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1 features ? fm double-conversion system ? integrated second if filter with software-controlled bandwidth ? completely integrated fm demodulator ? soft mute and multipath noise cancellation ? receiving condition analyzer ? am up/down-conversion system ? am preamplifier with agc and stereo capability ? 3-wire bus controlled ? search stop signal generation for am and fm ? automatic alignment possible electrostatic sensitive device. observe precautions for handling. description the U4255BM-M is a highly integrated am/fm front-end circuit manufactured using atmel?s advanced bicmos technology. it represents a complete, automatically adjust- able am/fm front end, containing a double-conversion system for fm and an up/down-conversion receiver for am with if1 = 10.7 mhz and if2 = 450 khz. the front end is suitable for digital or analog af-signal processing. together with the pll u4256bm, an automatically aligned high-performance am/fm tuner can be built. these ics are dedicated for highly sophisticated car radio applications. pin configuration figure 1. pinning sso44 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 44 43 42 41 40 39 38 37 36 35 34 33 32 31 30 29 28 27 26 25 24 23 dev if1out v3 if2in v3p mx2in if1ami oplpf gnd smute ifagch ifagcl mx2oa mx2ob if1ref if1fmi filadj mx1ama multip vs mx1oa mx1ob mx1fma mx1fmb mx1amb gndmx fmagc amvreg amagc amplpf meter adjac mpx v57 oscb osce gndosc oscout en clk data if2out int mx2lo am/fm receiver ic U4255BM-M preliminary rev. 4519c?audr?07/02
2 U4255BM-M 4519c?audr?07/02 pin description pin symbol function 1mx1fma1 st mixer fm input a 2mx1fmb1 st mixer fm input b 3 mx1amb 1 st mixer am input b 4 gndmx ground 1 st mixer, preamplifier agc 5 fmagc fm preamplifier agc 6 amvreg am control voltage 7 amagc am preamplifier agc 8 amplpf am agc lp filter 9 meter field strength output 10 adjac adjacent channel detection output 11 mpx multiplex signal 12 v57 5.7 v reference voltage 13 oscb oscillator basis 14 osce oscillator emitter 15 gndosc oscillator ground 16 oscout oscillator output 17 en 3-wire bus enable 18 clk 3-wire bus clock 19 data 3-wire bus data 20 if2out 2 nd if amplifier output 21 int interrupt, stop signal 22 mx2lo 10.25 mhz input for 2 nd mixer 23 mx2ob 2 nd mixer output b 24 mx2oa 2 nd mixer output a 25 gnd ground 26 mx2in 2 nd mixer input 27 v3p 3 v reference for ampin, amifagc, control, if2in 28 if2in 2 nd if amplifier input 29 v3 3 v reference for if1out, mx2in 30 if1out 1 st if amplifier output 31 dev deviation detect output, test output 32 oplpf operating point lpf 33 if1ami 1 st if am amplifier input 34 smute soft mute control input 35 ifagch if agc lp filter high time 36 ifagcl if agc lp filter low time constant 37 filadj filter adjust 38 if1fmi 1 st if fm amplifier input 39 if1ref 1 st if & mx1out reference, mx1am a, mx1am b 40 multip multipath detection output 41 mx1ama 1 st mixer am input a 42 vs supply voltage 43 mx1oa 1 st mixer output a 44 mx1ob 1 st mixer output b
3 U4255BM-M 4519c?audr?07/02 figure 2. block diagram functional description the U4255BM-M implements an am up/down-conversion reception path from the rf input signal to the am-demodulated audio frequency output signal, and for fm reception a double-conversion reception path from t he rf input signal to the fm-demodulated multiplex signal (mpx). a vco and an lo prescaler for am are integrated to generate the lo frequency for the 1 st mixer. automatic gain control (agc) circuits are imple- mented to control the preamplifier and if stages in the am and fm reception path. for improved fm performance, an integrated if filter with adjustable bandwidth, a soft- mute feature and an automatic multipath noise cancellation (mnc) circuit are fully integrated. a powerful set of sensors is provided for receiving condition analysis and stop signal generation. several register bits (bit 0 to bit 93) are used to control circuit operation and to adapt certain circuit parameters to the specific application. the control bits are organized in two 8-bit and three 24-bit registers that can be programmed by the 3-wire bus protocol. the bus protocol and the bit-to-register mapping is described in the section ?3-wire bus description?. the meaning of the control bits is mentioned in the following sections. reception mode the ic can be operated in four different modes. mode am, fm, wb, standby are selected by means of bit 92 and bit 93 according to table 1. in am mode the am mixer, the am rf-agc and the 1 st if am amplifier at pin 33 are activated. the input of the 2 nd if amplifier is connected to pin 28 and the output of the 2 nd if amplifier is fed to the am demodulator. the output of the am demodulator is available at mpx output pin 11. 30 29 mx2in mx2ob am 4 3 2 7 6 41 26 23 amagc amvreg mx1ama mx1amb gndmx mx1fmb amplpf mx1oa if1fmi 8 43 38 mx2oa if2in v3p if2out 24 28 27 20 if1ref if1ami if1out v3 39 33 agc 15 16 14 1 mx1fma oscout gndosc osce 13 oscb mx1ob 44 fm divider am fm osc agc v3 bus fmagc en clk data 17 18 19 5 bandgap meter v57 gnd vs 12 25 42 9 v3 adjac mx2lo 22 10 dev int multip smute 21 40 34 31 int adj. chan . stop multi- path agc am dem. 32 36 35 37 11 oplpf ifagcl ifagcch filadj mpx automatic adjustment soft mute dev. ana. fm dem.
