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Basic Information
Question 1
What kind of packages is the HT9172 supplied in?
Answer
In 18-pin DIP and SOP packages. The pin layout is the same as the HT9170 to allow for easy user interchange.
Functional Description
Question 1
What are the important functions and characteristics of the HT9033?
Answer
Working Voltage: 3.5V~5.5V
Bellcore CAS detection(Type Ⅱ)
High sensitivity：-33dBm
Low standby current：Only 1uA in Power Down Mode
Storage Temperature： -40°C ~ +150°C
Working temperature： 0°C ~ +70°C
For other information consult the Holtek Data Sheet
Question 2
What is the difference between the HT9172 and the HT9170?
Answer
1. Operating temperature:
HT9172：-40℃ to 85℃
HT9170：-20℃ to 75℃
2. Detect time.
The HT9172 detect time is shorter than the HT9170, about 11ms.
3. The HT9172 has enhanced noise rejection.
Application Description
Question 1
When using the HT9032 device to design a caller ID phone for China, why does it fail to display the caller ID when used in Taiwan?
Answer
The HT9032 is an FSK decoder device, however the system in
Taiwan uses DTMF, therefore a DTMF decoded device such as HT9170
should be used to decode the caller's telephone number.
Question 2 In my application circuit what op-amp would be suitable for use with the
HT9020B?
Answer
There are no specific limitations on what op-amp could be used, a device such as the LM324 would be suitable.
Question 3 When using the HT9020 datasheet application circuit to interface to the telephone line, why can I not decode CPT data?
Answer
Because the telephone line terminal has no reference ground, the HT9020 has no way to correctly decode the data. The supplied telephone terminal should be connected to a bridge rectifier, who's reference ground should be connected to the reference ground of the application circuit, to solve this problem.
Question 4 How can I interface the output of the HT9200 device to the telephone line?
Answer
You can use a transistor to connect the DTMF signal to the telephone line, see the enclosed drawing.
Question 5
What is the scope of applications for the HT9033?
Answer
The HT9033 is a CAS tone detector device. It can quickly and correctly receive CAS signals and inform the system controller to implement a call interrupt function. It is suitable for use in many kinds of telephone remote control systems, automatic call systems and industrial control systems etc.
Question 6
When the HT9200A/B is operating in the serial mode, are there any special considerations for the CLK pin?
Answer
When the HT9200A/B is in the serial mode, the initial condition of the CLK line is high and the device uses the falling edge of the clock to latch in data. Therefore in the serial data mode, first setup the data, then the CLK pin should experience a high to low transition. After all the data has been transmitted, the CLK line should be returned to its initial condition otherwise the device will not generate the DTMF signal.
Points to Note
Question 1
Can I connect the PDWN pin to ground directly in the HT9032C applications?
Answer
No, you should not do so. If the PDWN pin is tied to ground during power-on, the HT9032C won't reset properly and malfunction might occur. The PDWN pin may be set to low after the HT9032C device is completely powered-on.
Question 2
When using the HT9200B in the parallel mode, is there a latch function in the device? Will the data on D0~D3 be latched on the falling edge of the /CE line?
Answer
When the HT9200B is in the parallel mode, the device will have a latch function. This is activated on the falling edge of the /CE pin, which will latch in the data. Therefore when it is required output different DTMF signals, a high to low edge on /CE must be provided.
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