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 2.2V to 4.0V in the Temperature Range of –40°C to 85°C
•XTO Output for Clocking the Microcontroller, Thereby, Together with the ATAR090 or
ATAR890, Resulting in the Optimum System Cost-effectiveness
•One-chip Solution With Minimum External Circuitry
•Single-ended Open-collector Output (Same Antennas Can Be Used as in Discrete
Solutions, Simpler Matching of Magnetic Loop Antennas)
•ESD Protection According to MIL-STD 883 (4 KV HBM) Except Pins XTO1, XTO2, ANT
and LF
•Very Small SSO16 Package, Pitch 0.635, 150 mil
1. Description
The ATA2745 is a PLL transmitter IC which has been developed especially 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 ATA2745 are in the areas of outside temperature
metering, socket control, garage door openers, consumption metering, light/fan or air-
conditioning controls, jalousies, wireless keyboards, and various other consumer
market applications.
UHF ASK
Transmitter
ATA2745
4898B–RKE–08/06
2
4898B–RKE–08/06
ATA2745
Figure 1-1. System Block Diagram
Figure 1-2. Block Diagram
Demod.
IF Amp
LNA VCO
PLL XTO
Control
ATA3745
1...3
Micro-
controller
Power
amp.
XTO VCO
PLL
ATA2745
Antenna Antenna
UHF ASK
Remote control transmitter UHF ASK
Remote control receiver
Encoder
ATARx9x
1 Li cell
Keys
64
f
PA
n
f
OR
Power
up
VCO
XTO
ASK
EN
VCC
CLK
GND
LFVCC
LFGND
LF
GND
PWRSET
PWRVCC
ANT
PWRGND1
PWRGND2
XTO1
NC
ATA2745
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4898B–RKE–08/06
ATA2745
2. Pin Configuration
Figure 2-1. Pinning SSO16
VCC
CLK
GND
LFVCC
LFGND
LF
ASK
EN
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
PWRVCC
ANT
PWRGND1
PWRGND2
XTO1
NC
GND
PWRSET
ATA2745
Table 2-1. Pin Description
Pin Symbol Function
1 ASK Modulation input ASK
2 EN Enable input
3 VCC Supply voltage
4 CLK Clock output
5 GND Ground
6 LFVCC Supply voltage VCO
7 LFGND VCO ground
8 LF Circuit PLL loop
9 NC Not connected
10 XTO1 Connection for crystal
11 PWRGND2 Power GND2
12 PWRGND1 Power GND1
13 ANT RF output
14 PWRVCC Supply voltage power amplifier
15 PWRSET Applied to VCC
16 GND Ground
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4898B–RKE–08/06
ATA2745
3. 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 consid-
erably simplified adaptation of both a magnetic loop antenna of any form or a λ/ 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 fre-
quencies, crystals have a very fast start-up time (< 1.5 ms), whereby a wait time of 5 ms to
10 ms is required until the transmitter IC is locked. This means that the processor does not need
to poll a lock detect output.
4. Functional Description
4.1 ASK Transmission
The ATA2745 is activated by EN = VS. VASK must remain 0V for 5 ms, then the output power can
be modulated by means of pin ASK. VEN remains equal to VS during the transmission of the
message. The ASK input activates the power amplifier and the PLL.
4.2 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 oscillator to switch on
the ATA2745 with VEN = VS. 5 ms later, the 3.39-MHz clock frequency is present, so that the
message can be sent with crystal accuracy.
5. 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=1nF,
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 matching to
the appropriate impedance transformation is possible.
LFeed is an inductor for the antenna's DC current supply. A typical value is LFeed =220nH. L
Feed
can be either printed on the PC board or be a discrete component.
5
4898B–RKE–08/06
ATA2745
5.1 Output Power Measurement
The following output network (Figure 5-1 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 50Ω. The
following table shows the values for an output power of 2 mW and an RPWRSET =1.2kΩ.
Figure 5-1. Measurement Output Network
Figure 5-2. Application Circuit
Table 5-1. Transformation Network
f [MHz] C10 [pF] L10 [nH] ZLoad-opt [Ω]
315 2.7 56 260 + j330
433.92 1.8 33 185 + j268
PWRVCC
ANT
V
S
L
10
C
10
50Ω
ZLoad-op
t
161
2
3
4
5
6
7
8
15
14
13
12
11
10
9
64
f
PA
n
f
OR
Power
up
VCO
XTO
ASK
EN
VCC
CLK
GND
LFVCC
LFGND
LF
GND
PWRSET
PWRVCC
ANT
PWRGND1
PWRGND2
XTO1
NC
C
4
R
PWRSET
L
Feed
C
Loop1
13.56 MHz
C
3
+V
S
= 2.2 ... 4.0 V
C
Loop2
C
6
C
1
C
2
R
4
ASK
EN
CLK
3.39 MHz
C
5
ATA2745
Antenna
6
4898B–RKE–08/06
ATA2745
Electrostatic sensitive device.
