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L3916A
SPEECH AND 14 MEMORY DIALER WITH LED DRIVER
L3916ASPEECH AND 14 MEMORY DIALER WITH LED DRIVER
SPEECH CIRCUIT TO4 WIRES CONVERSION
PRESENT THE PROPER DC PATH FOR THE
LINE CURRENT AND THE FLEXIBILITY TO
ADJUSTIT AND ALLOW PARALLEL PHONE
OPERATION
PROVIDES SUPPLY WITH LIMITED CUR-
RENT FOR EXTERNAL CIRCUITRY
SYMMETRICAL HIGH IMPEDANCE MICRO-
PHONE INPUTS SUITABLE FOR DYNAMIC
ELECTRET OR PIEZOELECTRIC
TRANSDUCER
ASYMMETRICAL EARPHONE OUTPUT
SUITABLE FOR DYNAMIC TRANSDUCER
LINE LOSS COMPENSATION
INTERNAL MUTING TO DISABLE SPEECH
DURING DIALING
LIGHTED DIAL LED CONSUMING 25% OF
LINE CURRENT
DIALER CIRCUIT DIGITS FOR LAST NUMBER REDIAL
BUFFER DIGITS FOR13 MEMORY REDIAL
ALLOW MIXED MODE DIALINGIN EITHER
TONE OR PULSEMODE
PACIFIER TONE PROVIDES AUDIBLE INDI-
CATION OF VALID KEY PRESSED INA
BUZZER OR/ANDIN THE EARPHONE
TIMED PABX PAUSE
FLASH INITIATES TIMED BREAK: 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
DESCRIPTIONThe device consistsof the speech and the dialer. provides the DC line interface circuit that termi-
nates the telephone line, analog amplifier for
speech transmission and necessary signals for
either DTMFor loop disconnect(pulse) dialing.
March 2000
PIN CONNECTION (Top view)
KEYPAD CONFIGURATION
SO28
ORDERING NUMBER: L3916AD
Note: PAUSE/LND:
PAUSE and LND functionsare sharingthe samekey with different
sequence.Hereafter,PAUSE andLND keysare referringtothesame
key.
1/14
DESCRIPTION (continued)
When mated witha tone ringer,a complete tele-
phone canbe producedwith just two ICs.
The DC line interface circuit developsits own line
voltage across the device anditis adjustableby
external resistorto suit different country’s specifi-
cation.
The speech network provides the twoto four
wires interface, electronic switching between dial-
ing and speech and automatic gain control on
transmit and receive.
The dialing network buffersupto32 digits into the
LND memory that canbe later redialed witha sin-
gle key input. Additionally, another 13 memories
(including3 emergency memories)of 18 digits
memoryis available. Users can storeall 13 sig-
nalling keys and access several unique functions
with single key entries. These functions include:
Pause/Last Number Dialed (LND), Softswitch,
Flash.
The FLASH key simulatesa timed hook flashto
transfer callsorto activate other special features
providedby the PABXor central office.
The PAUSE key storesa timed pausein the num-
ber sequence. Redialis then delayed untilan out-
side line can be accessedor some other activity
occurs before normal signaling resumes. LND key input automatically redials the last
number dialed.
FUNCTION PIN DESCRIPTION
C1, C2, C3, C4, R5, R4, R3, R2, R1Keyboards inputs. Pins1,2,3,4, 24, 25, 26, 27,
28. The one chip phone interfaces with either the
standard 2-of-9 with negative commonor the sin-
gle-contact (FormA) keyboard.
BLOCK DIAGRAM
L3916A2/14
valid keypad entryis eithera single Row con-nectedtoa single Columnor GND simultaneously
presentedto botha single Row anda single Col-
unm. its quiescentor standby state, during normal
off-hook operation, either the Rowsor the Col-
umns areat logic level1 (VDD). Pulling one input
low enables the on chip oscillator. Keyboard
scanning then begins.
Scanning consistsof Rows and Columns alter-
nately switching high throughon chip pullups. Af-
ter botha Row and Column key have been de-
tected, the debounce counteris enabled and any
noise (bouncing contacts, etc)is ignoredfora de-
bounce period (TKD)of 32ms.At this time, the
keyboardis sampled andif both the Row and Col-
umn information are valid, the informationis buff-
ered into the LND location. After scanning starts,
the row and column inputs will assume opposite
states. the tone mode,if twoor more keysin the same
roworif twoor morekeysin the same column are
depresseda single tone will be output. The tone
will correspondsto the rowor column for which
the two keys were pushed. This featureis for test-
ing purposes, and single tone will notbe redialed.
