Preliminary 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, 3 V /+11 dBm / 17 mA Low supply voltage, 2.2 V to 3.6 V operation range Low external component cost. PLL-based transmitter with frequency range from 250MHz to 450MHz On-chip one-shot circuit 60 dB RF on-off ratio for OOK/ASK modulation SOT23-6 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, 233-1, Baociao Road, Sindian, Taipei 23145, Taiwan PT4455 APPLICATION CIRCUIT VDD BILL OF MATERIALS Part X1 R1 R2 R3 R4 C1 C2 C3 C4 C5 C6 C7 L1 L2 Value 315MHz 9.844M 10K 100K 0 0 NC 27p 1u 15p 8.2p 8.2p 2.2u 47n 39n 433.92MHz 13.56M 10K 100K 0 0 NC 39p 1u 22p 6.8p 8.2p 2.2u 39n 27n Unit Hz 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. PRE1.1 2 August 2010 PT4455 ORDER INFORMATION Valid Part Number PT4455 Package Type 6 Pins, SOT23 Top Code PT4455 PIN CONFIGURATION PIN DESCRIPTION PRE1.1 Pin Name XOUT VSS PAOUT DIN I/O O G O I VDD XIN P I Description Oscillator output Ground connection Power amplifier output Data input Power supply Oscillator input 3 Pin No. 1 2 3 4 5 6 August 2010 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 315 MHz 9.844 MHz 340 MHz 10.625 MHz 390 MHz 12.188 MHz 433.92 MHz 13.56 MHz 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 180 KHz 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 PRE1.1 4 August 2010 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 315 MHz, then the length of a λ/4 antenna is 22.6 cm. 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 0.8 mm to 1.6 mm) 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 30 mil, the length of the antenna, L (in cm), is calculated by L c 4 f r 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. PRE1.1 5 August 2010 PT4455 ABSOLUTE MAXIMUM RATINGS (VSS=0V) Parameter Supply Voltage Range I/O Voltage Operating Temperature Range Storage Temperature Range Symbol Min. Max. Unit VDD VI/O TA TSTG -0.3 -0.3 -40 -55 5 5 +85 +125 V V °C °C 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 °C ELECTRICAL CHARACTERISTICS Nominal conditions: VDD = 3.0 V, VSS = 0 V, TA = +27°C. 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 Standby Current Istandby DIN=Low; TDELAY>50ms 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) Harmonics 2x/3x fRF PHARM fRF = 315MHz PSPUR Crystal Spur 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 250 1 A 450 MHz dBm dBm dB dBc/Hz dBc dBc dBc 50 Kbps ms ms 11 10 60 -75 -40 -50 -50 0.5 50 2 1 Note: Depend on power amplifier output matching PRE1.1 6 August 2010 PT4455 PACKAGE INFORMATION 6 Pins, SOT23-6 Symbol A A1 A2 Min. 0.00 0.90 Nom. 1.15 Max 1.45 0.15 1.30 b c D E E1 e e1 0.30 0.080 0.130 2.90 BSC 2.80 BSC 1.60 BSC 0.95 BSC 1.90 BSC 0.50 0.200 L 0° - 8° 0.30 0.45 0.60 Notes; 1. Refer to JEDEC MO-178 2. All dimensions are in millimeter PRE1.1 7 August 2010 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, Taipei 23145, Taiwan Tel: 886-2-66296288 Fax: 886-2-29174598 http://www.princeton.com.tw PRE1.1 8 August 2010