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cmx469a 1200/2400/4800 baud ffsk/msk modem ? 2001 consumer microcircuits limited d/469a/2 may 2001 provisional issue features applications full - duplex ffsk/msk modem with separate rx and tx enable functions data - over radio perso nal/cordless telephone pin selectable data rates: 1200, 2400 or 4800 baud radio and general applications narrowband coax data channels pin select able xtal/clock inputs: 1.008mhz or 4.032mhz two way radio (mpt1327) signalling portable data terminals clock recovery facility carrier detect f acility low power operation (2.0ma typ. at 3.0v) 1.1 brief description the cmx469a is a single - chip cmos lsi circuit whi ch operates as a full - duplex 1200, 2400 or 4800 baud ffsk/msk modem. the mark and space frequencies are 1200/1800, 1200/2400 and 2400/4800 hz respectively. tone frequencies are phase continuous; transitions occur at the zero crossing point. a common xt al oscillator with a choice of two clock frequencies (1.008mhz or 4.032mhz) provides baud - rate, transmit frequencies, and rx and tx synchronization. the transmitter and receiver operate entirely independently, including the individual section powersave fu nctions. the cmx469a includes on - chip circuitry for carrier detect and rx clock recovery, both of which are made available as output pins. rx, tx and carrier detect paths contain bandpass filters to optimise signal conditions in each section of the modem . the cmx469a demonstrates good sensitivity and bit - error - rate under adverse signal conditions. the carrier detect time constant is set by an external capacitor, so that the product's performance can be optimised in high noise environments. this low - pow er device operates from a single supply between 2.7v and 5.5v, requires few external components and is available in a wide variety of plastic packages.
1200/2400/4800 baud ffsk/msk modem cmx469a ? 2001 consumer microcircuits limited 3 d/469a/2 contents section page 1.0 features and applications ................................ ................................ ....... 2 1.1 brief description ................................ ................................ ....................... 2 1.2 block diagram ................................ ................................ ........................... 4 1.3 signal list ................................ ................................ ................................ ... 5 1.4 external components ................................ ................................ ............... 7 1.5 general description ................................ ................................ .................. 8 1.6 application notes ................................ ................................ ...................... 9 1.7 performance specification ................................ ................................ ..... 10 1.7.1 electrical performance ................................ .............................. 10 1.7.2 packaging ................................ ................................ .................... 16
1200/2400/4800 baud ffsk/msk modem cmx469a ? 2001 consumer microcircuits limited 4 d/469a/2 1.2 block diagram figure 1 block diagram
1200/2400/4800 baud ffsk/msk modem cmx469a ? 2001 consumer microcircuits limited 5 d/469a/2 1.3 signal list cmx469a d3 e2 p6 signal description pin no. pin no. pin no. name type 1 1 1 clock/xtal i/p the input to the on - chip inverter, for use with either a 1.008mhz or a 4.032mhz xtal or an external clock. clock frequency selection is by means of the clock rate pin. this affects the operational data rate of the device. operation of any cml microcircuit without a xtal or clock input may cause device damage. 2 2 2 xtaln o/p the output of the on - chip inverter. 3 3 3 tx sync o/p o/p a squarewave, produced on - chip, to synchronize the input of logic data and transmission of the ffsk/msk signal. 4 5 5 tx signal o/p o/p whe n the transmitter is enabled, this pin outputs the ffsk/msk signal. with the transmitter disabled, this pin is set to a high - impedance state. 5 7 6 tx data i/p i/p the serial logic data to be transmitted is input to this pin. 6 8 7 tx enablen i/p a logi c ?0? will enable the transmitter. a logic ?1? at this input will put the transmitter into powersave whilst forcing tx sync output to a logic ?1? and tx signal output to a high - impedance state. this pin is internally pulled to v dd . 7 9 8 bandpass o/p o/p the output of the rx bandpass filter. this output impedance is typically 10k w and may require buffering prior to use. 8 10 9 rx enable i/p the control of the rx function 9 11 10 v bias bi the output of the on - chip analogue bias circuitry. held internally at v dd /2, this pin should be decoupled to v ss by a capacitor (c2). this bia s voltage is maintained under all powersave conditions. 10 12 11 v ss pwr negative supply rail (gnd). 11 13 12 unclocked data o/p o/p the recovered asynchronous serial data output from the receiver. 12 14 13 clocked data o/p o/p the recovered synchronous serial data output from the receiver. data is latched out by the recovered clock, available at the rx sync o/p.
