TX4915

TX4915 ETC

Document overview

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Technical content

Features

/G75 Fully Integrated Frequency Synthesizer /G75 2.2V to 5.5V V oltage Supply Range /G75 Low Current and Power Down Capability /G75 Integrated VCO and Reference Oscillator /G75 integeated 64/128 Dual Modulus Prescaler /G75 100MHz to 960MHz frequency Range /G75 Out-of-Lock inhibit Circuit Package and Pin Assignment 16 pin, plastic SSOP (dimensions in mm) OSCIN OSCOUT TXEN VSS PAOUT VSS1 VCC1 MODIN SW LD DO RES RESB VREFP VSS2 VCC2 TX 915 HiM ARK 0.25−−−0.10A1 −−− 3.80 −−− 0.40 5.80 4.80 0.19 0.20 −−− y θ D e L E b C 0.10−−− −−− 8° −−− 0.64 −−− −−− −−− −−− 0.25 1.45 5.00 −−− 1.27 4.00 6.20 0.30 0.25 −−− DIMENSIONS IN MILLIMETERS 1.35 MIN SYMBOLS A 1.60 NOM MAX 1.75 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 θ 0.010−−−0.004 −−− 0.150 −−− 0.016 0.228 0.189 0.007 0.008 −−− 0.004−−− −−− 8° −−− 0.025 −−− −−− −−− −−− 0.010 0.057 0.197 −−− 0.050 0.157 0.244 0.012 0.010 −−− DIMENSIONS IN INCHES 0.053 MIN 0.064 NOM MAX 0.069 the wireless IC company TX4915 VHF/UHF TRANSMITTER HiMARK Technology, Inc. reserves the right to change the product described in this datasheet. All information con- tained 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.

1O S C I N 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. 3T X E N 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. 9V C C 2 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 cen-

ter 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 estab- lish 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 divide- by-128 prescsaler.

V SS =0V Recommended Operating Conditions V SS =0V Parameter Rating Unit Supply voltage – 0.3 to + 7.0 V DC Control V oltage – 0.3 to + 7.0 V DC 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 Parameter Symbol Va l u e Unit min. typ. max. Supply voltage range V CC 2.2 3.0 5.5 V Operating temperature TA –40 +25 +85 oC TXEN OSC IN OSC OUT PAOUT 2 113 12 SWLDMODIN RES RES OSC VCO PFD and Charge Pump DC BIAS Prescaler Lock Detect

Electrical Characteristics

(VDD1, DD2 =2 . 2t o5V ,VSS, SS1, SS2=0V ,T A = –40 to +85 °C unless otherwise noted) Parameter Symbol Condition TX4915 Capability(Simulated) UnitValue min. typ. max. Power supply Supply V oltage V CC1, V CC2 2.2 3 5 V Total dc Current (normal operation) IDC TXEN=high , 50% Duty Cycle 10kHz data applied to the MODIN input.RMODIN (R3)=3kΩ mA Total dc Current (stand-by mode) I standby TXEN = low 1 µA Overall Frequency Range 100 960 MHz Modulation AM/ASK Modulation frequency MHz Incidental FM kHz P-P Output Power 50 Ω load dBm ON/OFF Ratio dB PLL and Prescaler Prescaler Divie Ratio 64/128 VCO gain, K VCO Frequency and board layout depen- dent 20 MHz/V PLL Phase Noise 10KHz Offset, 50kHz loop band- width dBc/Hz 100KHz Offset, 50kHz loop band- width dBc/Hz Harmonics with output tuning dBc Reference Frequency 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 I CP K PD =100uA/2Π 100 µA Power Down Control Power “ON” V TXEN Vcc-0.3V V Power “OFF” V TXEN 0.3 V Turn On Time 12 m s Turn Off Time 12 m s

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 out- of-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 oscilla- tor. 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 feed- back and a 360° phase shift. The tuned circuit is located in the collectors, and is comprised of internal varac- tors 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 divi- dor. 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 transmit- ter when the VCO is not phase-locked to the reference oscillator. This is necessary to avoid unwanted out- of-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 con- stant with an on-chi p s eries 1KΩ resistor. The time constant should be approximately 15 times the reference period.