4 U4255BM-M 4519c?audr?07/02 in fm mode the fm mixer, the fm rf-agc and the 1 st if fm amplifier at pin 38 are activated. the bandwidth of the output tank at pin 23, pin 24 is increased and the input of the 2 nd if amplifier can be switched between pin 23, pin 24 and pin 28. the output of the 2 nd if amplifier is fed to the integrated bandfilter and fm demodulator. the output of the fm demodulator is available at mpx output pin 11. wb mode is similar to fm mode but the input of the 2 nd if amplifier is fixed to pin 28, the range of the bandwidth control of the integrated band filter is shifted to lower bandwidth and the gain of the fm demodulator is increased. in standby mode the mixers, if amplifiers and agc circuits are deactivated to reduce current consumption. table 1. operating mode test mode a special test mode is implemented for final production test only. this mode is activated by setting bit 9 = 1. this mode is not intended to be used in customer application. for normal operation, bit 9 has to be set to 0. bit 18 to bit 30 are deactivated in normal operation mode. table 2. test mode vco an oscillator circuit is implemented to build a vco as proposed in the application sche- matic. the vco frequency is used to generate the lo frequency of the 1 st mixer stages. the control voltage of the vco is usually generated by the pll circuit u4256bm. the vco signal is provided at the buffered output pin 16 to be fed to the pll circuit. fm rf-agc the fm rf-agc circuit includes a wideband level detector at the input pin 1 of the fm mixer and an in-band level detector at the output of the fm if amplifier (pin 30). the outputs of these level detectors are used to control the current into the pin diode (see figure 3) in order to limit the signal level at the fm mixer input and the following stages. the maximum pin diode current is determined by r115 and the time constant of the agc control loop can be adjusted by changing the value of c111. the agc threshold level at the input of the fm mixer can be adjusted by bit 64 and bit 65 according to table 3. the in-band agc threshold referred to the fm mixer input (pin 1, pin 2) depends on the gain of the fm if amplifier and can be adjusted by bit 89 to bit 91. am/fm/weather channel bit 93 bit 92 standby 0 0 fm 0 1 am 1 0 weather band 1 1 mode bit 9 normal operation 0 testmode 1
5 U4255BM-M 4519c?audr?07/02 table 3. fm-agc threshold figure 3. fm rf-agc bit 92 am rf-agc the am rf-agc controls the current into the am pin diodes (pin 7) and the source drain voltage of the mosfet in the am preamplifier stage (pin 6) to limit the level at the am mixer input (pin 3, pin 41). this threshold level can be set by bit 62 and bit 63. if the level at the am mixer input exceeds the selected threshold, the current into the am pin diodes is increased. if this step is not sufficient, the source drain voltage of the mosfet is decreased. the time constant of the agc control loop can be adjusted by changing the value of the capacitor at pin 8. table 4. am-agc threshold fm 1 st mixer in the 1 st fm mixer stage, the fm reception frequency is down converted to the 1 st if frequency. the vco frequency is used as lo frequency for the mixer. am 1 st mixer the am 1 st mixer is used for up-conversion of the am reception frequency to the 1 st if frequency. therefore, an am prescaler is implemented to generate the necessary lo frequency from the vco frequency. the divide factor of the am prescaler can be selected according to table 5. fm-agc threshold bit 65 bit 64 104 db v00 101 db v01 98 db v10 92 db v11 agc b92 pin diode vs pin 42 pin 5 c111 r115 am-agc threshold bit 63 bit 62 99 db v00 102 db v01 104 db v10 105 db v11
6 U4255BM-M 4519c?audr?07/02 table 5. divide factor of the am prescaler fm 1 st if amplifier a programmable gain amplifier is used in fm and wb mode between pin 38 and pin 30 to compensate the loss in the external ceramic band filters. the gain of this amplifier is adjusted by bit 89 to bit 91. the input and the output resistance is 330 and fits to external ceramic filters. two different temperature coefficients of the fm if amplifier can be selected by bit 66. table 6. gain of the fm if amplifier table 7. temperature coefficient setting of fm if amplifier am 1 st if amplifier in am mode, the gain of the 1 st if amplifier is controlled by the if-agc to extend the control range of the if-agc. 2 nd mixer the 2 nd mixer is used in am, fm and wb mode. the mixer input has 330 input resis- tance and can be connected directly to an external ceramic filter. in fm mode, the high output resistance of the second mixer is reduced to increase the bandwidth of the tank at the mixer output. the output resistance can be selected by bit 60 and bit 61. table 8. 2 nd mixer output resistance in fm mode the lo frequency of the 2 nd mixer (10.25 mhz) has to be applied at pin 22. this signal is usually generated by the pll circuit u4256bm. divider am prescaler bit 93 bit 92 bit 84 bit 83 bit 82 bit 81 divide by 10 1 0 x 0 0 0 divide by 6 1 0 x 0 0 1 divide by 7 1 0 x 0 1 0 divide by 8 1 0 x 1 0 0 divide by 4 1 0 x 1 0 1 gain fm if bit 91 bit 90 bit 89 20 db 0 0 0 22 db 0 0 1 24 db 0 1 0 26 db 0 1 1 28 db 1 0 0 29 db 1 0 1 30 db 1 1 0 31 db 1 1 1 temperature coefficient (tc) of the if amplifier bit 66 tk min 0 tk max 1 bit 61 bit 60 output resistance (bit 54 = 0) output resistance (bit 54 = 1) 00 3.3 k ~ 100 k 01 0.63 k 0.78 k 10 0.47 k 0.55 k 11 0.29 k 0.32 k
