TO UPPER RADIUS OF
HEEL OF THE LEAD PARALLEL TO SEATING PLANE C.
DETAIL "A"
3. PACKAGE OUTLINE EXCLUSIVE OF MOLD FLASH & METAL BURR.
4. PACKAGE OUTLINE INCLUSIVE OF SOLDER PLATING.
5. COPLANARITY 4 MILS. MAX.
6. PIN 1 I.D. DOT IS 0.3 MM ÿ MIN. LOCATED ABOVE PIN 1.
PROPRIETARY INFORMATION
TITLE:
7. SOLDER THICKNESS MEASURED AT FLAT SECTION OF LEAD
BETWEEN 0.08mm AND 0.15mm FROM LEAD TIP.
PACKAGE OUTLINE, SOT-23, 8L BODY
8. MEETS JEDEC MO178.
APPROVAL
DOCUMENT CONTROL NO.
REV.
1
21-0078
D
1
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.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 _____________________ 9
© 2005 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products, Inc.
相关型号：
©2020 ICPDF网 联系我们和版权申明