TX4915 Low Power ASK Transmitter IC Princeton Technology Corp. reserves the right to change the product described in this datasheet. All information contained in this datasheet is subject to change without prior notice. Princeton Technology Corp. assumes no responsibility for the use of any circuits shown in this datasheet. Description The TX4915 is a low power ASK transmitter IC intended for applications in the North American and European VHF/UHF bands. The integrated voltage-controlled oscillator (VCO), phase/frequency detector, prescaler, and reference oscillator require only the addition of an external crystal to provide a complete phase-locked loop (PLL). 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 Output frequency range: 300 – 960 MHz Supply voltage range: 2.2 – 3.6 V Low current consumption with power down capability On-chip VCO with integrated PLL (÷ 64/128) dual modulus prescaler Out-of-lock inhibit circuit SSOP-16 package (0.64 mm pitch) Applications Wireless mouse Car alarm and home security systems Remote control systems Block Diagram SW LD DO RES RES NC VSS2 VCC2 16 15 14 13 12 11 10 9 LD VCO Prescaler ÷ 64/128 PFD and CP BIAS OSC AMP 1 2 3 4 5 6 OSC IN OSC OUT TXEN VSS TXOUT VSS1 For:Natertech Page 1 7 VCC1 8 MODIN March 2005 TX4915 Package and Pin Assignment SSOP-16 (0.64mm pitch) OSCIN 1 OSCOUT 2 16 SW HiMARK TX4915 TXEN 3 VSS 4 TXOUT 5 VSS1 6 VCC1 7 MODIN 8 Symbol Dimensions in mm 15 LD 14 DO 13 RES 12 RESB 11 VREFP 10 VSS2 9 VCC2 Dimensions in inches min. nom. max. min. nom. max. A 1.35 1.60 1.75 0.053 0.064 0.069 A1 0.10 — 0.25 0.004 — 0.010 A2 — 1.45 — — 0.057 — b 0.20 0.25 0.30 0.008 0.010 0.012 C 0.19 — 0.25 0.007 — 0.010 D 4.80 — 5.00 0.189 — 0.197 E 5.80 — 6.20 0.228 — 0.244 E1 3.80 — 4.00 0.150 — 0.157 e — 0.64 — — 0.025 — L 0.40 — 1.27 0.016 — 0.050 y — — 0.10 — — 0.004 θ 0° — 8° 0° — 8° For:Natertech Page 2 March 2005 TX4915 Pin Descriptions Number Name Description 1 OSCIN This pin is connected directly to the base of the reference oscillator transistor. The reference oscillator uses a modified Colpitts configuration. 2 OSCOUT This pin is connected directly to the emitter of the reference oscillator transistor. 3 TXEN Transmitter enable control (TXEN = low = power down mode; TXEN = high = normal operation mode). 4 VSS Ground connection for the transmit output amplifier. 5 TXOUT Transmitter output. This pin is an open collector output and requires a pull-up inductor for bias/matching and a tapped capacitor network for matching. 6 VSS1 Ground connection for the transmit driver amplifier. 7 VCC1 Nominal supply voltage for the transmit driver amplifier. 8 MODIN ASK modulation input. An external resistor, RMODIN, connected from the MODIN pin to supply voltage is used to bias the transmit amplifier chain. 9 VCC2 Nominal supply voltage for the VCO and PLL circuitry. 10 VSS2 Ground connection for the PLL circuitry. 11 NC No connection. 12 RES 13 RES 14 DO Output of the charge pump. An R-C network from this pin to ground is used to establish the PLL bandwidth. The DO pin is internally connected to the tuning voltage input of the VCO thru a 4 KΩ series resistor. 