Fig. 1 – PFD input/output waveforms 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 ampli- fier 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 transmit- ted. 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 high-Z high-Z high-Z fR fV DO LD high-Z Transmitte on

Frequency Band (MHz) Unit Specification 315 434 868 916.5 XTAL 4.92188 6.78125 6.78125 7.16016 MHz C1 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 % 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 k Ω 0603, +/-5 % L1 2 nH DELTA, 0805CS HiMARK TX4915 OSCIN OSCOUT TXEN VSS PAOUT VSS1 VCC1 MODIN SW RES RESB VREFP VSS2 VCC2 DO LD V CC MODIN SW V CC TXEN XTAL C1 C3L2 C9 C10 C11 L4 C12 C13 C15 C14C16 V CC

1 Dependent on the crystal. 2 Dependent on the antenna and the PCB layout. Test Circuit Transmitter power (1)315MHz L2 2 nH DELTA, 0805CS L3 18 18 8 8 nH DELTA, 0805CS L4 18 18 8 8 nH DELTA, 0805CS V CC Mod IN Res. Va l u e ( R 1 ) ICC (mA) PAOUT (dBm) V CC Mod IN Res. Value(R1) ICC (mA) PAOUT (dBm) V CC Mod IN Res. Value(R 1) ICC (mA) PAOUT (dBm) 2.4V 3.6V 3K 3K 3K 5.1K 5.1K 5.1K 6.8K 6.8K 6.8K 9.1K 9.1K 9.1K 11K 11K 11K 13K 13K 13K 15K 15K 15K 18K 18K 18K 22K 22K 22K Component Frequency Band (MHz) Unit Specification 315 434 868 916.5 HiMARK TX4915 OSCIN OSCOUT TXEN VSS PAOUT VSS1 VCC1 MODIN SW RES RESB VREFP VSS2 VCC2 DO LD V CC MODIN SW V CC TXEN XTAL C1 C3L2C4 C9 C10 C11 L4 C12 C13 C15 C14C16 V CC C17

(2)434MHz (3)868MHz (4)916.5MHz V CC Mod IN Res. Va l u e ( R 1 ) ICC (mA) PAOUT (dBm) V CC Mod IN Res. Value(R1) ICC (mA) PAOUT (dBm) V CC Mod IN Res. Value(R 1) ICC (mA) PAOUT (dBm) 2.4V 3.6V 3K 3K 3K 5.1K 5.1K 5.1K 6.8K 6.8K 6.8K 9.1K 9.1K 9.1K 11K 11K 11K 13K 13K 13K 15K 15K 15K 18K 18K 18K 22K 22K 22K V CC Mod IN Res. Va l u e ( R 1 ) ICC (mA) PAOUT (dBm) V CC Mod IN Res. Value(R1) ICC (mA) PAOUT (dBm) V CC Mod IN Res. Value(R 1) ICC (mA) PAOUT (dBm) 2.4V 3.6V 3K 3K 3K 5.1K 5.1K 5.1K 6.8K 6.8K 6.8K 9.1K 9.1K 9.1K 11K 11K 11K 13K 13K 13K 15K 15K 15K 18K 18K 18K 22K 22K 22K V CC Mod IN Res. Va l u e ( R 1 ) ICC (mA) PAOUT (dBm) V CC Mod IN Res. Value(R1) ICC (mA) PAOUT (dBm) V CC Mod IN Res. Value(R 1) ICC (mA) PAOUT (dBm) 2.4V 3.6V 3K 3K 3K 5.1K 5.1K 5.1K 6.8K 6.8K 6.8K 9.1K 9.1K 9.1K 11K 11K 11K 13K 13K 13K 15K 15K 15K 18K 18K 18K 22K 22K 22K