Ordering number : EN5743 CMOS IC LC72137, 72137M PLL Frequency Synthesizer for Electronic Tuning Overview Package Dimensions The LC72137 and LC72137M are PLL frequency synthesizers for use in radio/cassette players. They allow high-performance AM/FM tuners to be implemented easily. unit: mm 3059-DIP22S [LC72137] Features • High-speed programmable frequency divider — FMIN: 10 to 160 MHz.....Pulse swallower (divide-by-two prescaler built in) — AMIN: 2 to 40 MHz.........Pulse swallower 0.5 to 10 MHz......Direct division • IF counter IFIN: 0.4 to 12 MHz................For use as an AM/FM IF counter • Reference frequency — Selectable from one of eight frequencies (crystal oscillator: 75 kHz) 1, 3, 5, 3.125, 6.25, 12.5, 15, and 25 kHz • Phase comparator — Supports dead zone control — Built-in unlock detection circuit — Built-in deadlock clear circuit • Built-in MOS transistor for forming an active low-pass filter • I/O ports — Dedicated output ports: 4 — I/O ports: 2 — Supports clock time base output • Serial Data I/O — Supports CCB format communication with the system controller. • Operating ranges — Supply voltage: 2.5 to 3.6 V — Operating temperature: –20 to +70°C • Packages —DIP22S/MFP20 SANYO: DIP22S unit: mm 3036B-MFP20 [LC72137M] SANYO: MFP20 • CCB is a trademark of SANYO ELECTRIC CO., LTD. • CCB is SANYO’s original bus format and all the bus addresses are controlled by SANYO. SANYO Electric Co.,Ltd. Semiconductor Bussiness Headquarters TOKYO OFFICE Tokyo Bldg., 1-10, 1 Chome, Ueno, Taito-ku, TOKYO, 110-8534 JAPAN 70398RM(OT) No. 5743-1/23 LC72137, 72137M Specifications Absolute Maximum Ratings at Ta = 25°C, VSS = 0 V Parameter Symbol Maximum supply voltage Maximum input voltage Maximum output voltage Maximum output current Ratings Unit VDD –0.3 to +7.0 VIN1 max CE, CL, DI, AIN –0.3 to +7.0 V VIN2 max XIN, FMIN, AMIN, IFIN –0.3 to VDD + 0.3 V V VIN3 max IO1, IO2 –0.3 to +15 V VO1 max DO –0.3 to +7.0 V VO2 max XOUT, PD VO3 max BO1 to BO5, BOF, IO1, IO2, AOUT IO max Allowable power dissipation Conditions VDD max Pd max –0.3 to VDD + 0.3 V –0.3 to +15 V BO1 to BO4, IO1, IO2, DO, AOUT Ta ≤ 70°C: LC72136N (DIP22S) Ta ≤ 70°C: LC72136NM (MFP20) 0 to 6.0 mA 350 mW 180 mW Operating temperature Topr –20 to +70 °C Storage temperature Tstg –40 to +125 °C Allowable Operating Ranges at Ta = –20 to +70°C, VSS = 0 V Parameter Symbol Ratings Conditions min Supply voltage Input high-level voltage Input low-level voltage Output voltage Input frequency Guaranteed crystal oscillator frequency Unit max VDD VDD 2.5 3.6 V VIH1 CE, CL, DI 0.7 VDD 6.5 V VIH2 IO1, IO2 0.7 VDD 13 V VIL CE, CL, DI, IO1, IO2 0 0.3 VDD V V O1 DO 0 6.5 V V O2 BO1 to BO4, IO1, IO2, AOUT 0 fIN1 XIN: VIN1 13 75 V kHz fIN2 FMIN: VIN2 fIN3 AMIN: VIN3, SNS = 1 fIN4 AMIN: VIN4, SNS = 0 0.5 10 MHz fIN5 IFIN: VIN5 0.4 12 MHz XIN: fIN1 VIN1 Input amplitude typ 10 160 MHz 2 40 MHz 200 800 mVrms VIN2-1 FMIN: f = 10 to 130 MHz 20 800 mVrms VIN2-2 FMIN: f = 130 to 160 MHz 40 800 mVrms VIN3 AMIN: fIN3, SNS = 1 40 800 mVrms VIN4 AMIN: fIN4, SNS = 0 40 800 mVrms VIN5-1 IFIN: fIN5, IFS = 1 40 800 mVrms VIN5-2 IFIN: fIN6, IFS = 0 70 800 mVrms Xtal XIN, XOUT * 75 kHz * Note : Recommended crystal oscillator CI value : CI ≤ 35 kΩ No. 5743-2/23 LC72137, 72137M Electrical Characteristics within the allowable operating ranges Parameter Symbol Ratings Conditions min Internal feedback resistors Internal pull-down resistors Internal output resistor XIN 8.0 MΩ Rf2 FMIN 500 kΩ Rf3 AMIN 500 kΩ Rf4 IFIN 250 kΩ Rpd1 FMIN 200 kΩ Rpd2 AMIN 200 kΩ Rd XOUT 250 kΩ VHIS CE, CL, DI, IO1, IO2 Output high-level voltage VOH1 PD: IO = –1 mA VOL1 PD: IO = 1 mA Input high-level voltage Input low-level current Output off leakage current Unit max Rf1 Hysteresis Output low-level voltage typ 0.1 VDD V VDD – 1.0 V 1.0 V BO1 to BO4, IO1, IO2; IO = 1 mA 0.25 V BO1 to BO4, IO1, IO2; IO = 5 mA 1.25 V VOL3 DO: IO = 1 mA 0.25 V VOL4 AOUT, AIN = 1.3 V VOL2 0.5 IIH1 CE, CL, DI: VI = 6.5 V 5.0 µA IIH2 IO1, IO2: VI = 13 V 