FX118

CML Semiconductor Products PRODUCT INFORMATION FX118 Features/Applications Frequency Inversion Scrambling Full-Duplex Operation High Baseband and Carrier Rejection Audio Lowpass and Bandpass Filtering On-Chip Xtal Oscillator Stabilty Duplex Frequency Inverter for Cordless Telephones Publication D/118/3 July 1994 Low Power Requirement (3.0 Volt Minimum) Cordless Telephones Base and Handheld Applications Input Gain Adjustment Plastic DIL and S.O.I.C. Package Styles C1 AMP OUT LPF(1) LPF(1) OUT B MOD(1) IN BAL MOD (1) BPF(1) C1 IN C1 OUT +0.5dB INPUT AMP CHANNEL 1 (C1) -4.0dB +4.0dB V BIAS XTAL/CLOCK XTAL CLOCKS and LOGIC FILTER CLOCKS 111kHz CARRIER 3.3kHz V DD V BIAS V SS FX118 V BIAS INPUT AMP CHANNEL 2 (C2) -4.0dB C2 OUT C2 IN +0.5dB LPF(2) BAL MOD (2) +4.0dB BPF(2) C2 AMP OUT LPF(2) OUT B MOD(2) IN Fig.1 FX118 Duplex Frequency Inverter Brief Description The FX118 is a low-power, full-duplex frequency inverter available to provide voice privacy for cordless telephone systems by mixing the incoming audio with an internally produced carrier frequency (3.3kHz). This chip contains two completely separate audio channels (C1 and C2) each comprising a “componentadjustable” input amplifier, a 10th-order lowpass filter, a balanced modulator and a 14th-order bandpass filter output. The on-chip modulation process has the properties of high baseband and carrier frequency rejection which when combined with high-order output filtering, produces a high-quality recovered voiceband audio. 1 The frequency stability of the FX118 is achieved by an on-chip oscillator employing an external 4.433619MHz Xtal or clock input to produce the common carrier frequency and the sampling clocks for the switched capacitor low and bandpass filters. This microcircuit has a low power requirement of 3.0 volts (min.) and is encapsulated in either 16-pin DIL or small outline SMD (S.O.I.C.) plastic packages both of which are of a physical size suitable for either base or handset type telephone instruments as well as batteryportable and mobile communications systems. Pin Number FX118DW FX118P 1 Xtal: Output of clock oscillator inverter. Function 2 No Internal Connection: It is recommended that, to improve noise conditions, this pin is connected to VSS. 3 LPF(1) Out: The output of the Channel 1 Lowpass Filter. It is to be coupled to “B Mod(1) In” via a 1.0µF capacitor – see Figure 2. 4 B Mod(1) In: The input to Channel 1 balanced modulator. Internally biased at VDD/2 it is to be coupled to “LPF(1)” via a 1.0µF capacitor – see Figure 2. 5 VSS: Negative supply (GND). 6 C1 Out: The analogue output of Channel 1. 7 C1 Amp Output: Channel 1 amplifier with external components (see Figure 2) can be used to provide gain in the signal path. 8 C1 In: The negative input of Channel 1 Amplifier. Recommended external components are shown in Figure 2. 9 C2 In: The negative input of Channel 2 Amplifier. Recommended external components are shown in Figure 2. 10 C2 Amp Output: Channel 2 amplifier with external components (see Figure 2) can be used to provide gain in the signal path. 11 C2 Out: The analogue output of Channel 2. 12 VBIAS: The internal analogue bias line at VDD/2. It should be decoupled to VSS via a 1.0µF or greater capacitor. See Figure 2. 13 B Mod(2) In: The input to Channel 2 balanced modulator. Internally biased at VDD/2 it is to be coupled to “LPF(2)” via a 1.0µF capacitor – see Figure 2. 14 LPF(2) Out: The output of the Channel 2 Lowpass Filter. It is to be coupled to “B Mod(2) In” via a 1.0µF capacitor – see Figure 2. 15 VDD: The positive supply rail. A single positive supply voltage (3.0v – 5.0v) is required. Levels and voltages within the Duplex Frequency Inverter are dependent upon this supply. 16 Xtal/Clock: 4.433619 MHz Xtal or externally derived clock is injected at this pin. See Figure 2. Operation of the FX118 without a Xtal or clock input may cause device damage. 