HT12D RF Decoder IC

HT12D IC is a CMOS series 12-bit RF decoder. Mostly remote control applications have this technology. It gets to interface with the third device and helps it to decode 12-bits data. In this decoder, only 4-bits are data the remaining part is the address. The address will describe the location but 4-bits combination could make 16 types of different combinations. The HT12D decoder can not work alone. It works with another counterpart called an encoder. To receive the data between encoder and decoder address bits should be matched. The encoder can with any CMOS technology. Most modern applications use the encoder for decoding due to its simplicity and efficiency.

HT12D Pinout Diagram

This is a pinout diagram of a 12 bit RF decoder.

HT12D pinout diagram

Pin Configuration description

The device comes in multiple packages. Almost all packages have the same pins but some of them have some extra pins. These pins are not for any use that’s why they are represented by NC which means no connection. All the usable pins of HT12D are:

HT12D Pin Configuration

A0Pin 1NMOS Transmission GatePin1 to Pin8 are address pins. These pins mostly connected to the ground/power. In case of using any special address, the specific logic can be applied. The limit of logical voltages should not exceed these pins. Microcontroller and microprocessors can directly initialize the address to the HT12D.
A1Pin 2
A2Pin 3
A3Pin 4
A4Pin 5
A5Pin 6
A6Pin 7
A7Pin 8
VSSPin 9Pin 9 is the ground pin. The ground pin will make common ground with power supply and external ground. Common ground will help the decoder to operate with external devices and modules.
D8Pin 10CMOS OUTPin10 to Pin13 is the data pin of HT12D. The output data will be in the form of logical voltage. A total of 4 bits will come up with 16 different combinations. All these combinations will be the only available data on these pins. Any CMOS/TTL based device can be interface at the output pins to use the data.
D9Pin 11
D10Pin 12
D11Pin 13
DINPin 14CMOS INPin14 is the data input pin of the HT12D Decoder. The data input will be of 12-bits. It can be from any kind of CMOS/TTL based device. In most of the applications, RF and IR modules relate to it.
OSC2Pin 15OscillatorIC will operate according to the external clock. Pin15 will connect to the oscillator input and pin 16 will connect to the oscillator output. The oscillator will generate the pulse according to which the device will operate.
OSC1Pin 17


VTPin 17CMOS OUTPin 17 is an indication pin for data. This pin is known as the VT pin which means valid transmission. Pin18 will go high to indicate that the data has received. It is not necessary to use this pin. In most of the applications, this pin left unconnected.
VDDPin 18HT12D uses Pin 19 for power input. The power input on this pin should be according to the specification otherwise instead of making IC functional the power will burn it.

HT12D RF Decoder Features

  • HT12D designed with Low power CMOS technology.
  • The CMOS technology gives Low noise immunity to the Decoder.
  • A single IC can decode up to 12-bit data without using any third device.
  • RF and IR wireless modules can interface directly with the IC.
  • Valid transmission helps the external device to learn about decoding status.
  • IC has a builtin Oscillator which requires only a 5% resistor to operate.
  • There are two different packages of the IC, SOP, and DIP.

RF Decoder Electrical Specifications

  • 2.4 to 12V is the operating voltage range of the IC. The recommended and mostly used operating voltages with IC is 5V. 5V comes with multiple controllers and smart boards which makes it the most useful ones.
  • The standby Current of the decoder is 4uA at 5V and 400uA for 12V.
  • The oscillator frequency of the decoder is 150KHz with 51K ohm resistor at 5V.
  • The decoder operating temperature range is -20 to 75 degree but it also can store the temperature of -50 to 125 degrees.

How to use HT12D

To use the HT12D the pins connection should be according to its requirement. First, connect the power supply. Then connect it to the message receiving module which can be an RF receiver or IR receiver. After that connect the decoder with the receiving device. Keep the VT pin high on the IC. Most of the time VT kept high to indicate the valid transmission. The address pins will use to give the address. They should be on the LOW or HIGH state. All address pins represent an 8-bit address. In case of no state on any pins, the decoder would not be able to work properly. The 8-bits message could be a simple message or a complex one. Then, the output pin will connect to the external device which should work on different inputs. In the last attach the 470ohm resistor with the decoder.

All the pin configuration of the IC for proper use are:

HT12D Circuit

HT12D Example Circuits

Example circuit with RF Decoder

In this example, we will learn how the RF module communicates with the decoder. The output of the RF will attach to the decoder. RF receiver will receive the message in 12-bits. The message then 12-bit will generate a corrupt output. In the whole circuit, the address pins mostly attach to the ground. In a secure communication system, it is recommended to select an 8-bit code for secure communication. All same address bits mostly represent the open communication system. The RF module can replace with an IR receiver. Here’s the circuit of HT12D with RF receiver.

IR example

RF transmitter and Receiver Example HT12D and HT12E

RF transmitter and Receiver Exampe HT12D and HT12E


HT12D RF Receiver Example

RF module and IR module are the most common example with HT12D. Nowadays most of the IoT system uses the HT12D for communication to avoid flooding on the server. The HT12D is not only specific to a single transmitter and receiver. Whenever HT12D is attached to the RF or IR circuit, it receives every kind of incoming signal. The incoming signal then gives the output on the base of the address. If the first 8-bits of the input data gets a match with the 8-bit of the decoder then there will be output data. Otherwise, there will not be any output on the decoder.

RF example

Variable Address

As we know the address is 8-bit and they make 256 combinations. In most of the devices, a variable address is used to decode a message. The decoder address will be variate through an external node that is attached to the third circuit. rotating the node will variate the address on the decoder pins. If the user will be kept changing it then there will be output on the decoder in case any 12-bit signals get a match. some third party can use the address to control the device. This variable address feature sometimes allows the device to be controlled by an unknown person. In HT12D there are some security risks but most of the companies still prefer it due to its speed and performance.

HT12D Applications

  • Most of the car companies use RF technology in their car remote. In the coming signal from remote use the HT12D to decode the signal.
  • Bulger Alarm systems also come with HT12D.
  • The car and fire alarm system use HT12D to decode the incoming signal.
  • Most of the remote control systems like a garage, cordless telephones, security systems use the HT12D to decode their instructions.

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