UM3561 - Low-Cost CMOS LSI Sound Generator IC

Overview

The UM3561 is a cost-effective, low-power CMOS Large Scale Integration (LSI) integrated circuit specifically designed for alarm systems and toy applications. This versatile IC incorporates an internal oscillator and selector circuits, enabling the creation of compact sound modules with minimal external components. The device features a pre-programmed mask ROM that stores multiple sound patterns, making it ideal for applications requiring simple, reliable sound generation without complex programming.

With its typical operating voltage of 3V, the UM3561 is particularly suitable for battery-powered devices where power efficiency is crucial. The integrated power-on reset functionality ensures reliable initialization upon power-up, while its ability to directly drive magnetic speakers simplifies circuit design and reduces component count.

Key Features

• Multiple Sound Selection: Four distinct pre-programmed sounds available for selection
• Low Power Operation: CMOS technology enables efficient power consumption
• Integrated Oscillator: Built-in oscillator circuit reduces external component requirements
• Power Management: Includes power-on reset functionality for reliable initialization
• Speaker Drive Capability: Can directly drive magnetic speakers without additional amplification
• Wide Operating Voltage: Typically operates at 3V, suitable for battery-powered applications
• Compact Design: Minimal external components required for complete functionality

Applications

The UM3561's combination of features makes it ideal for various sound generation applications, particularly where cost, size, and power efficiency are critical factors:

Consumer Electronics

• Electronic toys and games
• Novelty items and greeting cards
• Educational devices

Security Systems

• Simple alarm systems
• Door and window sensors
• Personal security devices

Industrial Applications

• Equipment status indicators
• Warning systems
• Maintenance reminders

Electrical Characteristics

Absolute Maximum Ratings

• Supply Voltage (VDD): -0.3V to +5.0V
• Input Voltage (VIN): -0.3V to VDD + 0.3V
• Operating Temperature Range: -20°C to +70°C
• Storage Temperature Range: -40°C to +125°C

Recommended Operating Conditions

• Supply Voltage (VDD): 2.4V to 3.6V (3V typical)
• Operating Temperature: 0°C to +70°C
• Oscillator Frequency: Dependent on external resistor (typically 100kΩ to 1MΩ)

Electrical Parameters (VDD = 3V, TA = 25°C)

• Supply Current: 0.5mA typical (sound output active)
• Standby Current: < 1μA (no sound output)
• Output Current (Speaker Drive): 5mA typical
• Output Voltage Swing: Approximately VDD - 0.5V

Functional Description

Sound Generation

The UM3561 generates sound through its internal programmed mask ROM, which contains four distinct sound patterns. The specific sound output is selected through pin configuration during circuit design. The sounds are typically simple alarm tones or sequences suitable for attention-getting applications.

Oscillator Circuit

The integrated oscillator requires only a single external resistor to set the operating frequency. This resistor typically connects between the oscillator pin and VDD, with values ranging from 100kΩ to 1MΩ determining the output frequency characteristics. The simplicity of this configuration contributes to the IC's ease of use and minimal external component count.

Output Stage

The output stage is designed to directly drive a small magnetic speaker, typically in the 8Ω to 32Ω range. The output provides sufficient current to produce audible sound levels while maintaining low power consumption. For applications requiring louder output or different transducer types, a simple transistor buffer can be added.

Package Information

The UM3561 is commonly available in an 8-pin DIP (Dual In-line Package) or SOP (Small Outline Package) configuration. The package dimensions and pinout are as follows:

8-Pin DIP Package

• Package Dimensions: 9.8mm x 6.35mm (excluding leads)
• Lead Pitch: 2.54mm (standard DIP spacing)
• Lead Length: 3.3mm typical

Pin Configuration

• Pin 1: Sound Select 1
• Pin 2: Sound Select 2
• Pin 3: Oscillator Resistor Connection
• Pin 4: Ground (VSS)
• Pin 5: Speaker Output 1
• Pin 6: Speaker Output 2
• Pin 7: Test Pin (typically left unconnected)
• Pin 8: Power Supply (VDD)

Design Considerations

Power Supply

While the UM3561 can operate from 2.4V to 3.6V, a stable 3V supply is recommended for consistent performance. For battery-powered applications, two AA or AAA cells in series provide suitable voltage. A small decoupling capacitor (0.1μF) placed close to the VDD pin helps maintain stable operation.

Sound Selection

The four available sounds are selected by configuring the logic levels on the sound select pins (Pin 1 and Pin 2). The specific sound associated with each combination is determined by the mask ROM programming and should be verified with the manufacturer's documentation for the particular device version.

Speaker Connection

The speaker should be connected between the two output pins (Pin 5 and Pin 6). For optimal performance, the speaker impedance should match the output drive capability of the IC (typically 8Ω to 32Ω). Higher impedance speakers will produce quieter output, while lower impedance may overload the output stage.

Conclusion

The UM3561 represents an excellent solution for applications requiring simple, cost-effective sound generation. Its integrated oscillator, multiple sound options, and direct speaker drive capability make it particularly suitable for mass-produced consumer products where component count and power consumption are critical factors. While limited in sound complexity compared to more advanced audio ICs, the UM3561 provides reliable performance for basic alarm and attention-getting applications with minimal design effort.

Designers should consider the UM3561 for projects where simple, pre-programmed sounds are sufficient, and where the low power consumption and minimal external components offer significant advantages in terms of cost and size.