Obsolescence Notice This product is obsolete. This information is available for your convenience only. For more information on Zarlink’s obsolete products and replacement product lists, please visit http://products.zarlink.com/obsolete_products/ ZIF600 ZIF600 Pager Synthesiser and 4FSK Demodulator DS4771 - 1.2 October 1997 The ZIF600 synthesiser is for channel selection in 4FSK pagers. A reference frequency is generated by an on-chip crystal oscillator with an AFC external trimming varacator controlled by a DAC. RXQ 1 24 DSC2 RXI 2 23 DSC1 SRF 3 22 DATA DATA0 4 21 LE DATA1 5 20 CLOCK VSSD 6 19 VSSA VDDD 7 18 VCOFIN VREF 8 17 VDDA RBIAS 9 16 REFOSCB PDOUT 10 15 TSS PLLC 11 14 REFOSC DACOUT 12 13 VSSI The ZIF600 digital demodulator uses DSP techniques to optimise the data extraction in the presence of noise and also generates an AFC output to adjust the crystal frequency. Separate power controls allow the system current consumption to be minimised. All functions are controlled by a serial bus with a simple programming format and with four control pins which are used to control the power up and power down functions of the blocks to allow sequenced wake up and optimised power consumption. FEATURES ■ Low Voltage Operation, 2.7 to 3.3V ■ On-chip Reference Oscillator ■ Channel Select Synthesiser ■ Direct VCO input at up to 330MHz ■ 6400 Baud Digital 4FSK Demodulator ■ Serial Control Bus ■ Very Low Power Consumption ■ Small QSOP24 Package ZIF600 QP24 Fig.1 Pin connections - top view APPLICATIONS ■ Pagers - including small form factor designs such as credit card pagers, watch pagers and PCMCIA applications ■ Low data rate receivers - security/remote control ABSOLUTE MAXIMUM RATINGS To be defined. TSS VDDA VDDD DATA PLLC CONTROL LOGIC & POWER MANAGEMENT SRF CLOCK LE VREF DSC1 BIASES RBIAS DSC2 RXI DATA SLICER LIMI DATA0 DIGITAL DEMODULATOR RXQ AFC (DAC) LIMQ Demod. Clock REFOSC DACOUT REFERENCE DIVIDER REFOSB VCOFIN DATA1 PHASE DETECTOR TWO MODULUS PRESCALER VSSI PDOUT M AND A DIVIDERS VSSA VSSD Fig.2 ZIF600 block diagram 1 ZIF600 TARGET ELECTRICAL CHARACTERISTICS These characteristics are guaranteed over the following conditions (unless otherwise stated): VDDD, VDDA = 2.7 TO 3.3V, VDD1 = 0.95V to 1.6V (connected to REFOSCB via ext. resistor) and Tamb = —20 to + 70°C Characteristic Min. Typ. Max. Units Supply current at VDDD,VDDA = 3V - 1 - mA Supply current at VDD1 = 1.4V - 350 - µA VREF bias voltage input range 1.15 1.25 1.31 V Logic input HIGH, pins DATA, CLOCK, LE, DSC1, DSC2, PLLC, SRF, RXI, RXQ VDD - 0.3 - VDD + 0.3 V Logic input HIGH, pins DATA, CLOCK, LE, DSC1, DSC2, PLLC, SRF, RXI, RXQ VSS - 0.3 - VSS + 0.3 V Input capacitance (signal pins) - - 10 pF Pin voltage: VSS to VDD Input leakage (signal pins) - - 1 µA Pin voltage: VSS to VDD Control bus CLOCK frequency 0 - 10 MHz Synthesiser charge pump output leakage, pin PDOUT - 50 - nA Pin voltage: VSS to VDD Synthesiser charge pump output current, pin PDOUT 160 200 240 µA Pin VDD/2 Charge pump output compliance range, pin PDOUT VSS + 0.4 - VDD — 0.4 V Current within 10% of its value at VDD/2 Main synthesiser input frequency on VCOFIN 50 - 330 MHz VCOFIN input level 300 - 1000 mV pk - pk - 12.8 14.4 - MHz Logic output HIGH, pins DATA0, DATA1 VDD — 0.3 - VDD V Output current, IoH = 100µA Logic output LOW, pins DATA0, DATA1 VSS - VSS — 0.3 V Output current, IoL = 100µA. 0 - 2.375 V Not tested Output current 100nA VREF = 1.25V RXI, RXQ pull-up current 1.5 - - µA VDD — 0.3V RXI, RXQ pull-up current - - 40 µA VSS + 0.3V Input leakage (signal) pins with pull-downs - - 3 µA Pin voltage: VSS to VDD pins include