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overview the lc72121 and the lc72121m and the LC72121V are high input sensitivity (20 mvrms at 130 mhz) pll frequency synthesizers for 3 v systems. these ics are serial data (ccb) compatible with the lc72131, and feature the improved input sensitivity and lower spurious radiation (provided by a redesigned ground system) required in high-performance am/fm tuners. functions high-speed programmable divider fmin: 10 to 160 mhz ... pulse swallower technique (with built-in divide-by-2 prescaler) amin: 2 to 40 mhz ... pulse swallower technique 0.5 to 10 mhz ... direct division technique if counter ifin: 0.4 to 12 mhz ... for am and fm if counting reference frequency one of 12 reference frequencies can be selected (using a 4.5 or 7.2 mhz crystal element) 1, 3, 5, 9, 10, 3.125, 6.25, 12.5, 15, 25, 50, or 100 khz phase comparator supports dead zone control. built-in unlocked state detection circuit built-in deadlock clear circuit an mos transistor for an active low-pass filter is built in. i/o ports output-only ports: 4 pins i/o ports: 2 pins supports the output of a clock time base signal. operating ranges supply voltage: 2.7 to 3.6 v operating temperature: ?40 to 85? package dip22s, mfp24s, ssop24 comparison with the lc72131/m serial data compatible (ccb) identical pin functions two v ss pins were added. the dip version is pin compatible (v ss pins were inserted as the dip22s nc pins.) the mfp product provides a modified pin assignment (the mfp20 package was replaced by an mfp24 package, and extra v ss pins were added.) the ssop24 is a newly developed package that has the same pin assignment as the mfp24s product. cmos ic 70398rm (ot) no. 5815-1/22 preliminary sanyo electric co.,ltd. semiconductor bussiness headquarters tokyo office tokyo bldg., 1-10, 1 chome, ueno, taito-ku, tokyo, 110-8534 japan pll frequency synthesizers for electronic tuning lc72121, 72121m, 72121v ordering number : en * 5815a ccb is a trademark of sanyo electric co., ltd. ccb is sanyo? original bus format and all the bus addresses are controlled by sanyo.
package dimensions unit: mm 3059-dip22s unit: mm 3112-mfp24s unit: mm 3175a-ssop24 no. 5815- 2 /22 lc72121, 72121m, 72121v sanyo: dip22s [lc72121] sanyo: mfp24s [lc72121m] sanyo: ssop24 [LC72121V] pin assignments top view
no. 5815- 3 /22 lc72121, 72121m, 72121v block diagram
no. 5815- 4 /22 lc72121, 72121m, 72121v parameter symbol conditions ratings unit maximum supply voltage v dd max v dd ?.3 to +7.0 v v in 1 max ce, di, cl, ain ?.3 to +7.0 v maximum input voltage v in 2 max xin, fmin, amin, ifin ?.3 to v dd +0.3 v v in 3 max io1, io2 ?.3 to +15 v v o 1 max do ?.3 to +7.0 v maximum output voltage v o 2 max xout, pd ?.3 to v dd +0.3 v v o 3 max bo1 to bo4, io1, io2, aout ?.3 to +15 v maximum output current i o 1 max do, aout 0 to +6.0 ma i o 2 max bo1 to bo4, io1, io2 0 to +10.0 ma dip22s: 350 mw allowable power dissipation pd max (ta 85 c) mfp24s: 200 mw ssop24: 150 mw operating temperature topr ?0 to +85 c storage temperature tstg ?5 to +125 c specifications absolute maximum ratings at ta = 25 c, v ssd = v ssa = v ssx = 0 v parameter symbol conditions ratings unit min typ max supply voltage v dd v dd 2.7 3.6 v input high-level voltage v ih 1 ce, di, cl 0.7 v dd 6.5 v v ih 2 io1, io2 0.7 v dd 13 v input low-level voltage v il ce, di, cl, io1, io2 0 0.3 v dd v output voltage v o 1 do 0 6.5 v v o 2 bo1 to bo4, io1, io2, aout 0 13 v f in 1 xin: v in 1 1 8 mhz f in 2 fmin: v in 2 10 160 mhz input frequency f in 3 amin (sns = 1): v in 3 2 40 mhz f in 4 amin (sns = 0): v in 4 0.5 10 mhz f in 5 ifin: v in 5 0.4 12 mhz v in 1 xin: f in 1 200 800 mvrms v in 2-1 fmin: f = 10 to 130 mhz 20 800 mvrms v in 2-2 fmin: f = 130 to 160 mhz 40 800 mvrms input amplitude v in 3 amin (sns = 1): f in 3 40 800 mvrms v in 4 amin (sns = 0): f in 4 40 800 mvrms v in 5-1 ifin: f in 5, ifs = 1 40 800 mvrms v in 5-2 ifin: f in 5, ifs = 0 70 800 mvrms guaranteed crystal oscillator frequency xtal xin, xout: * 1 4.5 mhz xin, xout: * 2 7.2 mhz allowable operating ranges at ta = ?40 to +85 c, v ssd = v ssa = v ssx = 0 v notes: 1. recommended value for ci for the crystal oscillator element: ci < 120 2. recommended value for ci for the crystal oscillator element: ci < 70 parameter symbol conditions ratings unit min typ max rf1 xin 1 m internal feedback resistance rf2 fmin 500 k rf3 amin 500 k rf4 ifin 250 k internal pull-down resistance rpd1 fmin 100 200 400 k rpd2 amin 100 200 400 k hysteresis v his ce, di, cl 0.1 v dd v output high-level voltage v oh 1 pd: i o = ? ma v dd ?1.0 v electrical characteristics in the allowable operating ranges continued on next page.