15 LD Lock detector output. This pin is used to set the threshold of the lock detect circuitry which enables or disables the transmit amplifier. A shunt capacitor should be used to set an R-C time constant with the on-chip series 1 KΩ resistor. The time constant should be set to approximately 15 times the reference period. 16 SW Prescaler modulus control input (SW = high = ÷ 64; SW = low = ÷ 128). Differential open collector VCO outputs. For:Natertech Page 3 March 2005 TX4915 Absolute Maximum Ratings VSS, VSS1, VSS2 = 0V Parameter Rating Unit Supply voltage range –0.3 to +3.6 V Power-down voltage –0.3 to VCC V MODIN voltage –0.3 to +1.1 V Operating ambient temperature –40 to +85 °C Storage temperature –40 to +150 °C Recommended Operating Conditions VSS, VSS1, VSS2 = 0V Parameter Symbol Value min. typ. max. Unit Supply voltage range VCC 2.2 3.0 3.6 V Operating temperature TA –10 +25 +60 o For:Natertech Page 4 C March 2005 TX4915 Electrical Characteristics (VCC = 3 V, VSS, VSS1, VSS2 = 0 V, TXEN = high, TA = 25 °C, and fRF = 433.92 MHz unless otherwise noted) Parameter Symbol Value Condition min. typ. max. 2.2 3.0 3.6 Unit Power supply Supply voltage VCC Total dc current (normal operation) ICC 50% duty cycle, 10 KHz data applied to the MODIN pin (RMODIN = 10 KΩ) 12.5 mA Istandby TXEN = low 1 µA Total dc current (power-down mode) V Overall RF output frequency range fRF 300 Modulation 960 MHz 100 KHz ASK Modulation frequency fMOD Output power POUT 50Ω load 1 ON/OFF ratio 6 dBm 70 dB PLL Prescaler divide ratio SW = high = ÷ 64 SW = low = ÷ 128 64 128 Frequency and board layout dependent 20 MHz/V 10 KHz offset, 50 KHz loop BW –80 dBc/Hz 100 KHz offset, 50 KHz loop BW –89 dBc/Hz 2nd harmonic –30 dBc 3rd harmonic –40 dBc 7 MHz VCO gain KVCO Phase noise Reference frequency Crystal frequency spurs Charge pump current 50 KHz PLL loop BW –50 ICP -100 -45 dBc 100 µA Stand-by mode control Transmitter enable/disable voltage TXEN = high = normal operation Vcc – 0.3 V V TXEN = low = power-down mode 0.3 V Turn-on time 1 2 ms Turn-off time 1 2 ms For:Natertech Page 5 March 2005 TX4915 Functional Description The TX4915 is a low-power ASK transmitter IC designed for applications operating within the frequency range of 300 to 960 MHz. In particular, it is intended for transmitter applications in 315/433 MHz band remote keyless entry and 868/915 MHz ISM-band systems. In addition, the TX4915 possesses a PLL-only mode which allows it to be simply used as a local oscillator source. The integrated voltage-controlled oscillator (VCO), phase/frequency detector, prescaler, and reference oscillator require only the addition of an external crystal to provide a complete phase-locked loop. In addition to the normal operation mode, the chip also includes an automatic lock-detect feature that disables the transmitter output when the PLL is outof-lock. Reference crystal oscillator The OSCIN and OSCOUT inputs (pins 1 and 2) provide connections to an on-chip transistor which may be used to implement a Colpitts crystal oscillator. The Colpitts oscillator configuration is a low parts count topology which achieves reasonable phase noise performance. Optionally, an external signal may be accoupled into the OSCIN pin to provide a reference