U2745B [ATMEL]
UHF ASK TRANSMITTER; UHF ASK发送器
| 型号： | U2745B |
| 厂家： | 
ATMEL |
| 描述： | UHF ASK TRANSMITTER |
| 文件： | 总9页 (文件大小：186K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
Features
• Very High Transmitting Frequency Accuracy Compared to SAW Solutions
(Enables Receivers at Lower Bandwidth than with SAW Resonators)
• Lower Cost than the Usual Discrete Solutions Using SAW and Transistors
• Supply Voltage 2.2 V to 4.0 V in the Temperature Range of -40LC to 85LC
• XTO Output for Clocking the Microcontroller, Thereby Together with the ATAR090 or
ATAR890 Results in the Optimum System Cost-effectiveness
• One-chip Solution with Minimum External Circuitry
• Very Small SSO16 Package, Pitch 0.635, 150 mil
• “Single-ended Open-collector” Output (Same Antennas Can Be Used as in Discrete
Solutions, Simpler Adaptation of Magnetic Loop Antennas)
• ESD Protection According to MIL-STD.883 (4 KV HBM) Except Pins XTO1/ 2,
ANT and LF
UHF ASK
Transmitter
Electrostatic sensitive device.
Observe precautions for handling.
U2745B
Description
The U2745B is a PLL transmitter IC which has been especially developed for the
demands of RF low-cost data transmission systems at data rates up to 20 kBaud.
The transmitting frequency range is 310 MHz to 440 MHz. It can be used in ASK sys-
tems. The main applications of the U2745B are in the areas of outside temperature
metering, socket control, garage door opener, consumption metering, light/fan or air-
condition control, jalousies, wireless keyboard and various other consumer market
applications.
Rev. 4734A–RKE–11/03
Figure 1. System Block Diagram
UHF ASK
Remote control transmitter
UHF ASK
Remote control receiver
1 Li cell
U3745BM
U2745B
1...3
Demod.
IF Amp
Control
XTO
Encoder
PLL
ATARx9x
Keys
Antenna Antenna
XTO
VCO
PLL
Power
amp.
LNA
VCO
Figure 2. Block Diagram
ASK
EN
GND
OR
PWRSET
PWRVCC
ANT
Power
up
VCC
PA
VCO
CLK
f
PWRGND1
GND
64
PWRGND2
LFVCC
LFGND
LF
f
XTO
n
XTO1
NC
U2745B
2
U2745B
4734A–RKE–11/03
U2745B
Pin Configuration
Figure 3. Pinning SSO16
ASK
1
2
3
4
5
6
7
8
16
15
14
GND
PWRSET
EN
VCC
CLK
PWRVCC
13 ANT
U2745B
PWRGND1
GND
LFVCC
LFGND
12
11
10
9
PWRGND2
XTO1
NC
LF
Pin Description
Pin
Symbol
Function
1
ASK
Modulation input ASK
Enable input
2
EN
3
VCC
Supply voltage
Clock output
4
CLK
5
GND
Ground
6
LFVCC
LFGND
LF
Supply voltage VCO
VCO ground
7
8
Circuit PLL loop
Not connected
Connection for crystal
Power GND2
9
NC
10
11
12
13
14
15
16
XTO1
PWRGND2
PWRGND1
ANT
Power GND1
RF output
PWRVCC
PWRSET
GND
Supply voltage power amplifier
Applied to VCC
Ground
3
4734A–RKE–11/03
General Description
The fully integrated VCO and the “single-ended open-collector” output allow particularly
simple, low-cost RF miniature transmitters to be assembled. The single-ended output
enables a considerably simplified adaptation of both a magnetic loop antenna of any
form or a ꢀ/4 antenna. This is because the load impedance must not be balanced as
would be the case with a differential output.
The XTO's frequency can be selected to be either 13.56 MHz or 9.844 MHz (USA). At
these frequencies, crystals have a very fast start-up time (< 1.5 ms), whereby a wait
time of 5 to 10 ms is required until the transmitter IC is locked. This means that the pro-
cessor does not need to poll a lock detect output.
Functional
Description
ASK Transmission
The U2745B is activated by EN = VS. VASK must remain 0 V for 5 ms, then the output
power can be modulated by means of pin ASK. VEN remains = VS during the transmis-
sion of the message. The ASK input activates the power amplifier and the PLL.
Take-over of the Clock
Pulse in the
Microcontroller
The clock of the crystal oscillator can be used for clocking the microcontroller. The
ATAR090 and ATAR890 have the special feature of starting with an integrated RC oscil-
lator to switch on the U2745B with VEN = VS. 5 ms later, the 3.39-MHz clock frequency is
present, so that the message can be sent with crystal accuracy.
Application Circuit
The following component values are recommendations for a typical application. C4, C5,
and C6 are block capacitors. The values of these capacitors depend on the board layout.
C4 = 1 nF, C5 = 1 nF, and C6 = 22 nF are typically used here. For C5, the impedance
between f = 100 MHz and f = 1 GHz should be as low as possible.
CLoop1 and CLoop2 are selected so that the antenna oscillates in resonance and the adap-
tation to the appropriate impedance transformation is possible.
LFeed is an inductor for the antenna's DC current supply. A typical value is
LFeed = 220 nH. LFeed can be either printed on the PC board or be a discrete component.
Output Power
Measurement
The following output network (see Figure 4 on page 5) can be used for output power
evaluation, the exact values of L10 and C10 are dependent on the layout.
L10 and C10 form the transformation network to adopt the output impedance of the IC to
50 ꢁ. The following table shows the values for an output power of 2 mW and an
RPWRSET = 1.2 kꢁ.