no. 5815- 5 /22 lc72121, 72121m, 72121v parameter symbol conditions ratings unit min typ max v ol 1 pd: i o = 1 ma 1.0 v v ol 2 bo1 to bo4, io1, io2: i o = 1 ma 0.2 v output low-level voltage bo1 to bo4, io1, io2: i o = 8 ma 1.6 v v ol 3 do: i o = 5 ma 1.0 v v ol 4 aout: i o = 1 ma, ain = 1.3 v 0.5 v i ih 1 ce, di, cl: v i = 6.5 v 5.0 a i ih 2 io1, io2: v i = 13 v 5.0 a input high-level current i ih 3 xin: v i = v dd 1.3 8 a i ih 4 fmin, amin: v i = v dd 2.5 15 a i ih 5 ifin: v i = v dd 5.0 30 a i ih 6 ain: v i = 6.5 v 200 na i il 1 ce, di, cl: v i = 0 v 5.0 a i il 2 io1, io2: v i = 0 v 5.0 a input low-level current i il 3 xin: v i = 0 v 1.3 8 a i il 4 fmin, amin: v i = 0 v 2.5 15 a i il 5 ifin: v i = 0 v 5.0 30 a i il 6 ain: v i = 0 v 200 na output off leakage current i off 1 bo1 to bo4, io1, io2, aout: v o = 13 v 5.0 a i off 2 do: v o = 6.5 v 5.0 a high-level 3-state off leakage current i offh pd: v o = v dd 0.01 200 na low-level 3-state off leakage current i offl pd: v o = 0 v 0.01 200 na input capacitance c in fmin 6 pf i dd 1 v dd : xtal = 7.2 mhz, f in 2 = 130 mhz, 2.5 6 ma v in 2 = 20 mvrms supply current v dd : pll block stopped (pll inhibit mode) i dd 2 crystal oscillator operating 0.3 ma (crystal frequency: 7.2 mhz) i dd 3 v dd : pll block stopped, crystal oscillator 10 a stopped continued from preceding page. pin descriptions pin pin no. type function equivalent circuit name lc72121 xtal ?crystal oscillator element connections (4.5 or 7.2 mhz) xin xout 1 22 1 24 lc72121m LC72121V local oscillator signal input ?fmin is selected when dvs in the serial data is set to 1. ?input frequency: 10 to 160 mhz ? the signal is passed through an internal divide-by-two prescaler and then input to the swallow counter. ? the divisor can be set to a value in the range 272 to 65535. since the internal divide-by-two prescaler is used, the actual divisor will be twice the set value. fmin 16 17 local oscillator signal input ?amin is selected when dvs in the serial data is set to 0. ?when sns in the serial data is set to 1: ?input frequency: 2 to 40 mhz ?the signal is input to the swallow counter directly. ?the divisor can be set to a value in the range 272 to 65535. the set value becomes the actual divisor. ?when sns in the serial data is set to 0: ?input frequency: 0.5 to 10 mhz ?the signal is input to a 12-bit programmable divider directly. ?the divisor can be set to a value in the range 4 to 4095. the set value becomes the actual divisor. amin 15 16 continued on next page.