7 U4255BM-M 4519c?audr?07/02 table 9. fm bandwidth mixer 2 remark: the bandwidth is also depending from the values of the application circuit. 2 nd if amplifier in am and wb mode, the input of the second if amplifier is pin 28, which is externally connected to the 2 nd mixer tank through the am ceramic filter to achieve channel selec- tivity. during normal fm operation (bit 54 = 0), the input of the second if amplifier is connected to the 2 nd mixer output (pin 23, pin 24) and the integrated fm band filter is used for channel selectivity only. it is possible to use an additional external filter between the 2 nd mixer tank and pin 28 in fm mode by setting bit 54 to 1. table 10. 2 nd if filter in fm mode if-agc the if-agc controls the level of the 2 nd if signal that is passed to the am demodulator input or the integrated fm bandfilter and to the 2 nd if output pin 20. two different time constants of the if-agc can be selected by the capacitors at pin 35 (ifagch) and pin 36 (ifagcl). the short time constant (ifagcl) is used in fm mode and in am search mode. the long time constant (ifagch) is used for am reception. table 11. if-agc time constant in fm/wb mode, the output signal of the fm demodulator is applied to pin 35 via a series resistor of about 95 k . this low-pass filtered output signal of the fm demodula- tor is used for the fm demodulator fine adjustment, for muting and as a reference for the deviation sensor. 2 nd if output the 2 nd if after the gain-controlled 2 nd if amplifier is available at pin20 (bit 55 = 0). in am mode, this signal may be used for an exte rnal am stereo decoder. alternatively, a signal corresponding to the logarithmic field strength after the integrated fm band filter, which is used for multipath detection, can be switched to pin 20 by setting bit 55 = 1. bit 61 bit 60 fm bw mixer 2 0 0 150 khz 0 1 200 khz 1 0 250 khz 1 1 450 khz 2nd if filter bit 54 internal filter 0 external and internal filter 1 mode bit 92 bit 88 if agc time constant fm/wb 1 x ifagcl (fast) am reception 0 0 ifagch (slow) am search 0 1 ifagcl (fast)
8 U4255BM-M 4519c?audr?07/02 table 12. pin 20 output setting automatic if center frequency adjustment integrated active filters are used in the fm band filter, fm demodulator and adjacent channel sensor. the center frequency of these filters is automatically adjusted to the second if frequency of 450 khz. the frequency of 10.25 mhz at pin 22 is used as a reference for this alignment. figure 4. automatic if center frequency adjustment for fine tuning, the center frequency of all these integrated active filters (band filter, demodulator and adjacent channel sensor) can be shifted in steps of 6.25 khz by means of bit 56 to bit 59. additionally, the center frequency of the band filter can be adjusted separately by means of bit 14 to bit 17 if bit 4 is set to 1. if bit 4 is set to 0, the default setting is used. table 13. 2 nd if center frequency pin 20 bit 55 2 nd if output 0 multipath field strength 1 if center bit 59 bit 58 bit 57 bit 56 450.00 khz 0 0 0 0 456.25 khz 0 0 0 1 461.50 khz 0 0 1 0 468.75 khz 0 0 1 1 475.00 khz 0 1 0 0 481.25 khz 0 1 0 1 487.50 khz 0 1 1 0 493.75 khz 0 1 1 1 450.00 khz 1 0 0 0 443.75 khz 1 0 0 1 437.50 khz 1 0 1 0 431.25 khz 1 0 1 1 425.00 khz 1 1 0 0 418.75 khz 1 1 0 1 412.50 khz 1 1 1 0 406.25 khz 1 1 1 1 automatic frequency adjustment fm-demod fm- bandfilter adj.channel sensor + + bit 56...59 10.25mhz bit 14...17 bit 5,6 center freq. center freq. center freq. pin 37 pin 22
9 U4255BM-M 4519c?audr?07/02 table 14. fm band filter center frequency correction integrated fm band filter for fm reception a band filter with variable bandwidth is integrated in front of the demodulator to provide channel selectivity on the 2 nd if. the bandwidth of this filter can be adjusted by bit 0 to 3 (see table 15) to be suitable for the present receiving condi- tion. in wb mode, the bandwidth of the integrated filter is shifted to lower bandwidth values, while the necessary channel selectivity is achieved by an external ceramic filter. the center frequency of the integrated fm band filter can be adjusted by means of bit 14 to 17 (bit 4 set to 1). the field strength after the integrated fm band filter that is available at pin 20 (bit55 = 1) can be used for this purpose. table 15. bandwidth of the integrated fm band filter. if correction bit 17 bit 16 bit 15 bit 14 - 0 khz 000 0 - 6.25 khz 000 1 - 12.50 khz 0 0 1 0 - 18.75 khz 0 0 1 1 - 25.00 khz 0 1 0 0 - 31.25 khz 0 1 0 1 - 37.50 khz 0 1 1 0 - 43.75 khz 0 1 1 1 + 0 khz (default) 1 0 0 0 + 6.25 khz 100 1 + 12.50 khz 101 0 + 18.75 khz 101 1 + 25.00 khz 110 0 + 31.25 khz 110 1 + 37.50 khz 111 0 + 43.75 khz 111 1 if bandwidth bit 3 bit 2 bit 1 bit 0 200 khz 0 0 0 0 190 khz 0 0 0 1 180 khz 0 0 1 0 170 khz 0 0 1 1 160 khz 0 1 0 0 150 khz 0 1 0 1 140 khz 0 1 1 0 130 khz 0 1 1 1 120 khz 1 0 0 0 110 khz 1 0 0 1 100 khz 1 0 1 0 90 khz 1 0 1 1 80 khz 1 1 0 0 70 khz 1 1 0 1 60 khz 1 1 1 0 50 khz 1 1 1 1
