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

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

l/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 pro­cessor does not need to poll a lock detect output.

Functional
Description

ASK Transmission The U2745B is activated by EN = V

power can be modulated by means of pin ASK. V

. V

S

must remain 0 V for 5 ms, then the output

ASK

remains = VS during the transmis-

EN

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 oscil­lator to switch on the U2745B with V

= VS. 5 ms later, the 3.39-MHz clock frequency is

EN

present, so that the message can be sent with crystal accuracy.

Application Circuit The following component values are recommendations for a typical application. C

are block capacitors. The values of these capacitors depend on the board layout.

6

=1nF, C5 = 1 nF, and C6 = 22 nF are typically used here. For C5, the impedance

4

and C

Loop1

is an inductor for the antenna's DC current supply. A typical value is

Feed

= 220 nH. L

Feed

and C10 form the transformation network to adopt the output impedance of the IC to

10

are selected so that the antenna oscillates in resonance and the adap-

Loop2

can be either printed on the PC board or be a discrete component.

Feed

and C10 are dependent on the layout.

10

W. The following table shows the values for an output power of 2 mW and an

PWRSET

=1.2kW.

Output Power
Measurement

and C
C
between f = 100 MHz and f = 1 GHz should be as low as possible.

C
tation to the appropriate impedance transformation is possible.

L
L

The following output network (see Figure 4 on page 5) can be used for output power
evaluation, the exact values of L

L
50
R

, C5,

4

Table 1. Transformation Network

f/MHz C10/pF L10/nH Z

315 2.7 56 260 + j330

433.92 1.8 33 185 + j268

4

U2745B

/W

Load_opt

4734A–RKE–11/03

Figure 4. Measurement Output Network

PWRVCC

U2745B

V

S

L

10

Figure 5. Application Circuit

ASK

EN

C

CLK

3.39 MHz

ANT

Z

Load-opt

C

10

50 W

+VS = 2.2 ... 4.0 V

ASK

OR

EN

2

3

4

5

6

7

LF

8

Power

up

U2745B

VCO

f

f

64

PA

XTO

n

VCC

6

C

5

R

CLK

GND

LFVCC

LFGND

C

1

4

GND

161

PWRSET

15

PWRVCC

14

ANT

13

PWRGND1

12

PWRGND2

11

XTO1

10

NC

9

R

PWRSET

C

4

13.56 MHz

C

Loop2

L

Feed

C

Loop1

C

3

4734A–RKE–11/03

C

2

Antenna

5

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 V
Power dissipation P
Junction temperature T
Storage temperature T
Ambient temperature T

tot

stg

amb

S

j

-55 125 °C

-40 85 °C

6 V
250 mW
150 °C

Thermal Resistance

Parameters Symbol Value Unit

Junction ambient R

thJA

180 K/W

Electrical Characteristics

All parameters are refered to GND (pin 5), VS = 3 V, T
The possible operating ranges refer to different circuit conditions: V

= 25°C, unless otherwise specified

amb

= 2.2 V to 4.0 V at T

S

= -40°C to +85°C

amb

Parameters Test Conditions Symbol Min. Typ. Max. Unit

Supply current (power down) V
Supply current (power up, output OFF) V
Supply current (power up, output ON) V

Output power

, V

ASK

ASK

ASK

V

= 3 V, T

S

R

PWRSET

£ 0.3 V, VS < 3.6 V IS

FSK

= GND, VEN = VS, VS = 3 V IS
= VS, VS = 3 V, R

= 25°C, f = 433.92 MHz

amb

= 1.2 kW IS

PWRSET

= 1.2 kW P

off

on

transmit

Ref

210µA

4.7 6.2 mA
10 12.5 mA

135dBm

Output power variation for
f = 315 MHz compared to
f = 433.92 MHz

f = 315 MHz

= P

P

out

at P

+ DP

Ref

= 2.0 mW,

out

Ref

DP

Ref

1.5 dB

the load impedance must be selected
Maximum peak output
antenna voltage

to meet the V

requirement, the supply current is not

maximum

out

V

outmax

VS - 0.7 V V

(peak)

dependent on the load impedance

tolerance

f

±(n ´ fPC) where fPC = 6.78 MHz

o

Spurious emission

Load capacitance at CLK

f = 230 MHz to 470 MHz

f < 230 MHz, f > 470 MHz

Oscillator frequency XTO Crystal frequency = 13.56 MHz f

£ 3pF

Em
Em

XTO

13.56 -

30 ppm

13.56

-40

-58

13.56 +
30 ppm

dBC
dBC

MHz

For best LO noise
Loop bandwidth

Phase noise PLL

Phase noise VCO

Loop filter components:

= 3.9 nF, C1 = 15 nF, R4 = 220 W

C

2

Referring to the phase comparator

= 6.78 MHz

f

PC

at 1 MHz

at 36 MHz

B

PN

PN
PN

Loop

PLL

VCO
VCO

100 kHz

-111 -105 dBC/Hz

-90

-122

dBC/Hz

6

U2745B

4734A–RKE–11/03

Electrical Characteristics (Continued)

