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U3760MB
U3760MB Application and Adjustment Hints
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Information contained in this paper is intended to provide a product description. Such description does not in any way constitute assured characteristics in the legal sense, nor do those design hints provide information regarding delivery conditions or availability. TEMIC Semiconductor GmbH makes no representation that the use or the interconnection of the circuits described herein will not infringe on existing or future patent rights, nor do the descriptions contained herein imply the granting of licenses to make, use or sell equipment constructed in accordance therewith. The information presented in this paper is believed to be accurate and reliable. However, no responsibility is assumed by TEMIC Semiconductor GmbH for its use. Part of the publication may be reproduced without special permission on condition that author and source are quoted and that two copies of such extracts are placed at our disposal after publication. Written permission should be obtained from the publisher for complete reprints or translations. We reserve the right to amend any of the information without prior notice, including the issue of letters patent. Important note: Application examples have not been examined for series use or reliability, and no worst case scenarios have been developed. Customers who adapt any of these proposals must carry out their own tests and make sure that no negative consequences arise from the proposals.
Authors: Wilhelm Rauter Joachim Kuhnle
Publisher: TEMIC Semiconductor GmbH Theresienstrae 2 P.O.B. 3535 D - 74025 Heilbronn Phone : +49 7131 67-2594 Fax : +49 7131 67-2423 http://www.temic-semi.de
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Table of Contents
General ............................................................................................................................................5 Speech Circuit...............................................................................................................................5 Dialer ............................................................................................................................................5 Ringer............................................................................................................................................5 Adjustment Procedure for the Speech Circuit.............................................................................6 Adjustment Hints............................................................................................................................7 DC Characteristic..........................................................................................................................7 AC Impedance ..............................................................................................................................8 Transmit Gain and Frequency Response ......................................................................................9 Receive Gain and Frequency Response ......................................................................................10 AGC Characteristic.....................................................................................................................10 Side Tone ....................................................................................................................................12 Dialer ..........................................................................................................................................12 Ringer..........................................................................................................................................14
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General
The U3760MB is suitable for low-voltage, low-end telephone applications. It consists of a dialer, a ringer and a speech circuit in a single chip. The following sub-chapters describe the available functions of the dialer, the ringer and the speech circuit. (then 20 pps is selected) or to leave MODE open, then 10 pps is selected (Pin MODE). Flash times can be realized with the keys: * F1 = 94 ms * F2 = 250 ms * F3 = 600 ms Temporary DTMF dialing is available by using the key */T * Changes from pulse dialing mode (MODE = GND or floating) via key */T to DTMF mode, whereas pressing the key */T does not cause a DTMF signal but a key-tone control signal to be sent out (see also timing diagram in the data sheet). * If MODE = "High", key */T delivers a DTMF output signal The re-dial function is available when key R/P is pressed first after going off-hook. If the number of digits is >32, re-dialing is impossible. When key R/P is not the key pressed first after the off-hook condition, the next digit is sent out after a pause of 3.6 seconds. The dialer logic is driven by a 3.579545-MHz oscillator, stabilized by a crystal or a ceramic resonator of 3.579545 MHz. Due to internally integrated capacitors, no additional external components are needed when using a ceramic resonator. The latter is possible as the frequency deviation of the chip is low (see table 3).
Speech Circuit
The speech circuit contains a transmit amplifier suitable for dynamic, electret and piezo microphones, and a receive amplifier for driving dynamic earpieces. The latter is either connected symmetrically to RECO1/ RECO2 via CREC2 or asymmetrically connected to RECO1 against ground via CREC2 (see figure 7). The output amplifier can drive the piezo earpiece. The speech circuit also offers mute possibilities - internally by means of the dialer or externally by using Pin MUTE (internal pull-up resistor).
Dialer
To control the dialer functions, 16 keys (Pin = C1/C2/C3/R1/R2/R3/R4) are available. For indication that a key is pressed during pulse mode, the dialer has a key-tone output signal (Pin KT). The break-make ratio can be selected either by connecting pin B/M to ground (resulting in a ratio of 33/67) or by leaving the pin open which leads to a ratio of 40/60. DTMF mode can be selected by connecting MODE to High = VDD2. PULSE mode can be selected by connecting MODE either to ground
Table 1. Mode selection Low = GND = 20 pps 16.5 ms/ 33.5 ms 20 ms/ 30 ms
Ringer
The U3760MB has a two-tone ringer. Adjusting the oscillator frequency affects the repetition rate. Furthermore, the IC has an adjustable ringing impedance, an adjustable threshold for the ringing voltage detection and an adjustable ringer volume.
