IL34118DW

IL34118 INTEGRAL | Alldatasheet

Document overview

• Manufacturer or author: Provided By ALLDATASHEET.COM(FREE DATASHEET DOWNLOAD SITE)
• PDF pages: 12

Technical content

Voice Switched Speakerphone Circuit The IL34118 Voice Switched Speakerphone Circuit incorporates the necessary amplifiers, attenuators, level detectors, and control algorithm to form the heart of a high quality hands-free speakerphone system. Included are a microphone amplifier with adjustable gain and MUTE control, Transmit and Receive attenuators which operate in a complementary manner, level detectors at both input and output of both attenuators, and background noise monitors for both the transmit and receive channels. A Dial Tone Detector prevents the dial tone from being attenuated by the Receive background noise monitor circuit. Also included are two line driver amplifiers which can be used to form a hybrid network in conjunction with an external coupling transformer. A high pass filter can be used to filter out 60 Hz noise in the reseive channel, or for other filtering functions. A Chip Disable pin permits powering down the entire circuit to conserve power on long loops where loop current is at a minimum. The IL34118 may be operated from a power supply, or it can be powered from the telephone line, requiring typically 5.0 mA. The IL34118 can be interfaced directly to Tip and Ring (thro ugh a coupling transformer) for stand-alone operation, or it can be used in conjunction with a handset speech network and or other features of a featurephone.

• Improved Attenuator Gain Range: 52 dB Between Transmit and Receive
• Low Voltage Operation for Line-Powered Applications (3.0- 6.5 V)
• 4 Point Signal Sensing for Improved Sensitivity
• Background Noise Monitors for Both Transmit and Receive Paths
• Microphone Amplifier Gain Set by External Resistors - Mute Function Included
• Chip Disable for Active Standby Operation
• On Board Filter Pinned-Out for User Deined Function
• Dial Tone Detector to Inhibit Receive Idle Mode During Dial Tone Presence IL34118

ORDERING INFORMATION

TA = -25° to 70° C for all packages PIN ASSIGNMENT

The fundamental difference between the operation of a speakerphone and a handset is that of half-duplex versus full-duplex. The handset is full duplex since conversation can occur in both directions (transmit and receive) simultaneousiy. A speakerphone has higher gain levels in both paths, and attempting to converse full duplex results in oscillatory problems due to the loop that exists within the system. The loop is formed by the receive and transmit paths, the hybrid, and the acoustic coupling (speaker to microphone). The only practical and economical solution used to data is to design the speakerphone to function in a half duplex mode - i.e., only one person speaks at a time, while the other listens. To achieve this requires a circuit which can detect who is talking, switch on the appropriate path (transmit or receive), and switch off (attenuate) the other path. In this way, the loop gain is maintained less than unity. When the talkers exchange function, the circuit must quickly detect this, and switch the circuit appropriately.By providing speech level detectors, the circuit operates in a “hand-free” mode, eliminating the need for a “push-to-talk” switch. The handset, by the way, has the same loop as the speakerphone. But since the gains are considerably lower, and since the acoustic coupling from the earpiece to the mouthpiece is almost non-existent (the receiver is normally held against a person’s ear), oscillations don’t occur. The IL34118 provides the necessary level detectors, attenuators, and switching control for a properly operating speakerphone. The detection sensitivity and timing are externally controllable. Additionally, the IL34118 provides background noise monitors which make the circuit insensitive to room and line noise, hybrid amplifiers for interfacing to Tip and Ring, the microphone amplifier, and other associated functions. ATTENUATORS The transmit and receive attenuators are complementary in function, i.e., when one is at maximum gain (+6.0 dB), the other is at maximum attenuation (-46 dB), and vice versa. They are never both fully on or both fully off. The sum of their gains remains constant (within a nominal error band of ±0.1 dB) at a typical value of -40 dB. Their purpose is to control the transmit and receive paths to provide the half-duplex operation required in a speakerphone. The attenuators are non-inverting, and have a - 3.0 dB (from max gain) frequency of ≈100 KHz. The input impedance of each attenuator (TXI and RXI) is nominally 10 kΩ (see Figure 1), and the input signal should be limited to 350 mVrms (990 mVp-p) to prevent distortion. That maximum