SRF, PLLC DSC1, DSC2 Reference Frequency Crystal Trim DAC output voltage, pin DACOUT 2 Conditions Synthesiser locked and demodulator active. VDD1 connected to REFOSCB via external resistor. Pins REFOSC and REFOSCB ZIF600 DESCRIPTION OF FUNCTIONS Pin No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Pin Name RXQ RXI SRF DATA0 DATA1 VSSD VDDD VREF RBIAS PDOUT PLLC DACOUT VSS1 REFOSC TSS REFOSCB VDDA VCOFIN VSSA CLOCK LE DATA DSC1 DSC2 Pin Type In In In Out Out G P In In Out In Out G I/O In I/O P In G In In In In In Description Receiver "Quadrature" output Receiver "In Phase" output Symbol Rate Filter Data output to decoder Data output to decoder Digital Ground 2.7 to 3.3V Digital Power Supply 1.25 Volt Reference from ZIF100 Bias setting Resistor 120kΩ to VSSA max. parasitic capacitance = 5pF Charge pump output from synthesiser Synthesiser power down Trim DAC for crystal Ground (substrate) Reference Oscillator Test Scan Select, Normally logic 0 Reference Oscillator. External resistor to VDD1 2.7 to 3.3V Analog Power Supply VCO frequency input to synthesiser Analog Ground Control Bus Clock Control Bus Latch Enable Control Bus Data With DSC2 controls the operating mode of the demodulator With DSC1 controls the operating mode of the demodulator Table 1. List of pins FUNCTIONAL DESCRIPTION REFERENCE DIVIDERS The ZIF600 synthesiser is used to select the channel in 4FSK paging receivers and uses on-chip constant current charge pumps to drive an external passive loop filter. Common low cost reference crystals are used, at frequencies of 12.8 or 14.4MHz, and are divided to give the required 12.5, 20 or 25kHz channel spacings. The reference crystal oscillator uses external trimming to meet system requirements and is controlled by a DAC set by the digital demodulator. The reference frequency generated by the oscillator on pins REFOSC and REFOSCB is divided to give the comparison frequency clock. See Fig. 3. The digital demodulator takes the limited I and Q signals from the radio receiver and converts the 4-level FSK into 2 bit data output on pins DATA0 and DATA1. An AFC output from this demodulator is also included. Functions are controlled by a serial bus with a simple programming format and with four control pins to allow optimum power up sequences which help minimise the system current consumption. Crystal Comp. Total MHz freq. kHz division 12.8 25 512 14.4 25 576 12.8 20 640 14.4 20 720 12.8 12.5 1024 14.4 12.5 1152 12.8 10 1280 14.4 10 1440 RD1 RD2 RD3 0 1 0 1 0 1 0 1 0 0 1 1 0 0 1 1 0 0 0 0 1 1 1 1 Table 2 Reference divider ratios Ratio selection is five control bits RD1 (where LOW gives ÷ 8 mode), RD2 (where LOW gives ÷ 4 mode) and RD3 (where LOW gives ÷ 2 mode) which can be set to give the 8 options needed to get 10kHz, 12.5kHz, 20kHz or 25kHz from either a 12.8 or 14.4MHz crystal, as in Table 2. The additional control bits RD4 and RD5 allow the option of further division to allow for an off chip frequency multiplier. If both RD4 and RD5 are set low then this division stage is bypassed. Other settings for RD4 and RD5 offer division by 2, 3 or 4. Table 3 shows the additional division options available from RD4 and RD5. Power down options are available for both the synthesiser and demodulator, however the crystal oscillator and the reference divider must be kept running to give a timing signal to the demodulator whilst the demodulator is on. Additional division RD4 RD5 Bypass 2 3 4 0 0 1 1 0 1 0 1 Table 3 Additional divider ratios 3 ZIF600 200 kHz CLOCK TO DEMODULATOR CRYSTAL FREQUENCY 12·8 or 14·4 MHz ÷8 ÷ 8/9 ÷ 4/5 ÷ 2/4 ÷ 1/2/3/4 RD1 RD2 RD3 RD4 