Table 1. Transformation Network
f/MHz
315
C10/pF
2.7
L10/nH
56
ZLoad_opt/ꢀ
260 + j330
185 + j268
433.92
1.8
33
4
U2745B
4734A–RKE–11/03
U2745B
Figure 4. Measurement Output Network
VS
PWRVCC
L10
ANT
ZLoad-opt
C10
50 ꢀ
Figure 5. Application Circuit
+VS = 2.2 ... 4.0 V
ASK
GND
16
PWRSET
15
PWRVCC
14
ANT
13
PWRGND1
12
PWRGND2
11
XTO1
10
ASK
EN
1
OR
EN
CLoop2
2
RPWRSET
Power
up
VCC
3
C6
LFeed
C4
CLK
4
VCO
f
PA
CLK
3.39 MHz
CLoop1
GND
5
64
LFVCC
6
f
C5
13.56 MHz
XTO
LFGND
7
n
C3
C1
LF
8
NC
9
R4
U2745B
Antenna
C2
5
4734A–RKE–11/03
Absolute Maximum Ratings
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress rating
only and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of this
specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
Parameters
Symbol
VS
Min.
Max.
6
Unit
V
Supply voltage
Power dissipation
Junction temperature
Storage temperature
Ambient temperature
Ptot
250
150
125
85
mW
LC
Tj
Tstg
-55
-40
LC
Tamb
LC
Thermal Resistance
Parameters
Symbol
Value
Unit
Junction ambient
RthJA
180
K/W
Electrical Characteristics
All parameters are refered to GND (pin 5), VS = 3 V, Tamb = 25LC, unless otherwise specified
The possible operating ranges refer to different circuit conditions: VS = 2.2 V to 4.0 V at Tamb = -40LC to +85LC
Parameters
Test Conditions
Symbol
ISoff
Min.
Typ.
2
Max.
10
Unit
µA
Supply current (power down)
VASK, VFSK ? 0.3 V, VS < 3.6 V
Supply current (power up, output OFF) VASK = GND, VEN = VS, VS = 3 V
ISon
4.7
10
6.2
mA
mA
Supply current (power up, output ON)
V
ASK = VS, VS = 3 V, RPWRSET = 1.2 kꢀ
VS = 3 V, Tamb = 25LC, f = 433.92 MHz
PWRSET = 1.2 kꢀ
IStransmit
12.5
Output power
R
PRef
1
3
5
dBm
dB
Output power variation for
f = 315 MHz compared to
f = 433.92 MHz
f = 315 MHz
Pout = PRef + ꢁPRef
ꢁPRef
1.5
at Pout = 2.0 mW,
the load impedance must be selected
to meet the Vout maximum
requirement, the supply current is not
dependent on the load impedance
tolerance
Maximum peak output
antenna voltage
Voutmax
VS - 0.7 V
V(peak)
fo ±(n P fPC) where fPC = 6.78 MHz
Load capacitance at CLK ? 3 pF
f = 230 MHz to 470 MHz
Spurious emission
Em
Em
-40
-58
dBC
dBC
f < 230 MHz, f > 470 MHz
13.56 -
30 ppm
13.56 +
30 ppm
Oscillator frequency XTO
Loop bandwidth
Crystal frequency = 13.56 MHz
fXTO
BLoop
PNPLL
13.56
100
MHz
For best LO noise
Loop filter components:
C2 = 3.9 nF, C1 = 15 nF, R4 = 220 ꢀ
kHz
Referring to the phase comparator
fPC = 6.78 MHz
Phase noise PLL
Phase noise VCO
-111
-105
dBC/Hz
dBC/Hz
at 1 MHz
at 36 MHz
PNVCO
PNVCO
-90
-122
6
U2745B
4734A–RKE–11/03
U2745B
Electrical Characteristics (Continued)
All parameters are refered to GND (pin 5), VS = 3 V, Tamb = 25LC, unless otherwise specified
The possible operating ranges refer to different circuit conditions: VS = 2.2 V to 4.0 V at Tamb = -40LC to +85LC
Parameters
Test Conditions
Symbol
Min.
Typ.
Max.
Unit
Frequency range of the VCO
fVCO
310
440
MHz
Clock output
(CMOS microcontroller compatible)
Clkout
fout/128
MHz
pF
Load capacitance at CLK
CCLK
10
f
f
XTO = 13.56 MHz
XTO = 9.84 MHz
Rs
Rs
80
100
Series resonance R of the crystal
ꢀ
Duty cycle of the
modulation signal = 50%
ASK modulation frequency rate
fmodASK
0
20
kHz
CLK output
- Output current Low
- Output current Low
- Output current High
- Output current High
VCLK = 0.2 P VS
VCLK = 0.3 P VS
VCLK = 0.8 P VS
VCLK = 0.7 P VS
Iol
Iol
Ioh
Ioh
150
200
-150
-200
µA
µA
µA
µA
100
ASK input
- Low level input voltage
- High level input voltage
- Input current High
VASKl
VASKh
IASKh
0.3
V
V
µA
1.7
1.7
140
Enable ASK
VEN
VFSKl
VFSKh
IFSKh
- Low level input voltage
- High level input voltage
- Input current High
0.3
V
V
µA
140
7
4734A–RKE–11/03
Ordering Information
Extended Type Number
Package
SSO16
SSO16
Remarks
U2745B-MFB
Tube
U2745B-MFBG3
Taped and reeled
Package Information
8
U2745B
4734A–RKE–11/03
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4734A–RKE–11/03
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