5.0 µA IIH3 XIN: VI = VDD 0.16 0.9 µA IIH4 FMIN, AMIN: VI = VDD 2.5 15 µA IIH5 IFIN: VI = VDD 5.0 30 µA IIH6 AIN: VI = 6.5 V 200 nA IIL1 CE, CL, DI: VI = 0 V 5.0 µA IIL2 IO1, IO2: VI = 0 V IIL3 XIN: VI = 0 V IIL4 IIL5 IIL6 AIN: VI = 0 V 200 nA IOFF1 BO1 to BO4, AOUT, IO1, IO2: VO = 13 V 5.0 µA 5.0 µA 5.0 µA 0.16 0.9 µA FMIN, AMIN: VI = 0 V 2.5 15 µA IFIN: VI = 0 V 5.0 30 µA IOFF2 DO: VO = 6.5 V High-level three-state off leakage current IOFFH PD: VO = VDD 0.01 200 nA Low-level three-state off leakage current IOFFL PD: VO = 0 V 0.01 200 nA 6 mA Input capacitance Current drain CIN FMIN IDD1 VDD: Xtal = 75 kHz, fIN2 = 130 MHz, VIN2 = 20 mVrms 2.5 IDD2 VDD: PLL block stopped (PLL inhibit), Xtal oscillator operating (Xtal = 75 kHz) 20 IDD3 VDD: PLL block stopped, Xtal oscillator stopped 6 pF mA 10 µA No. 5743-3/23 LC72137, 72137M Pin Assignments No. 5743-4/23 LC72137, 72137M Block Diagram No. 5743-5/23 LC72137, 72137M Pin Descriptions Symbol Pin No. (MFP pin numbers are in parentheses.) XIN 20 (19) XOUT 21 (21) FMIN 13 (12) Type Functions Xtal • Crystal oscillator connections (75 kHz) Local oscillator signal input • FMIN is selected when the serial data input DVS bit is set to 1. • The input frequency range is from 10 to 160 MHz. • The input signal passes through the internal divide-bytwo prescaler and is input to the swallow counter. • The divisor can be in the range 272 to 65535. However, since the signal has passed through the divide-by-two prescaler, the actual divisor is twice the set value. Local oscillator signal input • AMIN is selected when the serial data input DVS bit is set to 0. • When the serial data input SNS bit is set to 1: — The input frequency range is 2 to 40 MHz. — The signal is directly input to the swallow counter. — The divisor can be in the range 272 to 65535, and the divisor used will be the value set. • When the serial data input SNS bit is set to 0: — The input frequency range is 0.5 to 10 MHz. — The signal is directly input to a 12-bit programmable divider. — The divisor can be in the range 4 to 4095, and the divisor used will be the value set. AMIN 12 (11) CE 2 (1) Chip enable • Set this pin high when inputting (DI) or outputting (DO) serial data. DI 3 (2) Input data • Inputs serial data transferred from the controller to the LC72137. CL 4 (3) Clock • Used as the synchronization clock when inputting (DI) or outputting (DO) serial data. DO 5 (4) Output data • Outputs serial data transferred from the LC72137 to the controller. The data output is determined by the DOC0 to DOC2 bits in the serial data. VDD 15 (14) Power supply • The LC72137 power supply pin. (VDD = 2.5 to 3.6 V) • The power on reset circuit operates when power is first applied. VSS 16 (15) Ground • The LC72137N ground Circuit configuration Continued on next page. No. 5743-6/23 LC72137, 72137M Continued from preceding page. Symbol Pin No. (MFP pin numbers are in parentheses.) BO1 6 (5) BO2 7 (6) BO3 8 (7) BO4 14 (13) IO1 9 (8) IO2 10 (9) PD 17 (16) AIN 18 (17) AOUT 19 (18) Type Functions Output ports • Dedicated outputs • The output states are determined by the BO1 to BO5 bits in the serial data. Data: 0 = open, 1= low • A time base signal (8 Hz) can be output from the BO1 pin. (When the serial data TBC bit is set to 1.) Input or output ports • I/O dual-use pins • The direction (input or output) is determined by bits IOC1 and IOC2 in the serial data. Data: 0 = input port, 1 = output port • When specified for use as input ports: The state of the input pin is transmitted to the controller over the DO pin. Input state: low = 0 data value high = 1 data value • When specified for use as output ports: The output states are determined by the IO1 and IO2 bits in the serial data. Data: 0 = open, 1 = low • These pins function as input pins following a power on reset. Charge pump output • PLL charge pump output When the frequency generated by dividing the local oscillator signal frequency by N is higher than the reference frequency, a high level