source. The OSCIN input drive level should be near 500 mVpk-pk to prevent overdriving the on-chip transistor in order to keep the phase noise and reference spurs to a minimum. Voltage controlled oscillator The VCO uses a tuned differential amplifier topology with the bases and collectors cross-coupled to provide positive feedback and the necessary 360° phase shift. A tuned circuit is connected to the open collector outputs and is comprised of both on-chip varactors and user-selectable off-chip inductors. The choice of inductor values determines the frequency band of operation. Dual-modulus prescaler A series of flip-flops divides the VCO frequency by either 64 or 128, depending upon the logic level of the SW input (pin 16). SW = high will select the ÷ 64 mode and SW = low will select the ÷ 128 mode. The divided-down signal is then applied to the phase/frequency detector where its phase/frequency is compared with the phase/frequency of the crystal reference. Phase/frequency detector and charge pump The phase/frequency detector (PFD) is implemented using the “tri-state comparator” topology while the charge pump (CP) consists of a current source and sink for charging and discharging the off-chip loop filter. When the VCO and reference inputs to the PFD are both phase- and frequency-locked, the CP output enters a high impedance state. Otherwise, the CP will either charge or discharge the loop filter. Out-of-lock inhibit circuitry The out-of-lock inhibit circuitry is used to disable the transmitter output when the VCO is not locked to the reference oscillator and comply with regulatory limits during the unlocked condition. An off-chip shunt capacitor connected to the LD output (pin 15) is used to set an R-C time constant (together with an on-chip series 1 KΩ resistor.) This time constant should be set to be approximately 15 times the reference period. Transmit amplifier chain A transmit amplifier chain consists of a driver amplifier followed by an open collector output stage. The open collector TXOUT output (pin 5) requires an external pull-up inductor for bias. This inductor may be used as part of an L-C matching circuit for transforming the amplifier output impedance to that of an external loop antenna. To achieve optimum power-added efficiency, the peak-to-peak RF voltage swing at the TXOUT pin should be twice the supply voltage. Also, the output amplifier has its own ground pin (VSS) in order to improve isolation. The transmitter chain is designed for amplitude-shift-keying/on-off keying (ASK/OOK), with the modulation data provided at the MODIN input (pin 8). When VMODIN > 0.7 V, an output signal is transmitted, and when VMODIN < 0.7 V, no output signal is transmitted. For:Natertech Page 6 March 2005 TX4915 Operation modes The table below summarizes the TX4915’s three operating modes — power-down, PLL-only and transmit, which are controlled by the TXEN and MODIN inputs. TXEN MODIN Operation Mode L L Power-down H L PLL-only H > 0.7 V Transmit For:Natertech Page 7 March 2005 TX4915 Application Circuits fRF = 315 MHz DIV SW 4.921 MHz 1 100 pF 100 pF 5 82 nH 47 pF 6.8 pF 3.3 pF 50 Ω ustrip 50 Ω ustrip VCC 6 330 nH 100 Ω 7 220 pF 10 nF 8 VCC 10 Ω 1 