The Attenuator Control Block has the seven inputs described above: - Tthe output of the comparator operated by RLO2 and TLO2 (microphone/speaker side) - designated C1. - The output of the comparator operated by RLO1 and TLO1 (Tip/Ring) side) - designated C2. - The output of the transmit background noise monitor - designated C3. - The output of the receive background noise monitor - designated C4. - The volume control. - The dial tone detector. - The AGC circuit. The single output of the Control Block controls the two attenuators. The effect of C1-C4 is as follows: Inputs Output C1 C2 C3 C4 Mode Tx Tx 1 X Transmit Tx Rx Y Y Fast Idle Rx Tx Y Y Fast Idle Rx Rx X 1 Receive Tx Tx 0 X Slow Idle Tx Rx 0 0 Slow Idle Rx Tx 0 0 Slow Idle Rx Rx X 0 Slow Idle X = Don’t Care; Y = C3 and C4 are not both 0 A definition of the above terms: 1) “Transmit” means the transmit attenuator is fully on (+6.0 dB), and the receive attenuator is at max. attenuation (-46 dB). 2) “Receive” means both attenuators are controlled by the volume control. At max. volume, the receive attenuator is fully on (6.0 dB), and the transmit attenuator is at max. attenuation (- 46 dB). 3) “Fast Idle” means both transmit and receive speech are present in approximately equal levels. The attenuators are quickly switched (30 ms) to idle until one speech level dominates the other. 4) “Slow Idle” means speech has ceassed in both transmit and receive path. The attenuators are then slowly switched (1 second) to the idle mode. 5) Switching to the full transmit or receive modes from any other mode is at the fast rate (30 ms). A summary of the truth table is as follows: 1) The circuit will switch to transmit if: a) both transmit level detectors sense higher signal levels relative to the respective receive level detectors (TLI1 versus RLI1, TLI2 versus RLI2), and b) the transmit background noise monitor indicates the presence of speech. 2) The circuit will switch to receive if: a) both receive level detectors sense higher signal levels relative to the respective transmit level detectors, and b) the receive background noise monitor indicates the presence of speech. 3) The circuit will switch to the fast idle mode if the level detectors disagree on the relative strengths of the signal levels, and at least one of the background noise monitors indicates speech. For example, refferring to the Expanded Logic Diagram (Figure 8), if there is sufficient signal at the microphone amp output (TLI2) to override the speaker signal (RLI2), and there is sufficient signal at the receive input (RLI1) to override the signal at the hybrid output (TLI1), and either or both background monitors indicate speech, then the circuit will be in the fast idle mode. Two conditions which can cause the fast idle mode to occur are a) when both talkers are attempting to gain control of the system by talking at the same time, and b) when one talker is in a very noisy environment, forcing the other talker to continually override that noise level. In general, the fast idle mode will occur infrequently. 4) The circuit will switch to the slow idle mode when a) both talkers are quiet (no speech present), or b) when one talker’s speech level is continuously overriden by noise at the other speaker’s location. The time required to switch the circuit between transmit, receive, fast idle and slow idle is determined in part by the components at the C T pin (Pin 14). A schematic of the CT circuitry is shown in Figure 4 and operates as follows: - RT is typically 120 kΩ , and CT typically 5.0 µF. - To switch to the receive mode, I 1 is turned on (I 2 is off), charging the external capacitor to +240 mV above V B. (An internal clamp prevents further charging of the capacitor.) - To switch to the transmit mode, I 2 is turned on (I 1 is off) bringing down the voltage on the capacitor to -240 mV with respect to V - To switch to idle quickly (fast idle), the current sources are turned off, and the internal 2.0 k Ω resistor is switched in, discharging the capacitor to VB with a time constant = 2.0 KΩ x CT. - To switch to idle slowly (slow idle), the current sources are turned off, the switch at the 2.0 k Ω resistor is open, and the capacitor discharges to VB through the external resistor R T with a time constant = RT x CT.

Figure 7. Low Pass Filter reduced operation possible down to 2.8 volts. well as their respective gains. the IC to conserve power and/or for muting purposes. With CD ≤0.8 volts, normal operation is in effect. 1F O Filter output. Output impedance is less than 50Ω . 2F I Filter input. Input impedance is greater than 1.0 MΩ . disables the IC to conserve power. Input impedance is nominally 90 KΩ . differential output, in conjunction with HTO-, to the hybrid transformer. 6 HTO- Output of the first hybrid amplifier. The gain of the amp is set by external resistors. 7H T I Input and summing node for the first hybrid amplifier. DC level is ≈VB. 8 TXO Output of the transmit attenuator. DC level is approximately V B. 11 MCI Input and summing node of the microphone amplifier. DC level is ≈VB.