2 Application Information V DD C3 C2 X1 C1 R1 XTAL 1 2 16 15 14 13 XTAL/CLOCK V DD LPF(2) OUT B MOD(2) IN LPF(1) OUT 3 4 C4 B MOD(1) IN C8 VSS C1 OUT CHANNEL 1 OUTPUT CHANNEL 1 INPUT C1 IN FX118 5 6 7 8 12 11 10 9 VBIAS C C2 OUT C2 AMP OUT VSS R5 7 R3 C1 AMP OUT CHANNEL 2 OUTPUT CHANNEL 2 INPUT C2 IN C5 R2 R4 C6 VSS Component R1 R2 R3 C5 R4 R5 C6 C1 = Value 1.0MΩ See Note See Note 47pF C2 C3 C4 = 33pF 0.47µF 1.0µF C7 C8 X1 = 1.0µF 1.0µF 4.433619MHz Tolerances C = ±20% R = ±10% NOTES 1. Configurations R2, R3, C5 and R4, R5, C6 should be chosen with respect to the specific application. 2. Operation of any CML microcircuit without a Xtal or clock input may cause device damage. To minimise damage in the event of a Xtal/drive failure, it is recommended that the power rail (VDD) is fitted with a current limiting device (resistor or fast-reaction fuse). Fig.2 Recommended External Components Rx Channel RF AMP IF AMP DETECTION BASE UNIT FX118 DE-EMPHASIS AF AMP FM CHANNEL 1 (C1) RF AMP PREEMPHASIS CHANNEL 2 (C2) FM HYBRID TRANSFORMER AF AMP TELEPHONE LINE MODULATION Tx Channel Rx Channel RF AMP IF AMP DETECTION FX118 DE-EMPHASIS AF AMP FM CHANNEL 1 (C1) RF AMP PREEMPHASIS CHANNEL 2 (C2) FM AF AMP MODULATION Tx Channel HANDHELD UNIT Fig.3 Example of the FX118 Employed in a Cordless Telephone Application 3 Application Information ...... +5 0 -3 Gain dB -10 Audio Input Level = 275mVrms VDD = 3.75V -20 -30 -40 0.1 0.2 0.3 0.5 1.0 2.0 3.0 7.0 Frequency kHz Fig.4 Typical Audio Frequency Response of a Single Scrambled or De-scrambled Channel System Gains When calculating the external components for the operation of the FX118 the following points should be considered: (a) The Input Lowpass Filter has a (typical) gain of 0.5dB. (b) The Balanced Modulator has a (typical) attenuation of 4.0dB. (c) The Output Bandpass Filter has a (typical) gain of 4.5dB. How the Inverter Works Carrier Frequency minus Input Voice Frequency equals Scrambled Voice Frequency (1) (2) A B C Input Voiceband Frequencies Lowpass Filtered Voiceband for Input to Balanced Modulator D Speech Band 0 1000Hz 2000Hz 3000Hz (3) Carrier Frequency (3300Hz) Generated On-Chip for Input to Balanced Modulator (4) C D B A Bandpass Filtered Voiceband Presented at the Ouput after Mixing with the Carrier Frequency in the Balanced Modulator 0 1000 2000 3000 0 1000 2000 3000 3300 Fig.5 A Pictorial Explanation of the FX118 “Scramble Operation” 4 Specification Absolute Maximum Ratings Exceeding the maximum rating can result in device damage. Operation of the device outside the operating limits is not implied. Supply voltage Input voltage at any pin (ref VSS = 0V) Sink/source current (supply pins) (other pins) Total device dissipation @ TAMB 25°C Derating Operating temperature range: Storage temperature range: Operating Limits All device characteristics are measured under the following conditions unless otherwise specified: VDD = 3.75V. TAMB = 25°C. Xtal/Clock f0 = 4.433619MHz. Audio level 0dB ref: = 388mV rms @ 1.0kHz. Characteristics See Note Min. 3.0 – 1.0 – – – 10.0 – – – -16.0 – – – – – – – Typ. 3.75 4.0 10.0 2.0 200 10.0 – 10.0 10.0 10.0 – 30.0 -40.0 -55.0 -40.0 3299 -42.0 -46.0 Max. 5.5 6.0 – – – – – – – – 4.0 – – – – – – – Unit V mA MΩ kΩ Ω kΩ MΩ kΩ V/V MHz dB dB dB dB dB Hz dB dBp FX118DW/P FX118DW/P -0.3 to 7.0V -0.3 to (VDD + 0.3V) +/- 30mA +/- 20mA 800mW Max. 10mW/°C -40°C to +85°C -40°C to +85°C Static Values Supply Voltage Supply Current Input Impedance (Amplifiers) Output Impedance (LP Filters) Output Impedance (C1, C2 ) Output Impedance (C1, C2 Amps) On-Chip Xtal Oscillator RIN ROUT Inverter Gain Gain/Bandwidth Product Dynamic Values Analogue Signal Input Levels SINAD 6 Unwanted Modulation Products 1, 2 Carrier Breakthrough 1, 2 Baseband Breakthrough 1, 2 Carrier Frequency Analogue Output Noise 3 Analogue Output Noise 5 Filters Input Lowpass Filter 1 Cut-Off Frequency (-3dB) Passband Ripple (300Hz - 3kHz) Attenuation at 3.3kHz Attenuation at 3.6kHz Passband Gain Output Bandpass Filter 1, 4 Passband Frequencies Passband Ripple Low Freq. Roll-Off