10 U4255BM-M 4519c?audr?07/02 fm demodulator for weather band reception, the gain of the fm demodulator is increased and can be adjusted by means of bit 71, bit 72 in order to increase the output voltage to compen- sate the low frequency deviation in weather band. an integrated demodulator fine adjustment allows automatic fine tuning of the demodu- lator center frequency to the average frequency of the received signal. this feature is implemented for use in weather band mode and can be activated by setting bit 53 to 0. figure 5. fm demodulator automatic fine tuning the center frequency of the fm demodulator can be adjusted by means of bit 56 to 59. at the center frequency, the dc voltage at the mpx output pin 11 is equal to the mpx offset voltage that can be measured at pin 11 while mpx mute is active (bit 7 = 1). this adjustment will affect the center frequency of all integrated filters as mentioned before. table 16. demodulator gain in weather band mode table 17. demodulator fine adjustment demodulator gain in weather band mode relative to fm mode bit 72 bit 71 12 db 0 0 15 db 0 1 18 db 1 0 21 db 1 1 demodulator fine adjustment bit 53 fine tuning on 0 fine tuning off 1 fm demod + (10nf) am agc b92 center freq. bit 53 automatic frequency adjustment mpx ifagch v3
11 U4255BM-M 4519c?audr?07/02 soft mute the soft mute functionality is implemented to reduce the output level of the fm demodu- lator at low input signal levels to limit the noise at mpx output in this case. if the input level falls below an adjustable threshold, continuously the output of the fm demodulator is continuously muted with decreasing input level until a maximum mute value is reached. the threshold for the start of soft mute and the maximum mute can be adjusted. the signal level for 3 db mute can be set by means of bit 68 to 70 and the maximum value for soft mute can be selected by bit 67. the steepness and the time constant of the soft mute can be adjusted by the resistor and capacitor between pin 34 and pin 29. the field strength signal available at pin 9 is used for soft mute. therefore, the soft mute threshold referred to the input of the fm mixer depends on the gain from fm mixer input to the field strength sensor. table 18. soft mute threshold table 19. maximum soft mute figure 6. soft mute relative soft mute threshold bit 70 bit 69 bit 68 soft mute off 0 0 0 -18 db 0 0 1 -15 db 0 1 0 -12 db 0 1 1 -9 db 1 0 0 -6 db 1 0 1 -3 db 1 1 0 0 db 1 1 1 maximum value of soft mute bit 67 28 db 0 24 db 1 pin 34 pin 29 + v3 bit 67 fs (pin9) bit 68..70 gain fm-demodulator
12 U4255BM-M 4519c?audr?07/02 mpx output the output of the am demodulator (am mode) or the output of the fm demodulator (fm/wb mode) are available at the mpx output (pin 11). the mpx output signal can be muted by setting bit 7 to 1. the bandwidth of the lowpass filter at the mpx output can be set by means of bit 79 to 90 khz or 180 khz. table 20. mpx output mute table 21. mpx output bandwidth receiving condition analyzer the U4255BM-M implements several sensors that provide information about the receiv- ing condition of the selected station. field strength sensor the field strength sensor provides a dc voltage at pin 9 which represents the logarith- mic field strength of the signal in the reception band. the field strength information can be retrieved either from a level detector at the input of the 2 nd mixer (pin 26) or from the if-agc depending on the setting of bit 80. the band- width of the field strength detection in the agc is smaller than by using the level detector because of additional selectivity between the 2 nd mixer and the 2 nd if amplifier particularly in am and wb, but the field strength detection in the agc is limited to the if agc range. usually the field strength from the level detector is used in fm mode and the agc field strength is used in am mode. table 22. field strength selection search stop detector a search stop detector is available in am and fm/wb mode. a stop condition is signaled if the frequency of the zf signal is within a window around the center frequency of 450 khz. the width of this search stop window can be set by bit 85 to 87 in the range of 0.5 khz to 80 khz. the frequency of the zf signal is measured by counting the num- ber of periods of the zf signal during a measurement time which is determined by bit 73 to 78. the inverted stop signal is availabl e at pin 21 according to table 25. the fre- quency of 10.25 mhz at pin 22 is used as time reference. mpx output bit 7 mpx out, pin 11 normal operation 0 mute on 1 bandwidth mpx lowpass filter bit 79 90 khz 0 180 khz 1 field strength narrow band / wide band bit 80 fieldstrength at pin 26 (wide band) 0 fieldstrength from if-agc (narrow band) 1