no. 5815- 6 /22 lc72121, 72121m, 72121v continued from preceding page. pin pin no. type function equivalent circuit name lc72121 chip enable ? this pin must be set high to enable serial data input (di) or serial data output (do). ce 3 3 lc72121m LC72121V input data ?input for serial data transferred from the controller di 4 4 clock ? clock used for data synchronization for serial data input (di) and serial data output (do). cl 5 5 output data ? output for serial data transmitted to the controller. the content of the data transmitted is determined by doc0 through doc2. do 6 6 power supply ?lc72121 power supply (v dd 2.7 to 3.6 v) ?the power on reset circuit operates when power is first applied. v dd 17 18 ground ?ground for the crystal oscillator circuit v ssx 2 2 ground ?ground for the low-pass filter mos transistor v ssa 21 22 ground ? ground for the lc72121 digital systems other than those that use v ssa or v ssx . v ssd 14 15 i/o port ?shared function i/o ports ?the pin function is determined by ioc1 and ioc2 in the serial data. when the data value 0: input port when the data value 1: output port ?when specified to function as an input port: the input pin state is reported to the controller through the do pin. when the input state is low: the data will be 0: when the input state is high: the data will be 1: ?when specified to function as an output port: the output state is determined by io1 and io2 in the serial data. when the data value is 0: the output state will be the open circuit state. when the data value is 1: the output state will be a low level. ?these pins are set to input mode after a power on reset. io1 io2 11 13 11 14 output port ?output-only ports ?the output state is determined by bo1 through bo4 in the serial data. when the data value is 0: the output state will be the open circuit state. when the data value is 1: the output state will be a low level. ? a time base signal (8 hz) is output from bo1 when tbc in the serial data is set to 1. bo1 bo2 bo3 bo4 7 8 9 10 7 8 9 10 charge pump output ?pll charge pump output a high level is output when the frequency of the local oscillator signal divided by n is higher than the reference frequency, and a low level is output when that frequency is lower. this pin goes to the high- impedance state when the frequencies match. pd 18 19 low-pass filter amplifier transistor ? connections for the mos transistor used for the pll active low-pass filter. ain aout 19 20 20 21 if counter ?the input frequency range is 0.4 to 12 mhz ?the signal is passed directly to the if counter. ?the result is output, msb first, through the do pin. ?four measurement periods are supported: 4, 8, 32, and 64 ms. ifin 12 13 12 23 nc nc pin ?no connection
procedures for input and output of serial data this product uses the ccb (computer control bus), which is sanyo? audio product serial bus format, for data input and output. this product adopts an 8-bit address ccb format. no. 5815- 7 /22 lc72121, 72121m, 72121v i/o mode address function b0 b1 b2 b3 a0 a1 a2 a3 ?control data input (serial data input) mode 1 in1 (82) 0 0 0 1 0 1 0 0 ?24 bits of data are input. ? see the ?i control data (serial data input)?section for details on the content of the input data. ?control data input (serial data input) mode 2 in2 (92) 1 0 0 1 0 1 0 0 ?24 bits of data are input. ? see the ?i control data (serial data input)?section for details on the content of the input data. ?data output (serial data output) mode 3 out (a2) 0 1 0 1 0 1 0 0 ?the number of bits output is equal to the number of clock cycles. ? see the ?o control data (serial data output)?section for details on the content of the output data. cl: normally high cl: normally low i/o mode determined
structure of the di control data (serial data input) ?in1 mode ?in2 mode no. 5815- 8 /22 lc72121, 72121m, 72121v