MODE = Open = floating =10 pps 33 ms/ 67 ms 40 ms/ 60 ms
B/M = Low = GND = 33/67 B/M = Open = float. = 40/60 pps = pulse per second
High = VDD2 = DTMF DTMF mode DTMF mode
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Adjustment Procedure for the Speech Circuit
Main steps in telephone adjustments: Step 1 Adjust the DC characteristic (due to the influence of RIMP1 and RIMP2, this step has to be carried out first). Step 2 Adjust the AC impedance (also called return loss), for example, 600 R or complex impedance (e.g., in Germany). Note: Never change the impedance after the second step, otherwise all further steps must be carried out once again (especially the side-tone adjustment). Step 3 Adjust the transmit gain and the transmit frequency response. Step 4 Adjust the AGC (Automatic Gain Control = gain correction dependent on the line current). The following adjustment steps are independent from step 1 to 6 (i.e., they can be carried out before or after step 1 to 6 ). Step 7 Adjust the ringer impedance. 8. Step. Adjust the ringer oscillator. 9. Step. Adjust the ringer threshold. 10.Step. Adjust the ringer volume. Step 5 Adjust the side tone (make sure that the impedance is already adjusted, see step 2). 6. Step. Adjust the receive gain and the receive frequency response.
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Adjustment Hints
DC Characteristic
The resistor RDC1, connected from Pin RDC to ground, sets the slope of the DC characteristic (see figure 3).
RDC1
RDC
Instead of using the bridge BR3, a diode can be added to shift the complete DC characteristic in parallel. At the maximum possible current in an application, adjust the voltage to less than 10 V. Calculation of the circuit's power dissipation in speech-/DTMF mode:
39 R 1W
Figure 1.
BR3
PU3760MB = VL x IL - [RDC1 x IRDC1] - [(RIMP1 + RIMP2) x 2 mA]
TIP
RDP1 100 k RDP2 33 K
T3
RDP3 2.7 k B2 B3
LINE
RING
Vtip/ring
T2
DP
IL
B1
B4 GND
The DC operating point in speech mode is given by: Vtip/ring = + + + + + VRDC1 + Voffset I VI x (RIMP1 + RIMP2) Ist x RIMP2 (RIMP1 + RIMP2) x Ielectr Vcesat (T3) 2 x Vdiode
Transmit amplifier VL CST1 Side-tone amplifier ST
IST
RIMP2 300 R RST1 1.5 K RST2 4.7 K RIMP1 390 R
4.7 nF
Ist 270 A, IVI 1.2 mA, Voffset 2.84 V
RECIN VI Supplycurrent generator
IVI V offset
47 nF CREC1
I electr
CIMP1 220 u RDC1 39 R
V RDC1
RDC
1 Watt
Figure 2.
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Line voltage VL / V
10 9 8 7 6 5 4 3 2 1 0 0 10 20 30 40 50 60 70 80 90 100
RDC = 56 RDC = 39 RDC = 27
Line current I L / mA
Figure 3. DC characteristic (typ.)
AC Impedance
To adjust the AC impedance, see figure 4. For 600-R measurement results, see figure 5. In general, the AC impedance consists of: (RIMP1 + RIMP2), CIMP1 and CIMP2. In a telephone application, there might only be a resistive impedance such as, for example, 600-R; or a complex impedance such as ZR, e.g., in Germany. Resistive impedance: (RIMP1 + RIMP2), CIMP1; where CIMP1 is for AC coupling only. Complex impedance: (RIMP1 + RIMP2), CIMP1 and CIMP2; where CIMP1 is for AC coupling only and CIMP2 is used to realize the complex impedance together with RIMP1 + RIMP2. The ratio RIMP1 to RIMP2 depends on the DC characteristic, the maximum transmit and the
Table 2. AC adjustment Country Japan Great Britain China Germany RIMP1 390 330 330 560 RIMP2 300 560 390 330
maximum receive level on VL (this depends on which country is concerned). For applications using high DC characteristics, RIMP1 may have the value 0. In this case, the AC impedance consists of RIMP2 and CIMP1 (resistive impedance) or RIMP2, CIMP1 and CIMP2 (complex impedance). Please note that each low-ohmic resistive load from the positive supply of bridge-to-ground influences the AC-impedance adjustment. This is valid especially for the resistor RDP3 (necessary for biasing transistor T3). The characteristic of RPD3 is as if it were connected in parallel to RIMP1 + RIMP2. Example (neglecting RDP3): Line = 600 (RIMP1+ RIMP2) = 620 Line = 900 (RIMP1 + RIMP2) = 910 Table 2 shows the AC adjustment for several countries (application circuit as shown in figure 22, RDP3 = 2.7 k).
