Rainbow Electronics U2745B User Manual
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 -40°C to 85°C
• 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.
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 systems. The main applications of the U2745B are in the areas of outside temperature
metering, socket control, garage door opener, consumption metering, light/fan or aircondition control, jalousies, wireless keyboard and various other consumer market
applications.
U2745B
Rev. 4734A–RKE–11/03
Figure 1. System Block Diagram
1 Li cell
Keys
Encoder
ATARx9x
Remote control transmitter
UHF ASK
U2745B
XTO
PLL
VCO
Antenna Antenna
U3745BM
UHF ASK
Remote control receiver
Demod.
IF Amp
PLL XTO
Control
1...3
controller
Micro-
Figure 2. Block Diagram
ASK
EN
VCC
CLK
GND
LFVCC
LFGND
Power
amp.
OR
Power
up
VCO
f
f
LNA VCO
GND
PWRSET
PWRVCC
PA
ANT
PWRGND1
64
PWRGND2
XTO
n
XTO1
LF
NC
U2745B
2
U2745B
4734A–RKE–11/03
Pin Configuration
Figure 3. Pinning SSO16
ASK
U2745B
1
16
GND
EN
VCC
3
CLK
5
GND
LFVCC
LFGND
8
LF
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
PWRSET
2
4
15
14
13
PWRVCC
ANT
U2745B
PWRGND1
12
PWRGND2
6
7
11
10
XTO1
NC
9
4734A–RKE–11/03
3
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