PT4455 PLL-based OOK/ASK Transmitter IC DESCRIPTION PT4455 is a high performance OOK/ASK transmitter for the Remote Keyless Entry (RKE) systems. It consists of a power amplifier, one-shot circuit and phase-locked loop with internal voltage controlled oscillator and loop filter. The one-shot circuit control the phase-locked loop and power amplifier to have fast start-up time in operation. APPLICATIONS • • • • • • FEATURES • • • • • Highly integrated OOK/ASK transmitter High output power, 3V /+11dBm /17mA Low supply voltage, 2.2V to 3.6V operation range Low external component cost. PLL-based transmitter with frequency range from 300MHz to 450MHz • On-chip one-shot circuit • 60dB RF on-off ratio for OOK/ASK modulation • Available in 6-pin, SOT-23 package Keyless entry systems Remote control systems Garage door openers Alarm systems Security systems Wireless sensors BLOCK DIAGRAM Tel: 886-66296288‧Fax: 886-29174598‧ http://www.princeton.com.tw‧2F, No. 233-1, Baociao Rd., Sindian Dist., New Taipei City 23145, Taiwan PT4455 APPLICATION CIRCUIT BILL OF MATERIALS Part X1 R1 R2 R3 R4 R5 C1 C2 C3 C4 C5 C6 C7 L1 L2 Value 315MHz 9.844M 10K 100K 0 0 560K 22p 22p 1μ 220p 8.2p 18p 2.2μ 180n 33n 433.92MHz 13.56M 10K 100K 0 0 560K 18p 18p 1μ 220p 4.7p 10p 2.2μ 180n 27n Unit Hz Ω Ω Ω Ω Ω F F F F F F F H H Notes: 1. C1/C2 can be used to trim the transmitted signal frequency for matching the specified value. 2. L2/C5/C6 value will depend on PCB layout. 3. The recommend maximum ESR value of X1 is 40Ω. 4. To populate the R5 over XIN will help to maintain good oscillation in high X1 ESR. V1.1 2 January 2013 PT4455 ORDER INFORMATION Valid Part Number Package Type Top Code PT4455 6-Pin, SOT23 PT4455 PIN CONFIGURATION PIN DESCRIPTION V1.1 Pin Name I/O Description XOUT O Oscillator output 1 VSS G Ground connection 2 PAOUT O Power amplifier output 3 DIN I Data input 4 VDD P Power supply 5 XIN I Oscillator input 6 3 Pin No. January 2013 PT4455 FUNCTION DESCRIPTION PA OUTPUT MATCHING The PA output is an open-drain structure. Its output connects a large choke inductor to supply voltage and follows by a DC block capacitor. After the DC block capacitor, a C-L-C-type matching network is used to tune with the antenna impedance. The inductor and capacitor values may be different from the suggestion value depending on PCB material, PCB thickness, ground configuration, and the layout traces length. For the open-drain structure in PA, the HBM (Human Body Mode) and MM (Machine Mode) ESD strength is 4KV and 400V. REFERENCE OSCILLATOR For a quartz crystal to oscillate in the specified frequency, it should work with vendor provided load capacitor value, called CL . The load capacitor is about 12pF to 18pF in general. In PT4455, the Pierce type crystal oscillator is used, and the shunt capacitor over XIN and XOUT is in series together equivalently. The shunt capacitor should be placed as 2x CL to oscillate with specified frequency. The temperature coefficient of quartz crystal will cause the VCO output frequency drift in high/low temperature range. With a fixed divided-by-32 PLL, the fREFOSC = fTX / 32. The following table list fREFOSC for some common transmit frequencies Transmit Frequency fTX Reference Oscillator Frequency fREFOSC 315MHz 9.844MHz 340MHz 10.625MHz 390MHz 12.188MHz 433.92MHz 13.56MHz The recommend maximum ESR value of reference oscillator is 40Ω. PHASE-LOCKED LOOP (PLL) The PT4455 own a fixed divided-by-32 PLL to generate the transmitter signal. The PLL consists of the voltage-controlled oscillator (VCO), crystal oscillator, asynchronous ÷ 32 divider, charge pump, loop filter and phase-frequency detector (PFD). All these circuits are integrated on-chip. The PFD compares two signals and produces an error signal which is proportional to the difference between the input phases. The error signal passes through a loop filter with an approximately 180KHz bandwidth, and is used to control the VCO. A frequency divider placed after the VCO and it will feedback the divided signal to PFD. In the final the VCO will get locked to reference signal as fVCO = fREFOSC * 32. The block diagram below shows the basic elements of the PLL. The PLL chain circuit is supplied by internal voltage regulator to ease the PA pulling and crystal spur issue V1.1 4 