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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
DIMENSIONS IN MILLIMETERS SYMBOLS
DIMENSIONS IN INCHES
A A1 A2 b C D E E1 e L y 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
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
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
Page 1
5 K1 R A9 M4 iX HT
K K K K K K K
Fully Integrated Frequency Synthesizer 2.2V to 5.5V Voltage Supply Range Low Current and Power Down Capability Integrated VCO and Reference Oscillator integeated 64/128 Dual Modulus Prescaler 100MHz to 960MHz frequency Range Out-of-Lock inhibit Circuit
Package and Pin Assignment
16 pin, plastic SSOP (dimensions in mm)
OSCIN 1 OSCOUT 2
16 SW 15 LD 14 DO 13 RES 12 RESB 11 VREFP 10 VSS2 9
VCC2
March 2000
the wireless IC company
TX4915
Pin Descriptions
Number 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Name OSCIN OSCOUT TXEN VSS PAOUT VSS1 VCC1 MODIN VCC2 VSS2 VREFP RESB RES DO Description This pin is connected directly to the base of reference oscillator transistor. The intended reference oscillator configuration is a modifiled Colpitts. This pin is connected directly to the emitter of reference oscillator transistor. 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. Ground connection for the PAOUT amp. Transmitter output. This pin is an open collector and require a pull-up inductor for bias/matching and a tapped capacitor for matching. Ground connection for the PAOUT buffer amplifier. This pin is used to supply bias to the PA buffer amplifier. 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. This pin is used to supply DC bias to the VCO, crystal oscillator, prescaler, PFD, and charge pump. Digital PLL ground connection. Bias voltage reference pin for bypassing the prescaler. The RES pins are used to supply DC voltage to the VCO, as well as to tune the center frequency of the VCO. see pin 12 Output of the charge pump. An RC network from this pin to ground is used to establish the PLL bandwidth. 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 1k resistor.This signal is used to clamp (enable or disable) the MODIN circuitry. The time constant should be approximately 15 times the reference period. Logic "High" input selects divide-by-64 prescaler. Logic "Low" input selects divideby-128 prescsaler.
15
LD
16
SW
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TX4915
Block Diagram
RES RES OSC IN OSC OUT
13
12
14
2
OSC
1
VCO PAOUT 5
PFD and Charge Pump DC BIAS Lock Detect Prescaler 64/128 2 TXEN
6
MODIN
5
LD
3
SW
Absolute Maximum Ratings
V SS = 0 V
Parameter Supply voltage Control Voltage Input RF Level Output Load VSWR Operating Ambient Temperature Storage Temperature Rating - 0.3 to + 7.0 - 0.3 to + 7.0 +10 -40 to +85 -40 to +85 -40 to +150 Unit VDC VDC dBm C C C
Recommended Operating Conditions
V SS = 0 V
Value Parameter Symbol min. Supply voltage range Operating temperature VCC TA 2.2 -40 typ. 3.0 +25 max. 5.5 +85 V
o
Unit
C
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TX4915
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 min. Power supply Supply Voltage Total dc Current (normal operation) IDC VCC1,VCC2 TXEN=high , 50% Duty Cycle 10kHz data applied to the MODIN input.RMODIN (R3)=3k TXEN = low 1 2.2 3 5 V Value typ. max. Unit
mA
Total dc Current (stand-by mode) Overall Frequency Range Modulation Modulation frequency Incidental FM Output Power ON/OFF Ratio PLL and Prescaler Prescaler Divie Ratio VCO gain, KVCO PLL Phase Noise
Istandby
A
100 AM/ASK
960
MHz
MHz kHz P-P 50 load dBm dB
64/128 Frequency and board layout dependent 10KHz Offset, 50kHz loop bandwidth 100KHz Offset, 50kHz loop bandwidth 20 MHz/V
dBc/Hz
dBc/Hz dBc 17 MHz MHz mH 100 A
Harmonics Reference Frequency crystal Frequency Spurs Max crystal Rs Max crystal Motional Inductance Charge pump current Power Down Control Power "ON" Power "OFF" Turn On Time Turn Off Time VTXEN VTXEN ICP
with output tuning
50KHz PLL loop bandwidth For a typ. 1ms turn-on time For a typ. 1ms turn-on time KPD=100uA/2
Vcc-0.3V 0.3 1 1 2 2
V V ms ms
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the wireless IC company
TX4915
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 eries 1K resistor. The time constant should be approximately 15 times the reference period.