1200/2400/4800 baud ffsk/msk modem cmx469a ? 2001 consumer microcircuits limited 6 d/469a/2 cmx469a d3 e2 p6 signal description pin no. pin no. pin no. name type 13 15 14 carrier detect o/p o/p when an ffsk/msk signal is being received this output is a logic ?1?. 14 16 15 rx signal i/p i/p the ffsk/msk signal input for the receiver. this input should be coupled via a capacitor, c3. 15 18 17 rx sync o/p o/p a flywheel squarewave output. this clock will synchronize to incoming rx ffsk/msk data. 16 19 16 1200/2400 baud select i/p a logic ?1? on this pin selects the 1200 baud option. tone frequencies are: one cycle of 1200hz represents a logic ?1,? one - and - a - half cycles of 1800hz represents a logic ?0.? a logic ?0? on th is pin selects the 2400 baud option. tone frequencies are: one - half cycle of 1200hz represents a logic ?1,? one cycle of 2400hz represents a logic ?0.? this function is also used, in part, to select the 4800 baud option. this pin has an internal 1m w pullup resistor. 17 20 18 4800 baud select i/p a logic ?1? on this pin combined with a logic ?0? on the 1200/2400 baud select pin will select the 4800 baud option (1m w pulldown resistor). tone frequencies are: one - half cycle of 2400hz represents a logic ?1,? one cycle of 4800hz represents a logic ?0.? operation at 4800 baud is only achieved by using a 4.032mhz xtal or clock. 18 21 19 clock rate i/p a logic input to select and allow the use of either a 1.008mhz or 4.032mhz xtal/clock. logic ?1? = 4.032mhz, log ic ?0? = 1.008mhz. this input has an internal pulldown resistor (1.008mhz). 19 22 20 carrier detect time constant bi part of the carrier detect integration function. the value of c4 connected to this pin will affect the carrier detect response time and he nce noise performance. 20 24 22 v dd pwr positive supply rail. a single 2.7 to 5.0 volt supply is required. this pin should be decoupled to v ss by a capacitor (c5). 4, 6, 17, 23 4, 21 no internal connection, do not use. notes: i/p = input o/p = output bi = bidirectional pwr = power
1200/2400/4800 baud ffsk/msk modem cmx469a ? 2001 consumer microcircuits limited 7 d/469a/2 1.4 external components component value r1 1.0m w c1 33.0pf c2 1.0f c3 0.1f c4 0.1f c5 1.0f c6 1.0f c7 33.0pf x1 1.008mhz or 4.032mhz notes: 1. v bias may be decoupled to v ss and v dd using c2 and c6 when input signals are referenced to the v bias pin. for input signals referenced to v ss , de couple v bias to v ss using c2 only. 2. the performance of the carrier detect function will be affected by the nature of the noise spectrum in the received channel. the value of c4 determines the carrier detect time constant. a long time constant results in improved noise immunity but increased response time. c4 may be varied to trade - off response time for noise immunity. 3. a 4.032mhz xtal/clock is required for 4800 baud operation. figure 2 recommended external components
1200/2400/4800 baud ffsk/msk modem cmx469a ? 2001 consumer microcircuits limited 8 d/469a/2 1.5 general description the cmx469a has two sections, apart from the xtal oscillator circuit and clock dividers. these sections may be independently powersaved. transmitter the transmitter is enabled by taking tx enablen low. serial data applied to tx data input is sampled internally and an ffsk/msk sequence is generated. after filtering, this is output at tx signal o/p and the transmit clock derived from this signal is output at tx sync o/p. receiver the receiver is enabled by taking rx enable high. the signal applied to rx signal i/p is filtered and recovered as serial data from the unclocked data o/p. a flywheel synchroniser is used to extract a clock from the recovered serial data stream. the clock is available at rx sync o/p an d the retimed serial data is available at clocked data o/p. the integrated peak values of the rx amplitude are compared with out - of - band noise levels and used to make a signal - to - noise assessment, which is available at carrier detect o/p. a bandpass o/ p is also available from the output of the first rx filter stage, but will require buffering before use.