13 U4255BM-M 4519c?audr?07/02 table 23. search stop detector measurement time table 24. search stop window table 25. signals available at digital output pin 21 deviation sensor the deviation sensor is active in am and fm/wb mode and measures the modulation of the signal. it is implemented as a peak detector of the lowpass-filtered mpx signal (see figure 7). the output voltage at pin 31 is proportional to the frequency deviation in fm/wb or the modulation depth in am respectively. figure 7. deviation sensor time window for stop signal bit 78 bit 77 bit 76 bit 75 bit 74 bit 73 1 3.1969 ms 0 0 0 0 0 1 ..... 63 3.1969 ms 1 1 1 1 1 1 search stop window bit 87 bit 86 bit 85 0.5 khz 0 0 0 1.1 khz 0 0 1 2.3 khz 0 1 0 4.8 khz 0 1 1 10 khz 1 0 0 20 khz 1 0 1 40 khz 1 1 0 80 khz 1 1 1 bit 88 bit 92 int (pin 21) 00 (am) 1 0 1 (fm/wb) not mpint 10 (am) not stop 1 1 (fm/wb) not (stop and not mpint) mpx 25k 4k + pin 31
14 U4255BM-M 4519c?audr?07/02 adjacent channel sensor the adjacent channel sensor is active in fm mode only and measures the field strength outside the reception band. by setting the center frequency of the band filter of the adja- cent channel sensor below or above the 2 nd if frequency (bit 5, bit 6), it can be determined whether the disturbance signal is located above or below the reception fre- quency (see table 28). the bandwidth of the band filter used in the adjacent channel sensor can be changed by means of bit 10 to 13. if bit 4 = 0 the default bandwidth set- ting is used. the output of the adjacent channel sensor is independent of the bandwidth setting of the integrated fm band filter. figure 8. adjacent channel sensor table 26. bandwidth of the adjacent channel detector filter table 27. center frequency adjacent channel sensor bw adjustment bit 13 bit 12 bit 11 bit 10 3 khz 0 0 0 0 16 khz 0 0 1 0 32 khz 0 1 0 0 50 khz 0 1 1 0 65 khz 1 0 0 0 80 khz 1 0 1 0 95 khz 1 1 0 0 110 khz 1 1 1 0 50 khz 0 0 0 1 65 khz 0 0 1 1 80 khz (default) 0 1 0 1 95 khz 0 1 1 1 110 khz 1 0 0 1 130 khz 1 0 1 1 145 khz 1 1 0 1 160 khz 1 1 1 1 center frequency bit 6 bit 5 450 khz 0 0 300 khz 0 1 700 khz 1 0 filter off 1 1 log intergr. fm bandfilter if log 4k 50k + pin 10 + -
15 U4255BM-M 4519c?audr?07/02 table 28. output voltage of adjacent channel sensor for different receiving conditions and center frequencies multipath sensor the multipath sensor is active in fm mode only and measures the disturbance due to multipath reception. the multipath sensor detects drops in the field strength after the integrated band filter by calculating the difference between an averaged maximum field strength and the current field strength. the maximum depth of these drops is repre- sented by the voltage of the peak detector at pin 40 (multip). the level of this voltage represents the degree of disturbance in the received signal. figure 9. multipath sensor a multipath noise canceller (mnc) is implemented to reduce disturbance of the received signal in multipath reception conditions. if the difference between the momen- tary and the averaged field strength falls below a threshold adjustable by bit 81 to 84 (see table 30), the mpx signal may be muted and this situation (mpint) can be signal- ized at pin 21 (int) according to table 25. muting of the mpx signal during multipath disturbances can be activated be setting bit 8. table 29. multipath noise canceller adjacent channel disturbance 300 khz 450 khz 600 khz no high low high below high high low above low high high multipath noise canceller bit 8 active 0 not active 1 + pin40 4k
16 U4255BM-M 4519c?audr?07/02 table 30. sensitivity of the mnc 3-wire bus description the register settings of U4255BM-M are programmed by a 3-wire bus protocol. the bus protocol consists of separate commands. a defined number of bits is transmitted sequentially during each command. one command is used to program all bits of one register. the different registers avail- able (see table 31) are addressed by the length of the command (number of transmitted bits) and by three address bits that are unique for each register of a given length. 8-bit registers are programmed by 8-bit commands and 24-bit registers are programmed by 24-bit commands. each bus command starts with a rising edge on the enable line (en) and ends with a falling edge on en. en has to be kept high during the bus command. the sequence of transmitted bits during one command starts with the lsb of the first byte and ends with the msb of the last byte of the register addressed. the data is evaluated at the rising edges of clk. the number of low to high transitions on clk during the high period of en is used to determine the length of the command. the bus protocol and the register addressing of U4255BM-M are compatible to the addressing used in u4256bm. that means U4255BM-M and u4256bm can be operated on the same 3-wire bus as shown in the application circuit. sensitivity mnc (threshold) bit 93 bit 92 bit 84 bit 83 bit 82 bit 81 off x10000 low x10001 x10010 (-18 db) x 1 0 0 1 1 x10100 x10101 x10110 normal (-12 db) x 1 0 1 1 1 x11000 x11001 x11010 x11011 x11100 x11101 x11110 high (-9 db) x 1 1 1 1 1
17 U4255BM-M 4519c?audr?07/02 figure 10. pulse diagram figure 11. bus timing 8-bit command en clk data lsb msb byte 1 24-bit command clk data lsb lsb msb msb byte 3 byte 2 msb lsb byte 1 en t r t s t hda enable data clock t r t s t r t h t l t f t f t f t hen