no. 5815- 9 /22 lc72121, 72121m, 72121v di control data no. control block/data function related data 1 programmable divider data p0 to p15 dvs, sns specifies the divisor for the programmable divider. this is a binary value in which p15 is the msb. the lsb changes depending on dvs and sns. ( * : don? care) * lsb: when p4 is the lsb, p0 to p3 are ignored. 2 reference divider data r0 to r3 xs reference frequency selection * pll inhibit mode in this mode, the programmable divider and the if counter block are stopped, the fmin, amin, and ifin pins are pulled down to ground, and the charge pump output goes to the high-impedance state. crystal oscillator element selection data xs = 0: 4.5 mhz xs = 1: 7.2 mhz note that 7.2 mhz is selected after a power on reset. 3 if counter control data cte gt0, gt1 ifs if counter measurement start command data cte = 1: starts the counter cte = 0: resets the counter determines the if counter measurement time. dvs sns lsb set divisor (n) actual divisor 1 * p0 272 to 65535 twice the set value 0 1 p0 272 to 65535 the set value 0 0 p4 4 to 4095 the set value gt1 gt0 measurement time wait time 0 0 4 ms 3 to 4 ms 0 1 8 3 to 4 1 0 32 7 to 8 1 1 64 7 to 8 r3 r2 r1 r0 reference frequency 0 0 0 0 100 khz 0 0 0 1 50 0 0 1 0 25 0 0 1 1 25 0 1 0 0 12.5 0 1 0 1 6.25 0 1 1 0 3.125 0 1 1 1 3.125 1 0 0 0 10 1 0 0 1 9 1 0 1 0 5 1 0 1 1 1 1 1 0 0 3 1 1 0 1 15 1 1 1 0 pll inhibit + xtal osc stop 1 1 1 1 pll inhibit these pins select the signal input to the programmable divider (fmin or amin) and switch the input frequency range. * see the ?tructure of the programmable divider?section for details. * see the ?tructure of the if counter?section for details. dvs sns input pin frequency range accepted by the input pin 1 * fmin 10 to 160 mhz 0 1 amin 2 to 40 mhz 0 0 amin 0.5 to 10 mhz ( * : don? care) continued on next page.
no. control block/data function related data no. 5815- 10 /22 lc72121, 72121m, 72121v continued from preceding page. 4 i/o port setup data ioc1,ioc2 specifies input or output for the shared function i/o pins (io1 and io2). data = 0: input port data = 1: output port 5 output port data bo1 to bo4 io1,io2 determines the output state of the bo1 through bo4, io1, and io2 output ports. data = 0: open data = 1: low level the data is reset to 0, setting the pins to the open state, after a power on reset. ioc1 ioc2 6 do pin control data doc0 doc1 doc2 determines the do pin output. the open state is selected after a power on reset. * 1. end-uc: if counter measurement end check (1) when end-uc is selected and an if count is started (by switching cte from 0 to 1), the do pin automatically goes to the open state. (2) when the if counter measurement period completes, the do pin goes to the low level, allowing applications to test for the completion of the count period. (3) the do pin is set to the open state by performing a serial data input or output operation (when the ce pin is set high). * 2. the do pin will go to the open state if the corresponding io pin is set up to be an output port. note: during the data input period (the period that ce is high in in1 or in2 mode), the do pin goes to the open state regardless of the do pin control data (doc0 to doc2). during the data output period (the period that ce is high in out mode) the do pin state reflects the internal do serial data in synchronization with the cl clock, regardless of the do pin control data (doc0 to doc2). ul0, ul1 cte ioc1 ioc2 7 unlocked state detection data ul0, ul1 selects the width of the phase error (?) detected for pll lock state discrimination. the state is taken to be unlocked if a phase error in excess of the detection width occurs. * when the pll is unlocked, the do pin goes low and ul in the serial data output is set to 0. dead zone width: dza < dzb < dzc < dzd doc0 doc1 doc2 8 phase comparator control data dz0, dz1 controls the phase comparator dead zone doc2 doc1 doc0 do pin state 0 0 0 open 0 0 1 low when the pll is unlocked 0 1 0 end-uc * 1 0 1 1 open 1 0 0 open 1 0 1 the io1 pin state * 2 1 1 0 the io2 pin state * 2 1 1 1 open ul1 ul0 ? detection width detection output 0 0 stopped open 0 1 0 ? is output directly 1 0 0.55 s ? is extended by 1 to 2 ms 1 1 1.11 s ? is extended by 1 to 2 ms dz1 dz dead zone mode 0 0 dza 0 1 dzb 1 0 dzc 1 1 dzd continued on next page.