is output from the PD pin. Similarly, when that frequency is lower, a low level is output. The PD pin goes to the high-impedance state when the frequencies match. LPF amplifier transistor connections • The n-channel MOS transistor used for the PLL active low-pass filter. IFIN 10 (9) IF counter • Accepts an input in the frequency range 0.4 to 12 MHz. • The input signal is directly transmitted to the IF counter. • The result is output starting the MSB of the IF counter using the DO pin. • Four measurement periods are supported: 4, 8, 16, and 32 ms. NC 1 (–) 22 (–) NC Pin • No connection Circuit configuration No. 5743-7/23 LC72137, 72137M Serial Data I/O Procedures The LC72137 inputs and outputs data using the Sanyo CCB (computer control bus) audio IC serial bus format. This IC adopts an 8-bit address format CCB. I/O mode Address B0 B1 B2 B3 A0 A1 A2 A3 Function 1 IN1 (82) 0 0 0 1 0 1 0 0 • Control data input mode (serial data input) • 24 data bits are input. • See the “DI Control Data (serial data input) Structure” item for details on the meaning of the input data. 2 IN2 (92) 1 0 0 1 0 1 0 0 • Control data input mode (serial data input) • 24 data bits are input. • See the “DI Control Data (serial data input) Structure” item for details on the meaning of the input data. 0 • Data output mode (serial data output) • The number of bits output is equal to the number of clock cycles. • See the “DO Output Data (Serial Data Output) Structure” item for details on the meaning of the output data. 3 OUT (A2) 0 1 0 1 0 1 0 No. 5743-8/23 LC72137, 72137M DI Control Data (serial data input) Structure 1. IN1 Mode 2. IN2 Mode No. 5743-9/23 LC72137, 72137M DI Control Data Descriptions No. Control block/data Description Related data Programmable divider data • Data that sets the programmable divider P0 to P15 A binary value in which P15 is the MSB. The LSB changes depending on DVS and SNS. (*: Don’t care.) DVS SNS LSB Divisor setting (N) 1 * P0 272 to 65535 Actual divisor 0 1 P0 272 to 65535 The value of the setting 0 0 P4 4 to 4095 The value of the setting Twice the value of the setting Note: P0 to P3 are ignored when P4 is the LSB. (1) DVS, SNS • Selects the signal input pin (AMIN or FMIN) for the programmable divider, switches the frequency range. (*: Don’t care.) DVS SNS Input pin Input frequency range 1 * FMIN 10 to 160 MHz 0 1 AMIN 2 to 40 MHz 0 0 AMIN 0.5 to 10 MHz Note: See the “Programmable Divider” item for details. Reference divider data R0 to R3 (2) • Reference frequency (fref) selection data R3 R2 R1 R0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 0 0 1 1 0 0 1 1 0 1 0 1 0 1 0 1 Reference frequency (kHz) 1 1 1 1 0 0 0 0 0 0 1 1 0 1 0 1 5 5 5 1 1 1 1 1 0 0 0 1 3 15 1 1 1 0 PLL INHIBIT + Xtal OSC STOP 1 1 1 1 PLL INHIBIT 25 25 25 25 12.5 6.25 3.125 3.125 Note: PLL INHIBIT The programmable divider and IF counter blocks are stopped, the FMIN, AMIN, and IFIN pins go to the pulled-down state, and the charge pump output pin goes to the high-impedance state. IF counter control data CTE • IF counter measurement start specification CTE = 1: Counter start CTE = 0: Counter reset GT0, GT1 • IF counter measurement time determination (3) GT1 GT0 0 0 Measurement time (ms) Wait time (ms) 4 3 to 4 0 1 8 3 to 4 1 0 16 7 to 8 1 1 32 7 to 8 IFS Note: See the “IF Counter Structure” item for details. (4) (5) I/O port specification data IOC1, IOC2 • Data that specifies input or output for the I/O dual-use pins (IO1, IO2) Data: 0 = input mode, 1 = output mode Output port data BO1 to BO4, IO1, IO2 • BO1 to BO4, IO1, and IO2 output state data Data: 0 = open, 1 = low • “Data = 0: Open” is selected following a power-on reset. IOC1 IOC2 Continued on next page. No. 5743-10/23 LC72137, 72137M Continued from preceding page. No. Control block/data DO pin control data DOC0, DOC1, DOC2 Description Related data • Data that determines DO pin output DOC2 DOC1 DOC0 0 0 0 0 0 0 1 1 0 1 0 1 Open Low when the unlock state is detected end-UC*1 Open DO pin state 1 1 1 1 0 0 1 1 0 1 0 1 Open The IO1 pin state*2 The IO2 pin state*2 Open The open state is selected following a power-on reset. Note: 1. end-UC: IF counter measurement completion check UL0, UL1, CTE, IOC1, IOC2 (6) ➀ When end-UC is set and an IF count is started (CTE = 0 → 1), the DO pin automatically goes to the open state. ➁ When the IF count measurement completes, the DO pin goes low and the count completion check operation is enabled. ➂ The DO pin goes to the open state due to serial data I/O (CE: high). 