1200/2400/4800 baud ffsk/msk modem cmx469a ? 2001 consumer microcircuits limited 9 d/469a/2 1.6 application notes rx enable the control of the relevant outputs with reference to the rx enable input is described below: rx enable rx function clock data o/p carrier detect o/p rx sync out ?1? enabled enabled enabled enabled ?0? powersave ?0? ?1? or ?0? ?1? or ?0? after enabling the receiver, a time of at least 8 bit periods plus 2ms should be allow ed for the carrier detect circuit to stabilise and give a valid output. operational data rate configurations operational data rate configurations are as described below: xtal/clock frequency 1.008mhz 4.032mhz clock rate ?0? ?0? ?1? ?1? ?1? 1200/2400 select ?1? ?0? ?1? ?0? ?0? 4800 select ?0? ?0? ?0? ?0? ?1? baud rate 1200 2400 1200 2400 4800 test set up figure 3 suggested cmx469a test set - up
1200/2400/4800 baud ffsk/msk modem cmx469a ? 2001 consumer microcircuits limited 10 d/469a/2 1.7 performance specification 1.7.1 electr ical performance absolute maximum ratings exceeding these maximum ratings can result in damage to the device. min. max. units supply (v dd - v ss ) - 0.3 7.0 v voltage on any pin to v ss - 0.3 v dd + 0.3 v current into or out of v dd and v ss pins - 30 +30 ma current into or out of any other pin - 20 +20 ma d3 package min. max. units total allowable power dissipation at tamb = 25c 800 mw ... derating 13 mw/c storage temperature - 55 +12 5 c operating temperature - 40 +85 c e2 package min. max. units total allowable power dissipation at tamb = 25c 320 mw ... derating 5.3 mw/c storage temperature - 55 +125 c operating temperature - 40 +85 c p6 package min. max. un its total allowable power dissipation at tamb = 25c 800 mw ... derating 13 mw/c storage temperature - 55 +125 c operating temperature - 40 +85 c
1200/2400/4800 baud ffsk/msk modem cmx469a ? 2001 consumer microcircuits limited 11 d/469a/2 operating limits correct operation of the device outside these limits is not implied. n otes min. max. units supply (v dd - v ss ) 2.7 5.5 v operating temperature - 40 +85 c xtal frequency 1 4.028 4.036 mhz note 1: a xtal frequency of 1.008mhz (1200/2400 baud only) or 4.032mhz is required for correct operation. a frequency toleranc e of 0.1% is recommended, but ultimately the tolerance selected will depend upon system requirements. operating characteristics for the following conditions unless otherwise specified: v dd = 2.7v at tamb = 25 c and v dd = 3.0v to 5.5v at tamb = - 40 c to +85 c, xtal/clock frequency = 4.032mhz, bit rate = 1200 baud, rx input level = 300mvrms. notes min. typ. max. units static values i dd rx enabled, tx disabled (v dd = 5.0v) 2 - 3.6 - ma i dd rx and tx enabled (v dd = 5.0v) 2 - 4.5 - ma i dd rx and tx disabled (v dd = 5.0v) 2 - 650 - a i dd rx enabled, tx disabled (v dd = 3.0v) 2 - 1.5 - ma i dd rx and tx enabled (v dd = 3.0v) 2 - 2.0 - ma i dd rx and tx disabled (v dd = 3.0v) 2 - 300 - a logic ?1? level 1 70% - - v dd log ic ?0? level 1 - - 30% v dd digital output impedance - 4.0 - k w analogue and digital input impedance 100 - - k w tx output impedance (v dd = 5.0v) - 0.6 1.0 k w dynamic values receiver signal input dynamic range snr = 50db 3, 4 100 2 30 1000 mvrms bit error rate at snr = 12db 4, 5 1200 baud - 2.5 - 10 - 4 2400 baud - 1.5 - 10 - 3 4800 baud - 1.5 - 10 - 3 bit error rate at snr = 20db 4, 5 1200/2400/4800 baud - <1.0 - 10 - 8 receiver synchronization at snr = 12db pr obability of bit 16 being correct 7 - 0.995 -
1200/2400/4800 baud ffsk/msk modem cmx469a ? 2001 consumer microcircuits limited 12 d/469a/2 notes min. typ. max. units carrier detect 3 sensitivity 1, 7, 8 - - 150 mvrms probabilty of cd being high after bit 16: with snr = 12db 9 0.995 with 230mvrms noise and no sig nal 9 0.05 transmitter output tx output level 1 - 775 - mvrms output level variation for 1200/1800hz or 1200/2400hz or 2400/4800hz 0 - +/ - 1.0 db output distortion 10 - 3.0 5.0 % 3rd harmonic distortion 10 - 2.0 3.0 % isochr onous distortion 1200hz - 1800hz/1800hz - 1200hz - 25.0 40.0 s 1200hz - 2400hz/2400hz - 1200hz - 20.0 30.0 s 2400hz - 4800hz/4800hz - 2400hz - 10.0 20.0 s logic ?1? carrier frequency 1200 baud 6 - 1200 - hz 2400 baud 6 - 1200 - hz 4800 baud 6 - 2400 - hz logic ?0? carrier frequency 1200 baud 6 - 1800 - hz 2400 baud 6 - 2400 - hz 4800 baud 6 - 4800 - hz notes: 1. measured at v dd = 5.0 volts. signal levels and thresholds are proportional to v dd. 2. excludes any current drawn by external components, but includes current drawn by the crystal components. 3. see figure 6 (typical variation of ber with input signal level). 4. snr = signal - to - noise ratio in the bit - rate bandwidth. 5. see figure 7 (typical rx ber vs signal - to - noise ratio). 6. dependent upon xtal tolerance. 7. with an alternating (1010...) pattern. 8. measured with a 150mvrms input signal (no noise). 9. a signal level of 230mvrms is used in c.d. probability measurements. noise bandwidth is 5khz (1200/2400 baud operati on) or 8khz (4800 baud operation). see section 1.4, note 2 for details on optimising noise immunity. 10. for an unmodulated carrier.