CIMP1 220 u 220 u 220 u 220 u
CIMP2 2.2 n 220 n 68 n 68 n
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The test circuit for line-impedance adjustment is shown in figure 4.
100 F 47 F 600 ZPABX
VGEN 600
TIP L2 U3760MB L1 RIMP CIMP RING
IL ZIMP
Figure 4. Test circuit for line-impedance adjustment
Best matching for the line impedance can be achieved when the bridge is balanced (i.e., ZIMP = ZPABX), where ZPABX is the impeddance which should be matched. Return losses are acceptable if RL is minimized [RL (dB) = L2 (dBm) - L1 (dBm)]. Figure 5 shows an example of AC-impedance adjustment.
Transmit Gain and Frequency Response
The entire gain consists of a fixed microphoneamplifier gain and a constant transmit amplifier gain.
The output level on the line is dependent on the AC impedance and the microphone-ampli-fier input level. The only method of adjusting the transmit level is to adapt the input circuit to the microphone sensitivity. * In the case of an electret microphone, the level as well as the frequency response can be adjusted via RMI1/ RMI2/ RMI3/ RMI4/ RMI6 and CMI1/ CMI2/ CMI4. Both resistors - either RMI1/RMI2 or RMI6 - are recommended for gain adjustment. * In the case of a dynamic microphone, the microphone can be connected directly to MIC1/MIC2. If a level reduction is necessary, this can be done via a parallel resistor. The frequency response can be affected with a parallel capacitor or by changing the housing conditions (damping material, additional holes or the hole diameters of the microphone). Another possibility of adjusting the level as well as the frequency response is connecting a network between pins MICO and TIN. This is, however, not recommended, as a net between these two pins will not only influence the transmit signal but also the DTMF signal.
Typical return-loss measurement for 600 (referred to the application circuit figure 22) -10 -12 -14 Mask
Return loss (dB)
-16 -18 -20 -22 -24 -26 0 500 1000 1500 2000 2500 3000 3500 Frequency (Hz)
Figure 5. Example of ac-impedance adjustment
600-R termination RIMP2 = 300 R, RIMP1 = 390 R
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Transmit frequency response * CMI4 cuts high frequencies and reduces electromagnetic influence (EMI). * CMI1 and CMI2, along with RMI6, cut low frequencies. * CTIN cuts low frequencies, and also affects the DTMF frequency response. The input impedance of the microphone amplifier is 75 k typically. The output impedance of the microphone amplifier is * 400 typ. in speech mode * 16 k typ. (bias on) in dial mode the input impedance of TIN is 5.8 k typ. is a voltage divider for the receive signal (see figure 2). Maximum gain is achieved if RIMP2 = 0 R. Make sure that the sum of RIMP2 and RIMP1 is always kept constant so as not to affect the AC impedance. A further adjustment possibility is to use a resistor in series with the earpiece (RREC1). Receive frequency response The frequency response can be adjusted high ohmic via an RC net at RECIN (CREC1, 60 k typ.) or low ohmic at the ear-piece output RECO1/ RECO2 or directly at the ear piece. * CREC1/ CREC2 cut low frequencies * CREC3 cuts high frequencies * An increase of RREC1 also increases the receiver's dynamic range * An increase of RIMP2 decreases the RECIN input (as a result, the total RX gain is smaller) An adjustment at RECIN is not recommended as this could influence the side-tone characteristics.
TO-VI 100 nF CMI1 RMI6 5.6 k MIC1 MIC2 Micro amplifier MICO TIN VL
Receive amplifier
Electret micro CMI4
RMI1 1K RMI3 15 K
10 nF
RMI2 1K RMI4 15 K
100 nF CMI2
CTIN 220 nF
Receive attenuation
ST RECIN RECO1 RECO2 CREC1 47 nF CREC2 2.2 F S5 CREC3 100 nF RREC1 100 R H2 H1
+
fix gain 30 dB
Figure 7.
