18.2 DTMF Decoder
Figure 62: DTMF Decoder Module
Features
- Operating voltage: 2.4V~12V
- Low power and high noise immunity CMOS technology
- Low standby current
- Capable of decoding 12 bits of information
- Binary address setting
- Received codes are checked 3 times
- Address/Data number combination
- Lt-in oscillator needs only 5% resistor
- Valid transmission indicator
- Easy interface with an RF or an infrared transmission medium
- Minimal external components
- Pair with Holteks 212 series of encoders
- 18-pin DIP, 20-pin SOP package
- HT12D: 8 address bits and 4 data bits HT12F: 12 address bits only
Applications
- Burglar alarm system
- Smoke and fire alarm system
- Garage door controllers Car door controllers
- Car alarm system
- Security system
- Cordless telephones
- Other remote control systems
General Description
The 212 decoders are a series of CMOS LSIs for remote control system applications. They are paired with
Holteks 212 series of encoders (refer to the encoder/decoder cross reference table). For proper operation, a pair of encoder/decoder with the same number of addresses and data format should be chosen.
The decoders receive serial addresses and data from a programmed 212 series of encoders that are transmitted by a carrier using an RF or an IR transmission medium. They compare the serial input data three times continuously with their local addresses. If no error or unmatched codes are found, the input data codes are decoded and then transferred to the output pins. The VT pin also goes high to indicate a valid transmission.
The 212 series of decoders are capable of decoding information that consist of N bits of address and 12N bits of data. Of this series, the HT12D is arranged to provide 8 address bits and 4 data bits, and HT12F is used to decode 12 bits of address information.
Selection Table
Pin Description
| Pin Name | I/O | Internal | Description |
|---|---|---|---|
| A0~A11 (HT12F) | I | NMOS | Input pins for address A0~A11 setting |
| A0~A7 (HT12D) | Input pins for address A0~A7 setting | ||
| D8~D11 (HT12D) | O | CMOS OUT | Output data pins, power-on state is low. |
| DIN | I | CMOS IN | Serial data input pin |
| VT | O | CMOS OUT | Valid transmission, active high |
| OSC1 | I | Oscillator | Oscillator input pin |
| OSC2 | O | Oscillator | Oscillator output pin |
| VSS | Negative power supply, ground | ||
| VDD | Positive power supply |
Absolute Maximum Ratings
| Supply Voltage ..........................................0.3V to 13V | Storage Temperature............................50C to 125C |
|---|---|
| Input Voltage ................................VSS0.3 to VDD+0.3V | Operating Temperature...........................20C to 75C |
Note: These are stress ratings only. Stresses exceeding the range specified under Absolute Maximum Ratings may cause substantial damage to the device. Functional operation of this device at other conditions beyond those listed in the specification is not implied and prolonged exposure to extreme conditions may affect device reliability.
| Symbol | Parameter | Test Conditions | Min. | Typ. | Max. | Unit | |
|---|---|---|---|---|---|---|---|
| VDD | Conditions | ||||||
| VDD | Operating Voltage | 2.4 | 5 | 12 | V | ||
| ISTB | Standby Current | 5V | Oscillator stops | 0.1 | 1 | A | |
| 12V | 2 | 4 | A | ||||
| IDD | Operating Current | 5V | No load, fOSC=150kHz | 200 | 400 | A | |
| IO | Data Output Source Current (D8~D11) | 5V | VOH=4.5V | 1 | 1.6 | mA | |
| Data Output Sink Current (D8~D11) | 5V | VOL=0.5V | 1 | 1.6 | mA | ||
| IVT | VT Output Source Current | 5V | VOH=4.5V | 1 | 1.6 | mA | |
| VT Output Sink Current | VOL=0.5V | 1 | 1.6 | mA | |||
| VIH | H Input Voltage | 5V | 3.5 | 5 | V | ||
| VIL | L Input Voltage | 5V | 0 | 1 | V | ||
| fOSC | Oscillator Frequency | 5V | ROSC=51k | 150 | kHz |
Operation
- The 212 series of decoders provides various combinations of addresses and data pins in different packages so as to pair with the 212 series of encoders.
- The decoders receive data that are transmitted by an encoder and interpret the first N bits of code period as addresses and the last 12N bits as data, where N is the address code number. A signal on the DIN pin activates the oscillator which in turn decodes the incoming address and data. The decoders will then check the received address three times continuously. If the received address codes all match the contents of the decoders local address, the 12N bits of data are decoded to activate the output pins and the VT pin is set high to indicate a valid transmission. This will last unless the address code is incorrect or no signal is received.
- The output of the VT pin is high only when the transmission is valid. Otherwise it is always low
16-Bit I/O Expander with Serial Interface