no. control block/data function related data no. 5815- 11 /22 lc72121, 72121m, 72121v continued from preceding page. no. control block/data function related data 9 clock time base tbc setting the tbc bit to 1 causes an 8-hz clock time base signal with a 40% duty to be output from the bo1 pin. (the bo1 data will be ignored.) bo1 10 charge pump control data dlc forcibly controls the charge pump output. * if the circuit deadlocks due to the vco control voltage (vtune) being 0 and the vco being stopped, applications can get out of the deadlocked state by setting the charge pump output to low and setting vtune to v cc . (deadlock clear circuit) 11 if counter control data ifs this data is normally set to 1. setting this data to 0 sets the circuit to reduced input sensitivity mode, in which the sensitivity is reduced by about 10 to 30 mv rms. * see the ?f counter operation?section for details. 1 i/o port data 12, i1 ?data latched from the i/o port io pin states. ?these bits reflect the pin states regardless of the i/o port mode (input or output). the data is latched at the point the circuit enters data output mode (out mode). i1 ? the io1 pin state h : 1 i2 ? the io2 pin state l : 0 ioc1 ioc2 12 test data test0 to 2 test data test0 test1 all these bits must be set to 0. test2 all these bits are set to 0 after a power on reset. 13 dnc ?this bit must be set to 0. dlc charge pump output 0 normal operation 1 forced to low structure of the do output data (serial data output) ?out mode do output data 2 pll unlocked state data ul indicates the state of the unlocked state detection circuit. ul ? 0: when the pll is unlocked. ul ? 1: when the pll is locked or in the detection disabled mode. ul0 ul1 3 if counter binary data c19 to c0 indicates the value of the if counter (20-bit binary counter). c19 ? msb of the binary counter c0 ? lsb of the binary counter cte gt0 gt1
serial data input (in1/in2) t su , t hd , t el , t es , t eh 3 0.75 s t lc < 0.75 s cl: normal (high) no. 5815- 12 /22 lc72121, 72121m, 72121v cl: normal (low) serial data output (out) t su , t hd , t el , t es , t eh 3 0.75 s t dc , t dh < 0.35 s cl: normal (high) cl: normal (low) note: the data conversion times (t dc and t dh ) depend on the value of the pull-up resistor and the printed circuit board capacitance since the do pin is an n-channel open-drain circuit.
serial data timing no. 5815- 13 /22 lc72121, 72121m, 72121v when cl is stopped at the low level when cl is stopped at the high level parameter symbol conditions ratings unit min typ max data setup time t su di, cl 0.75 s data hold time t hd di, cl 0.75 s clock low level time t cl cl 0.75 s clock high level time t ch cl 0.75 s ce wait time t el ce, cl 0.75 s ce setup time t es ce, cl 0.75 s ce hold time t eh ce, cl 0.75 s data latch change time t lc 0.75 s data output time t dc do, cl these values differ depending on the value of the pull-up 0.35 s t dh do, ce resistor used and the printed circuit board capacitance. 0.35 s
structure of the programmable divider sample programmable divider divisor calculations for fm with a step size of 50 khz (dvs = 1, sns = *: fmin selected) fm rf = 90.0 mhz (if +10.7 mhz) fm vco = 100.7 mhz pll fref = 25 khz (r0 = 0, r1 = 1, r2 = 0, r3 = 0) 100.7 mhz (fm vco) ? 25 khz (fref) ? 2 (for the fmin 1/2 prescaler) 2014 ? 07de (hexadecimal) * : don? care no. 5815- 14 /22 lc72121, 72121m, 72121v dvs sns input pin set divisor actual divisor input frequency range a 1 * fmin 272 to 65535 twice the set value 10 to 160 mhz b 0 1 amin 272 to 65535 the set value 2 to 40 mhz c 0 0 amin 4 to 4095 the set value 0.5 to 10 mhz for sw with a step size of 5 khz (dvs = 0, sns = 1: amin high-speed operation selected) sw rf = 21.75 mhz (if +450 khz) sw vco = 22.20 mhz pll fref = 5 khz (r0 = 0, r1 = 1, r2 = 0, r3 = 1) 22.2 mhz (sw vco) ? 5 khz (fref) = 4440 ? 1158 (hexadecimal) for mw with a step size of 9 khz (dvs = 0, sns = 0: amin low-speed operation selected) mw rf = 1008 khz (if +450 khz) wm vco = 1458 khz pll fref =9 khz (r0 = 1, r1 = 0, r2 = 0, r3 = 1) 1458 (mw vco) ? 9 khz (fref) = 162 ? 0a2 (hexadecimal)
structure of the if counter the lc72121 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. the if frequency (fc) is measured by determining how many pulses were input to the if counter in the stipulated measurement time, gt. c fc = (c = fc x gt) c: counted value (the number of pulses) gt no. 5815- 15 /22 lc72121, 72121m, 72121v gt1 gt0 measurement time measurement time (gt) wait time (t wu ) 0 0 4 ms 3 to 4 ms 0 1 8 3 to 4 ms 1 0 32 7 to 8 ms 1 1 64 7 to 8 ms if counter frequency measurement examples when the measurement time (gt) is 32 ms and the counted value (c) is 53980 (hexadecimal) or 342,400 decimal. if frequency (f c ) = 342400 ? 32 ms = 10.7 mhz when the measurement time (gt) is 8 ms and the counted value (c) is e10 (hexadecimal) or 3600 decimal. if frequency (f c ) = 3600 ? 8 ms = 450 khz