Pin No Designation Description 12 MUT Mute input. A logic low (<0.8 V) sets normal operation. A logic high (>2.0 V) mutes the microphone amplifier without affecting the rest of the circuit. Input impedance is nominally 90Ω . 13 VLC Volume control input. When VLC = V B, the receive attenuator is at maximum gain when in the receive mode. When VLC = 0.3 V B, the receive gain is down 35 dB. Does not affect the transmit mode. 14 C T An RC this pin sets the response time for the circuit to switch modes. 15 V B An output voltage ≈VCC/2. This voltage is a system ac ground, and biases the volume control. A filter cap is required. 16 CPT An RC at this pin sets the time constant for the transmit background monitor. 17 TLI2 Input to the transmit level detector on the mike speaker side.

18 TLO2 Output of the transmit level detector on the mike/speaker side, and input to the

transmit background monitor. 19 RLO2 Output of the receive level detector on the mike/speaker side. 20 RLI2 Input to the receive level detector on the mike/speaker side. 21 RXI Input to the receive attenuator and dial tone detector. Max input level is 350 mV RMS. Input impedance is ≈10 KΩ . 22 RXO Output of the receive attenuator. DC level is approximately V B. 23 TLI1 Input to the transmit level detector on the line side. 24 TLO1 Output of the transmit level detector on the line side.

25 RLO1 Output of the receive level detector on the line side, and input to the receive

background monitor. 26 RLI1 Input the receive level detector on the line side. 27 CPR An RC at this pin sets the time constant for the receive background monitor. 28 GND Ground pin for the entire IC. MAXIMUM RATINGS* Symbol Parameter Value Unit VCC Supply Voltage (Pin 14) -1.0 to +7.0 V VIN Input Voltage at CD(Pin 3), MUT (Pin 12) -1.0 toV CC +1.0 V V VIN Input Voltage at VLC (Pin 13) -1.0 toV CC +0.5 V V VIN Input Voltage at TXI(Pin 9), RXI (Pin 21), FI (Pin 2) -0.5 toV CC +0.5 V V Tstg Storage Temperature Range -65 to +150 °C * Maximum Ratings are those values beyond which damage to the device may occur. Functional operation should be restricted to the Recommended Operating Conditions.

RECOMMENDED OPERATING CONDITIONS Symbol Parameter Min Max Unit VCC Supply Voltage (Pin 4) 3.5 6.5 V VIN Input Voltage at CD (Pin 3), MUT (Pin12) 0 V CC V IVB VB Current (Pin 15) 500 µA VIN Input Voltage at VLC (Pin 13) 0.3 x V B VB V VIN Attenuator Input Signal Voltage (Pins 9, 21) 0 350 mVrms G Microphone Amplifier, Hybrid Amplifier Gain 0 40 dB IL Load Current RXO, TXO Pins 8,22) MCO (Pin 10) HTO-, HTO+ (Pins 6,5) 2.0 1.0 5.0 mA TA Operating Temperature -25 +70 °C This device contains protection circuitry to guard against damage due to high static voltages or electric fields. However, precautions must be taken to avoid applications of any voltage higher than maximum rated voltages to this high-impedance circuit. For proper operation, V IN and V OUT should be constrained to the range GND≤(VIN or VOUT)≤VCC. Unused inputs must always be tied to an appropriate logic voltage level (e.g., either GND or V CC). Unused outputs must be left open. ELECTRICAL CHARACTERISTICS(TA = -25 to +70°C, VCC = 5.0 V , CD = 0.8 V, unless noted) Symbol Parameter Test Conditions Guaranteed Limits Unit Min Max POWER SUPPLY ICC VCC Sypply Current V CC =6.5 V, CD =0.8 V VCC =6.5 V, CD =2.0 V 1.0 mA RCD CD Input Resistance V CC = VCD = 6.5 V 37.5 - KkΩ VCDH CD Input High Voltage V CC = VCD = 6.5 V 2.0 V CC V VCDL CD Input Low Voltage V CC = VCD = 6.5 V 0 0.8 V VB VB Output Voltage 13.5 3.0 V ATTENUATOR (VLC = VB, unless noted) GRX GRX ∆GRX1 ∆GRX2 GRX1 ∆GRX3 Receive Attenuator Gain ( f =1.0 KHz) Rx Mode, RXI=150 mVrms, (VCC=5.0 V) Rx Mode, RXI=150 mVrms CC=3.5 V) Gain Change -VCC=3.5 V versus VCC =5.0 V AGC Gain Change - VCC=2.8 V versus VCC=5.0 V Idle Mode, RXI=150mVrms Range (Rx to Tx Mode) 1.5 1.5 -0.5 -25 10.0 10.0 +0.5 -15 -15 dB VCR * Volume Control Range Rx Mode, 0.3V B<VLC<VB 27 - dB (continued)

