TX4915 VHF/UHF TRANSMITTER the wireless IC company HiMARK Technology, Inc. reserves the right to change the product described in this datasheet. All information contained in this datasheet is subject to change without prior notice. HiMARK Technology, Inc. assumes no responsibility for the use of any circuits shown in this datasheet. Description The TX4915 is a monolithic integrated circuit intended for use as a low-cost AM/ASK transmitter. The chip can be used in applications in the north American and European VHF/UHF bands. The integrated VCO, phase detector, prescaler, and reference oscillator transistor require only the addition of an external crystal to provide a complete phaselocked loop. In addition to the standard power-down mode, the chip also includes an automatic lock-detect feature that disables the transmitter output when the PLL is out-of-lock. Features K Fully Integrated Frequency Synthesizer K 2.2V to 5.5V Voltage Supply Range K Low Current and Power Down Capability K Integrated VCO and Reference Oscillator K integeated 64/128 Dual Modulus Prescaler K 100MHz to 960MHz frequency Range K Out-of-Lock inhibit Circuit Package and Pin Assignment 16 pin, plastic SSOP (dimensions in mm) θ OSCIN 1 OSCOUT 2 DIMENSIONS IN MILLIMETERS SYMBOLS A A1 A2 b C D E E1 e L y θ MIN 1.35 0.10 −−− 0.20 0.19 4.80 5.80 3.80 −−− 0.40 −−− 0° NOM 1.60 −−− 1.45 0.25 −−− −−− −−− −−− 0.64 −−− −−− −−− MAX 1.75 0.25 −−− 0.30 0.25 5.00 6.20 4.00 −−− 1.27 0.10 8° DIMENSIONS IN INCHES MIN 0.053 0.004 −−− 0.008 0.007 0.189 0.228 0.150 −−− 0.016 −−− 0° NOM 0.064 −−− 0.057 0.010 −−− −−− −−− −−− 0.025 −−− −−− −−− MAX 0.069 0.010 −−− 0.012 0.010 0.197 0.244 0.157 −−− 0.050 0.004 8° TXEN 3 VSS 4 PAOUT 5 VSS1 6 VCC1 7 MODIN 8 TX H 49 iM A 15 RK 16 SW 15 LD 14 DO 13 RES 12 RESB 11 VREFP 10 VSS2 9 VCC2 NOTE 1. PACKAGE BODY SIZES EXCLUDE MOLD FLASH AND GATE BURRS 2. DIMENSION L IS MEASURED IN GAGE PLANE 3. TOLERANCE 0.10 mm UNLESS OTHERWISE SPECIFIED 4. CONTROLLING DIMENSION IS MILLIMETER. CONVERTED INCH DIMENSIONS ARE NOT NECESSARILY EXACT. 5. FOLLOWED FORM JEDEC MO-137 Page 1 March 2000 TX4915 the wireless IC company Pin Descriptions Number Name Description 1 OSCIN This pin is connected directly to the base of reference oscillator transistor. The intended reference oscillator configuration is a modifiled Colpitts. 2 OSCOUT This pin is connected directly to the emitter of reference oscillator transistor. 3 TXEN Enable control for all circuitry. When this pin is a logic “low” all circuiits are turn off. When this pin is logic “high”, all circuits are operating normally. 4 VSS Ground connection for the PAOUT amp. 5 PAOUT Transmitter output. This pin is an open collector and require a pull-up inductor for bias/matching and a tapped capacitor for matching. 6 VSS1 Ground connection for the PAOUT buffer amplifier. 7 VCC1 This pin is used to supply bias to the PA buffer amplifier. 8 MODIN AM analog or ASK digital modulation can be imparted to the carrieer by an input to this pin. An external resistor is used to bias the output amplifiers through this pin. 9 VCC2 This pin is used to supply DC bias to the VCO, crystal oscillator, prescaler, PFD, and charge pump. 10 VSS2 Digital PLL ground connection. 11 VREFP Bias voltage reference pin for bypassing the prescaler. 