Observe precautions for handling.
6. 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 Min. Max. Unit
Supply voltage VS6V
Power dissipation Ptot 250 mW
Junction temperature Tj150 °C
Storage temperature Tstg –55 125 °C
Ambient temperature Tamb –40 85 °C
7. Thermal Resistance
Parameters Symbol Value Unit
Junction ambient RthJA 180 K/W
8. Electrical Characteristics
All parameters are refered to GND (pin 5), VS = 3V, Tamb = 25°C, unless otherwise specified
The possible operating ranges refer to different circuit conditions: VS = 2.2V to 4.0V at Tamb = –40°C to +85°C
Parameters Test Conditions Symbol Min. Typ. Max. Unit
Supply current (power down) VASK, VFSK ≤0.3V, VS < 3.6V ISoff 210µA
Supply current (power up, output OFF) VASK = GND, VEN = VS, VS = 3V ISon 4.7 6.2 mA
Supply current (power up, output ON) VASK = VS, VS = 3V, RPWRSET = 1.2 kΩIStransmit 10 12.5 mA
Output power VS = 3V, Tamb = 25°C, f = 433.92 MHz
RPWRSET = 1.2 kΩPRef 135dBm
Output power variation for
f = 315 MHz compared to
f = 433.92 MHz
f = 315 MHz
Pout = PRef + ∆PRef
∆PRef 1.5 dB
Maximum peak output
antenna voltage
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
Voutmax VS – 0.7V V(peak)
Spurious emission
fo ±(n × fPC) where fPC = 6.78 MHz
Load capacitance at CLK ≤3pF
f = 230 MHz to 470 MHz
f < 230 MHz, f > 470 MHz
Em
Em
–40
–58
dBC
dBC
Oscillator frequency XTO Crystal frequency = 13.56 MHz fXTO 13.56 –
30 ppm 13.56 13.56 +
30 ppm MHz
7
4898B–RKE–08/06
ATA2745
Loop bandwidth
For best LO noise
Loop filter components:
C2 = 3.9 nF, C1 = 15 nF, R4 = 220ΩBLoop 100 kHz
Phase noise PLL Referring to the phase comparator
fPC = 6.78 MHz PNPLL –111 –105 dBC/Hz
Phase noise VCO At 1 MHz
At 36 MHz
PNVCO
PNVCO
–90
–122 dBC/Hz
Frequency range of the VCO fVCO 310 440 MHz
Clock output
(CMOS microcontroller compatible) Clkout fout /128 MHz
Load capacitance at CLK CCLK 10 pF
Series resonance R of the crystal fXTO = 13.56 MHz
fXTO = 9.84 MHz
Rs
Rs
80
100 Ω
ASK modulation frequency rate Duty cycle of the
modulation signal = 50% fmodASK 020kHz
CLK output
- Output current Low
- Output current Low
- Output current High
- Output current High
VCLK = 0.2 × VS
VCLK = 0.3 × VS
VCLK = 0.8 × VS
VCLK = 0.7 × VS
Iol
Iol
Ioh
Ioh
150
200
–150
–200 100
µA
µA
µA
µA
ASK input
- Low level input voltage
- High level input voltage
- Input current High
VASKl
VASKh
IASKh
1.7
0.3
140
V
V
µA
Enable ASK
- Low level input voltage
- High level input voltage
- Input current High
VEN
VFSKl
VFSKh
IFSKh
1.7
0.3
140
V
V
µA
8. Electrical Characteristics (Continued)
All parameters are refered to GND (pin 5), VS = 3V, Tamb = 25°C, unless otherwise specified
The possible operating ranges refer to different circuit conditions: VS = 2.2V to 4.0V at Tamb = –40°C to +85°C
Parameters Test Conditions Symbol Min. Typ. Max. Unit
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ATA2745
10. Package Information
9. Ordering Information
Extended Type Number Package Remarks
ATA2745M-TCQY SSO16 Taped and reeled, Pb-free
9
4898B–RKE–08/06
ATA2745
11. Revision History
Please note that the following page numbers referred to in this section refer to the specific revision
mentioned, not to this document.
Revision No. History
4898B-RKE-08/06 • Put datasheet in a new template
• Section 9 “Ordering Information” on page 8 changed
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