Figure 6.
Receive Gain and Frequency Response
Receive gain The receive gain can be adjusted by modifying the ratio of RIMP2 to RIMP1. RIMP2/RIMP1
AGC Characteristic
The resistor RAGC1 defines the amount of gain reduction for transmit and receive mode. An open input de-activates the AGC. Please note that AGC characteristic is influenced by the DC characteristic (RDC1). There-
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fore, the adjustment of the DC characteristic has to be carried out first, as it is stated in the chapter "Main Adjustment Steps", and must not be changed afterwards, otherwise the AGC must be adjusted once again. Please note also that in dial mode, the AGC function is switched off. A typical AGC characteristic is shown in figures 9 and 10.
AGC RAGC1 12 k
Figure 8.
0 -1 gain (relative) / dB -2 -3 -4 -5 -6 0 10 20 30 40 50 60 Line current I L/ mA 70 80 90 100
RAGC = 5.6 k RAGC = 12 k
RAGC = 18 k
Figure 9. AGC characteristic (typ.), receive mode
0 -1 gain (relative) / dB -2 -3 -4 -5 RAGC = 12 k -6 -7 0 10 20 30 40 50 60 Line current I L/ mA 70 80 90 100 RAGC = 5.6 k RAGC = 18 k
Figure 10. AGC characteristic (typ.), transmit mode
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Side Tone
The amplified microphone signal controls two current sources, Imod and Ist. The ratio of Imod/Ist is 20. An increase of Imod will also cause Ist to increase. The line voltage VL will then go down, while the voltage across Zst (Vzst) will go up. If the side-tone network Zst is perfectly matched to the lumped line impedance ZL (impedance of the telephone RIMP1 + RIMP2 in parallel to the impedance of the line itself), the voltage at ST will remain constant, thus resulting in a perfect side-tone cancellation. This description assumes, that RIMP2 is 0 (Zst is directly connected to VL). In all other cases, the voltage divider RIMP1/ RIMP2 has to be taken into account as shown in the equation for the constant a (see below).
I mod VL Z ST MIC1 MICO MIC2 ST I ST I ST = 1 20 I mod RECIN 60 k RECO2 Z ST = a a = 20 ZL ZL RIMP1 RIMP1 + RIMP2 RECO1 VZST Z TEL Z LT
* Then change CST1 while keeping the ratio of RST1/RST2 constant. * For fine adjustment, repeat the second and the third step to achieve a better result. In certain cases, especially if the DC characteristic is flat, the receive level high and the line current low, the negative half cycle of the receive signal might cause dynamic range problems, thus making it impossible to adjust the side tone. In such cases, RIMP1 and RIMP2 act as a divider for the receive signal and can prevent the dynamic range problem. However, if the receive signal is divided, the receive output level is reduced.
CIMP2 68 nF Transmit amplifier ZD1 13 V CST1 4.7 nF ST RST1 1.5 K RST2 4.7 K RIMP1 390 R CIMP1 100 RIMP2 300 R
VL
Side-tone amplifier
Receive attenuation
CREC1 47 nF RECIN RECO1
RECO2 Receive amplifier
CREC2 H1 2.2 uF Dynamic earpiece S5 RREC1 100 R H2
Figure 11.
How to adjust the side-tone network * Monitor RECO1/RECO2 while tuning RST1, RST2, CST1 until a flat frequency response characteristic is gained. * For first try, use the following estimation: RST1 + RST2 is about 20 times the parallel impedance of RIMP1 + RIMP2 and the real part of ZLT, the line network terminal (do not forget the parallel impedance of RDP3). * As a first approach, try to use the ratio of RST1/RST2 while keeping CST1 (about 2.2 nF) constant.
Figure 12.
Dialer
Pulse dialing (see figure 14) For pulse dialing, there is no adjustment necessary. The dial pulse comes from pin DP and goes to T2/T3 to realize the break/ make. For T2 and T3, it is recommended to use bipolar transistors instead of MOS transistors. This is because during low supply-voltage operation, a MOS transistor might not work due to his high threshold voltage.