12 RESB The RES pins are used to supply DC voltage to the VCO, as well as to tune the center frequency of the VCO. 13 RES see pin 12 14 DO Output of the charge pump. An RC network from this pin to ground is used to establish the PLL bandwidth. 15 LD This pin is used to set the threshold of the lock detect circuit. A shunt capacitor should be used to set an RC time constant with the on-chip series 1kΩ resistor.This signal is used to clamp (enable or disable) the MODIN circuitry. The time constant should be approximately 15 times the reference period. 16 SW Logic “High” input selects divide-by-64 prescaler. Logic “Low” input selects divideby-128 prescsaler. Page 2 March 2000 TX4915 the wireless IC company Block Diagram RES RES 13 12 OSC IN OSC OUT 2 1 14 OSC VCO PAOUT 5 PFD and Charge Pump DC BIAS Lock Detect 6 MODIN 2 TXEN Prescaler 64/128 5 3 LD SW Absolute Maximum Ratings V SS = 0 V Parameter Rating Unit Supply voltage – 0.3 to + 7.0 VDC Control Voltage – 0.3 to + 7.0 VDC Input RF Level +10 dBm Output Load VSWR –40 to +85 °C Operating Ambient Temperature -40 to +85 °C Storage Temperature -40 to +150 °C Recommended Operating Conditions V SS = 0 V Value Parameter Symbol Unit min. typ. max. Supply voltage range VCC 2.2 3.0 5.5 V Operating temperature TA –40 +25 +85 o Page 3 C March 2000 TX4915 the wireless IC company Electrical Characteristics (VDD1, DD2 = 2.2 to 5 V, VSS, SS1, SS2 = 0 V, TA = –40 to +85 °C unless otherwise noted) TX4915 Capability(Simulated) Parameter Symbol Condition Value Unit min. typ. max. 2.2 3 5 Power supply Supply Voltage VCC1,VCC2 IDC TXEN=high , 50% Duty Cycle 10kHz data applied to the MODIN input.RMODIN (R3)=3kΩ Istandby TXEN = low Total dc Current (normal operation) Total dc Current (stand-by mode) V mA 1 µA 960 MHz Overall Frequency Range 100 Modulation AM/ASK Modulation frequency MHz kHz P-P Incidental FM Output Power 50Ω load dBm ON/OFF Ratio dB PLL and Prescaler Prescaler Divie Ratio 64/128 VCO gain, KVCO Frequency and board layout dependent PLL Phase Noise 10KHz Offset, 50kHz loop bandwidth dBc/Hz 100KHz Offset, 50kHz loop bandwidth dBc/Hz with output tuning dBc Harmonics 20 Reference Frequency MHz/V 17 MHz crystal Frequency Spurs 50KHz PLL loop bandwidth MHz Max crystal Rs For a typ. 1ms turn-on time Ω Max crystal Motional Inductance For a typ. 1ms turn-on time mH Charge pump current ICP KPD=100uA/2Π µA 100 Power Down Control Power “ON” VTXEN Power “OFF” VTXEN Vcc-0.3V V 0.3 V Turn On Time 1 2 ms Turn Off Time 1 2 ms Page 4 March 2000 TX4915 the wireless IC company Functional Description The TX4915 is a low-cost AM/ASK VHF/UHF transmitter designed for applications operating within the frequency range of 100MHz to 960MHz. In particular, it is intended for 315/433MHz band systems remote keyless entry systems, and 868/915MHz ISM Application. It can also be used as a local oscillator signal source. The integrated VCO, phase detector, prescaler, and reference oscillator require only the addition of an external crystal to provide a complete phase-locked loop. In addition to the standard power-on mode, the chip also includes an autonatic lock-detect feature that disables the transmitter output when the PLL is outof-lock. The TX4915 Functional Blocks A PLL consists of