et- 34018 linear integrated circuit voice switched speaker- phone circuit sop-28 description the contek kgm34018 speaker-phone integrated circuit incorporates the necessary functions to produce a high quality hands-free speaker-phone system. the applications include household and office speaker-phones, intercom systems, hand free kit for mobile phones, and others dip-28 features *all necessary level detection nd attenuation controls for a a hand-free telephone included. *background noise level monitoring with long time constant. *background sound level com pensation for transmit and receive levels as well as the background level. *wide operating dynamic range through signal compression. *on-chip voltage regulators illuminate external regulators for lining operation. *power audio amplifier for typical 100mw output (into 25 ohms)with peak limiting for speaker to minimize distortion. *chip select pin for active/stand by operation. *volume control function for external volume control. *standard 28-pin plastic dip and sop package. absolute maximum ratings (ta=25 c ,voltages referred to pin 22 ) parameter value unit v+ terminal voltage (pin 16) +12,-1.0 v cs (pin 18 +12,-1.0 v speaker amplifier ground(pin 14) +3.0,-1.0 v vlc(pin 24) +vcc,-1.0 v storage temperature -65 ~ +150 c recommended operation conditions parameter value unit v+ terminal voltage (pin 16) +6.0 to +11 v cs (pin 18) 0 to +11 v vcc (pin 20) 0 to 3.0 ma vlc(pin 24) 0.55vb to vb v receive signal(pin 27) 0 to 250 mvrms microphone signal(pin 9) 0 to 5.0 mvrms speaker amplifier ground (pin 14) -10 to +10 mvdc ambient temperature -20 to +60 c beijing estek electronics co.,ltd 1
internal block diagram mic mic amp transmit channel transmit attenuator transmit output transmit level detector side tone side tone receive level detector transmit/ receive comparator receive attenuator attenuator control signal/noise detector peak limiter speake r amp receive channel spe ake r contek receive volume control enable input vcc regulator receive input dc input telephone line fig 1 pin configurations pin name description 1 rr a resistor to ground provides a reference current for the transmit and receive attenuators 2 rtx a resistor to ground determines the nominal gain of th e transmit attenuator ,the transmit channel gain is inversely proportional to rtx resistance. 3 txi input to the transmit attenuator. input resistance is nominally 5.0k ohms. 4 txo output of the transmit attenuator. the txo output signal drivers the input of transmit level detector, as well as the external circuit which drivers the telephone line. 5 tli input of the transmit level detector. an external resistor ac coupled to the t pin sets the detection level. li decreasing this resistor increases the sensitivity to transmit channel signals. 6 tlo output of the transmit level detector. the external re sistor and capacitor set the time the comparator will hold the system in the transmit mode after speech ceases. 7 rli input of the receive level detector. an external resistor ac coupled to the rli pin sets the detection level. decreasing this resistor increases the sensitivity to receive channel signals 8 rlo output of the receive level detector. the external re sistor and capacitor set the time the comparator will hold the system in the receiv e mode after speech ceases 9 mci microphone amplifier input. input impedance is nominally 10k ohms and the dc bias voltage is approximately equal to vb 10 mco microphone amplifier output. the mic amp gain is internally set at 34db(50v/v) 11 cp1 a parallel resistor and capacitor connected between this pin and vcc holds a voltage corresponding to the background noise level. the tr ansmit detector compares the cp1 voltage with the speech signal from 12 cp2 a capacitor at this pin peak detects the speech si gnals for comparison with the background noise level held at cp1. 