18 U4255BM-M 4519c?audr?07/02 data transfer table 31. control registers a24_100 m s b byte 3 ls b msb byte 2 ls b msb byte 1 ls b addr. am/fm/wb gain fm if amplifier sear ch width of window osc divider/multipath sensitivity field stren gth bwm px time window stop signal 100amfm b9 3 b9 2 b9 1 b9 0 b8 9 b88 b8 7 b8 6 b8 5 b8 4 b8 3 b8 2 b8 1 b80 b79 b7 8 b7 7 b7 6 b7 5 b7 4 b7 3 a24_101 m s b byte 3 ls b msb byte 2 ls b msb byte 1 ls b addr. wb- demod- gain start smute smu te tk- fm if fm-agc am-agc fm bw 2 nd mixer if2 center frequency mp fs fm ext de m. adj. not use d 101 x b7 2 b7 1 b7 0 b6 9 b6 8 b67 b66 b6 5 b6 4 b6 3 b6 2 b6 1 b6 0 b59 b58 b5 7 b5 6 b5 5 b5 4 b5 3 b5 2 a24_111 m s b byte 3 ls b msb byte 2 ls b msb byte 1 ls b addr. used in test mode only center frequency of bandfilter bandwidth adj. channel sensor 111 xx 1 0 000101 b3 0 b2 9 b2 8 b2 7 b2 6 b25 b24 b2 3 b2 2 b2 1 b2 0 b1 9 b1 8 b17 b16 b1 5 b1 4 b1 3 b1 2 b1 1 b1 0 a8_100 m s b byte 1 ls b addr. te s t mp off mut e adj. channel sensor 100 0 b9 b8 b7 b6 b5 a8_101 m s b byte 1 ls b addr. optimi ze band width 101 b4 b3 b2 b1 b0
19 U4255BM-M 4519c?audr?07/02 absolute maximum ratings all voltages are referred to gnd (pin 25) parameters symbol value unit supply voltage pin 42 v s 10 v power dissipation p tot 1000 mw junction temperature t j 150 c ambient temperature range t amb -40 to +85 c storage temperature range t stg -50 to +150 c thermal resistance parameters symbol value unit junction ambient, soldered to pcb r thja 60 k/w operating range all voltages are referred to gnd (pin 25) parameters symbol min. typ. max. unit supply voltage range pin 42 v s 7.5 8.5 10 v ambient temperature t amb -40 +85 c electrical characteristics test conditions (unless otherwise specified): v s = 8.5 v, t amb = 25c. no. parameters test conditions pin symbol min. typ. max. unit type* 1 power supply 1.1 supply voltage 42 v s 7.5 8.5 10 v c 1.2 supply current standby mode (bit 92 = 0, bit 93 = 0) 42 i stby 20 25 ma a 1.3 supply current other operation modes 42 i s 50 60 ma a 2vco 2.1 frequency range f vco 70 160 mhz d 2.2 dc bias voltage 13 2.8 3.0 3.2 v a 2.3 buffer output voltage f osc = 120 mhz 16 130 150 250 mvrms a 2.4 buffer output resistance 16 70 d 2.5 buffer output dc voltage 16 2.8 3.0 3.2 v a *) type means: a =100% tested, b = 100% correlation tested, c = characterized on samples, d = design parameter
20 U4255BM-M 4519c?audr?07/02 3fm rf-agc 3.1 saturation voltage no input signal 5 8.3 v a 3.2 saturation voltage no input signal 5 v s -0.2 v b 3.3 threshold level in-band signal 30 110 dbv d 3.4 maximum threshold level out-of-band signal (110 mhz), bit 64, 65 = 0 1 100 102 104 db va 4 am rf-agc, am mode (bit 92 = 0, bit 93 = 1) 4.1 saturation voltage no input signal 7 8.3 v a 4.2 saturation voltage no input signal 7 v s -0.2 v b 4.3 output voltage for minimum gain bit 92 = 1 7 6.5 6.8 7.1 v a 4.4 output voltage for minimum gain bit 92 = 1 7 v s -1.7 v b 4.5 maximum control voltage v(pin 8) = 3 v 6 6.5 7.0 7.5 v a 4.6 maximum control voltage v(pin 8) = 3 v 6 v s -1.5 v b 4.7 minimum control voltage v(pin 8) = 6 v 6 0.2 0.7 v a 4.8 minimum threshold level bits 62, 63 = 0 41 97 99 101 dbv a 5 am mixer, am mode (bit 92 = 0, bit 93 = 1) 5.1 supply current sum of current in pins 43, 44 43, 44 14 16 20 ma a 5.2 conversion conductance 3, 41, 43, 44 4.1 ms d 5.3 3 rd -order input intercept point pin 3 ac-grounded 41 ip3 ammix 132 dbv c 5.4 noise figure (ssb) generator resistance 2.5 k (pin 41) 43, 44 nf ammix 14 db c 5.5 input bias dc voltage 3, 41 2.4 2.6 2.9 v a 5.6 input resistance single-ended, pin 39 ac-grounded 3, 41 2.5 k d 5.7 input capacitance 3, 41 3 pf d 5.8 maximum output voltage differential 43, 44 12 vpp d 5.9 output resistance 43, 44 100 k d 6 fm mixer (fm mode (bit 92 = 1, bit 93 = 0) 6.1 supply current sum of current in pins 43, 44 43, 44 15 17.5 20 ma a 6.2 conversion conductance 1, 2, 43, 44 7msd electrical characteristics (continued) test conditions (unless otherwise specified): v s = 8.5 v, t amb = 25c. no. parameters test conditions pin symbol min. typ. max. unit type* *) type means: a =100% tested, b = 100% correlation tested, c = characterized on samples, d = design parameter
21 U4255BM-M 4519c?audr?07/02 6.3 3 rd -order intercept point 1, 2 ip3 fmmix 120 db vc 6.4 noise figure (dsb) generator resistance 200 43, 44 nf fmmix 10 db c 6.5 input resistance 1, 2 1.6 k d 6.6 input capacitance pin 2 ac-grounded 1 5 pf d 6.7 maximum differential output vltage v s = 8.5 v 43, 44 12 vpp d 6.8 output resistance 43, 44 100 k d 71 st if fm amplifier, fm mode (bit 92 = 1, bit 93 = 0) 7.1 minimum voltage gain bits 89, 90, 91 = 0 38, 30 19 21 23 db a 7.2 temperature coefficient of gain bit 66 = 0 tk min 0.039 db/k d 7.3 temperature coefficient of gain bit 66 = 1 tk max 0.044 db/k d 7.4 input resistance pin 39 ac-grounded 38 270 330 400 d 7.5 input capacitance pin 39 ac-grounded 38 5 pf d 7.6 output resistance 30 270 330 400 d 81 st if am amplifier, am mode (bit 92 = 0, bit 93 = 1) 8.1 maximum voltage gain 330 load at pin 30 30, 33 16 db d 8.2 gain control range 26 db d 8.3 noise figure generator resistance 2.5 k nf ifam 20 db c 8.4 input resistance 33 10 k d 8.5 input capacitance pin 39 ac-grounded 33 1 pf d 8.6 output resistance 30 270 330 400 d 92 nd mixer 9.1 fm supply current bit 92 = 1, bit 93 = 0 23, 24 10 14 16 ma a 9.2 am/wb supply current bit 92 = 0, bit 93 = 1 23, 24 8 10 12 ma d 9.3 conversion conductance 26, 23, 24 2msd 9.4 noise figure (ssb) generator resistance 330 (pin 26) 23, 24 nf mix2 23 db c 9.5 3 rd -order input intercept point 26 ip3 mix2 132 dbv c 9.6 am/wb output resistance bit 92 = 0, bit 93 = 1 23, 24 100 k d 9.7 maximum differential output voltage am/wb v s = 8.5 v 23, 24 12 vpp d electrical characteristics (continued) test conditions (unless otherwise specified): v s = 8.5 v, t amb = 25c. no. parameters test conditions pin symbol min. typ. max. unit type* *) type means: a =100% tested, b = 100% correlation tested, c = characterized on samples, d = design parameter