2. Goes to the open state if the IO pin itself is set to be an output port. Caution: The DO pin always goes to the open state during the data input period (during the period when CE is high in mode IN1 or IN2), regardless of the values of the DO pin control data (DOC0 to DOC2). Also, the DO pin outputs the content of the internal DO serial data in synchronization with the CL pin signal during the data output period (during the period when CE is high in the OUT mode) regardless of the values of the DO pin control data (DOC0 to DOC2). Unlock detection data UL0, UL1 • Selects the phase error (øE) detection range for PLL lock discrimination. When a phase error greater than the specified range occurs, the LC72136N determines that the PLL is unlocked. (*: Don’t care.) UL1 (7) UL0 øE detection width Detector output 0 0 Stopped Open 0 1 0 øE is output directly 1 * ±6.67 µs øE is extended by 1 to 2 ms DOC0, DOC1, DOC2 Note: When unlocked, the DO pin goes low and the serial data output UL bit is 0. Phase comparator control data DZ0, DZ1 (8) • Phase comparator dead zone control data DZ1 DZ0 0 0 Dead zone mode DZA 0 1 DZB 1 0 DZC 1 1 DZD Dead zone width: DZA < DZB < DZC < DZD (9) Clock time base TBC • An 8 Hz 40% duty clock time base signal can be output from BO1 by setting TBC to 1. (The BO1 data will be ignored.) Charge pump control data DLC • Data that forcibly controls the charge pump output DLC (10) 0 BO1 Charge pump output Normal operation 1 Forced low Note: The LC72137 provides a technique for escaping from deadlock by setting Vtune to VCC (deadlock clear circuit). This is used when the circuit is deadlocked due to the VCO oscillator being stopped by the VCO control voltage (Vtune) being 0 V. Continued on next page. No. 5743-11/23 LC72137, 72137M Continued from preceding page. No. Control block/data (11) IF counter control data IFS LSI test data TEST 0 to TEST2 (12) Description Related data • This data should be set to 1 in normal operation. Setting this data to 0 switches the LC72137 to a reduced input sensitivity mode in which the sensitivity is reduced by 10 to 30 mVrms. • IC test data TEST0 TEST1 All three bits must be set to 0. TEST2 All the test data is set to 0 at a power-on reset. (13) DNC Data is set to 0 DO Output Data (Serial Data Output) Structure 3. OUT mode DO Output Data No. Control block/data I/O port data I2, I1 (1) Description • Data latched from the states of the I/O ports, pins IO1 and IO2. • This data reflects the pin states, regardless of whether they are in input or output mode. • The data is latched when OUT mode is selected. I1 ← IO1 pin state I2 ← IO2 pin state Related data IOC1, IOC2 High: 1 Low: 0 (2) PLL unlock data UL • Data latched from the state of the unlock detection circuit UL ← 0: Unlocked UL ← 1: Locked or in detection stopped mode UL0, UL1 (3) IF counter binary data C19 to C0 • Data latched from the state of the IF counter, which is a 20-bit binary counter. C19 ← Binary counter MSB C0 ← Binary counter LSB CTE, GT0, GT1 No. 5743-12/23 LC72137, 72137M Serial Data Input (IN1/IN2) tSU, tHD, tEL, tES, tEH, ≥ 0.75 µs, tLC < 0.75 µs 1. CL: Normal high 2. CL: Normal low Serial Data Output (OUT) tSU, tHD, tEL, tES, tEH, ≥ 0.75 µs, tDC, tDH < 0.35 µs 1. CL: Normal high 2. CL: Normal low Note: Since the DO pin is an n-channel open drain circuit, the times for the data to change (tDC and tDH) will differ depending on the value of the pull-up resistor, printed circuit board capacitance. No. 