ICM7226A Universal Counter and LED Display Driver

Overview

The ICM7226A is a fully integrated Universal Counter and LED display driver designed for high-performance frequency and period measurement applications. This CMOS-based component combines multiple functional blocks, including a high-frequency oscillator, decade timebase counter, 8-decade data counter with latches, 7-segment decoder, digit multiplexer, and segment/digit drivers capable of directly driving large LED displays. With a maximum input frequency of 10MHz in frequency and unit counter modes (2MHz in other modes), the ICM7226A serves as a comprehensive solution for digital measurement systems requiring direct display drive capability.

Key Features

• CMOS Design: Provides very low power consumption for energy-efficient operation
• Integrated Display Drivers: Directly drives both digits and segments of large 8-digit LED displays without external components
• Wide Measurement Range: Measures frequencies from DC to 10MHz and periods with high accuracy
• Multiple Operating Modes: Supports frequency, period, time interval, and unit counting modes
• High-Speed Operation: 10MHz maximum input frequency in frequency and unit counter modes (2MHz in other modes)
• Complete Counter Solution: Integrates timebase counter, data counter, latches, and display drivers in single package
• Digital Inputs: Accepts digital signals, though may require external amplification/level shifting for some applications

Applications

The ICM7226A is ideal for various measurement and display applications including:

• Digital frequency counters and meters
• Period measurement instruments
• Time interval measurement systems
• Universal counting and display applications
• Test and measurement equipment
• Industrial process monitoring systems
• Educational laboratory instruments
• Embedded measurement systems requiring direct LED display drive

Electrical Characteristics

Absolute Maximum Ratings

• Supply Voltage (V+ to V-): 12V
• Input Voltage (any input): (V-) -0.3V to (V+) +0.3V
• Operating Temperature Range: 0°C to +70°C
• Storage Temperature Range: -65°C to +150°C

Recommended Operating Conditions

• Supply Voltage: +5V ±5%
• Input Frequency (Frequency/Unit Counter Modes): 0 to 10MHz
• Input Frequency (Other Modes): 0 to 2MHz
• Operating Temperature: 0°C to +70°C

DC Electrical Characteristics

• Supply Current (all segments on): 50mA max
• Input High Voltage: 2.0V min (V+ = 5V)
• Input Low Voltage: 0.8V max (V+ = 5V)
• Input Leakage Current: ±1μA max
• Segment Output Current: 25mA max per segment
• Digit Output Current: 100mA max per digit

AC Electrical Characteristics

• Maximum Input Frequency (Frequency Counter Mode): 10MHz
• Maximum Input Frequency (Period/Time Interval Modes): 2MHz
• Timebase Accuracy: ±0.01% over temperature range
• Display Refresh Rate: 500Hz typical

Functional Description

The ICM7226A integrates several key functional blocks to provide a complete counting and display solution. The high-frequency oscillator serves as the timebase for precise measurements, while the decade timebase counter provides the necessary timing intervals. The 8-decade data counter with latches allows for accumulation and storage of measurement results. The integrated 7-segment decoder converts binary data into display formats, and the multiplexed digit drivers sequentially activate each display digit while the segment drivers provide the appropriate illumination pattern.

Input Stages

Both counter inputs accept digital signals, though the input circuitry may require external conditioning for certain applications. The device supports direct frequency measurement up to 10MHz in frequency counter mode, with appropriate signal conditioning. For period and time interval measurements, the maximum input frequency is 2MHz.

Display Drive

The ICM7226A features powerful output drivers capable of directly driving common anode LED displays without external transistors. The multiplexed display drive scheme reduces component count while maintaining excellent display brightness. The device supports 8-digit displays with full 7-segment plus decimal point capability for each digit.

Package Information

Available Packages

• 28-pin Plastic Dual In-line Package (PDIP)
• 28-pin Shrink Small Outline Package (SSOP)

Package Dimensions (28-pin PDIP)

• Overall Length: 36.32mm max
• Overall Width: 13.97mm max
• Lead Pitch: 2.54mm (100 mil)
• Body Thickness: 4.57mm max

Pin Configuration

The 28-pin package includes pins for:

• Power supply (V+, V-)
• Counter inputs (A, B)
• Mode control inputs
• Display segment outputs (a-g, DP)
• Digit driver outputs (D1-D8)
• Timebase control inputs
• Latch and reset controls

Design Considerations

Power Supply Decoupling

Proper power supply decoupling is essential for stable operation. A 0.1μF ceramic capacitor should be placed as close as possible to the V+ and V- pins, with additional bulk capacitance (10μF) for systems with long power traces.

Display Interface

When driving large LED displays, consider the total current requirements and ensure the power supply can handle the peak currents during multiplexing. For very large displays or high brightness requirements, external drivers may still be necessary despite the integrated drive capability.

Input Conditioning

For non-digital input signals, appropriate conditioning circuitry including amplification, level shifting, and wave shaping may be required to ensure reliable counting operation. Schmitt trigger inputs can help improve noise immunity for marginal signals.

Conclusion

The ICM7226A represents a highly integrated solution for universal counting applications requiring direct LED display drive. Its combination of high-frequency counting capability, flexible operating modes, and integrated display drivers makes it particularly suitable for compact instrument designs where component count and power consumption are critical factors. With proper design implementation, the ICM7226A can serve as the foundation for a wide range of measurement and display applications.