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DTMF filter (see figure 13) In most countries, a DTMF filter is not needed. If a DTFM filter is necessary, the following procedure has to be carried out: Use the structure shown in figure 13 and adjust the components to fulfill the desired specification. The DTMF signal is finally fed into the transmit path on pin MICO.
CMF2 MICO RMF2 CMF1 RMF1 CMF4 RMF3 22 k MFO CMF3 100 nF
Errormax = (dialer error) + (xtal deviation from 3.579545 MHz) (xtal tolerance range) Example: CSA3.58MG300 - FGA given xtal frequency = 3.566 MHz Deviation from 3.579645 MHz is -0.38% The maximum frequency deviation gained from the specified value is: * R2: -0.52% - 0.38% - 0.4% = -1.3% * R1: +0.74% - 0.38% + 0.4% = +0.76%
Table 3. DTMF output frequencies (oscillator: 3.579545 MHz) R1 R2 R3 R4 C1 C2 C3 Specified/Hz 697 770 852 941 1209 1336 1477 Actual /Hz 699 766 848 948 1216 1332 1472 Error % +0.28 -0.52 -0.47 +0.74 +0.57 -0.30 -0.34
Figure 13.
VDD2 RVD2 220 k RDP3 2.7 k RDP2 CRING1 820 nF 250 V
TIP RRING2 470 R
RDP1 100 k
T3
S4 B2
B3
LINE
RVD1 5M RING
T2 DP VL
B1
B4 GND
Figure 14.
MFO, MICO MFO is a source-follower output. A 10-k to 22-k resistor at MFO to ground is necessary for current flow. Direct AC coupling overdrives the TIN input. Therefore, a series resistor has to be used to achieve an appropriate TIN level. Biasing of the MFO output is about 1/2 VDD1 during dial mode only. MFO is grounded by an internal N-channel FET, except when bursting out the DTMF signal. The MICO output bias is always 1.0 V. VDD1, VDD2 The line current is controlled by make/ break action during pulse dialing. During the break period, there is no VL from the line. Due to this behavior, VDD1 is no longer fed from the line current and VDD2 becomes the supply voltage of CVD1. For this reason, CVD1 needs a relatively large capacitor ( 220 F). Max. current consumption at VDD2 = 2.5 V: Pulse dial mode DTMF mode IDD1 + IDD2 < 600 A IDD1 + IDD2 < 1 mA
13
Mode switching * Pin MODE selects DTMF/pulse (10/20 pps) * B/M ratio in pulse mode is selected by BM * The DTMF signal remains as long as the key is pressed DTMF output frequencies Ceramic resonators from MURATA can be connected directly to XT and XTB; external components are not needed. The maximum frequency error can be calculated by the formula:
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Flash mode IDD1 + IDD2 < 500 A Memory retention for re-dial The re-dial function is possible when VDD2 > 1.0 V and the last number is 32 digits. During on-hook state, there is no VDD1 supply. When CVD1 discharges and VDD2 < 1.0 V, the re-dial memory is not retained. To avoid this, the current must be supplied directly from the line through a high-impedance resistor. In the standard application circuit, this can be achieved by RVD1 = 5 M/ RVD2 = 220 k (see figure 14). Key tone In pulse dialing mode, each key strike generates a 50-ms burst of 1240 Hz to indicate keyboard activities. This signal can be fed to the earpiece as shown on the demo board schematic. The loudness can be adjusted by means of RMEL1 and CMEL1. If RMEL1 > 10 k, CMEL1 can be omitted in some applications. Privacy The "privacy" function is a convenient feature when muting during conversation is desired. The PRIVACY pin has an integrated toggle switch and can be controlled between normal mode and mute as its input switches from HIGH to LOW. If this function is not used, PRIV pin can be left open. When the peripheral noise is high, this noise may switch the PRIV function on and off, resulting in unstable speech function. Connecting the capacitor to ground or a 100-k resistor of from PRIV pin to VI increases the noise immunity. In order to debounce the key, a capacitor must be connected to ground. Please note that the privacy function is reset automatically by the MUTE signal or by going on-hook. VDD2 operation range: 2.0 V up to 5.5 V. When the line current is high, a 5-V Zener diode is necessary at VDD2. It also ensures ESD protection. Please note that in pulse-/DTMF dial mode, microphone and receiver are both muted by the dialer. Muting can also be activated by an external switch to GND at pin MUTE. GND1, GND2 GND1 is internally connected to the speechand ringer-block ground. GND2 is internally connected to the dialer-block ground. These two grounds must be connected together as close as possible to the pins GND1, GND2. DTMF monitor volume The tone output can be monitored at the receiver during DTMF dialing. The U3760MB turns off the side-tone amplifier during DTMF output and mutes the receiver amplifier by 29 dB approx. This mute level is fixed. The VL output tone signal goes directly to RIMP2, to the side-tone network and to RECIN. Meanwhile, the side-tone amplifier is off. Therefore, the receiver sound is only determined by the line signal. The tone output from VL is divided by RIMP1 and RIMP2, and fed to RECIN. Between RECO1/2 and RECIN, it is muted by 29 dB. Example: RIMP2 and RIMP1 are at a ratio of 1:1 between VL and VI. The signal is fed from the connection of RIMP2 and RIMP1 to RECIN, the following tone-signal level is expected at RECO1/RECO2 regardless of the line conditions. (monitor output at RECO1/RECO2) = (DTMF output level at VL ) - (loss of divider 6 dB) - (mute = -29 dB).