5743-13/23 LC72137, 72137M Serial Data Timing CL Stopped at the Low Level CL Stopped at the High Level Symbol Pins Data setup time Parameter tSU DI, CL 0.75 µs Data hold time tHD DI, CL 0.75 µs Clock low-level time tCL CL 0.75 µs Clock high-level time tCH CL 0.75 µs CE wait time tEL CE, CL 0.75 µs CE setup time tES CE, CL 0.75 µs CE hold time tEH CE, CL 0.75 Data latch change time tLC Data output time tDC tDH DO, CL Conditions These times depend on the pull-up resistance DO, CE and the printed circuit board capacitances. min typ max Unit µs 0.75 µs 0.35 µs 0.35 µs No. 5743-14/23 LC72137, 72137M Programmable Divider Structure DVS SNS Input pin Set divisor Actual divisor: N A 1 * FMIN 272 to 65535 Twice the set value Input frequency range (MHz) B 0 1 AMIN 272 to 65535 The set value 2 to 40 C 0 0 AMIN 4 to 4095 The set value 0.5 to 10 10 to 160 Note: * Don’t care. Sample Programmable Divider Divisor Calculations 1. For a 50 kHz FM step size (DVS = 1, SNS = *: FMIN selected) • FM RF = 90.0 MHz (IF = +10.7 MHz) FM VCO = 100.7 MHz PLL fref = 25 kHz (R0 to R1 = 1, R2 to R3 = 0) 100.7 MHz (FM VCO) ÷ 25 kHz (fref) ÷ 2 (FMIN: divide-by-two prescaler) = 2014 → 07DE (HEX) 2. For a 5 kHz SW step size (DVS = 0, SNS = 1: AMIN high-speed side selected) • SW RF = 21.75 MHz (IF = +450 kHz) SW VCO = 22.20 MHz PLL fref = 5 kHz (R0 = R2 = 0, R1 = R3 = 1) 22.2 MHz (SW VCO) ÷ 5 kHz (fref) = 4440 → 1158 (HEX) 3. For a 9 kHz MW step size (DVS = 0, SNS = 0: AMIN low-speed side selected) • MW RF = 1008 kHz (IF = +450 kHz) MW VCO = 1458 kHz PLL fref = 3 kHz (R0 to R1 = 0, R2 to R3 = 1) 1458 kHz (MW VCO) ÷ 3 kHz (fref) = 486 → 1E6 (HEX) No. 5743-15/23 LC72137, 72137M IF Counter Structure The LC72137 IF counter is a 20-bit binary counter, and takes the IF signal from the IFIN pin as its input. The result of the count can be read out serially, MSB first, from the DO pin. Measurement time GT1 GT0 0 0 4 3 to 4 0 1 8 3 to 4 Measurement period (GT) (ms) Wait time (tWU) (ms) 1 0 16 7 to 8 1 1 32 7 to 8 The IF frequency (Fc) is measured by determining how many pulses were input to the IF counter in the stipulated measurement time, GT. Fc = C GT (C = Fc × GT) C: count value (number of pulses) Sample IF Counter Frequency Calculations 1. For a measurement time (GT) of 32 ms and a count value (C) of 53980 (hexadecimal), which is 342,400 (decimal) IF frequency (Fc) = 342,400 ÷ 32 ms = 10.7 MHz 2. For a measurement time (GT) of 8 ms and a count value (C) of E10 (hexadecimal), which is 3600 (decimal) IF frequency (Fc) = 3600 ÷ 8 ms = 450 kHz No. 5743-16/23 LC72137, 72137M IF Counter Operation Before starting the IF count, the IF counter must be reset in advance by setting CTE in the serial data to 0. The IF count is started by changing the CTE bit in the serial data from 0 to 1. The serial data is latched by the LC72137 when the CE pin is dropped from high to low. The IF signal must be supplied to the IFIN pin in the period between the point the CE pin goes low and the end of the wait time at the latest. Next, the value of the IF count at the end of the measurement period must be read out during the period CTE is 1. This is because the IF counter is reset when CTE is set to 0. Note: When operating the IF counter, the control microcontroller must first check the state of the IF-IC SD (station detect) signal and only after determining that the SD signal is present turn on IF buffer output and execute an IF count operation. Auto-search techniques that use only the IF counter are not recommended, since it is possible for IF buffer leakage output to cause incorrect stops at points where there is no station. If the auto-search technique is implemented using only the IF counter in combination with an IF-IC without SD output, sensitivity-degradation mode ( IFS = 0 ) should be selected. No. 5743-17/23 LC72137, 72137M Unlock Detection Timing 1. Unlock Detection Determination Timing Unlock detection is performed in the reference frequency (fref) period (interval). Therefore, in