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M3541
SINGLE NUMBER PULSE TONE SWITCHABLE DIALER
.SELECTABLELOOPDI .ALLOWS .LNRFACI .SELECTABLEMAKE/ .SELECTABLEI .USESI .TI .OPERATES .CAPABLE
PRELIMINARY DATA
SCONNECT OR DTMF DIALLING MODES USER TO SWITCH FROM LD TO DTMF DIALLING DURING A CALL LITY ALLOWS UP TO 31 DIGITS TO BE RETAINED FOR REDIALLING BREAK RATIOS 2:1 AND 3:2 NTERDIGIT PAUSE 500ms OR 800ms NEXPENSIVE 560KHz RESONATOR MED BREAK RECALL (timed flash) WITH INEXPENSIVE SINGLE CONTACT KEYPAD OF BATTERY-LESS OPERATION. LOW POWER CMOS PROCESS ALLOWS DIRECT OPERATION FROM TELEPHONE LINES
DIP20
SO20
ORDERING NUMBERS : M3541B/1 M3541D
PIN CONNECTION (Top view)
DESCRIPTION The M3541 is a keypad switchable LD/DTMF dialer devices designed for use in low cost, dual dialing mode telephone instruments. It is suitable for sending telephone numbers without limit and an on-chip memory allows numbers of up 31 digits to be retained for redialling later. The low power CMOS design allows the number in the memory to be maintained indefinitely (until overwritten) by a minimal current leaked from the telephone line. A particular feature of this device is the facility for the user to switch dialling mode from LD to DTMF via the keypad during the course of a call. This is intended for uses such as home banking, access to long distancetrunk service, credit cardverificatios and other applications which require data to be sent at low speed once a connection has been established.
July 1993 1/12
M3541
ABSOLUTE MAXIMUM RATINGS
Symbol Parameter Supply Voltage V DD - VSS Voltage on any Pin Except HSW Voltage on any Pin HSW (current limited to < 100A) Current at any Pin Except FILTOUT and FILTIN Current at Pin FILTIN Current at Pin FILTOUT Operating Temperature Storage Temperature Min. - 0.3 VSS - 0.3 VSS - 0.3 -1 0 -5 - 10 - 55 Typ. Max. 6.5 VDD + 0.3 +1 0.1 0 + 55 + 125 Unit V V V mA mA mA C C
* Stresses above those listed under 'Absolute Maximum Ratings' may cause permanent damage to the device. This is a stress rating only and functional operation of the device at these or any other condition above those indicated in the operational sections of this specification is not implied. Exposure to absolute maximum ratings for extended periods may affect device reliability.
D. C. ELECTRICAL CHARACTERISTICS (VDD = 2.5V, Tamb = 25oC unless otherwise specified)
Symbol VDD IDD Parameter Supply Voltage - Off-hook Supply Current - On-hook at 3.0V Supply Current - Off-hook (idle) Supply Current - MF tone sending Supply Current - LD impulsing VHSW VOH VOL Hookswitch Input - On-hook Hookswitch Input - Off-hook MASK, MUTE and IMP Outputs, Load - 1mA MASK, MUTE and IMP Outputs, Load + 1mA MF OUT D.C. Level During Tone Sending MF OUT Output Resistance GDP RON ROFF Darlington Pair Current Gain at IE = 100A, VCE = 2V "Key not Pressed" Resistance "Key not Pressed" Resistance 500 600 2 k k 0.8 VDD 2.2 0.3 0.9 VDD 3 k V V Min. 2.4 Typ. Max. 5.7 1 1 1.0 200 0.2 VDD Unit V A A mA A
A. C. ELECTRICAL CHARACTERISTICS (VDD = 2.5V, Tamb = 25oC unless otherwise specified)
Symbol VTONE GAR Parameter Tone Amplitude Low Group Tone Amplitude High Group Total Harmonic Distortion 0 - 4kHz 0 - 10kHz 0 - 50kHz 0 - 200kHz tTBR Time Break Recall (FLASH) } no Load Min. 57 1.5 Typ. 64 81 2 2 2.5 5 6.5 100 Max. 91 2.5 Unit mVRMS mVRMS dB % % % % ms
Ratio of High to Low Group Amplitude
10
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M3541
PIN FUNCTIONS
Pin Name ROW 1 ROW 2 ROW 3 ROW 4 COL 1 COL 2 COL 3 COL 4 VDD VSS SELECT OSCIN - OSCOUT HSW MASK IMP MF OUT FILTOUT - FILTIN MUTE Function
Connections for 16 Buttons, Single Contact Keyboard
Positive Supply Negative Supply LD/MF Selection, IDP and B/M Ratio Programming Oscillator Connection Hookswitch. A logic '1' voltage at this pin is used to indidcate 'off-hook'. Output to disable speech circuit during pulse dialling and recall (see note 1). 'Loop Disconnect' Dialling Output Unfiltered, Dual Tone Output Unity Gain Amplifier Input and Output for 2-pole Filter Output Active During Keying and Tone Transmission (see note 2)
Notes : 1. The MASK output may be used to disconnect the whole speech circuit in order to maintain the break condition whilst on-hook, during a TBR (Timed Flash) operation or for LD dialling. 2. The MUTE output is provided to disable the microphone while maintaining the loop condition during DTMF transmission.
