UM3561 is an 8-pin low power sound generator chip consisting of a programmed mask ROM and a tone generator. The tone generator produces different tones depending on the information written by the ROM. This low-power and low-cost chip is suitable for simulating siren sounds in alarm circuits and toys. Additionally, we can attach an external speaker through a bypassing transistor.
UM3561 Pinout Diagram
The pinout diagram shows that it has two selection pins that we use to select a tone. Refer to the pin configuration section for details of each pin.
Pin Description
UM3561 consists of an oscillator and a selector circuit. The description of pins functions is given below:
Pin#01, 06: SEL1, SEL2
These are selection pins for sound effect. They are used to change the tone.
Pin#02, 05: Vss, Vdd
The chip is supplied with positive and negative voltage supply through these two pins.
Pin#03: Output
The output pin generates a mono-tone sound signal.
Pin#04: NC
This pin is left unconnected. These pins may have an internal function, but they do not have any external functions.
Pin#07, 08: OSC1, OSC2
These two are oscillator pins used to set the frequency of an internal oscillator. We connect the external crystal oscillator to this pin.
UM3561 Features
The features of UM3561 are as follows:
- Enables you to generate four different types of sounds.
- Provides monotone output along with fast test capability.
- DC voltage supply range is -3V to +5V but typically 3V is applied for normal operation.
- Output voltage range = -3V to +3V.
- The value of operating current is 150 µA and output current is 3 mA.
- The chip has a power-on reset ability due to which it starts in the same condition on powering IC.
- It has a magnetic speaker which can be driven by connecting an NPN transistor.
- The ambient operating temperature range is -10°C to 60°C.
Where to use it?
A simple audio circuit can be designed using only a few external components along with this chip. The UM3561 IC is a three-siren sound generator that can work down to 2.4 Volts. It is designed for use in alarm applications and toys. You can create circuits for ambulance siren or Police siren etc. If you are designing an alarm or a siren circuit, then you can use this IC.
How to use Sound Generator UM3561?
UM3561 IC generates a multitone output signal. Pin7 and piN8 are used to control the frequency of the internal oscillator by connecting an external resistor between these two pins. A 220 kΩ resistor is normally used between these two pins. These oscillations are then transferred to the control circuit which selects a tone based on the inputs of pin6 and pin2 select pins. Then the control circuit will pass this signal to the address counter and from address counter to ROM and then to an output pin. An NPN transistor is usually connected at the output to amplify the sound since the sound signal produced is very weak.
Truth Table
The tones can be changed by changing selection pins connections. The table is given below.
UM3561 Example Circuits
It is used in alarms and siren circuits. Few circuit examples of this chip are as follows:
Two Sound circuit
The circuit shown below can produce police siren and machine-gun sound. Select pin 2 is connected to a power supply through a switch and Select pin 1 is left unconnected. When the switch is OFF, it will produce the sound of a police siren. When the switch is ON, it will produce machine gun sound.
Three sound circuits
It generates three different sounds by designing a circuit with the help of only a few components and a UM3561 chip. The circuit shown in the figure below can produce police siren, ambulance siren, and fire engine siren by using only select 1 pin. As you can see from the table mentioned above, SEL2 pin is left unconnected in producing these three sounds. When SEL1 pin is left unconnected it will produce police siren. When SEL1 is High, it will generate a fire engine siren and it will produce ambulance siren when grounded. You can use a three-way switch at the SEL1 pin to control the connections.
Four Sound circuits
This circuit is similar to the previous one with slight modifications which are shown in the circuit below. You can select 1 out of 4 sirens through changing select pins connections.