Alsoin the tone mode, the output toneis continu-
ousin the manual dialing as longas the keyis
pushed. The output tone duration follows the Ta-
ble1. When redialingin the tone mode, each
DTMF output has 100ms duration, and the tone
separation (inter signal delay)is 100ms.
Table1: Output Tone Duration
Key-Push Time,T Tone Output
T<= 32ms
32ms<=T<= 100ms+
Tkd>= 100ms+ Tkd output, ignoredby
one chip phone.
100ms Duration
Output Duration=T- Tkd
OSCOutput. Pin5. Only one pinis neededto connect
the ceramic resonatorto the oscillator circuit. The
other endof the resonatoris connectedto GND
(pin 8). The nominal resonator frequency is
3.579545MHz and any deviation from this stand-
ardis directly reflectedin the Tone output fre-
quencies. The ceramic resonator provides the
time reference forall circuit functions.A ceramic
resonator with toleranceof ±0.25%is recom-
mended
PULSEOutput. Pin6. Thisis an output consistingof an
open drain N-Channel device. During on-hook,
pulse outputpinisin high impedance and once off-
hooked,it willbe pulled highby external resistor.
MODE/PACIFIER TONEInput (MODE). Pin7. MODE determines the di-
aler’s default operating mode. When the deviceis
powered upor the hookswitch inputis switched
from on-hook (VDD)to off-hook (GND), the default
determines the signalling mode.A VDD connec-
tion defaultsto tone mode operation anda GND
connection defaultsto pulse mode operation.
When dialingin the pulse mode,a softswitch fea-
ture will allowa changeto the tone mode when-
ever the* keyis depressed. Subsequent* keyin-
puts will cause the DTMF code for an*to be
dialed.. The softswitch will only switch from pulse tone. After returningto on-hook and backto off-
hook, the phone willbein pulse mode. Redialby
the LND keyor the MEM key will repeat the soft-
switch.
Output (PACIFIER TONE). Pin7.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), acti-
vates the pacifier tone. The pacifier tone provides
audible feedback, confirming that key has been
properly entered and accepted.Itisa 500Hz
square wave activated upon acceptanceof valid
key input after the 32ms debounce time. The
square wave terminates aftera maximum of
75msor when the valid keyisno longer present.
The pacifier tone signalis simultaneously sentto
earphone and the buzzer. The buzzer can be re-
moved without affecting this function.
HKSInput. Pin8. Thisis the hookswitch inputto the one
chip phone. Thisisa high impedance input and
mustbe switched highfor on-hookoperationor low
for off-hook operation.A transition on this input
causes the on chip logicto initialize, terminating
any operationin progressat the time. The signaling
mode defaultsto the mode selectedat pin7. Fig-
ures1 and2 illustrate the timingfor this pin.
GNDPin9is the negative line terminalof the device.
Thisis the voltage referenceforall specifications.
RXOUT, GRX, RXINRXOUT (pin 10), GRX (pin 11) and RXIN (pin 12).
The receive amplifier has one input RXIN anda
non inverting output RXOUT. Amplification from
RXINto RXOUTis typically 31dB andit can be
adjusted between 11dB and 41dBto suit the sen-
sitivityof the earphone used. The amplificationis
proportionalto the external resistor connected be-
tween GRX and RXOUT.
FUNCTION PIN DESCRIPTION (continued)
L3916A3/14
IREFPin 13. An external resistorof 3.6kOhm con-
nected between IREF and GND will set the inter-
nal current level. Any changeof this resistor value
will influence the microphone gain, DTMF gain,
earphone gain and sidetone.
VCCPin 14, VCCis the positive supplyof the speech
network.Itis stabilizedbya decoupling capacitor
between VCC and GND. The VCC supply voltage
may also be usedto supply external peripheral
circuits.
LEDPin 15. Lighted dial indicator.The LED connected this pin will lightup when the telephoneis off-
hook and consuming 25%of the line current.