principle, unlock determination requires a time longer than the period of the reference frequency. However, immediately after changing the divisor N (frequency) unlock detection must be performed after waiting at least two periods of the reference frequency. Figure 1 Unlock Detection Timing For example, if fref is 1 kHz (and thus the period is 1 ms), after changing the divisor N, the system must wait at least 2 ms before checking for the unlocked state. Figure 2 Circuit Structure No. 5743-18/23 LC72137, 72137M 2. Unlock Detection Software Figure 3 3. When Outputting Unlock Data Using Serial Data Output: Once the LC72137 detects an unlocked state, it does not reset the unlock data (UL) until the next data output (or data input) operation is performed. At the data output ① point in Figure 3, although the VCO frequency is stable (locked), the unlock data remains set to the unlocked state since no data output has been performed since the value of N was changed. Thus, even though the frequency became stable (locked), from the point of view of the data, the circuit is in the unlocked state. Therefore, the data output ① immediately following a change to the value of N should be seen as a dummy data, and the data from the second data output (data output ②) and later outputs should be seen as valid data. Lock Determination Flowchart No. 5743-19/23 LC72137, 72137M When directly outputting data from the DO pin (set up by the DO pin control data) Since the DO pin outputs the unlocked state (locked: high, unlocked: low) the timing considerations in the technique described in the previous section are not necessary. After changing the value of N, the locked state can be determined after waiting at least two periods of the reference frequency. Notes on Clock Time Base Usage When the clock time base output is used, the value of the pull-up resistor for the output pin (BO1) must be at least 100 kΩ. We recommend the use of a Schmitt input on the receiving controller (microprocessor) to prevent chattering.This is to avoid degradation of the VCO C/N characteristics when using the built-in low-pass filter transistor to form the loop filter. Since the clock time base output pin and the low-pass filter transistor ground are the same mode in the IC, the time base output pin current fluctuations must be suppressed to limit the influence on the low-pass filter. Other Items 1. Notes on the Phase Comparator Dead Zone DZ1 DZ0 Dead-zone mode Charge pump 0 0 DZA ON/ON Dead zone 0 1 DZB ON/ON –0 s 1 0 DZC OFF/OFF +0 s 1 1 DZD OFF/OFF + +0 s – –0 s Since correction pulses are output from the charge pump even if the PLL is locked when the charge pump is in the ON/ON state, the loop can easily become unstable. This point requires special care when designing application circuits. The following problems may occur in the ON/ON state. • Side band generation due to reference frequency leakage • Side band generation due to both the correction pulse envelope and low frequency leakage No. 5743-20/23 LC72137, 72137M Schemes in which a dead zone is present (OFF/OFF) have good loop stability, but have the problem that acquiring a high C/N ratio can be difficult. On the other hand, although it is easy to acquire a high C/N ratio with schemes in which there is no dead zone, it is difficult to achieve high loop stability. Therefore, it can be effective to select DZA or DZB, which have no dead zone, in applications which require an FM S/N ratio in excess of 90 to 100 dB, or in which an increased AM stereo pilot margin is desired. On the other hand, we recommend selecting DZC or DZD, which provide a dead zone, for applications which do not require such a high FM signal-to-noise ratio and in which either AM stereo is not used or an adequate AM stereo pilot margin can be achieved. Dead Zone The phase comparator compares fp to a reference frequency (fr) as shown in Figure 4. Although the characteristics of this circuit (see Figure 5) are such that the output voltage