U2741B

U2741B ATMEL | Alldatasheet

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Technical content

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/g176C to 70/g176C Supply Voltage 2.2 V to 5.5 V in the Temperature Range -40/g176C to 85/g176C  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

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. UHF ASK/FSK Transmitter U2741B

2 U2741B

Figure 1. System Block Diagram Figure 2. Block Diagram

1 Li cell

Figure 3. Pinning SSO16

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

16 DIVIC

4 U2741B

4733A–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 /g108/4 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 at either 13.56 MHz (USA 9.844 MHz) or 6.78 MHz (USA 4.9219 MHz). Thus, it is possible to use not only exceptionally small SMD crystals at 13.56 MHz but also very low- cost 6.78 MHz crystals in a wired metal package (e.g., in the HC49S housing). The frequency is selected by connecting pin 16 (DIVC) to either GND or V At high frequencies, crystals have a very fast start-up time (< 1.5 ms at 13.56 MHz, < 3 ms at 6.78 MHz), 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 The IC can be switched on at both the FSK and the ASK input. The IC's ChipSelect is performed by the logical OR operation of ASK and FSK input. In the case of V FSK, VASK /g1630.3 V, the power-down supply current is IS off < 0.35 µA. The ASK input activates the power amplifier and the PLL. The FSK input only activates the PLL and, if capacitor C 3 is installed, pulls the crystal to the lower frequency, whereby the transmitter is FSK modulated. After switching on at FSK, the VCO locks onto the 32 or 64 times higher fre- quency of the crystal oscillator. FSK Transmission The U2741B is switched on by V FSK = VS. 5 ms later, V S is applied to V ASK. The output can then be modulated by means of pin FSK. This is done by connecting capacitor C3 in parallel to the load capacitor C4. ASK Transmission The U2741B is activated by VFSK = VS. VASK remains 0 V for 5 ms, then the output power can be modulated by means of pin ASK. In this case, VFSK remains = VS during the mes- sage, the capacitor C3 is not mounted. 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 U2741B with V FSK = 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. C 5, C6, and C7 are block capacitors. The values of these capacitors depend on the board layout. C5 =1n F , C6 = 1 nF, and C 7 = 22 nF are typically used here. For C 5, the impedance between f = 100 MHz and f = 1 GHz should be as low as possible. C3 is not needed in ASK transmitter applications. In the case of FSK, C 3 is selected in such a way that the desired transmission frequency deviation is achieved (typical ±30 kHz). The capacitance here depends upon the crystal's load capacity (C 4) recom- mended by the manufacturer of the crystal. C2 = 3.9 nF, C1 = 15 nF, and R4 = 220 /g87. 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.

exact values of L10 and C10 depend on the layout. 50 /g87. Table 1 shows the values for an output power of 2 mW and an RPWRSET = 1.2 k/g87. Figure 4. Measurement Output Network Figure 5. Application Circuit Table 1. Transformation Network

13.56 MHz

3.39 MHz

6 U2741B

4733A–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 V S 6V Power dissipation P tot 250 mW Junction temperature T j 150 /g176C Storage temperature T stg -55 125 /g176C Ambient temperature T amb -40 105 /g176C Thermal Resistance Parameters Symbol Value Unit Junction ambient R thJA 180 K/W

Electrical Characteristics

All parameters are refered to GND (pin 5). The possible operating ranges refer to different circuit conditions: VS = 2.0 V to 5.5 V at Tamb = -20/g176C to +70/g176C, VS = 2.2 V to 5.5 V at Tamb = -40/g176C to +85/g176C (typically 25/g176C, 3 V) Parameters Test Conditions Symbol Min. Typ. Max. Unit Supply current (power down) V ASK, VFSK /g163 0.3 V, VS < 3.6 V IS off 0.35 µA Supply current (power up, output OFF) VASK = GND, VFSK = VS, Vs = 3 V IS on 4.7 6.2 mA Supply current (power up, output ON) V ASK = VS, VS = 3 V, RPWRSET = 1.2 k/g87 IStransmit 10 12.5 mA Output power VS = 3 V, Tamb = 25/g176C, f = 433.92 MHz RPWRSET = 1.2 k/g87 RPWRSET = 1.8 k/g87 PRef PRef 1.5 -0.5 dBm dBm Output power variation for the full temperature range Tamb = -40/g176C to +85/g176C, f = 433.92 MHz, VS = 3.0 V VS = 2.4 V Tamb = -20/g176C to +85/g176C, f = 433.92 MHz, VS = 2.0 V Pout = PRef + /g68PRef /g68PRef /g68PRef /g68PRef -1.5 -4.0 -5.5 dB dB dB Output power variation for f = 315 MHz compared to f = 433.92 MHz f = 315 MHz P out = PRef + /g68PRef /g68PRef 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 at Tamb = 25/g176C fo ±(n /g180 fPC) where fPC = 6.78 MHz Load capacitance at CLK/g1633p F f = 230 MHz to 470 MHz f < 230 MHz, f > 470 MHz Em Em -40 -58 dBC dBC

4733A–RKE–11/03 Oscillator frequency XTO M-version: at Tamb = 25/g176C N-version: full temperature range (monitoring) Crystal frequency = 13.56 MHz Crystal frequency = 6.78 MHz Load capacity of the crystal must be selected accordingly f XTO fXTO 13.56 - 30 ppm 6.78 - 30 ppm 13.56 6.78 13.56 + 30 ppm 6.78 + 30 ppm MHz MHz Loop bandwidth For best LO noise Loop filter components: C 2 = 3.9 nF , C1 = 15 nF , R4 = 220 /g87 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 PNVCO -91 -123 -87 -119 dBC/Hz Frequency range of the VCO f VCO 300 450 MHz Clock output (CMOS microcontroller compatible) Clkout fout/128 MHz Load capacitance at CLK C CLK 10 pF Series resonance R of the crystal fXTO = 13.56 MHz fXTO = 9.84 MHz fXTO = 6.78 MHz fXTO = 4.90 MHz Rs Rs Rs Rs 100 150 225 /g87 FSK modulation frequency rate Duty cycle of the modulation signal = 50% fmodFSK 02 0 k H z ASK modulation frequency rate Duty cycle of the modulation signal = 50% fmodASK 02 0 k H z CLK output - Output current Low - Output current Low - Output current High - Output current High V CLK = 0.2 /g180 VS VCLK = 0.3 /g180 VS VCLK = 0.8 /g180 VS VCLK = 0.7 /g180 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 FSK input - Low level input voltage - High level input voltage - Input current High VFSKl VFSKh IFSKh 1.7 0.3 140 V V µA Electrical Characteristics (Continued) All parameters are refered to GND (pin 5). The possible operating ranges refer to different circuit conditions: VS = 2.0 V to 5.5 V at Tamb = -20/g176C to +70/g176C, VS = 2.2 V to 5.5 V at Tamb = -40/g176C to +85/g176C (typically 25/g176C, 3 V) Parameters Test Conditions Symbol Min. Typ. Max. Unit

8 U2741B

4733A–RKE–11/03

Package Information

Ordering Information

Extended Type Number Package Remarks U2741B-NFB SSO16 Tube, optimized power-supply rejection, value of C4 differs from M-version, enhanced XTO stability U2741B-NFBG3 SSO16 Taped and reeled, see above

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