COMPARISON FREQUENCY RD5 Fig.3 Reference divider configuration SYNTHESISER The Synthesiser divides the VCOFIN frequency by the 16bit number FCH programmed from the serial bus and then the phase detector compares the result with the comparison frequency signal to generate correction pulses. The division ratio range is 4,032 to 65,535. An embedded two modulus prescaler is used to minimise power consumption but its programming is arranged to be transparent to the user. By using a digital phase and frequency detector the loop will pull in over an unlimited range and then by using a reset signal fed back from the output current drivers any delays in the output path do not give a dead band in the phase response. The charge pump currents are set by internal biasing. The current level fixed by the circuit has been selected to give minimum loop disturbance from external interference, while also not taking excessive current from the supply line. It is expected that adequate high frequency decoupling will be provided on the power supplies to eliminate any significant noise. Powering up the synthesiser requires that VREF, IBIAS and PLLC have been turned on for an adequate time before the synthesiser is required to be functioning. As the demodulator takes its clock from the synthesiser reference divider, the synthesiser reference oscillator and divider circuits must be on and have settled before the demodulator is turned on. Setting the "DMO" bit in the control bus allows the main parts of the synthesiser to be kept in a low power mode with only the reference oscillator and reference divider operating, when PLLC is high. This effectively allows the demodulator to be used standalone with its required clock being provided by the reference oscillator/divider. COMPARISON FREQUENCY (FROM REFERENCE DIVIDER) Φ UP PHASE DETECTOR PDOUT Φ DOWN 16 BIT DIVIDER VCOFIN CHARGE PUMP RESET FCH FROM BUS (16 bit) Fig.4 Basic block diagram of synthesiser "DMO" bit 0 1 0 1 PLLC 0 0 1 1 Synthesiser Mode Synthesiser off Synthesiser off Synthesiser on Reference oscillator and divider on, remainder of synthesiser circuitry off Table 4. Synthesiser mode control 4 ZIF600 DIGITAL DEMODULATOR By using digital signal processing techniques it is possible to get a very robust demodulator for 4-level FSK. The demodulator produces a digital level depending on the received frequency. A digital data slicer is used to encode the DATA0 and DATA1 signals. Extra functions are included to give an AFC signal to the 8 bit Trim DAC for the crystal oscillator. The DAC output will lag the incoming data, and will require some external filtering to smooth DAC transitions (it is recommended to connect a 10µF capacitor from DACOUT to Ground). The demodulator receives "I" and "Q" signals from the ZIF100. Fig.5 shows the DATA0 and DATA1 response to a 4 level I/Q input at ±4.8kHz from te ZIF100. Table 5 maps the input frequency represented by the I/Q demodulator inputs to the DATA0 and DATA1 outputs. The decoder will recover the symbol clock and sample the DATA0 and DATA1 signals at the appropriate time. DATA1 will have multiple edges during symbol transmissions. Symbol Transitions I (4.8KHz) Q Jitter DATA0 DATA1 Typical Sampling Point Fig.5 Response of DATA0 and DATA1 to a ±4.8kHz I/Q input DATA1 DATA0 1 1 0 0 0 1 1 0 Frequency Deviation +4.8kHz +1.6kHz —1.6kHz —4.8kHz In a typical application the ZIF600 receives real time control from a decoder interface and provided the decoder with DATA0 and DATA1. Fig.6 illustrates the sequence of applied signals from the Decoder in a typical application. Note that other system