is proportional to the phase difference ø (line A), a region (the dead zone) in which it is not possible to compare small phase differences occurs in actual ICs due to internal circuit delays and other factors (line B). A dead zone as small as possible is desirable for products that must provide a high S/N ratio. However, since a larger dead zone makes this circuit easier to use, a larger dead zone is appropriate for popularlypriced products. This is because it is possible for RF signals to leak from the mixer to the VCO and modulate the VCO in popularly-priced products in the presence of strong RF inputs. When the dead zone is narrow, the circuit outputs correction pulses and this output can further modulate the VCO and generate beat frequencies with the RF signal. Figure 4 Figure 5 2. Notes on the FMIN, AMIN, and IFIN Pins Coupling capacitors must be placed as close as possible to their respective pin. A capacitance of about 100 pF is desirable. In particular, if a capacitance of 1000 pF or over is used for the IF pin, the time to reach the bias level will increase and incorrect counting may occur due to the relationship with the wait time. 3. Notes on IF Counting → SD must be used in conjunction with the IF counting time When using IF counting, always implement IF counting by having the microprocessor determine the presence of the IF-IC SD (station detect) signal and turn on the IF counter buffer only if the SD signal is present. Schemes in which auto-searches are performed with only IF counting are not recommended, since they can stop at points where there is no signal due to leakage output from the IF counter buffer. No. 5743-21/23 LC72137, 72137M 4. DO Pin Usage Techniques In addition to data output mode times, the DO pin can also be used to check for IF counter count completion and for unlock detection output. Also, an input pin state can be output unchanged through the DO pin and input to the controller. 5. Power Supply Pins A capacitor of at least 2000 pF must be inserted between the power supply VDD and VSS pins for noise exclusion. This capacitor must be placed as close as possible to the VDD and VSS pins. 6. Note on VCO designing VCO ( local oscillator ) must keep its oscillation even if the control voltage ( Vtune ) goes to 0V. When there is a possibility of oscillation halt, Vtune must be forcibly set to VCC temporarily to prevent the PLL from being deadlocked. ( Deadlock clear circuit ) Pin States at a Power-On Reset No. 5743-22/23 LC72137, 72137M Sample Application System (Using the MFP20 package) ■ No products described or contained herein are intended for use in surgical implants, life-support systems, aerospace equipment, nuclear power control systems, vehicles, disaster/crime-prevention equipment and the like, the failure of which may directly or indirectly cause injury, death or property loss. ■ Anyone purchasing any products described or contained herein for an above-mentioned use shall: ➀ Accept full responsibility and indemnify and defend SANYO ELECTRIC CO., LTD., its affiliates, subsidiaries and distributors and all their officers and employees, jointly and severally, against any and all claims and litigation and all damages, cost and expenses associated with such use: ➁ Not impose any responsibility for any fault or negligence which may be cited in any such claim or litigation on SANYO ELECTRIC CO., LTD., its affiliates, subsidiaries and distributors or any of their officers and employees jointly or severally. ■ Information (including circuit diagrams and circuit parameters) herein is for example only; it is not guaranteed for volume production. SANYO believes information herein is accurate and reliable, but no guarantees are made or implied regarding its use or any infringements of intellectual property rights or other rights of third parties. This catalog provides information as of July, 1998. Specifications and information herein are subject to change without notice. PS. No. 5743-23/23