Rainbow Electronics U2741B 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 2.0 V to 5.5 V in the Temperature Range -20°C to 70°C
Supply Voltage 2.2 V to 5.5 V in the Temperature Range -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 as in Discrete Solutions Can
Be Used, Simpler Adaptation of Magnetic Loop Antennas)
• Very Large FSK Frequency Deviation Achievable by ±100 ppm Pulling of the Reference
Crystal
• Enables Receivers at Lower Bandwidth than with SAW Resonators
• ESD Protection According to MIL-STD.883 (4 KV HBM) Except Pins XTO1/ 2,
ANT and LF
Electrostatic sensitive device.
Observe precautions for handling.
Description
UHF ASK/FSK
Transmitter
U2741B
The U2741B 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 300 MHz to 450 MHz. The device can be used in
both FSK and ASK systems.
Rev. 4733A–RKE–11/03
Figure 1. System Block Diagram
1 Li cell
Encoder
ATARx9x
Keys
Figure 2. Block Diagram
UHF ASK/FSK
Remote control transmitter
U2741B
PLL
XTO
ASK
FSK
VCC
VCO
Power
amp.
OR
Power
up
Antenna Antenna
UHF ASK/FSK
Remote control receiver
U3741BM
Demod.
IF Amp
LNA VCO
DIVC
PWRSET
PWRVCC
Control
PLL XTO
1...3
controller
Micro-
CLK
GND
LFVCC
LFGND
LF
U2741B
VCO
f
f
PA
ANT
PWRGND1
64
PWRGND2
XTO
n
XTO1
XTO2
2
U2741B
4733A–RKE–11/03
Pin Configuration
Figure 3. Pinning SSO16
U2741B
ASK
1
FSK
VCC
3
CLK
GND
5
LFVCC
LFGND
LF
8
Pin Description
Pin Symbol Function
1 ASK Modulation input ASK
2 FSK Modulation input FSK
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 XTO2 FM modulation output
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
Pitch factor setting for crystal
16 DIVIC
L: high crystal frequency
H: low crystal frequency
DIVIC
16
2
4
15
14
13
PWRSET
PWRVCC
ANT
U2741B
PWRGND1
12
PWRGND2
6
7
11
10
XTO1
XTO2
9
4733A–RKE–11/03
3
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