KEYPAD OPERATION The device will accept keypad inputs only in the 'offhook' condition when the key is pressed for more than 14ms. Any key pressed during the 'on-hook' condition will be ignored and the oscillator inhibited. This ensures that the current drain 'on-hook' is low and used only for memory retention. KEYPAD FORMAT
LD/DTMF MODE SELECTION The initial dialling mode afterthe telephonegoes offhook is determined as follows : DTMF - Connect SELECT pin to VDD LD Option IDP 800ms 500ms 500ms 800ms B/M Ratio 2:1 2:1 3:2 3:2 Connect SELECT pin to : VSS COL 1 COL 2 COL 3
LD dialling is at 10 i.p.s. for all options KEYPAD LD/DTMF MODE CHANGE If the initial dialling mode is LD, pressing either the * or # key will cause all subsequentlyentered digits to be dialled in DTMF. The first press of either * or # will not cause a digit to be dialled, but once in MF mode, pressing * or # will causethe appropriate tone pair to be transmitted. If the TBR (Timed Flash) key is pressed, or an Earth Loop Recall operation is signalled tothe chip, further dialling is set to the initial mode.
LNR = Redial digits in "LNR"store TBR = Timed Break Recall (timed flash)
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M3541
LAST NUMBER REDIAL The function of the Last Number Redial store is to automatically retain the last number dialled so that it can be redialled later simply by pressing the LNR key. Either LD or MF numbers will be retained in the store. When numbers containing an LD part followed by an MF part are dialled, only the LD part will be retained in order that security codes, etc., dialled in MF are not automatically stored. To redial a number, go off-hook and press LNR once. Alternatively, digits may be keyed manually before LNR is pressed. If the digits keyed correspond with the first digits in the LNR store, theremaining digits will be automatically redialled when LNR is pressed (this feature allows manual keying of an access code followed by a pause before dialling out the rest of the number). If, however, a digit is keyed which differs from the corresponding digit in the stored number, then redialling is inhibited. HOOKSWITCH OPERATION The hookswitch input is used to inform the M3541 of whether the telephone is on- or off-hook. When the telephone is on-hook the M3541 will adopt a static low power mode in which dialling functions are inhibited and only a minimal current is consumed to maintain the store contents. The M3541 recognizes the on-hook condition when the hookswitch input (HSW) goes from logic '1' (the off-hook condition) to logic '0' for greater than 300ms. Short line voltage interruptions of less than 200ms, such as those created by the exchange during connection, will not be recognizedby the M3541 as an on-hook indication. The MASK output will go to logic '0' instantly whenever, and for as long as, the hookswitch input is at logic '0' in order to disconnect the speech circuit. This conserves current so that the store contentsare not lost. POWER-ON RESET A Power-on Reset is internally generated when power is applied to the chip and causes the number store to be cleared. LOOP DISCONNECT MODE In this mode the MASK output is used to disable the speech circuit during dialling. The MASK output is logic '0' during impulsing and interdigit pauses. The IMP output signals a break to line when at logic '0' (VSS). Make periods and I.D.P. times are signalled by logic '1' on the output. During the non-dialling period the impulsing output is at logic '0'. Timing of the output is shown below.