a reference oscillator, a phase detector, a loop filter, a voltage control oscilator (VCO), and a programmable divider in the feedback path. The TX4915 includes all of these internally, except for the loop filter and the reference oscillator’s crystal and two feedback capacitors. Reference crystal oscillator Pins 1 (OSCIN) and 2 (OSCOUT) provide connections to a transistor that is used as a Colpitts type oscillator. The Colpitts configuration is a low parts count topology with realiable performance and reasonable phase noise. Alternatively, an external signal could be injected into the Pins 1 (OSCIN). The drive level should, in either case, be around 500mVpp. This level prevents overdriving the device and keeps the phase noise and reference spurs to a minimum. Voltage Controlled Oscillator VCO is a tuned differential amplifier with the bases and collectors cross-coupled to provide positive feedback and a 360° phase shift. The tuned circuit is located in the collectors, and is comprised of internal varactors and external inductors. The designer selects the inductors for the desired frequency of operation. These inductor also provide DC bias for the VCO. Prescaler Using a series of flip-flops divide the VCO frequency by either 64 or 128, depending upon the logic level present at the SW pin. A high logic level will select the 64 divider. A low logic level will select the 128 dividor. This divided signal is then fed into the phase detector where it is compared with the reference frequency. Phase dector and Charge pump Phase dector is implemented using flip-flops in “digital tri-state comparator” topology. It compares the phase of the reference oscillator to the phase of the VCO. The charge pump consists of two transistors, one for charging the loop filter and the other for discharging the loop filter. When both inputs of the flip-flops are identical, the signals are both frequency and phase locked. If they are different, they will provide signals to the charge pump which will either charge or discharge the loop filter, or enter into a high impedance state. Lock-detect Protection The Lock-detect circuitry connect to the output of the phase dector ciruits and is used to disable the transmitter when the VCO is not phase-locked to the reference oscillator. This is necessary to avoid unwanted outof-band transmission and to provide compliance with regulatory limits during an unlocked condition. Pin 15 (LD) is used to set the threshold of the lock-detect circuit. A shunt capacitor is used to set an RC time constant with an on-chip series 1KΩ resistor. The time constant should be approximately 15 times the reference period. Page 5 March 2000 TX4915 the wireless IC company Fig. 1 – PFD input/output waveforms fR fV DO high-Z high-Z high-Z high-Z Transmitte on LD Power Amplifier A two-stage amplifier consisting of a driver and an open collector final stage. The PAOUT open collector output requires an external pull up coil to provide bias. The coil is part of the tuning and matching LC circuit to get best performance with the external loop antenna. To achieve the best power amplifier efficiency the high frequency voltage swing at the PAOUT pin should be two times the supply voltage. The power amplifier has its own ground pin (VSS,VSS1) in order to reduce the aount of coupling to the other circuits. The device is an ASK/OOK transmitted, with the data provided at the MODIN pin. When the MODIN is a high logic level, the carrier is transmitted. When MODIN is a low logic level, then the carrier is not transmitted. Power Mode The IC provides three power modes, the POWER DOWN MODE, the PLL ENABLE MODE and the TRANSMIT MODE. How to get in this modes is described in the table below. TXEN MODIN L X POWER DOWN MODE H L PLL ENABLE MODE H H TRANSMIT MODE Page 6 March 2000 TX4915 the wireless IC company Application Circuit SW C16 XTAL C1 VCC L2 TXEN C3 OSCIN SW OSCOUT LD HiMARK TX4915 C4 C14 R4 C2 C5 C15 TXEN VSS L1 PAOUT VSS1 VCC1 MODIN C12 L4 DO VCC C13 R3 RES L3 RESB VREFP VSS2 VCC2 VCC R2 R1 C6 C7 C9 C8 C10 C11 MODIN Bill of Materials Component XTAL Frequency Band (MHz) 315 434 868 916.5 Unit Specification 4.92188 6.78125 6.78125 7.16016 MHz 1 68 68 68 68 pF 0603, +/-5 % C2 1 33 33 33 33 pF 0603, +/-5 % C3 2 4.7 pF 0603, +/-5 % C4 2 4.7 pF 0603, +/-5 % C5 3.3 pF 0603, +/-5 % C1 C6 100 100 100 100 pF 0603, +/-5 % C7 68 68 22 22 pF 0603, +/-5 % C8 10 10 10 10 nF 0603, +/-5 % C9 68 68 22 22 pF 0603, +/-5 % C10 10 10 10 10 nF 0603, +/-5 % C11 10 10 10 10 nF 0603, +/-5 % C12 68 68 22 22 pF 0603, +/-5 % C13 10 10 10 10 nF 0603, +/-5 % C14 1000 1000 470 470 pF 0603, +/-5 % C15 100 100 47 47 pF 0603, +/-5 % C16 18 18 18 18 nF 0603, +/-5 % R2 10 10 10 10 Ω 0603, +/-5 % R3 10 10 10 10 Ω 0603, +/-5 % R4 11 11 22 22 kΩ 0603, +/-5 % nH DELTA, 0805CS L1 2 Page 7 March 2000 TX4915 the wireless IC company Frequency Band (MHz) Component 315 434 868 916.5 Unit Specification nH DELTA, 0805CS L22 L3 18 18 8 8 nH DELTA, 0805CS L4 18 18 8 8 nH DELTA, 0805CS 1 Dependent on the crystal. 2 Dependent on the antenna and the PCB layout. Test Circuit SW C16 XTAL C1 TXEN C3 L2 OSCIN SW OSCOUT LD HiMARK TX4915 C4 C14 R4 C2 C5 C15 TXEN VSS PAOUT VSS1 L1 VCC1 C17 VCC C13 R3 RES L3 RESB VREFP VSS2 VCC2 VCC MODIN C12 L4 DO R2 VCC R1 C6 C7 C9 C8 C10 C11 MODIN Transmitter power (1)315MHz VCC Mod IN Res. Value (R1) ICC (mA) PAOUT (dBm) VCC Mod IN Res. Value(R1) ICC (mA) PAOUT (dBm) VCC Mod IN Res. Value(R1) 1K 1K 3K 3K 3K 5.1K 5.1K 5.1K 6.8K 6.8K 6.8K 9.1K 2.4V ICC (mA) PAOUT (dBm) 1K 9.1K 3V 9.1K 3.6V 11K 11K 11K 13K 13K 13K 15K 15K 15K 18K 18K 18K 22K 22K 22K Page 8 March 2000 TX4915 the wireless IC company (2)434MHz VCC Mod IN Res. Value (R1) ICC (mA) PAOUT (dBm) VCC Mod IN Res. Value(R1) ICC (mA) PAOUT (dBm) VCC Mod IN Res. Value(R1) 1K 1K 3K 3K 3K 5.1K 5.1K 5.1K 6.8K 6.8K 6.8K 9.1K 9.1K 2.4V ICC (mA) PAOUT (dBm) ICC (mA) PAOUT (dBm) ICC (mA) PAOUT (dBm) 1K 9.1K 3V 3.6V 11K 11K 11K 13K 13K 13K 15K 15K 15K 18K 18K 18K 22K 22K 22K (3)868MHz VCC Mod IN Res. Value (R1) ICC (mA) PAOUT (dBm) VCC 1K Mod IN Res. Value(R1) ICC (mA) PAOUT (dBm) VCC 1K Mod IN Res. Value(R1) 1K 3K 3K 3K 5.1K 5.1K 5.1K 6.8K 6.8K 6.8K 9.1K 9.1K 2.4V 9.1K 3V 3.6V 11K 11K 11K 13K 13K 13K 15K 15K 15K 18K 18K 18K 22K 22K 22K (4)916.5MHz VCC Mod IN Res. Value (R1) ICC (mA) PAOUT (dBm) VCC Mod IN Res. Value(R1) ICC (mA) PAOUT (dBm) VCC Mod IN Res. Value(R1) 1K 1K 1K 3K 3K 3K 5.1K 5.1K 5.1K 6.8K 6.8K 6.8K 9.1K 9.1K 2.4V 3V 9.1K 3.6V 11K 11K 11K 13K 13K 13K 15K 15K 15K 18K 18K 18K 22K 22K 22K Page 9 March 2000