SGS Thomson Microelectronics L3916AD Datasheet
SPEECH AND 14 MEMORYDIALER WITH LED DRIVER
SPEECH CIRCUIT
2 TO 4 WIRESCONVERSION
PRESENTTHE PROPER DC PATH FOR THE
LINE CURRENT AND THE FLEXIBILITY TO
ADJUST IT AND ALLOW PARALLEL PHONE
OPERATION
PROVIDES SUPPLY WITH LIMITED CURRENT FOREXTERNALCIRCUITRY
SYMMETRICAL HIGH IMPEDANCE MICROPHONE INPUTS SUITABLE FOR DYNAMIC
ELECTRET OR PIEZOELECTRIC
TRANSDUCER
ASYMMETRICAL EARPHONE OUTPUT
SUITABLEFOR DYNAMICTRANSDUCER
LINELOSS COMPENSATION
INTERNAL MUTING TO DISABLE SPEECH
DURING DIALING
LIGHTED DIAL LED CONSUMING 25% OF
LINE CURRENT
DIALER CIRCUIT
32 DIGITS FOR LAST NUMBER REDIAL
BUFFER
18 DIGITS FOR 13 MEMORY REDIAL
ALLOW MIXED MODE DIALING IN EITHER
TONE OR PULSEMODE
PACIFIER TONE PROVIDES AUDIBLE INDI-
CATION OF VALID KEY PRESSED IN A
BUZZER OR/AND IN THE EARPHONE
TIMEDPABX PAUSE
FLASHINITIATESTIMEDBREAK:585ms.
CONTINUOUS TONE FOR EACH DIGIT UN-
TIL KEY RELEASE
USES INEXPENSIVE 3.579545MHz CE-
RAMIC RESONATOR
POWERED FROM TELEPHONE LINE, LOW
OPERATING VOLTAGE FOR LONG LOOP
APPLICATION
SO28
ORDERING NUMBER: L3916AD
PIN CONNECTION
(Top view)
KEYPADCONFIGURATION
L3916A
DESCRIPTION
The device consists of the speech and the dialer.
It provides the DC line interface circuit that terminates the telephone line, analog amplifier for
speech transmission and necessary signals for
either DTMF or loopdisconnect(pulse)dialing.
March 2000
Note: PAUSE/LND:
PAUSE and LND functions are sharing the same key with different
sequence.Hereafter, PAUSEandLND keysarereferring tothe same
key.
1/14
L3916A
BLOCK DIAGRAM
DESCRIPTION
(continued)
When mated with a tone ringer, a complete telephone can be producedwith just two ICs.
The DC line interface circuit develops its own line
voltage across the device and it is adjustable by
external resistor to suit different country’s specification.
The speech network provides the two to four
wires interface, electronic switching between dialing and speech and automatic gain control on
transmit and receive.
The dialing network buffers up to 32 digits into the
LND memory that can be later redialed with a single key input. Additionally, another 13 memories
(including 3 emergency memories) of 18 digits
memory is available. Users can store all 13 signalling keys and access several unique functions
with single key entries. These functions include:
Pause/Last Number Dialed (LND), Softswitch,
Flash.
2/14
The FLASH key simulates a timed hook flash to
transfer calls or to activate other special features
providedby the PABX or central office.
The PAUSE key storesa timedpause in the number sequence.Redial is then delayed until an outside line can be accessed or some other activity
occurs before normal signaling resumes.
A LND key input automatically redials the last
numberdialed.
FUNCTIONPIN DESCRIPTION
C1, C2, C3, C4, R5, R4, R3, R2, R1
Keyboards inputs. Pins 1, 2, 3, 4, 24, 25, 26, 27,
28. The one chip phone interfaces with either the
standard 2-of-9 with negative common or the single-contact(FormA) keyboard.
L3916A
FUNCTIONPIN DESCRIPTION
(continued)
A valid keypad entry is either a single Row connected to a single Column or GND simultaneously
presented to both a single Row and a single Colunm.
In its quiescent or standby state, during normal
off-hook operation, either the Rows or the Columns are at logic level 1 (V
). Pulling one input
DD
low enables the on chip oscillator. Keyboard
scanningthen begins.
Scanning consists of Rows and Columns alternately switching high through on chip pullups. After both a Row and Column key have been detected, the debounce counter is enabled and any
noise (bouncing contacts, etc) is ignored for a debounce period (TKD) of 32ms. At this time, the
keyboardis sampled and if boththe Row and Column information are valid, the information is buffered into the LND location. After scanning starts,
the row and column inputs will assume opposite
states.
In the tone mode, if two or more keys in the same
row or if two or morekeys in the same column are
depressed a single tone will be output. The tone
will corresponds to the row or column for which
the two keys were pushed. This feature is for testing purposes, and single tone will not be redialed.
Also in the tone mode, the output tone is continuous in the manual dialing as long as the key is
pushed. The output tone duration follows the Table 1. When redialing in the tone mode, each
DTMF output has 100ms duration, and the tone
separation (inter signal delay) is 100ms.
pulseoutput pin is in high impedanceandonceoffhooked,itwillbepulledhighby externalresistor.