nF OSCOUT TXEN VSS TX4915 4 TX OUT SW 16 1 nF 220 pF 2 3 POWER DOWN OSCIN PAOUT LD DO RES RESB 15 2.2 nF 4.7 K Ω 14 VCC 68 nH 13 100 Ω 220 pF 12 10 Ω 10 nF 68 nH 11 VSS1 NC VCC1 VSS2 10 MODIN VCC2 9 10K Ω 10 nF 220 pF 220 pF 10 nF fRF = 434 MHz DIV SW 6.78 MHz 1 100 pF 100 pF 5 56 nH 47 pF 5.6 pF 2.2 pF 50 Ω ustrip 50 Ω ustrip 6 330 nH VCC 100 Ω 10 nF 7 220 pF 8 VCC 10 Ω 1 nF 10 nF OSCOUT TXEN VSS TX4915 4 TX OUT SW 16 1 nF 220 pF 2 3 POWER DOWN OSCIN PAOUT LD DO RES RESB 15 4.7 K Ω 14 VCC 33 nH 13 100 Ω 220 pF 12 10 Ω 10 nF 33 nH 11 VSS1 NC VCC1 VSS2 10 MODIN VCC2 10K Ω 2.2 nF 9 220 pF 10 nF 220 pF For:Natertech Page 8 March 2005 TX4915 fRF = 868 MHz DIV SW 13.577 MHz 1 100 pF 100 pF 5 27 nH 22 pF 0.8 pF 2.2 pF 50 Ω ustrip 50 Ω ustrip VCC 6 180 nH 100 Ω 7 220 pF 10 nF 8 VCC 10 Ω 1 nF 10 nF OSCOUT TXEN VSS TX4915 4 TX OUT SW 16 1 nF 220 pF 2 3 POWER DOWN OSCIN PAOUT LD DO RES RESB 15 2.2 nF 10 K Ω 14 VCC 6.8 nH 13 100 Ω 220 pF 12 10 Ω 10 nF 6.8 nH 11 VSS1 NC VCC1 VSS2 10 MODIN VCC2 9 10K Ω 10 nF 220 pF 220 pF fRF = 916 MHz DIV SW 14.318 MHz 1 100 pF 100 pF 5 27 nH 22 pF 0.8 pF 2.2 pF 50 Ω ustrip 50 Ω ustrip 6 4.7 nH VCC 100Ω 10 nF 7 220 pF 8 VCC 10 Ω 1 nF 10 nF OSCOUT TXEN VSS TX4915 4 TX OUT SW 16 1 nF 220 pF 2 3 POWER DOWN OSCIN PAOUT LD DO RES RESB 15 14 VCC 5.6 nH 13 100 Ω 220 pF 12 10 Ω 10 nF 5.6 nH 11 VSS1 NC VCC1 VSS2 10 MODIN VCC2 3.3K Ω 2.2 nF 10 K Ω 9 220 pF 10 nF 220 pF For:Natertech Page 9 March 2005 TX4915 Typical Performance Characteristics Output Power vs. RMODIN (fRF = 433 MHz) RMODIN (Ω) VCC = 2.0 V VCC = 2.4 V VCC = 2.8 V VCC = 3.2 V VCC = 3.6 V ICC (mA) POUT (dBm) ICC (mA) POUT (dBm) ICC (mA) POUT (dBm) ICC (mA) POUT (dBm) ICC (mA) POUT (dBm) 1K 18.4 4.4 22.2 6.1 25.8 7.2 30.0 8.1 36.5 8.6 3K 16.7 4.6 19.6 6.0 21.3 7.1 24.0 8.1 26.7 9.0 5K 15.8 4.2 18.5 5.5 20.4 6.4 22.1 7.1 24.3 7.8 7K 15.1 3.6 17.7 4.9 19.6 5.7 20.7 6.4 22.3 7.1 9K 14.4 2.8 16.8 4.0 18.3 4.8 19.2 5.4 20.6 6.1 11 K 13.5 1.7 15.7 3.0 17.2 3.9 18.5 4.6 19.9 5.3 13 K 13.1 1.2 15.1 2.4 16.3 3.1 17.5 3.7 18.5 4.2 15 K 12.6 0.4 14.4 1.8 15.7 2.7 16.9 3.4 18.1 4.1 17 K 12.3 0.1 14.1 1.4 15.1 2.2 16.2 2.8 17.3 3.3 19 K 11.9 –0.6 13.5 0.9 14.7 1.8 15.8 2.5 16.9 3.1 21 K 11.5 –1.1 11.5 0.4 14.2 1.2 15.1 1.8 16.2 2.4 Phase Noise fRF = 433 MHz, VCC = 3.0 V, RMODIN = 3 KΩ, 10 KHz offset * RBW 1 kHz * VBW 10 Hz Ref 10 dBm Att 40 dB SWT 20 s 10 Marker 1 [T1 FXD] 0.99 dBm 433.874800000 MHz 1 0 1 SA CLRWR Delta 2 [T1 PHN] -91.90 dBc/Hz 10.000000000 kHz PHN 1.314 dBm * A -10 -20 -30 PRN -40 -50 2 -60 -70 -80 PHN -90 Center 433.8748 MHz Comment A: TX4915 Date: 29.AUG.2003 10 kHz/ Span 100 kHz 07:36:47 For:Natertech Page 10 March 2005 TX4915 fRF = 433 MHz, VCC = 3.0 V, RMODIN = 3 KΩ, 100 KHz offset * RBW 1 kHz * VBW 10 Hz Ref 10 dBm Att 40 dB SWT 40 s 10 1 0 1 SA CLRWR PHN 1.314 dBm Delta 2 [T1 PHN] -89.10 dBc/Hz 100.000000000 kHz Marker 1 [T1 FXD] 1.04 dBm 433.874800000 MHz A -10 -20 -30 PRN -40 -50 2 -60 -70 -80 PHN -90 Center 433.8748 MHz Comment A: TX4915 Date: 29.AUG.2003 20 kHz/ Span 200 kHz 07:35:59 Output Impedance VCC=2.0V VCC=3.3V VCC=3.0V Input Reflection Coefficient Zin916MHz Zin868MHz Zin315MHz Zin433MHz freq (300.0MHz to 1.000GHz) For:Natertech Page 11 March 2005