ILINEPin 16.A recommended external resistor of
20ohmis connected between ILINE and GND.
Changing this resistor value will have influenceon
microphone gain, DTMF gain, sidetone, maximum
output swingon LN andon the DC characteristics
(especiallyin the low voltage region).
Pin 17. LNis the positive line terminalof the de-
vice.
REGPin 18. The internal voltage regulator hasto be
decoupledbya capacitor from REGto GND. The characteristics canbe changed withan exter-
nal resistor connected between LN and REGor
between REG and ILINE.
GTX, MIC–, MIC+GTX (pin 19), MIC– (pin 20) and MIC+ (pin 21).
The one chip phone has symmetrical microphone
inputs.The amplification from microphone inputstois 51.5dB andit canbe adjusted between 43.5
and 51.5dB. The amplificationis proportionalto ex-
ternal resistor connected between GTX and REG.
GDTMFPin 22. When the DTMF inputis enabled, the mi-
crophone inputs and the receive amplifier input will muted and the dialing tone will be sentto the
line. The voltage amplification from GDTMFto LN 40dB. Final ouput levelon LN can be adjusted
via the external resistor connected between
GDTMF and GND througha decoupling capaci-
tor.A confidence toneis sentto the earphone
during tone dialing. The attenuationof the confi-
dence tone from LNto Vearis –32dB typically.
VDDPin 23. VDDis the positive supply for the dialing
network and must meet the maximum and mini-
mum voltage requirements.
DEVICE OPERATIONDuring on-hookall keypad inputs are high imped-
ance internally andit requires very low currentfor
memory retention.At anytime, Row and Column
inputs assume opposite statesat off-hook. The
circuit verifies thata valid key has been entered alternately scanning the Row and Column in-
puts.If the inputis still valid following 32msof de-
bounce, the digitis stored into memory, and dial-
ing begins after a pre-signal delay of
approximately 40ms (measured from the initial
key closure). Output tone durationis shownin Ta-
ble1.
The device allows manual dialingofan indefinite
numberof digits, butif more than 32 digits are di-
aled,it will ”wrap around”. Thatis, the extra digits
beyond32 will be storedat the beginningof LND
buffer, and the first 32 digits will no longer be
availablefor redial.
Table2: DTMF Output Frequency
Key Input Stadard
Frequency
Actual
Frequency % DeviationROW1
ROW2
ROW3
ROW4
+0.31
+0.74
COL1
COL2
COL3
+0.57
NORMAL DIALING D2 D3 ....etc
Normal dialingis straighforward,all keyboard en-
tries will be storedin the buffer and signaledin
succession.
PROGRAMMING AND REPERTORY DIALING program, enter the following:
PROG D1 D2 D3... Dn MEM (Location0-9)
PROG D1 D2... .Dn E1-E3
During programming, dialingis inhibited.
FUNCTION PIN DESCRIPTION (continued)
L3916A4/14
diala number from repertory memory (HKSmustbe low), enter the following:
MEM (Location 0-9)or E1-E3 save the last number dialed, enter the follow-
ing:
PROG MEM (location 0-9)or E1-E3
HOOK FLASH FLASH D2 ...etc
Hook flash may be entered into the dialed se-
quenceat any pointby keyingin the function key,
FLASH. Flash consists ofa timed break of
585ms, 300msor 100ms dependingon the Mask
option. Whena FLASH keyis pressed,no further
key inputs will be accepted until the hookflash
function has been dialed. The key input following FLASH will be storedas the initial digitof the
new number, overwriting the number dialed be-
fore the FLASH, unlessitis another FLASH.
FLASH key pressed immediately after hookswitch LND will not clear the LND buffer unless digits
are entered following the FLASH key.
Example:FLASH
LND not cleared
LND FLASH
LND not cleared
LND FLASH D1 D2
LND buffer will contain D1, D2
PAUSE/LAST NUMBER DIALED the PAUSE/LND keyis pressed right after off
hookor FLASH key,itis consideredas LND,ifit pressed aftera digit,it will be consideredas
PAUSE.
LAST NUMBERED DIALED
OFF-HOOK PAUSE/LNDor FLASH PAUSE/LND
Last number dialingis accomplishedby entering
the PAUSE/LND key.