MODE/PACIFIERTONE
Input (MODE). Pin 7. MODE determines the dialer’s default operating mode. When the device is
powered up or the hookswitch input is switched
from on-hook (V
determines the signalling mode. A V
) to off-hook(GND), the default
DD
DD
connection defaults to tone mode operation and a GND
connectiondefaultsto pulse mode operation.
When dialing in the pulse mode, a softswitch feature will allow a change to the tone mode whenever the * key is depressed. Subsequent* key inputs will cause the DTMF code for an * to be
dialed.. The softswitch will only switch from pulse
to tone.After returning to on-hook and back to offhook, the phone will be in pulse mode. Redial by
the LND key or the MEM key will repeat the softswitch.
Output (PACIFIER TONE). Pin 7. In pulse mode,
all valid key entries activate the pacifier tone. In
tone mode, any non DTMF entry (FLASH,
PROG, PAUSE, LND, MEM, E1, E2 and E3), activates the pacifier tone. The pacifier tone provides
audible feedback, confirming that key has been
properly entered and accepted. It is a 500Hz
square wave activated upon acceptance of valid
key input after the 32ms debounce time. The
square wave terminates after a maximum of
75ms or when the valid key is no longer present.
The pacifier tone signal is simultaneously sent to
earphone and the buzzer. The buzzer can be removedwithout affecting this function.
Table 1:
Key-Push Time, T Tone Output
T<= 32ms
32ms < = T < = 100ms +
Tkd
T > = 100ms + Tkd
OutputToneDuration
No output, ignored by
one chip phone.
100ms Duration
Output Duration = T - Tkd
OSC
Output. Pin 5. Onlyone pin is needed to connect
the ceramic resonator to the oscillator circuit. The
other end of the resonator is connected to GND
(pin 8). The nominal resonator frequency is
3.579545MHz and any deviation from this standard is directly reflected in the Tone output frequencies. The ceramic resonator provides the
time reference for all circuit functions. A ceramic
resonator with tolerance of ±0.25% is recommended
PULSE
Output. Pin 6. This is an output consisting of an
open drain N-Channel device. During on-hook,
HKS
Input.Pin 8. This is the hookswitchinputto the one
chip phone. This is a high impedance input and
mustbe switched highfor on-hookoperationorlow
for off-hook operation. A transition on this input
causes the on chip logic to initialize, terminating
anyoperationinprogressat the time. The signaling
mode defaults to the mode selected at pin 7. Figures1and2illustrate thetimingforthispin.
GND
Pin 9 is the negative line terminal of the device.
This is the voltage reference for all specifications.
RXOUT, GRX, RXIN
RXOUT(pin 10), GRX (pin 11) and RXIN (pin 12).
The receive amplifier has one input RXIN and a
non inverting output RXOUT. Amplification from
RXIN to RXOUT is typically 31dB and it can be
adjusted between 11dB and 41dB to suit the sensitivity of the earphone used. The amplification is
proportionalto the external resistor connectedbetween GRX and RXOUT.
3/14
L3916A
FUNCTIONPIN DESCRIPTION
(continued)
IREF
Pin 13. An external resistor of 3.6kOhm connected between IREF and GND will set the internal current level. Any changeof this resistor value
will influence the microphone gain, DTMF gain,
earphone gain and sidetone.
V
CC
Pin 14, VCCis the positive supply of the speech
network. It is stabilized by a decoupling capacitor
between V
and GND. The VCCsupply voltage
CC
may also be used to supply external peripheral
circuits.
LED
Pin 15. Lighted dial indicator.The LED connected
to this pin will light up when the telephone is offhook andconsuming 25% of theline current.
I
LINE
Pin 16. A recommended external resistor of
20ohm is connected between I
LINE
and GND.
Changingthis resistor value will have influenceon
microphonegain, DTMF gain, sidetone, maximum
output swing on LN and on the DC characteristics
(especiallyin the low voltageregion).
is 40dB. Final ouput level on LN can be adjusted
via the external resistor connected between
GDTMF and GND through a decoupling capacitor. A confidence tone is sent to the earphone
during tone dialing. The attenuation of the confidencetone from LN to Vear is –32dB typically.
V
DD
Pin 23. VDDis the positive supply for the dialing
network and must meet the maximum and minimum voltage requirements.
DEVICEOPERATION
During on-hook all keypad inputs are high impedance internally and it requires very low currentfor
memory retention. At anytime, Row and Column
inputs assume opposite states at off-hook. The
circuit verifies that a valid key has been entered
by alternately scanning the Row and Column inputs. If the input is still valid following 32ms of debounce, the digit is stored into memory, and dialing begins after a pre-signal delay of
approximately 40ms (measured from the initial
key closure). Outputtone duration is shown in Table1.
The device allows manual dialing of an indefinite
number of digits, but if more than 32 digits are dialed, it will ”wrap around”.That is, the extra digits
beyond 32 will be stored at the beginning of LND
buffer, and the first 32 digits will no longer be
availableforredial.
