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HT9205A/B/C/D/K
5-Memory/6-Memory Tone/Pulse Dialer
Features
Universal specification
Operating voltage: 2.0V~5.5V
Low stand-by current
Low memory retention current: 0.1µA (Typ.)
Tone/pulse switchable
Interface with LCD driver
32 digits for redialing
32 digits for the SA memory dialing
One-key redialing
Pause and PT key for PBX
4×5 keyboard matrix
3.58MHz crystal or ceramic resonator
Hand-free control
Hold-line control
Pause, PT can be saved for redialing
Resistor options:
M/B ratio
Flash function and flash time
Pause and PT duration
Pulse number
Keyboard form
Memory number:
HT9205A/B/C/D: 5 memories
HT9205K: 6 memories
General Description
The HT9205 series tone/pulse dialers are CMOS
LSIs for the telecommunication system. They are
designed to meet various dialing specifications
through resistor options matrix.
The HT9205 series tone/pulse dialers are of-
fered in various packages from 18 DIP to 24
SDIP. The 18 DIP version is suitable for low cost
applications, while the 24 SDIP version sup-
plies versatile functions such as: Hold-line,
Hand-free and LCD dialing number display in-
terface, all of which are suitable for feature
phone applications.
Selection Table
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Package Information
HT9205A/B/C/D/K
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Keyboard Information
HT9205A/B/C/D/K
Block Diagram
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HT9205A/B/C/D/K
Pin Description
Pin Name
C1~C5
R1~R4
X1
X2
XMUTE
HKS
PO
I/O
Internal
Connection
Description
These pins construct a 4×5 keyboard matrix to perform the
keyboard input detecting and dialing specification setting
functions. When on-hook (HKS=high) all the pins are set to high.
While off-hook the column group (C1~C5) stays low and the row
group (R1~R4) is set to high for key input detecting.
I/O
CMOS
IN/OUT
An inexpensive single contact 4×5 keyboard can be used as an
input device. Pressing a key connects a single column to a single
row, and actuates the system oscillator to result in a dialing
signal output. If more than two keys are pressed at the same
time, no response can be brought about. The key-in debounce
time is 20ms. Refer to the keyboard table for keyboard
arrangement and to the functional description for dialing
specification selection.
The system oscillator consists of an inverter, a bias resistor
I and the necessary load capacitor on chip. Connecting a
OSCILLATOR
standard 3.579545MHz crystal or ceramic resonator to X1 and
X2 terminals can implement the oscillator function. The
O oscillator is turned off in the stand-by mode, and is actuated
whenever a keyboard entry is detected.
The XMUTE is an NMOS open drain structure pulled to VSS
O
NMOS OUT
during dialing signal transmitting. Otherwise, it is an open
circuit. The XMUTE is used to mute the speech circuit when
transmitting the dial signal.
CMOS IN
(HT9205A/B/
C/D)
This pin is used to monitor the status of the hook-switch and
its combination with HFI can control the PO pin output to
make or break the line.
HKS=VDD: On-hook state (PO=low). Except HFI/HDI (hand-
I free/hold-line control input), other functions are
CMOS IN
all disabled.
Pull-High HKS=VSS: Off-hook state (PO=high). The chip is in the stand-by
(HT9205K)
mode and ready to receive the key input.
The pull-high resistance of the HT9205K is 200Ktypically.
This pin is a CMOS output structure which receives HKS and
HFO signals to control the dialer so as to connect or disconnect
the telephone line.
PO outputs low to break line when HKS is high (on-hook) and
O CMOS OUT HFO is low (hand-free inactive). PO outputs high to make line
when HKS is low (off-hook) or HFO is high or HDO is high.
During the off-hook state, the pin also outputs the dialing
pulse train in pulse mode dialing. While in the tone mode, this
pin is always high.
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HT9205A/B/C/D/K
Pin Name
I/O
Internal
Connection
Description
MODE
This is a three-state input/output pin, provided to the user for
selecting a dialing mode among Tone/20pps/10pps.
MODE=VDD: Pulse mode, 10pps.
I/O
CMOS
IN/OUT
MODE=OPEN: Pulse mode, 20pps.
MODE=VSS: Tone mode.
During the pulse mode dialing, switching this pin to the tone
mode changes the following entrance of digits to the tone
mode. When the chips are working in the tone mode, the
switching from tone to the pulse mode will be recognized.
DTMF
This pin is active only when the chip transmits tone dialing
O
CMOS OUT
signals. Otherwise, it always outputs low. The pin outputs
tone signals to drive the external transmitter amplifier circuit.
The load resistor should not be less than 5K.
HDI
This pin is a schmitt trigger input structure. Active low.
I
CMOS IN
Pull-High
Applying a negative going pulse to this pin can toggle the HDO
output once.
An external RC network is recommanded to use for the input
debouncing. The pull-high resistance is 200Ktypically.
HDO
The HDO is a CMOS output structure. Its output is toggle-
controlled by a negative transition on HDI. When HDO is
toggled to high, PO keeps high to hold the line. The hold
O
CMOS OUT
function can be released by setting HFO high or by an on-off
hook operation or by another HDI input. The HDO pin can
directly drive the HT3810 series melody generator to produce
hold-line back ground melody. Refer to the functional
description for the hold-line function.
This pin is a schmitt trigger input structure. Active high.
Applying a positive going pulse to HFI can toggle the HFO
HFI
I
CMOS IN
Pull-Low
once and hence control the hand-free function. The pull-low
resistance of HFI is 200Ktypically.
An external RC network is recommanded to use for the input
debouncing.
HFO
The HFO is a CMOS output structure. Its output is toggle-
controlled by a positive transition on the HFI pin. When HFO is
high, the hand-free function is enabled and PO outputs high to
O
CMOS OUT
connect the line.
The hand-free function can be released by an on-off-hook
operation or by another HFI input or by setting HDO high.
Refer to the functional description for the hand-free functional
operation.
DOUT
This is an NMOS open drain output pin. It outputs the BCD
O
NMOS OUT
code of the dialing digits to the LCD driver chip (HT16XX
series) or µC for dialing number display. Refer to the
functional description for the detailed timing.
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