s
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TX4915
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 L H H MODIN X L H POWER DOWN MODE PLL ENABLE MODE TRANSMIT MODE
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the wireless IC company
TX4915
Application Circuit
SW C16 XTAL C2 C5 VCC L2 C4 TXEN C3 L1 C1
OSCIN OSCOUT SW LD DO RES RESB VREFP VSS2 VCC2
C15 R4
C14
TXEN VSS PAOUT VSS1 VCC1 MODIN
L4 L3
C12
C13 R3
VCC
R2 R1 C6 C7 C8
HiMARK TX4915
VCC
C9
C10
C11
MODIN
Bill of Materials
Component XTAL C1
1 1 2 2
Frequency Band (MHz) 315 4.92188 68 33 434 6.78125 68 33 868 6.78125 68 33 916.5 7.16016 68 33 4.7 4.7 3.3 100 68 10 68 10 10 68 10 1000 100 18 10 10 11 100 68 10 68 10 10 68 10 1000 100 18 10 10 11 100 22 10 22 10 10 22 10 470 47 18 10 10 22 100 22 10 22 10 10 22 10 470 47 18 10 10 22
Unit MHz pF pF pF pF pF pF pF nF pF nF nF pF nF pF pF nF k nH
Specification
0603, +/-5 % 0603, +/-5 % 0603, +/-5 % 0603, +/-5 % 0603, +/-5 % 0603, +/-5 % 0603, +/-5 % 0603, +/-5 % 0603, +/-5 % 0603, +/-5 % 0603, +/-5 % 0603, +/-5 % 0603, +/-5 % 0603, +/-5 % 0603, +/-5 % 0603, +/-5 % 0603, +/-5 % 0603, +/-5 % 0603, +/-5 % DELTA, 0805CS
C2 C3 C4
C5 C6 C7 C8 C9 C10 C11 C12 C13 C14 C15 C16 R2 R3 R4 L12
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the wireless IC company
TX4915
Frequency Band (MHz) 315 434 868 916.5
Component L22 L3 L4
Unit nH
Specification DELTA, 0805CS DELTA, 0805CS DELTA, 0805CS
18 18
18 18
8 8
8 8
nH nH
1 Dependent on the crystal. 2 Dependent on the antenna and the PCB layout.
Test Circuit
SW C16 XTAL C2 C5 C4 L2 TXEN C3 C1
OSCIN OSCOUT SW LD DO RES RESB VREFP VSS2 VCC2
C15 R4
C14
TXEN VSS PAOUT
L4 L3
C12
C13 R3
VCC
HiMARK TX4915
L1 C17 VCC
VSS1 VCC1 MODIN
R2 R1 C6 C7 C8
VCC
C9
C10
C11
MODIN
Transmitter power (1)315MHz
VCC Mod IN Res. Value (R1) 1K 3K 5.1K 6.8K 9.1K 2.4V 11K 13K 15K 18K 22K 3V 11K 13K 15K 18K 22K ICC (mA) PAOUT (dBm) VCC Mod IN Res. Value(R1) 1K 3K 5.1K 6.8K 9.1K 3.6V 11K 13K 15K 18K 22K ICC (mA) PAOUT (dBm) VCC Mod IN Res. Value(R1) 1K 3K 5.1K 6.8K 9.1K ICC (mA) PAOUT (dBm)
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TX4915
(2)434MHz
VCC Mod IN Res. Value (R1) 1K 3K 5.1K 6.8K 9.1K 2.4V 11K 13K 15K 18K 22K 3V 11K 13K 15K 18K 22K ICC (mA) PAOUT (dBm) VCC Mod IN Res. Value(R1) 1K 3K 5.1K 6.8K 9.1K 3.6V 11K 13K 15K 18K 22K ICC (mA) PAOUT (dBm) VCC Mod IN Res. Value(R1) 1K 3K 5.1K 6.8K 9.1K ICC (mA) PAOUT (dBm)
(3)868MHz
VCC Mod IN Res. Value (R1) 1K 3K 5.1K 6.8K 9.1K 2.4V 11K 13K 15K 18K 22K 3V 11K 13K 15K 18K 22K ICC (mA) PAOUT (dBm) VCC Mod IN Res. Value(R1) 1K 3K 5.1K 6.8K 9.1K 3.6V 11K 13K 15K 18K 22K ICC (mA) PAOUT (dBm) VCC Mod IN Res. Value(R1) 1K 3K 5.1K 6.8K 9.1K ICC (mA) PAOUT (dBm)
(4)916.5MHz
VCC Mod IN Res. Value (R1) 1K 3K 5.1K 6.8K 9.1K 2.4V 11K 13K 15K 18K 22K 3V 11K 13K 15K 18K 22K ICC (mA) PAOUT (dBm) VCC Mod IN Res. Value(R1) 1K 3K 5.1K 6.8K 9.1K 3.6V 11K 13K 15K 18K 22K ICC (mA) PAOUT (dBm) VCC Mod IN Res. Value(R1) 1K 3K 5.1K 6.8K 9.1K ICC (mA) PAOUT (dBm)
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