Ringer
Ringer impedance In on-hook condition, a telephone must have a well-defined input impedance for incoming ringing signals at Tip and Ring.
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The U3760MB uses a standard input configuration (see figure 15) which consists of the series resistors RRING2 and RRING1 plus the decoupling capacitor CRING2 and the input impedance of the chip. The real part of the input impedance is mainly formed by the two resistors. A total value of about 2 k will guarantee good results for most applications. Especially at low frequencies (< 20 Hz), the major part of the input impedance is given by the capacitor CRING2. A range of 0.8 F to 1.5 F will suit almost every specification. The input impedance of the chip is in the range of 5 k to 8 k (see figure 21). This is valid as long as the chip is below the turn-on threshold and thus the output stage is off. Ringer threshold The start-up threshold for the ringer output signal is adjustable in a very wide range by simply modifying the resistor RTH1(see figure 19). DC values between 10 V and 24 V at VRIAC can be chosen. Figure 20 shows the resulting adjustment range in the standard application. The comparator in the chip uses a hysteresis with a fixed lower threshold of about 5.6 V at VRIAC. Once the ringer has reached the upper threshold, it will continue to drive the buzzer as long as the VRIAC voltage remains above 5.6 V. In some countries, the ringer must stop at a certain time after the input signal at TIP and RING has disappeared. In those applications, a diode, DRING1, must be added. The full-wave rectified signal at VRIAC will then be used to trigger an internal mono-flop. As long as the mono-flop is periodically re-triggered, the circuit will continue with the melody. As soon as the input pulses disappear, the chip will wait until the time of the mono-flop (toff 65 ms) has elapsed and automatically stop the melody generator. If this feature is not needed, the diode DRING1 must be shorted. Ringer melody The ringer circuit of the U3760MB generates a two-tone melody. The tone frequencies and the audio-sequence frequency are controlled by a common oscillator circuit. Thus, changing tone frequencies will also change the audio-sequence frequency. The ratio of the higher output frequency to the repetition rate is fixed to f1H/f2 = 80. The audio-sequence frequency can also be calculated by f2 = fosc/320. The oscillator frequency is defined by R and C connected to pin RCK. It is recommended to use 75 k R 330 k and 470 pF C 2.2 nF The oscillator frequency is given by the following calculation (see also figure 17): 1 t 1 = ( UB - UA ) x x C I UB t 2 = R x C x ln UA where UB = 3.2 V typ. UA = 0.65 V typ. I = 420 A typ. 1 1 thus, fOsc = = t1 + t 2 T The audio-sequence frequency, f2, is a function of the oscillator frequency, derived from internal dividers: f2 = fOsc 320
Example: Derived from the oscillator frequency and the ratio of low frequency to high frequency, the ringing frequency is f1H/f1L = 5/4 which means: f1H = fOsc f and f1L = Osc 4 5
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Example: R = 150 k and C = 1 nF (see figure 18)
f Osc = 1 = t1 + t 2
* MICO Speech mode: 400 dial mode: 16 k (bias on) * TIN: 5.8 k * VL: AC impedance > 50 k * ST: High input impedance ( 290 A current source) * RECIN: 60 k (input) * RECO1/RECO2: 10 (differential, output) * VRIAC: diode x 2 (series) + 80 k * THA: 30 k
V UB
1 = 4079 Hz 2.55 V x 1 nF + 150 k x 1 nF x ln 4.923 420 A
thus,
1 f1H = fOsc = 1020 Hz, 4 1 f1L = fOsc = 816 Hz, 5 f f2 = Osc = 12.7 Hz 320
RBUZ1 4.7 k Piezo buzzer
Figure 16.