ICs will require additional contol, and this may affect the sequencing given. Table 5. Frequency map for DATA output pins DSC2 DSC1 0 1 0 1 0 0 1 1 Demodulator Mode Off, Hold Data Slicing and AFC loop values On, Fast Tracking for Data Slicingand AFC loop On, Slow Tracking for Data Slicingand AFC loop Off, Hold applied to Data Slicing and AFC loop values Table 6. Demodulator mode control SRF 0 1 Symbol Rate Symbol Rate Filter 1600sps Symbol Rate Filter 3200sps Table 7. Symbol rate filter control 5 ZIF600 45mS Signal Previous Signal ZIF 600 Mode Off 20mS 70mS 25mS "A" -> Frame Sync 2 Info BS1 Fast PLL Settle Track 1·76 Sec. Block 0 Slow Track Block 10 Next Signal Hold Off 1.25v VREF 0v PLLC DSC1 DSC2 SRF All Off Track On VREF On Fast SRF=1600 XTAL On Demod. On Synth. On Synth.On Demod. Off Fast AFC On Hold Track SRF=1600/3200 Demod. On Synth.On Hold AFC Slow Track On SRF=1600 or 3200 Demod. On Synth.On Slow AFC On SRF=1600 Demod. Off Synth.On Hold AFC All Off Fig.6 Control signal timing diagram for ZIF600 receiving data CONTROL BUS The ZIF600 has its synthesiser and demodulator configured by a three wire control bus (CLOCK, DATA, LE). The ZIF600 must have these commands applied to it before it can be used. Each command must be complete. Data is clocked into the ZIF600 on the rising edg of the clock. Data is latched into the internal registers when ENABLE is high. Since the ENABLE pin gives a direct load and also resets some circuits, there will be a phase discontinuity if data is loaded after the synthesser has settled. The bus clock does not need to run between messages and to minimise interference to radio receiver circuits it is recommended that the clock is stopped whenever it is not needed. Fig. 7 shows the format of the control bus. th 20nS ts tpw tse 20nS 50nS 20nS Control bus timing (provisional) CLOCK DATA B15 B0 LE CLOCK DATA LE th ts tpw Fig.7 Control bus waveforms 6 tse tpe ADD tpe 50nS ZIF600 PROGRAMMING FORMAT (PRELIMINARY) Time Order First...... Bit No. (B) 15 14 ...Last 13 12 11 10 9 Synthesiser 8 7 6 5 4 3 2 1 0 FCH "0" System Set-up "0" "0" "0" "0" "0" "0" "0" "0" ADD "0" "0" DMO RD5 RD4 RD3 RD2 RD1 "0" "1" Table 8. Programming format Within each field parameters are ordered MSB first and thenin descending order. Data is retained by ZIF600 until VDDD is removed. Name FCH Length 16 bit word RD5 -> RD1 5 Bits DMO 1 Meaning Synthesiser programmable divider ratio programming word to set crystal reference division ratio Demodulator only operation. Set to "1" to power up only the reference oscillator and divider with "PLLC" pin, generating demod. clock & leaving the remainder of PLL in power down. Table 9. Control bus bit definitions APPLICATIONS INFORMATION By using constant current charge pumps the synthesiser loop filter is purely passive. See Fig.8. It is recommended that the primary filter is placed as close to the synthesiser circuit as possible to minimise interference caused by charge pump current pulses. The high frequency clean-up filter, if needed at all, can be placed nearer the VCO as required for board layout. Suggested component values for ∆kHz comparison frequency with a 5MHz/volt VCO are: R1 = 15kΩ To VCO PDOUT RF R1 CP CF C1 PRELIMINARY FILTER C1 = 220nF CP = 18nF Fig.8 Typical synthesiser loop filter RF = 47kΩ CF = 1.8nF 7 For more information about all Zarlink products visit our Web Site at www.zarlink.com Information relating to products and services furnished herein by Zarlink Semiconductor Inc. or its subsidiaries (collectively “Zarlink”) is believed to be reliable. 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