U2745B-MFB - Atmel Corporation

Rev. 4734A–RKE–11/03

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

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 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.

UHF ASK

Transmitter

U2745B

2U2745B

4734A–RKE–11/03

Figure 1. System Block Diagram

Figure 2. Block Diagram

Demod.

IF Amp

LNA VCO

PLL XTO

Control

U3745BM

1...3

Micro-

controller

Power

amp.

XTO VCO

PLL

U2745B

Antenna Antenna

UHF ASK

Remote control transmitter UHF ASK

Remote control receiver

Encoder

ATARx9x

1 Li cell

Keys

Power

VCO

XTO

ASK

VCC

CLK

GND

LFVCC

LFGND

GND

PWRSET

PWRVCC

ANT

PWRGND1

PWRGND2

XTO1

U2745B

4734A–RKE–11/03

Pin Configuration

Figure 3. Pinning SSO16

VCC

CLK

GND

LFVCC

LFGND

ASK

PWRVCC

ANT

PWRGND1

PWRGND2

XTO1

GND

PWRSET

U2745B

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

4U2745B

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 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 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=1nF, C

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

RPWRSET =1.2kW.

Table 1. Transformation Network

f/MHz C10/pF L10/nH ZLoad_opt/W

315 2.7 56 260 + j330

433.92 1.8 33 185 + j268

U2745B

4734A–RKE–11/03

Figure 4. Measurement Output Network

Figure 5. Application Circuit

PWRVCC

ANT

L10

C10

50 W

ZLoad-opt

161

Power

VCO

XTO

ASK

VCC

CLK

GND

LFVCC

LFGND

GND

PWRSET

PWRVCC

ANT

PWRGND1

PWRGND2

XTO1

RPWRSET

LFeed

CLoop1

13.56 MHz

+VS = 2.2 ... 4.0 V

CLoop2

ASK

CLK

3.39 MHz

U2745B

Antenna

6U2745B

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 Min. Max. Unit

Supply voltage VS6 V

Power dissipation Ptot 250 mW

Junction temperature Tj150 °C

Storage temperature Tstg -55 125 °C

Ambient temperature Tamb -40 85 °C

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 = 25°C, unless otherwise specified

The possible operating ranges refer to different circuit conditions: VS = 2.2 V to 4.0 V at Tamb = -40°C to +85°C

Parameters Test Conditions Symbol Min. Typ. Max. Unit

Supply current (power down) VASK, VFSK £ 0.3 V, VS < 3.6 V ISoff 210µA

Supply current (power up, output OFF) VASK = GND, VEN = VS, VS = 3 V ISon 4.7 6.2 mA

Supply current (power up, output ON) VASK = VS, VS = 3 V, RPWRSET = 1.2 kWIStransmit 10 12.5 mA

Output power VS = 3 V, Tamb = 25°C, f = 433.92 MHz

RPWRSET = 1.2 kWPRef 135dBm

Output power variation for

f = 315 MHz compared to

f = 433.92 MHz

f = 315 MHz

Pout = PRef + DPRef

DPRef 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 - 0.7 V 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

-40

-58

dBC

Oscillator frequency XTO Crystal frequency = 13.56 MHz fXTO 13.56 -

30 ppm 13.56 13.56 +

30 ppm MHz

Loop bandwidth

For best LO noise

Loop filter components:

C2 = 3.9 nF, C1 = 15 nF, R4 = 220 W

BLoop 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

-90

-122 dBC/Hz

U2745B

4734A–RKE–11/03

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

100 W

ASK modulation frequency rate Duty cycle of the

modulation signal = 50% fmodASK 020kHz

CLK output

- Output current Low

- Output current High

VCLK = 0.2 ´ VS

VCLK = 0.3 ´ VS

VCLK = 0.8 ´ VS

VCLK = 0.7 ´ VS

Iol

Ioh

150

200

-150

-200 100

µA

ASK input

- Low level input voltage

- High level input voltage

- Input current High

VASKl

VASKh

IASKh

1.7

0.3

140

µA

Enable ASK

- Low level input voltage

- High level input voltage

- Input current High

VEN

VFSKl

VFSKh

IFSKh

1.7

0.3

140

µA

Electrical Characteristics (Continued)

All parameters are refered to GND (pin 5), VS = 3 V, Tamb = 25°C, unless otherwise specified

The possible operating ranges refer to different circuit conditions: VS = 2.2 V to 4.0 V at Tamb = -40°C to +85°C

Parameters Test Conditions Symbol Min. Typ. Max. Unit

8U2745B

4734A–RKE–11/03

Package Information

Ordering Information

Extended Type Number Package Remarks

U2745B-MFB SSO16 Tube

U2745B-MFBG3 SSO16 Taped and reeled

Printed on recycled paper.

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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.

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4734A–RKE–11/03

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