if counter operation applications must first, before starting an if count operation reset the if counter by setting cte in the serial data to 0. the if counter operation is started setting cte in the serial data from 0 to 1. although the serial data is latched by dropping the ce pin from high to low, the if signal input to the ifin pin must be provided within the wait time from the point ce goes low. next, the readout of the if counter after measurement is complete must be performed while cte is still 1, since the counter will be reset if cte is set to 0. note: if if counting is used, applications must determine whether or not the if ic sd (station detect) signal is present in the microcontroller software, and perform the if count only if that signal is asserted. this is because auto-search techniques that use if counting only are subject to incorrect stopping at points where there is no station due to if buffer leakage. note that the lc72121 input sensitivity can be controlled with the ifs bit in the serial data. reduced sensitivity mode (ifs = 0) must be selected when this ic is used in conjunction with an if ic that does not provide an sd output and auto-search is implemented using only if counting. ifin minimum sensitivity standard no. 5815- 16 /22 lc72121, 72121m, 72121v ifs data 0.4 f < 0.5 0.5 f < 0.8 8 f 12 1(normal mode) 40 mvrms (0.1 to 3 mvrms) 40 mvrms 40 mvrms (1 to 10 mvrms) 0 (degraded sensitivity mode) 70 mvrms (10 to 15 mvrms) 70 mvrms 70 vrms (30 to 40 mvrms) input frequency : f [mhz] note: values in parentheses are actual performance values that are provided for reference purposes.
unlocked state detection timing unlocked state detection timing unlocked state detection is performed during the reference frequency (fref) period (interval). this means that a period at least as long as the period of the reference frequency is required to recognize the locked/unlocked state. however, applications must wait at least twice the period of the reference frequency immediately after changing the divisor (n) before checking the locked/unlocked state. no. 5815- 17 /22 lc72121, 72121m, 72121v figure 1 unlocked state detection timing for example, if fref is 1 khz (a period of 1 ms) applications must wait at least 2 ms after the divisor n is changed before performing a locked/unlocked check. figure 2 circuit structure
figure 3 combining with software outputting the unlocked state data in the serial data at the point of data output 1 in figure 3, the unlocked state data will indicate the unlocked state, since the vco frequency is not stable (locked) yet. in cases such as this, the application should wait at least one whole period and then check again whether or not the frequency has stabilized with the data output 2 operation in the figure. applications can implement even more reliable recognition of the locked state by performing several more checks of the state and requiring that the locked state be detected sequentially. directly outputting the unlocked state to the do pin since the unlocked state (high level when locked, low when unlocked) is output from the do pin, applications can check for the locked state by waiting at least two reference frequency periods after changing the divisor n. however, in this case also, even more reliable recognition of the locked state can be achieved by performing several checks of the state and requiring that the locked state be detected sequentially. wait at least 2 reference frequency periods. valid output data is acquired by using an interval of at least one reference frequency period. * : even more reliable recognition of the locked state can be achieved by performing several checks of the state and requiring that the locked state be detected sequentially. divisor n changed (data input) data output (1) data output (2) no. 5815- 18 /22 lc72121, 72121m, 72121v locked state check yes no a10180
clock time base usage notes when using the clock time base output function, the output pin (bo1) pull-up resistor must have a value of over 100 k . the use of a schmitt input in the microcontroller that accepts this signal is recommended to reduce chattering. this is to prevent degradation of the vco c/n characteristics when combining with a loop filter that uses the internal transistor provided to form a low-pass filter. although the ground for the clock time base output pin (v ssd ) and the ground for the transistor (v ssa ) are isolated internally on the chip, applications must take care to avoid ground loops and minimize current fluctuations in the time base pin to prevent degradation of the low-pass filter characteristics. no. 5815- 19 /22 lc72121, 72121m, 72121v pin states after a power on reset
sample application circuit (using the dip22s package) no. 5815- 20 /22 lc72121, 72121m, 72121v since this is a high-impedance circuit, it is susceptible to noise. therefore, lines in the printed circuit board pattern should be made as short as possible and it should be surrounded by the ground pattern.