LN
Pin 17. LN is the positive line terminal of the device.
REG
Pin 18. The internal voltage regulator has to be
decoupled by a capacitor from REG to GND. The
DC characteristicscan be changed with an external resistor connected between LN and REG or
between REG and I
LINE
.
GTX, MIC–, MIC+
GTX (pin 19), MIC– (pin 20) and MIC+ (pin 21).
The one chip phone has symmetrical microphone
inputs.Theamplificationfrommicrophoneinputsto
LN is 51.5dB and it can be adjustedbetween 43.5
and 51.5dB.Theamplification is proportionaltoexternalresistorconnectedbetweenGTXandREG.
GDTMF
Pin 22. When the DTMF input is enabled, the microphoneinputs and the receiveamplifier input will
be muted and the dialing tone will be sent to the
line. The voltage amplification from GDTMF to LN
Table 2: DTMF Output Frequency
Key Input
ROW 1
ROW 2
ROW 3
ROW 4
COL 1
COL 2
COL 3
Stadard
Frequency
697
770
852
941
1209
1336
1477
Actual
Frequency
699.1
766.2
847.4
948.0
1215.9
1331.7
1471.9
% Deviation
+0.31
–0.49
–0.54
+0.74
+0.57
–0.32
–0.35
NORMAL DIALING
D1 D2 D3 ....etc
Normal dialing is straighforward, all keyboard entries will be stored in the buffer and signaled in
succession.
PROGRAMMING AND REPERTORY DIALING
To program, enter the following:
PROG D1 D2 D3. . . Dn MEM (Location0-9)
or
PROG D1 D2.. . .Dn E1-E3
During programming,dialingis inhibited.
4/14
L3916A
FUNCTIONPIN DESCRIPTION
(continued)
To dial a number from repertory memory (HKS
must be low), enter the following:
MEM (Location 0-9) or E1-E3
To save the last number dialed, enter the following:
PROG MEM (location 0-9) or E1-E3
HOOK FLASH
D1 FLASH D2 ...etc
Hook flash may be entered into the dialed sequence at any point by keying in the function key,
FLASH. Flash consists of a timed break of
585ms, 300ms or 100ms dependingon the Mask
option. When a FLASH key is pressed, no further
key inputs will be accepted until the hookflash
function has been dialed. The key input following
a FLASH will be stored as the initial digit of the
new number, overwriting the number dialed before theFLASH,unless it isanotherFLASH.
FLASH key pressed immediatelyafter hookswitch
or LND will not clear the LND buffer unless digits
are enteredfollowingthe FLASH key.
Example:
FLASH
LND not cleared
LND FLASH
LND not cleared
LND FLASH D1 D2
LND bufferwill contain D1, D2
PAUSE/LASTNUMBER DIALED
If the PAUSE/LND key is pressed right after off
hook or FLASH key, it is considered as LND, if it
is pressed after a digit, it will be considered as
PAUSE.
LAST NUMBEREDDIALED
OFF-HOOKPAUSE/LNDor FLASH PAUSE/LND
Last number dialing is accomplished by entering
the PAUSE/LND key.
PAUSE
OFF-HOOK D1 PAUSE/LND D2 ...etc
A pause may be enteredinto the dialed sequence
at any point by keying in the special function key,
PAUSE/LND. Pause inserts a 3.1 second delay
into the dialing sequence. The total delay, including pre-digit and post-digit pauses is shownin Table 3.
Table 3: SpecialFunction Delays
Each delay shown below represents the time re-
quired after the special function key is depressed
until a new digit is dialed. The time is considered
”FIRST” key if all previous inputs have been completelydialed. The time is considered”AUTO”if in
redial,or if previous dialling is still in progress.
Function First/Auto
SOFTSWITCH FIRST
AUTO
PAUSE FIRST
AUTO
Delay (seconds)
Pulse Tone
0.2
1.0
2.6
3.4
3.0
3.1
SOFTSWITCHFUNCTIONUSING TONE/PULSE
MODE SWITCH
When dialing in Pulse mode after off-hook,
switching TONE/PULSE mode switch from Pulse
to Tone will cause the device to change the signaling mode into tone signal and store the softswitch function in the LND memory for redial. To
redial the softswitch function(mixed mode dialing)
in the pulse mode after going on-hook and back
to off-hook,you have to switch the TONE/PULSE
modeswitch back to pulse mode either before going on-hook or after off-hook or during on-hook.
Subsequent mode change from Tone to Pulse will
change the signaling mode to pulse dialing sequence but this mode change will not be stored in
.the LND memory.
When dialing in Tone mode after off-hook, a
switching of TONE/PULSE mode Switch from
Tone to Pulse will cause the device to changethe
signaling mode into pulse mode but this mode
change will not be stored in the LND memory.
When LND key is pressed in Tone mode after going off-hook, the device will output all tone signals.
A pacifier tone of 75msis providedafter 32ms debounce time when switching from Pulse to Tone
mode.
Redial by the LND key will repeat the mixed dialing sequence in Pulse mode.
5/14
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