1200/2400/4800 baud ffsk/msk modem cmx469a ? 2001 consumer microcircuits limited 13 d/469a/2 interface timing diagrams t x e n a b l e t x s y n c t x d a t a 2 4 0 0 b a u d t x o u t p u t 1 2 0 0 b a u d t x o u t p u t o p e n c i r c u i t o p e n c i r c u i t o p e n c i r c u i t o p e n c i r c u i t d c = d o n ' t c a r e d v = d a t a v a l i d d v d c d v d c d v d c d c t e s e t t t x d t d s e t d s e t t d h t t d r t t d r tx data must be valid at the time of the rising edge of tx sync. therefore the optimum time to change tx data is on the falling edge of tx sync. figure 4 transmitter timing r x s i g n a l i / p 1 2 0 0 b a u d r x s i g n a l i / p 2 4 0 0 / 4 8 0 0 b a u d r x s y n c o / p ( 1 2 0 0 h z ) c l o c k e d d a t a o / p 1 1 0 0 l o g i c ' 1 ' t i d t r d r u n d e t e r m i n e d s t a t e l o g i c ' 0 ' l o g i c ' 1 ' l o g i c ' 0 ' the optimum time to sample the clocked data o/p is on the falling edge of rx sync o/p. figure 5 receiver timing
1200/2400/4800 baud ffsk/msk modem cmx469a ? 2001 consumer microcircuits limited 14 d/469a/2 1.7.1 electrical performance (continued) inter face timings notes min. typ. max. units t eset tx delay, signal to disable time 2 2.0 - 800 s t dset data set - up time 1 2.0 - - s t dh data hold time 2.0 - - s t txd tx delay to o/p time - 1.2 - s t tdr tx data rate period 2 - 833 - s t rdr rx data rate period 2 800 - 865 s undetermined state (see figure 5) - - 2.0 s t id internal rx delay - 1.5 - ms notes: 1. consider the xtal/clock tolerance. 2. 1200 baud example. 1 5 0 2 0 0 3 0 0 5 0 0 7 0 0 8 0 0 i n p u t s i g n a l l e v e l ( m v r m s ) b i t e r r o r r a t e 2 5 0 1 0 0 5 0 1 x 1 0 - 5 1 x 1 0 - 4 1 x 1 0 - 3 1 x 1 0 - 2 1 x 1 0 - 1 1 0 d b s n r * 1 2 d b s n r * 2 0 d b s n r * * b i t r a t e b a n d w i d t h figure 6 typical variation of bit error rate with input l evel
1200/2400/4800 baud ffsk/msk modem cmx469a ? 2001 consumer microcircuits limited 15 d/469a/2 figure 7 typical rx bit error rate vs signal - to - noise ratio
1200/2400/4800 baud ffsk/msk modem cmx469a ? 2001 consumer microcircuits limited 16 d/469a/2 1.7.2 packaging figure 8 d3 mechanical outline: order as part no. cmx469ad3 figure 9 e2 mechanical outline: order as par t no. CMX469AE2
1200/2400/4800 baud ffsk/msk modem cmx469a handling precautions: this product includes input protection, howeve r, precautions should be taken to prevent device damage from electro - static discharge. cml does not assume any responsibility for the use of any circuitry described. no ipr or circuit patent licences are implied. cml reserves the right at any time witho ut notice to change the said circuitry and this product specification. cml has a policy of testing every product shipped using calibrated test equipment to ensure compliance with this product specification. specific testing of all circuit parameters is n ot necessarily performed. oval park - langford maldon - essex cm9 6wg - england telephone: +44 (0)1621 875500 telefax: +44 (0)1621 875600 e - mail: sales@cmlmicro.co.uk http://www.cmlmicro.co.uk figure 12 p6 mechanical outline: order as part no. cmx469ap6

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