PAUSE
OFF-HOOK D1 PAUSE/LND D2 ...etc pause maybe entered into the dialed sequence any pointby keyingin the special function key,
PAUSE/LND. Pause insertsa 3.1 second delay
into the dialing sequence. The total delay, includ-
ing pre-digit and post-digit pausesis shownin Ta-
ble3.
Table3: SpecialFunction Delays
Each delay shown below represents the time re-
quired after the special function keyis depressed
untila new digitis dialed. The timeis considered
”FIRST” keyifall previous inputs have been com-
pletely dialed. The timeis considered”AUTO”ifin
redial,orif previous diallingis stillin progress.
Function First/Auto Delay (seconds)
Pulse ToneSOFTSWITCH FIRST
AUTO
PAUSE FIRST
AUTO
SOFTSWITCH FUNCTION USING TONE/PULSE
MODE SWITCH
When dialing in Pulse mode after off-hook,
switching TONE/PULSE mode switch from Pulse Tone will cause the deviceto change the sig-
naling mode into tone signal and store the soft-
switch functionin the LND memory for redial. To
redial the softswitch function (mixed mode dialing) the pulse mode after going on-hook and back off-hook, you haveto switch the TONE/PULSE
mode switch backto pulse mode either before go-
ing on-hookor after off-hookor during on-hook.
Subsequent mode change from Toneto Pulse will
change the signaling modeto pulse dialing se-
quence but this mode change will notbe storedin
.the LND memory.
When dialingin Tone mode after off-hook,a
switching of TONE/PULSE mode Switch from
Toneto Pulse will cause the deviceto change the
signaling mode into pulse mode but this mode
change will not be storedin the LND memory.
When LND keyis pressedin Tone mode after go-
ing off-hook, the device will output all tone sig-
nals. pacifier toneof 75msis provided after 32ms de-
bounce time when switching from Pulseto Tone
mode.
Redialby the LND key will repeat the mixed dial-
ing sequencein Pulsemode.
FUNCTION PIN DESCRIPTION (continued)
L3916A5/14
Figure1: Tone Mode Timing
Figure2: Pulse Mode Timing
L3916A6/14
ABSOLUTE MAXIMUM RATINGS
Symbol Parameter Value UnitVLN Positive Line VoltageContinuous 12 V
ILN Line Current 140 mA
VDD Logic Voltage 7.0 V Maximum Voltageon Any Pin GND(-0.3) VDD(+0.3) V
Tamb Operating Temperature Range -25to +75 °C
Tstg Storage Temperature -40to 125 °C
Ptot Total Power Dissipation 700 mW
ELECTRICAL CHARACTERISTICS(IL=10to 120mA; VDD= 3V;f= 1KHz; Tamb =25°C, unless other-
wise specified)
Symbol Parameter Test Condition Min. Typ. Max. Unit Fig.VLN Line Voltage IL= 4mA= 15mA= 120mA= 68KΩ IL= 15mA= 39KΩ IL= 15mA
3.15 3.50
VDD Logic Voltage) TONE MODE
PULSE MODE
IDD Supply Current Into VDD TONE MODE
PULSE MODE
ICC Supply Current Into VCC IL= 15mA 1.30 mA 3
ILED Supply Currentto LED IL= 15mA= 120mA
VMR Memory Retention Voltage 1.50 V 4
IMR Memory Retention Current 1.00 μA4 Off-HookStand-by Current VDD= 4.0V 150 250 μA3
IPL Pulse Output Sink Current VO= 0.5V 1.00 3.00 mA 3
IPO Pacifier Tone Sink/Source
Current= 0.5V (Sink)= 2.5V (Source)
VIL HKS, Mode, Keyboard Inputs
Low
0.3xVDD V-
VIH HKS, Mode, Keyboard Inputs
High
0.7xVDD V-
GTX Transmit Gain Vmic= 2mVrms= 15mA RGTX= 68KΩ= 60mA; RGTX= 68KΩ
AGTX Transmit Gain Variation with
RGTX= 15mA
Vmic= 2mVrms
RGTX= 43KΩ
RGTX= 27KΩ
0dB
DTX Transmit Distortion IL= 15mA VLN= 1Vrms 2 % 6
NTX Transmit Noise IL= 15mA; Vmic=0V –72 dBmp 6
ZMIC Microphone Input Impedance 65 KΩ
L3916A7/14