13 xdi input to the transmit detector system. the microphone amplifier output is ac coupled to the xdi pin through an external resistor 14 skg high current ground pin for the speaker amplifier output stage. the skg voltage should be within 10mv of the ground voltage at pin 22 15 sko speaker amplifier output. the sko pin will source and sink up to 100ma when ac coupled to the speaker. the speaker amplifier gain is internally set at 34db(50v/v). 16 v+ input dc supply voltage. v+ can be powered from tip and ring if an ac decoupling inductor is used to prevent loading ac line signals. the required v+ volt age is 6.0v to 11v(7.5v nominal ) at 7.0ma 17 agc a capacitor from this pin to vb stabilizes the sp eaker amplifier gain control loop, and additionally controls the attack and decay time of this circuit. the gain control loop limits the speaker amplifier input to prevent clipping at sko. the internal resistance at agc pin is nominally 110k ohms. 18 cs digital chip select input. when at a logic "0" (<0.7v) the vcc regulator is enabled. when at a logic "1" (>1.6v),the chip is in the sta ndby mode drawing 0.5ma.an open cs pin is a logic "0". input impedance is nominally 140k ohms. the input voltage should not exceed 11v 19 ski input to the speaker amplifier. input impedance is nominally 20k ohms 20 vcc a 5.4v regulated output which powers all circ uits except the speaker amplifier output stage 21 vb an output voltage equal to approximately vcc/2 which series as an analog ground for the speakerphone system. up to 1.5ma of external load current may be sourced from vb. output impedance is 250 ohms. a filter capacitor is required 22 gnd ground pin for the ic(except the speaker amplifier) beijing estek electronics co.,ltd 2 et- 34018
(continued) pin name description 23 xdc transmit detector output. a resistor and capacitor at his pin hold the system in the transmit mode during pauses between words or phrases. when the xdc pin volt age decays to ground, the attenuators switch from the transmit mode to idle mode. the internal resi stor at xdc is nominally 2.6k ohms(see fig.1). 24 vlc volume control input>connecting this pin to the slider of a variable resistor provides receive mode volume control. the vlc pin voltage should be less than or equal to vb 25 acf attenuator control filter. a capa citor connected to this pin reduces noi se transient as the attenuator control switches le vel of attenuation 26 rxo output of the receive attenuator. normally this pin is ac coupled to the input of the speaker amplifier 27 rxi input of the receive attenuator. input impedance is nominally is 5.0k ohms 28 rrx a resistor to ground determines the nominal gain of the receive attenuator. the receive channel gain is directly proportional to the rrx resistance electrical characteristics (referred to fig. 1) parameter symbol min typ max unit supply voltages v+ supply current v+=11v, pin 18=0.7v v+=11v, pin 18=1.6v i v+ 9.0 800 ma a vcc voltage (v+=7.5v) line regulation (6.5v temperature characteristics (-20 to +60 c ) parameter pin typ change unit v+ supply current ( v+ 11v,pin 18 = 0.7v ) 16 -0.2 %/ c v+ supply current(v+ 11v,pin 18 = 1.6v ) 16 -0.4 %/ c vcc voltage( v+ = 7.5v ) 20 +0.1 %/ c attenuator gain ( max and min setting ) +-0.003 db/ c delta rxo,txo voltage 4,26 +-0.24 %/ c speaker amp gain 15,19 +-0.001 db/ c microphone amp gain 9,10 +-0.4 db/ c microphone amp input resistance 9 +0.4 %/ c tx-rx switching threshold (20 a) 5,7 +-0.2 na/ c 220k 68k 4.7k 2.7k 0.01 f 0.05 f s1 hook switch r t 22k 3.3k 470k 470k 47k 0.068 f 4700pf 4700pf 0.01 f 47k 15k 8.2k 1 0 0 0 f 0 . 0 6 8 f 2.2k 470k 1 0 f 0.1 f 8.2k 33k 47k 8.2k 47k 6.8k 0.01 f 0.01 f 0.1 f 1.0 f 4.7 f 47 f 100k vcc 3.3k 0.068 f 0.068 f 4.7k 0.1 f 0.05 f s 2 2k mic vb speaker 47 f vb 20k 24k volume control 47 f 47 f 91k 30k 18k 4.3k 0.01 f 0.05 f 4.7 f 4.7 f 200k 2.2m 2.2m 1.0 f 1.0 f 3 x ? c xd 10 13 4 txo 5 tli 11 cp1 acf 25 agc 17 v+ 16 cs 18 rli 7 rxi 27 gnd 22 rlo 8 6 tlo 23 xdc 12 cp2 19 ski 26 rxo 28 rrx 1 rr 2 rtx vcc 20 vb 21 vlc 24 skg 14 15 sko 9 mci 0.1 f fig 2 - basic line powered speakerphone beijing estek electronics co.,ltd 4 et- 34018
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