January 2013 PT4455 ONE-SHOT CIRCUIT AND POWER-DOWN CONTROL During the signal transmission, the crystal oscillator start-up time will limit its wake-up time to work. A one-shoot circuit is used to solve this problem by turning on/off the power amplifier and PLL circuit separately. When apply “HIGH” to DIN, will enable the PLL chain and PA. When applied “LOW” to DIN, the PA will be turn-off immediately, and the PLL chain will be turn-off after one-shot period about 50ms. To calculate the re-triggerable one-shot delay time, it can be counted as 688128 / fREFOSC . For fREFOSC = 9.844MHz and 13.56MHz, the delay time is about 70ms and 50ms. ANTENNA DESIGN AND PCB LAYOUT CONSIDERATION For a λ/4 dipole antenna and operating frequency, f (in MHz), the required antenna length, L (in cm), may be calculated by using the formula. L= 7132 f For example, if the frequency is 315MHz, then the length of a λ/4 antenna is 22.6cm. If the calculated antenna length is too long for the application, then it may be reduced to λ/8, λ/16, etc. without degrading the input return loss. Usually, when designing a λ/4 dipole antenna, it is better to use a single conductive wire (diameter about 0.8mm to 1.6mm) rather than a multiple core wire. If the antenna is printed on the PCB, ensure there is neither any component nor ground plane underneath the antenna on the backside of PCB. For an FR4 PCB (εr = 4.7) and a strip-width of 30mil, the length of the antenna, L (in cm), is calculated by L= c 4× f × εr where “c” is the speed of light (3 x1010 cm/s) Proper PCB layout is extremely critical in achieving good RF performance. At the very least, using a two-layer PCB is strongly recommended, so that one layer may incorporate a continuous ground plane. A large number of via holes should connect the ground plane areas between the top and bottom layers. Careful consideration must also be paid to the supply power and ground at the board level. The larger ground area plane should be placed as close as possible to all the VSS pins. Grounding the metal case of quartz crystal and isolate the XIN/XOUT trace to other can suppress the crystal spur signal over PA output. V1.1 5 January 2013 PT4455 ABSOLUTE MAXIMUM RATINGS (VSS=0V) Parameter Supply Voltage Range I/O Voltage Operating Temperature Range Storage Temperature Range Symbol VDD VI/O TOPR TSTG Min. -0.3 -0.3 -40 -40 Max. 5 5 +85 +150 Unit V V ℃ ℃ RECOMMENDED OPERATING CONDITIONS (VSS=0V) Parameter Supply Voltage Range Operating Temperature Range Symbol Min. Max. Unit VDD TA -0.3 -40 3.6 +85 V ℃ ELECTRICAL CHARACTERISTICS Nominal conditions: VDD = 3.0 V, VSS = 0 V, TA = +27℃. Parameter Symbol Conditions General Characteristics Supply Voltage VDD DIN=High(CW mode); POUT=12dBm, fRF=315MHz (Note) Operating Current IDD DIN=High(CW mode); POUT=10dBm, fRF=434MHz DIN=Low, TDELAY>50ms Standby Current Istandby RF Frequency Range fRF fRF=315MHz Power Amplifier Output Power (Note) Pout fRF=434MHz RF Power On / Off Ratio PEXT 315MHz, 10KHz offset Phase Noise PNOISE (Note) 2x/3x fRF Harmonics PHARM fRF=315MHz Crystal Spur PSPUR fRF=434MHz Data Input and One-shot Data Rate DRATE CL not connected Crystal Oscillator Start-up Time TON One-shot Delay Time TDELAY Min. Typ. Max. Unit 2.2 3.0 3.6 V - 17 - mA - 19 - mA - - 1 μA 300 - 11 10 60 -75 -40 -40 -40 450 - MHz dBm dBm dB dBc/Hz dBc dBc dBc 0.5 50 2 1 - 50 - Kbps ms ms Note: Depend on power amplifier output matching V1.1 6 January 2013 PT4455 PACKAGE INFORMATION 6-PIN, SOT23 Symbol Min. Nom. Max A - - 1.45 A1 0.00 - 0.15 A2 0.90 1.15 1.30 b 0.30 - 0.50 c 0.080 0.130 0.200 e 0.95 BSC. e1 1.90 BSC. D 2.90 BSC. E 2.80 BSC. E1 1.60 BSC. L 0.30 0.45 0.60 θ 0° - 8° Notes; 1. Refer to JEDEC MO-178 2. All dimensions are in millimeter V1.1 7 January 2013 PT4455 IMPORTANT NOTICE Princeton Technology Corporation (PTC) reserves the right to make corrections, modifications, enhancements, improvements, and other changes to its products and to discontinue any product without notice at any time. PTC cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a PTC product. No circuit patent licenses are implied. Princeton Technology Corp. 2F, 233-1, Baociao Road, Sindian Dist., New Taipei City 23145, Taiwan Tel: 886-2-66296288 Fax: 886-2-29174598 http://www.princeton.com.tw V1.1 8 January 2013