ELECTRICAL CHARACTERISTICS(TA = -25 to +70°C, VCC = 5.0 V , CD = 0.8 V, unless noted) Symbol Parameter Test Conditions Guaranteed Limits Unit Min Max ∆VRXO ∆RXO DC Voltage Rx to Tx Mode - ±190 mV VRXOH RXO High Voltage I OUT= -1.0 mA,RXI=VB+1.5V, VCT=2.6 V 2.8 - V VRXOL RXO Low Voltage I OUT= +1.0 mA,RXI=VB-1.0V, VCT=2.6 V Output measured with respect to V B -V B-0.75 V RRXI RXI Input Resistance RXI=350 mVrms, f = 1.0 KHz 5.25 17.5 kΩ GTX GTXI ∆GTXI Trasmit Attenuator Gain ( f =1.0 KHz) Tx Mode, TXI=150 mVrms Idle Mode, RXI=-150 mVrms Range (Tx to Rx Mode) 1.5 -25 10.0 -15 dB ∆VTXO ∆TXO DC Voltage Tx to Rx Mode - ±190 mV VTXOH TXO High Voltage I OUT= -1.0 mA,TXI=VB+1.5V, VCT=1.6 V 2.8 - V VTXOL TXO Low Voltage I OUT= +1.0 mA,TXI=VB-1.0V, VCT=1.6 V Output measured with respect to V B -V B-0.75 V RTXI TXI Input Resistance TXI=350 mVrms, f = 1.0 KHz 5.25 17.5 KΩ ATTENUATOR CONTROL ICTR CT Source Current (switching to Rx mode) f = 1 KHz, VLC = VB =CT -106 -30 µA ICTT CT Sink Current (switching to Tx mode) f = 1 KHz, VLC = VB =CT +30 +106 µA RFI * CT Fast Idle Internal Resistance 1.5 3.6 KΩ VDT * Dial Tone Detector Threshold 10 20 mV MICROPHONE AMLIFIER (VMUT ≤ 0.8 V, A+ = 31 dB, unless otherwise noted) MCOVOS Output Offset V MCO - VB, Freedback R= 180 KΩ -62 +62 mV AVOLM Open Loop Gain f = 100 Hz 60 - dB VMCOH Output High Voltage I OUT=-1.0 mA,VMCI=VB+1.5 V 2.8 - V VMCOL Output LowVoltage I OUT=1.0 mA, VMCI=VB - 1.0 V - 250 mV GMT Muting (∆Gain) f = 1.0 Khz,VMCI = 150 mV 0.8 V ≤ VMUT ≤ 2.0 V 52 - dB RMUT MUT Input Resistance V CC = VMUT = 6.5 V 37.5 - KΩ VMUTH MUT Input-High 2.0 V CC V VMUTL MUT Input-Low 0 0.8 V (continued)

ELECTRICAL CHARACTERISTICS(TA = -25 to +70°C, VCC = 5.0 V , CD = 0.8 V, unless noted) Symbol Parameter Test Conditions Guaranteed Limits Unit Min Max HYBRID AMPLIFIERS HVOS HTO - Offset V HTO- - VB, Freedback R= 51 KΩ VB - 25 V B +25 mV HBVOS HTO - to HTO+ Offset Freedback R= 51 KΩ VB - 37 V B +37 mV AVOLH Open Loop Gain HTI to HTO-, f = 100 Hz, VHTI = 20 mV 57 - dB AVCLH Closed Loop Gain HTO- to HTO+ -2.8 2.2 dB VHT-H HTO- High Voltage I OUT=-5.0 mA, VHTI=VB -1.0 V 2.8 - V VHT-L HTO- Low Voltage I OUT=5.0 mA, VHTI=VB +1.5 V - 375 mV VHT+H HTO+ High Voltage I OUT=-5.0 mA,VHTI=VB +1.5 V 2.8 - V VHT+L HTO+ Low Voltage I OUT=5.0 mA, VHTI=VB -1.0 V - 562 mV LEVEL DETECTORS AND BACKGROUND NOISE MONITORS ITH * Transmit-Recieve Switching Threshold Ratio of Current at RLI1 + RLI2 to 20 µA at TLI1 + TLI2 to switch from Tx to Rx 0.8 1.2 FILTER FOVOS Voltage Offset at FO VFO -VB, 220 KΩ from VB to FI VB- 250 VB +25 mV IFO FO Sink Current V B = VFO, VFI = 0 V 112 500 µA Note. 1. All currents into a device pin are positive, those out of a pin are negative. Algebraic convention rather than magnitude is used to define limits. * @25°C