U2745B

All parameters are refered to GND (pin 5), VS = 3 V, T
The possible operating ranges refer to different circuit conditions: V

= 25°C, unless otherwise specified

amb

= 2.2 V to 4.0 V at T

S

= -40°C to +85°C

amb

Parameters Test Conditions Symbol Min. Typ. Max. Unit

Frequency range of the VCO f
Clock output

(CMOS microcontroller compatible)
Load capacitance at CLK C

f

= 13.56 MHz

Series resonance R of the crystal

ASK modulation frequency rate

XTO

f

= 9.84 MHz

XTO

Duty cycle of the

modulation signal = 50%

f

VCO

Clk

out

CLK

Rs
Rs

modASK

310 440 MHz

f

/128 MHz

out

10 pF
80

100

W

020kHz

CLK output

- Output current Low

- Output current Low

- Output current High

- Output current High

V

CLK

V

CLK

V

CLK

V

CLK

= 0.2 ´ V
= 0.3 ´ V
= 0.8 ´ V
= 0.7 ´ V

S
S
S
S

I

ol

I

ol

I

oh

I

oh

150
200

-150

-200 100

µA
µA
µA
µA

ASK input

- Low level input voltage

- High level input voltage

- Input current High
Enable ASK

- Low level input voltage

- High level input voltage

- Input current High

V

V

I

ASKh

V

V

V

I

FSKh

ASKl

ASKh

EN

FSKl

FSKh

1.7

1.7

0.3

140

0.3

140

µA

µA

V
V

V
V

4734A–RKE–11/03

7

Ordering Information

Extended Type Number Package Remarks

U2745B-MFB SSO16 Tube
U2745B-MFBG3 SSO16 Taped and reeled

Package Information

8

U2745B

4734A–RKE–11/03

Atmel Corporation Atmel Operations

2325 Orchard Parkway
San Jose, CA 95131, USA
Tel: [phone]
Fax: [phone]

Regional Headquarters

Europe

Atmel Sarl
Route des Arsenaux 41
Case Postale 80
CH-1705 Fribourg
Switzerland
Tel: [phone]
Fax: [phone]

Asia

Room 1219
Chinachem Golden Plaza
77 Mody Road Tsimshatsui
East Kowloon
Hong Kong
Tel: [phone]
Fax: [phone]

Japan

9F, Tonetsu Shinkawa Bldg.
1-24-8 Shinkawa
Chuo-ku, Tokyo 104-0033
Japan
Tel: [phone]
Fax: [phone]

Memory

2325 Orchard Parkway
San Jose, CA 95131, USA
Tel: [phone]
Fax: [phone]

Microcontrollers

2325 Orchard Parkway
San Jose, CA 95131, USA
Tel: [phone]
Fax: [phone]

La Chantrerie
BP 70602
44306 Nantes Cedex 3, France
Tel: [phone]
Fax: [phone]

ASIC/ASSP/Smart Cards

Zone Industrielle
13106 Rousset Cedex, France
Tel: [phone]
Fax: [phone]

1150 East Cheyenne Mtn. Blvd.
Colorado Springs, CO 80906, USA
Tel: [phone]
Fax: [phone]

Scottish Enterprise Technology Park
Maxwell Building
East Kilbride G75 0QR, Scotland
Tel: [phone]
Fax: [phone]

RF/Automotive

Theresienstrasse 2
Postfach 3535
74025 Heilbronn, Germany
Tel: [phone]
Fax: [phone]

1150 East Cheyenne Mtn. Blvd.
Colorado Springs, CO 80906, USA
Tel: [phone]
Fax: [phone]

Biometrics/Imaging/Hi-Rel MPU/
High Speed Converters/RF Datacom

Avenue de Rochepleine
BP 123
38521 Saint-Egreve Cedex, France
Tel: [phone]
Fax: [phone]

Literature Requests

www.atmel.com/literature

Disclaimer: Atmel Corporation makes no warranty for the use of its products, other than those expressly contained in the Company’s standard
warranty which is detailed in Atmel’s Terms and Conditions located on the Company’s web site. The Company assumes no responsibility for any
errors which may appear in this document, reserves the right to change devices or specifications detailed herein at any time without notice, and
does not make any commitment to update the information contained herein. No licenses to patents or other intellectual property of Atmel are
granted by the Company in connection with the sale of Atmel products, expressly or by implication. Atmel’s products are not authorized for use
as critical components in life support devices or systems.

© Atmel Corporation 2003. All rights reserved.

®

and combinations thereof are the registered trademarks of Atmel Corporation or its subsidiaries.

Atmel

Other terms and product names may be the trademarks of others.

Printed on recycled paper.

4734A–RKE–11/03