other items notes on the phase comparator dead zone when the charge pump is used with one of the on/on modes, correction pulses are generated from the charge pump even if the pll is locked. as a result, it is easy for the loop to become unstable, and special care is required in application design. the following problems can occur if an on/on mode is used. sidebands may be created by reference frequency leakage. sidebands may be created by low-frequency leakage due to the correction pulse envelope. although the loop is more stable when a dead zone is present (i.e. when an off/off mode is used), a dead zone makes it more difficult to achieve excellent c/n characteristics. on the other hand, while it is easy to achieve good c/n characteristics when there is no dead zone, achieving good loop stability is difficult. accordingly, the dza and dzb settings, in which there is no dead zone, can be effective in situations where a signal-to-noise ratio of 90 to 100 db or higher is required in fm reception, or where it is desirable to increase the pilot margin in am stereo reception. however, if such a high signal-to-noise ratio is not required for fm reception, if an adequate pilot margin can be acquired in am stereo reception, or if am stereo is not required, then either dzc or dzd, in which there is a dead zone, should be chosen. dead zone as shown in figure 1, the phase comparator compares a reference frequency (fr) with fp. as shown in figure 2, the phase comparator's characteristics consist of an output voltage (v) that is proportional to the phase difference ? however, due to internal circuit delay and other factors, an actual circuit has a region (the dead zone, b) where the circuit cannot actually compare the phases. to implement a receiver with a high s/n ratio, it is desirable that this region be as small as possible. however, it is often desirable to have the dead zone be slightly wider in popularly-priced models. this is because in certain cases, such as when there is a strong rf input, popularly-priced models can suffer from mixer to vco rf leakage that modulates the vco. when the dead zone is small, the circuit outputs signals to correct this modulation and this output further modulates the vco. this further modulation may then generate beats and the rf signal. notes on the fmin, amin, and ifin pins coupling capacitors should be placed as close to their pin as possible. a capacitance of about 100 pf is desirable for these capacitors. in particular, if the ifin pin coupling capacitor is not held under 1000 pf, the time to reach the bias level may become excessive and incorrect counts may result due to the relationship with the wait time. notes on if counting ? use the sd signal in conjunction with if counting when counting the if frequency, the microcontroller must determine the presence or absence of the if ic sd (station detect) signal and turn on the if counter buffer output and execute the if count only if there is an sd signal. auto- search techniques that only use the if counter are subject to incorrect stopping at points where there is no station due to if buffer leakage. no. 5815- 21 /22 lc72121, 72121m, 72121v dz1 dz0 dead zone mode charge pump dead zone 0 0 dza on/on ??s 0 1 dzb on/on ?s 1 0 dzc off/off +0s 1 1 dzd off/off + +0s figure 1 figure 2
ps no. 5815- 22 /22 lc72121, 72121m, 72121v this catalog provides information as of july, 1998. specifications and information herein are subject to change without notice. n 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. n anyone purchasing any products described or contained herein for an above-mentioned use shall: 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: 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. n 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. do pin usage the do pin can be used for if counter count completion checking and as an unlock detection output in addition to its use in data output mode. it is also possible to have the do pin reflect the state of an input pin to input that state to the microcontroller. ? power supply pins capacitors must be inserted between the power supply v dd and v ss pins for noise exclusion. these capacitors must be placed as close as possible to the v dd and v ss pins. ? vco setup applications must be designed so that the vco (local oscillator) does not stop, even if the control voltage (vtune) goes to 0 v. if it is possible for the oscillator to stop, the application must use the control data (dlc) to temporarily force vtune to v cc to prevent deadlock from occurring. (deadlock clear circuit) front end connection example since this product (and the lc72131 as well) is designed with the relatively high resistance of 200 k for the pull- down (on) resistors built in to the fmin and amin pins, a common am/fm local oscillator buffer can be used as shown in the following circuit. pd pin note that the charge pump output voltage is reduced when this ic, which is a 3-v system, is used to replace the lc72131, which is a 5-v system. this means that since the loop gain is reduced, the loop filter constants, the lock time (sd wait time), and other related parameters must be reevaluated in the end product design.

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