OUT
UA
t1 t
t2
time
Ringing loudness To adjust the ringing volume, a resistor in series to a piezo transducer is used (see figure 16). Impedances of some ports * MFO Active: low impedance (source follower) others: ground (NMOS switch on)
Figure 17.
C R
RCK
Figure 18.
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24 22
V RIAC / Volt
20 18 16 14 12 10 0 20 40 60 R THA / k 80 100 120 VRIAC = 10.2 V, R THA = infinite
Figure 19. Threshold switch on ringer voltage (VRIAC = fRTHA measured values)
50 45
Vtip_ring / Volt
40 35 30 25 20 15 10 5 0 10 15 20 25 30 35 Ringing frequency / Hz RRING1 = 470 CRING1 = 1 uF RRING2 = 1.8 k
R THA = 0
R THA = infinite
40
45
50
Figure 20. Ringing-voltage threshold (typ.) at tip/ring as a function of the ringing frequency
8.00 7.50 7.00 6.50 6.00 5.50 5.00 0 5 10 15 V RIAC / Volt 20 25
R RIAC / k
Figure 21. Ringer impedance in off-state (typ.)
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ELEKTRET-MICRO TIP
RVD2 220K CRING2 1uF 250V RRING2 470R RHK2 1M CMI4 RMI1 RDP1 RHK3 RMI2 RDP2 33K
RHK1
M1
M2
220K
T1
9014C 1K 10nF
2N5401
100K
1K RMI4 15K RDP3 B2 RVD1 5M 1N4004 CPRIV 47nF B1 GND CIMP2 RIMP2 330R TRANSMIT AMPLIF. ZD1 13V B4
MPSA42
S4 T3
B3 VAR1 75V
CHK1 100nF 470K CVD1 220 RMI3 15K
RMF2 10K
LINE
U3761MB
TO-H2
BRAKE/MAKE SELECTION RMI6 To VI(Pin-17) CMF3 100nF 100nF CMI1 RMI7 CTIN 220nF 100nF CMI2 RMF3 22K 10K
CRISTAL or CERAMIC RESON. MODE SELECTION
2k7
3.579545-MHZ T2 S3
2.2nF
Q1
ZD2 5V1
S2
CMEL1 47nF
RING
S1 XT/ MIC2 10
MICRO AMPLIF. + SIDETONE AMPLIF.
RMEL1 10K
XT MICO 11 13 12 6 33 7 35 36 32 31
HKS/
MODE
DP/
VDD2
VDD1
MFO
MIC1
B/M 34
5
TIN PRIVACY 16 23
VL
CST1 3.3nF RST1 560R RST2 2.7K
CLOCK GENERATOR
KEYTONE
KT
4 MUTE-CONTROL
MUTE/ 18
24
ST
RIMP1 390R
DYNAMIC EARPEACE
DIALER
SUPP LY CURRENT
READ- /WRITE COUNTER
C1 REGULATOR PULSE
CONTROL
1
RECEIVE ATTENUATION
20
RECIN
CREC1 47nF CREC2 2.2F
C2
2
C3
3
22
RECO1
H1
R1 RAM LOGIC
AGC OFF IN DTMF
37
21
RECEIVE AMPLIF. RECO2 RREC1 100R H2
CONTROL-LOGIC
1
2
3
F1
AGC CURRENT GENERATION
R2 38
Figure 22. Demo board
4
5
6
F2
26
AGC
RAGC1 12K RDC RDC1
R3 39 D/A
CONVERTER
KEYBOARD-CONTROL
7 ADDRESS LATCH
DATA LATCH AND DECODER
ROW AND COLUMN PROGRAMMABLE COUNTER
8
9
F3
SPEECH-IC
14 17 19
R4
40
*/T
0
#
R/P
VI
39R 1Watt
VBG 28 VRING
CRING1 10
CIMP1 220
RRING1 1.8K
CRCK1 1nF
RCK SUPPLY
29
RINGER
POWER ON RESET
DRING1 ZDRING1
27V
RRCK1 150K
27 CLOCK-SIGNAL OSCILLATOR DIVIDER TONE -SIGNAL GENERATOR
VRIAC RBUZ1
GND1
9
30 OUT
4k7
OUT
GND2 DIVIDER
8 BANDGAP REFERENCE COMPARATOR WITH HYSTERESIS 25
THA RTH1 15K GND
PIEZZO BUZZER
Pin-Nr shown for SDIP40
01.99
PULSE
CONTROL
R1 RAM LOGIC
41
24
RECO2 RREC1 RECEIVE AMPLIF.