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M3541
Figure 1 : Timing Diagram
FIgure 2 : Timing Data
t1 t2 t3 t4 t5
= Pre-digit pause (=t5) = Break period (60ms or 67ms) = Make period (40ms or 33ms) = Post-digit make (= t3) = Inter-digit pause (500 or 800ms)
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M3541
DTMF MODE The MUTE output goes to logic '1' when a key is activated and remains active for the duration of the tone transmission. The tone rate will be 100ms on, 100ms off minimum. TONE FREQUENCIES
Keypad Nominal Frequency (Hz) Deviation from Nominal (%) R1 697 - 0.07 R2 770 - 0.10 R3 852 +0.19 R4 941 - 0.15 C1 1209 - 0.17 C2 1336 - 0.20 C3 1477 - 0.22
There wi ll be an additi onal error due t o the deviation of the oscil lator f requency from 560K Hz.
Figure 3 : Timing Diagram.
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M3541
TONE OUTPUT Facility has been made for tone filtering as shown below. This also allows the user to adjust tone amFigure 4. plitudes as required. The tone amplitude is proportional to the chip supply voltage, VDD, andcan be adjusted by changing the ratio of R3 and R4.
TYPICAL VALUES
R1 = 56k R2 = 56k R3 + R4 = 10k C1 = 1.3nF C2 = 470pF The fi lter components shown have been chosen to give a second order But terwort h response wi th a cut- off fr equency of about 3.5kHz. T he pass-band insertion l oss i s nominall y 0.5dB.
DTMF APPLICATION CIRCUITS The DTMF circuit in figure 5 uses a constant current supply and a 2.5V reference diode to produce the stabilised supply voltage which determines the MF tone level of the M3541. If the speech circuit pro-
vides a stabilised voltage, then figure 6 shows how it may be used to power the M3541. Diode D1 prevents the speech circuit from taking current whilst the telephone is on-hook, and D2 compensates for the voltage dropped across D1 when off-hook.
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M3541
Figure 5.
Figure 6.
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M3541
SWITCHABLE LD/MF APPLICATION CIRCUITS The circuit in figure 7 uses a constantcurrent supply to take current from the telephone line which is used to power the M3541. The 2.5V reference diode produces a stabilised supply voltage which determines the MF tone level of the M3541. In figure 8, a stabilising voltage from the speech is used to supply the M3541 during MF dialling to give accurate tone levels. Figure 7. The M3541 is powered via the 150K resistor during TBR operations and LD dialling breaks, and via Q1 during dialling makes. This configuration minimises the component count at the expense of allowing a leakage current of about 450A during dialling breaks. The 47F reservoir capacitor maintains and smooths the supply to the chip.
Figure 8.
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M3541
DIP20 PACKAGE MECHANICAL DATA
DIM. Min. a1 B b b1 D E e e3 F i L Z 3.3 1.34 8.5 2.54 22.86 7.1 3.93 0.130 0.053 0.254 1.39 0.45 0.25 25.4 0.335 0.100 0.900 0.280 0.155 1.65 mm Typ. Max. Min. 0.010 0.055 0.018 0.010 1.000
DIP20.TBL
inch Typ. Max.
0.065
a1
I
b Z e3
B
e Z
L
b1
E
D
20
11
1
10
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PM-DIP20.EPS
F
M3541
SO20 PACKAGE MECHANICAL DATA
DIM. Min. A a1 a2 b b1 C c1 D E e e3 F L M S 7.4 0.5 12.6 10 1.27 11.43 7.6 1.27 0.75 8 (max.)
o
mm Typ. Max. 2.65 0.1 0.2 2.45 0.35 0.23 0.5 45o (typ.) 13.0 10.65 0.496 0.394 0.49 0.32 0.014 0.009 0.004 Min.
inch Typ. Max. 0.104 0.008 0.096 0.019 0.013 0.020
0.510 0.419 0.050 0.450
0.291 0.020
0.300 0.050 0.030
L C c1
a2
A
e3
E
D M
20
11
1
10
F
a1
b
e
s
b1
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M3541
Information furnished is believed to be accurate and reliable. However, SGS-THOMSON Microelectronics assumes no responsibility for the consequences of use of such information nor for any infringement of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of SGS-THOMSON Microelectronics. Specifications mentioned in this publication are subject to change without notice. This publication supersedes and replaces all information previously supplied. SGS-THOMSON Microelectronics products are not authorized for use as critical components in life support devices or systems without express written approval of SGS-THOMSON Microelectronics. (c) 1994 SGS-THOMSON Microelectronics - All Rights Reserved SGS-THOMSON Microelectronics GROUP OF COMPANIES Australia - Brazil - France - Germany - Hong Kong - Italy - Japan - Korea - Malaysia - Malta - Morocco - The Netherlands Singapore - Spain - Sweden - Switzerland - Taiwan - Thaliand - United Kingdom - U.S.A.
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