22 U4255BM-M 4519c?audr?07/02 9.8 maximum differential output voltage fm 23, 24 1 vpp d 9.9 input resistance 26 270 330 400 d 9.10 lo input voltage 22 80 500 mvpp d 9.11 lo input resistance 22 1 k d 9.12 lo input bias voltage 22 2.8 3.0 3.2 v a 10 2 nd if amplifier (bit 55 = 0) 10.1 input resistance pin 27 ac-grounded 28 3 k d 10.2 maximum voltage gain am/wb mode (bit 93 = 1) 28, 20 44 47 50 db a 10.3 gain control range am/wb mode (bit 93 = 1) 44 db d 10.4 maximum voltage gain fm mode (bit 92 = 1, bit 93 = 0, bit 54 = 0) 23, 24 20 37 db d 10.5 dc output voltage 20 3.1 3.4 3.7 v a 10.6 ac output voltage unmodulated signal, 82 dbv at pin 1 (if agc active) 20 145 175 200 mvrms a 10.7 output impedance small signal 20 70 d 11 fm demodulator integrated bandfilter, fm mode (bit 92 = 1, bit 93 = 0), bw setting 2 nd if filter = 120 khz 11.1 ac output voltage deviation = 75 khz, f mo d = 1 khz 11 420 480 540 mvrms a 11.2 stereo roll-off deviation = 75 khz, f mod = 38 khz (reference: 1 khz) 11 -2.3 -2.0 -1.7 db a 11.3 total harmonic distortion deviation = 75 khz, f mod = 1 khz 11 thd fm 0.4 0.7 % a 11.4 maximum signal-to- noise ratio dev. = 22.5 khz, f mod = 1 khz, 50 s de-emphase, signal input at 450 khz 11 (s/n) fm 62 65 db a 12 soft mute, fm mode (bit 92 = 1, bit 93 = 0, bit 80 = 0) 12.1 mute gain bit 67 = 0, v (pin 34) = 2 v 11 -31 -28 -26 db a 12.2 mute gain bit 67 = 1, v (pin 34) = 2 v 11 -26 -24 -22 db a 12.3 soft mute threshold bits 89-91 = 0, bits 68-70 = 1 1 505356dbvb 13 am demodulator, am mode (bit 92 = 0, bit 93 = 1) 13.1 ac output voltage modulation depth = 80%, f mod = 1 khz 11 350 400 450 mvrms a 13.2 total harmonic distortion modulation depth = 80%, f mod = 1 khz, v(pin 35) = const. 11 thd am 0.6 2 % a electrical characteristics (continued) test conditions (unless otherwise specified): v s = 8.5 v, t amb = 25c. no. parameters test conditions pin symbol min. typ. max. unit type* *) type means: a =100% tested, b = 100% correlation tested, c = characterized on samples, d = design parameter
23 U4255BM-M 4519c?audr?07/02 13.3 maximum signal-to- noise ratio modulation depth = 80%, f mod = 1 khz, 74 dbv at pin 41 11 (s/n) am 52 54 db a 14 mpx output 14.1 dc output voltage bit 7 = 1 11 2.15 2.25 2.4 v a 14.2 mute gain bit 7 = 1, fm dev. = 75 khz, f mod =1khz 11 -70 -50 db a 14.3 output resistance small signal 11 60 d 15 search stop detector, int output 15.1 low saturation voltage 21 0 0.5 v a 15.2 low output resistance 21 0.3 k d 15.3 high saturation voltage 21 4.54.755.0 v a 15.4 high output resistance 21 1 k d 16 deviation sensor, fm mode (bit 92 = 1, bit 93 = 0) 16.1 offset voltage fm dev. = 0 khz 31 20 150 mv a 16.2 output voltage fm dev. = 75 khz, f mod =1khz 31 1.7 2.0 2.5 v a 17 field strength sensor, fm mode (bit 92 = 1, bit 93 = 0, bit 89-91 = 0, bit 80 = 0) 17.1 offset voltage no signal 9 0.4 0.75 1.1 v a 17.2 output voltage unmodulated signal 84 dbv at pin 1 92.73.03.3va field strength sensor, am mode (bit 92 = 0, bit 93 = 1, bit 80 = 1) 17.3 output voltage low field strength 63 dbv at pin 28 90.70.91.1va 17.4 output voltage high field strength 94 dbv at pin 28 92.32.52.7va 18 multipath sensor, fm mode (bit 92 = 1, bit 93 = 0) 18.1 offset voltage unmodulated signal, 60 dbv at pin 1 40 20 200 mv a 18.2 output voltage am modulation depth = 60%, f mod = 20 khz, 60 dbv at pin 1 40 1.4 1.8 2.2 v a 19 adjacent channel sensor, fm mode (bit 92 = 1, bit 93 = 0), bit 4 = 0 (default bw setting) 19.1 offset voltage unmodulated signal 10 100 300 mv a 19.2 output voltage fm dev. = 50 khz, f mod = 1 khz 10 0.6 1.0 v a electrical characteristics (continued) test conditions (unless otherwise specified): v s = 8.5 v, t amb = 25c. no. parameters test conditions pin symbol min. typ. max. unit type* *) type means: a =100% tested, b = 100% correlation tested, c = characterized on samples, d = design parameter
24 U4255BM-M 4519c?audr?07/02 19.3 output voltage desired fm dev. = 75 khz, f mod = 1 khz undesired: unmodulated rf level undesired/desired: +30 db frequency offset = -150 khz 10 1.0 1.2 1.6 v a 20 3-wire bus 20.1 input voltage low 17, 18, 19 0.8 v d 20.2 input voltage high 17, 18, 19 2.7 v d 20.3 leakage current v = 0 v, 5 v 17, 18, 19 10 a d 20.4 clock frequency 18 1.0 mhz d 20.5 period of clk high low t h t l 250 250 ns ns d 20.6 rise time en, data, clk t r 400 ns d 20.7 fall time en, data, clk t f 100 ns d 20.8 set-up time t s 100 ns d 20.9 hold time en t hen 250 ns d 20.10 hold time data t hda 0nsd 21 internally generated reference voltages 21.1 output voltage 12 5.5 5.7 6.0 v a 21.2 output voltage 29 3.0 v d 21.3 output voltage 27 3.0 v d 21.4 output voltage 39 3.0 v d electrical characteristics (continued) test conditions (unless otherwise specified): v s = 8.5 v, t amb = 25c. no. parameters test conditions pin symbol min. typ. max. unit type* *) type means: a =100% tested, b = 100% correlation tested, c = characterized on samples, d = design parameter