DYNAMIC EARPEACE
1
2
3
F1
AGC CURRENT GENERATION
AGC OFF IN DTMF
CREC3
47 0nF
01.99
Electr. micro
M1 M2
RVD2 220K RHK1 RHK2 *) LF1,CF1 not necessary, if not on board, change CIMP2 from 2.2nF to 68nF
CRING2
CMF1 68nF CMI4
470K
1M
RDP1
RMI2
T1
9 01 4C
CHK1 100nF 1M RMI4 B2 MPSA92 B1 GND 1N400 4 B4 B3 CVD1 220 RMI3 10K 1N4148 DCLIP2 RHK3
RMI1
RDP2 390K
820nF 250V
RRING2 470R
TIP
1M
5,1V ZD5
RRMF1 1 0K
MPSA92 RDP3 33K RVD1 4.7M
1K
22n 10K
RMI6
.39K CPRIV 47nF
1K
T3
S4
CF2 68n
*) LF2 1.5mH
LINE
95V CF1 68n
TO-H2 Q1 green
BRAKE/MAKE SELECTION MODE SELECTION
CRISTAL or CERAMIC RESON.
3.579545-MHZ S2
22nF
RMI7 8.2K MPSA42 1N4148 DCLIP1 CMF3 33nF CMI1
RMF2 1 2K To VI(Pin-19) 33 nF CMI2 RTIN CTIN 3.3k 1uF
RING
T2 S3
CIMP2
2.2nF
S1 XT/ MODE VDD1 33
MICRO AMPLIF. +
BR1 HKS/ DP/ MFO MIC1 13 14 15 MICO 10 TIN PRIV 18 25 MIC2 39 34 VDD2 38
RMF 3 18K
+-
RIMP2 330R
LF 1 1.5mH
RMEL1 10K
XT 8
ZD1 TRANSMIT AMPLIF.
if RMEL1 > 10k, no coupling capacitor necessary
B/M 37
36 9 CLOCK GENERATOR
16 VL
CST1 15nF
9.1V
RST1 560R
ZDP 3.6V
KEYTONE
KT
7 MUTE-CONTROL
MUTE/ 20
SIDETONE AMPLIF.
RST2 5.1K
26
ST
RIMP1 560R
DIALER
SUPPLY CURRENT READ-/WRITE COUNTER
C1 REGULATOR
1
RECEIVE ATTENUATION
22
RECIN
CREC1 47nF H1
C2
2
C3
3
23
RECO1
CREC2 2.2 F
CONTROL-LOGIC
R2 42
270 R
H2
4
5
6
F2
28
AGC
R3 43 D/A
CONVERTER
KEYBOARD-CONTROL
7 ADDRESS LATCH
DATA LATCH AND DECODER
ROW AND COLUMN PROGRAMMABLE COUNTER
8
9
F3
SPEECH-IC
17 19 21 VI
1Watt
RDC1 39R BR3 RRING1
R4 44
*/T
0
#
R/P
Figure 23. Typical application for Germany
VBG
CIMP1 47
1.8K
CRCK1 1nF
RCK SUPPLY
31
RINGER
POWER ON RESET
30
VRING
BR2 CRING1 10
DRING1 ZDRING1
27V
RRCK1 150K
29 CLOCK-SIGNAL OSCILLATOR DIVIDER TONE -SIGNAL GENERATOR 32
VRIAC
GND1(Analog)
DTH1/DTH2
12
OUT
RBUZ1 10K
L1
GND2(Digital) DIVIDER
11 BANDGAP REFERENCE COMPARATOR WITH HYSTERESIS 27
THA RTH1 82K
PIEZZO BUZZER
L2
Pin-Nr shown for SSO44
U3760MB
19

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