25 U4255BM-M 4519c?audr?07/02 diagrams the following data was measured with the application board (see figure 20). in the measurement setup, a 50- generator is terminated by 50 and connected to the antenna input by a 50- series resistor to achieve 75- termination at the antenna input. the generator level specified is the output voltage of this 50- generator at 50 load. if the application board is replaced by a 75- resistor, the voltage at this resistor is 6 db below the specified voltage level of the 50 generator. figure 12. fm demodulator integrated bandfilter bw setting: 120 khz, bits 0 to 2 = 0, bit 3 = 1; 1 khz modulation frequency; 50 s de-emphasis (thd) figure 13. multipath sensor am modulation frequency 20 khz; generator level 40 db v 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 0 10203040 5060 7080 90100 frequency deviation ( khz ) mpx output voltage ( vrms ) 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 thd ( % ) mpx thd +85c -40c +85c -40c 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 020406080100 am modulation depth (%) sensor output voltage (v) -40c +25c +85c
26 U4255BM-M 4519c?audr?07/02 figure 14. multipath sensor frequency response generator level 40 db v figure 15. deviation sensor fm modulation frequency: 1 khz; bw setting 2 nd if filter = 120 khz 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 100 1000 10000 100000 am modulation frequency (hz) sensor output voltage (v] 90% at +85c 90% at +25c 90% at -40c 60% at +85c 60% at +25c 60% at -40c 0 1 2 3 4 5 0 20000 40000 60000 80000 100000 frequency deviation (hz) deviation sensor output voltage (v) +85c -40c
27 U4255BM-M 4519c?audr?07/02 figure 16. deviation sensor frequency response fm frequency deviation: 22.5 khz figure 17. fm input level sweep soft mute threshold bits 68, 69 = 0, bit 70 = 1; soft mute gain bit 67 = 1 gain fm if amplifier bit 89 = 1, bits 90, 91 = 0 0.0 0.5 1.0 100 1000 10000 100000 fm modulation frequency (hz) sensor output voltage ( v ) -70 -60 -50 -40 -30 -20 -10 0 10 -20 0 20 40 60 80 100 120 input level (dbv) mpx output (db) 1 1.5 2 2.5 3 3.5 4 4.5 5 fieldstrength sensor output voltage (v) signal sensor output noise
28 U4255BM-M 4519c?audr?07/02 figure 18. selectivity integrated bandfilter bw setting: 120 khz desired signal level adjusted to 40 db s/n without undesired signal undesired signal level adjusted to 26 db s/n -70 -60 -50 -40 -30 -20 -10 0 10 20 -250 -200 -150 -100 -50 0 50 100 150 200 250 frequency offset ( khz ) pdes/pundes ( db ) 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 adjacent channel output voltage ( v ) pdes/pundes adjacent
29 U4255BM-M 4519c?audr?07/02 figure 19. test circuit 330 1k 600 4n7 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 24 23 26 25 28 27 30 29 32 31 34 33 36 35 38 37 40 39 42 41 44 43 vs 100n 10n 10n 100n bus 10n 10k vs 82p vs vs 100n p41 10n 100n 100n 100n 220n 47p 22p 6p8 5k6 1n 10k 100 10 15p 100p 270 2k2 100n p29 200k p29 p31 22n 2k2 10k 2n2 p41 10n 10k v 220n p29 u4256bm pin1 pin19 pin15 test point u4255bm-b
30 U4255BM-M 4519c?audr?07/02 figure 20. application circuit 12 13 u4255bm 14 15 16 17 18 19 20 21 22 33 32 31 30 29 28 27 26 25 24 23 44 43 42 41 40 39 38 37 36 35 34 1 2 3 4 5 6 7 8 9 10 11 18p c203 22u c131 c132 f131 bb804 1 2 3 4 5 6 7 8 9 10 u4256bm 20 19 18 17 16 15 14 13 12 11 c314 10n f102 c112 10u c113 100n swo1 dac3 swo2 swo3 swo4 int if2out data clk en gnd mpx adjac meter c310 f302 multip dev c208 c205 c202 f201 q151 r407 10 r106 10 r152 10 c312 10n 1n c309 r303 1k 220n c207 r305 1k5 x301 r304 1k3 r34 27 kr201 r313 390 c111 470n c in f201 100p c307 10n c209 r29 10 c308 100n vs (+8,5v...10,5v) r311 2k2 r105 100 r115 1k t102 bc858 c109 c108 r102 68k c110 4n7 r121 68k r122 68k c56 10p c104 10n r112 47k l102 r104 470 c117 c107 2u2 c106 27p f101 bb804 d101 c103 c102 10n c311 100n r103 1k 3p9 d103 s391d 10n d302 l301 4u7 l303 2m2 l302 100uh c306 c319 12p 6p8 bc 858c c316 r308 2k2 220n r307 47 c315 220n c302 10n r306 470k r151 8k2 c152 330p c134 1n c151 10n c158 10n c159 c157 10n 10n c154 c153 c155 c156 10n 10,25mhz 12p* 12p* 100n c114 220n c133 6p8 47p 22p r131 5k6 kf302 kr202 220n 220n c204 c206 r111 200k 1u 10n 10u 470n c116 c115 100n 100n 10n t301 t302 bc848 t111 j109 t101 bfr93a ant fm 75 ohm s391d d301 s391d c201 100n d131 d102 bb804 1n 6p8 *depends on q151
31 U4255BM-M 4519c?audr?07/02 package information ordering information extended type number package remarks U4255BM-Mfn sso44 tube U4255BM-Mfng3 sso44 taped and reeled technical drawings according to din specifications package sso44 dimensions in mm 0.25 0.10 0.3 0.8 18.05 17.80 16.8 2.35 9.15 8.65 7.50 7.30 10.50 10.20 0.25 44 23 1 22
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