CA3162E - 3-Digit A/D Converter with Multiplexed BCD Output

Overview

The CA3162E and CA3162AE are I²L monolithic A/D converters designed to provide a 3-digit multiplexed BCD output. These components are specifically engineered to work in conjunction with the CA3161E BCD-to-Seven-Segment Decoder/Driver, enabling a complete 3-digit display solution with minimal external components. The CA3162AE variant offers identical functionality to the CA3162E but features an extended operating temperature range for more demanding environments.

These devices utilize dual-slope conversion technology, which provides excellent noise rejection and stable performance. The integrated design makes them particularly suitable for digital panel meters, portable instruments, and other applications requiring accurate voltage measurement and display.

Key Features

• Dual Slope A/D Conversion: Provides excellent noise immunity and stable, accurate measurements.
• Multiplexed BCD Display Output: Enables efficient 3-digit display when paired with the CA3161E decoder/driver.
• Ultra-Stable Internal Band Gap Voltage Reference: Ensures consistent performance across varying operating conditions.
• Single-Supply Operation with Negative Input Capability: Can measure inputs as low as -99mV while operating from a single positive supply.
• Differential Input: Allows for flexible measurement configurations and common-mode rejection.
• Internal Timing: Eliminates the need for an external clock source, simplifying system design.
• Selectable Conversion Rates: Choose between low speed (4Hz) for maximum resolution or high speed (96Hz) for faster updates.
• Hold Function: Inhibits conversion while maintaining the last valid reading.
• Overrange Indication: Provides clear visual feedback for out-of-range conditions through "EEE" (positive overrange) or "-" (negative overrange) displays.
• Extended Temperature Version Available: The CA3162AE variant offers operation across a wider temperature range.

Applications

The CA3162E is ideally suited for a variety of measurement and display applications, including:

• Digital panel meters
• Portable test equipment
• Battery monitoring systems
• Process control instruments
• Automotive diagnostic tools
• Laboratory measurement equipment
• Industrial control systems
• Consumer electronics with display requirements

Electrical Characteristics

Absolute Maximum Ratings

• Supply Voltage (V+ to V-): 15V
• Input Voltage (Differential): ±2V
• Input Voltage (Common Mode): (V-) -0.3V to (V+) +0.3V
• Operating Temperature Range (CA3162E): 0°C to +70°C
• Operating Temperature Range (CA3162AE): -55°C to +125°C
• Storage Temperature Range: -65°C to +150°C

Recommended Operating Conditions

• Supply Voltage: +5V ±10%
• Input Voltage Range: ±1.999V full scale
• Reference Voltage: Typically 1.000V
• Conversion Rate: 4Hz or 96Hz (selectable)
• Operating Temperature (CA3162E): 0°C to +70°C
• Operating Temperature (CA3162AE): -55°C to +125°C

Performance Characteristics

• Resolution: 1mV (3-digit display)
• Linearity Error: ±1 count maximum
• Zero Error: ±1 count maximum
• Reference Voltage Temperature Coefficient: 30ppm/°C typical
• Power Consumption: 10mW typical at 5V
• Input Impedance: >100MΩ

Package Information

The CA3162E is available in a standard 18-pin dual in-line package (DIP) with the following mechanical specifications:

• Package Type: PDIP-18
• Package Dimensions: 22.86mm x 6.35mm x 4.57mm (body)
• Lead Pitch: 2.54mm
• Lead Material: Copper alloy
• Lead Finish: Solder plated
• Mounting Style: Through-hole
• RoHS Compliance: Available in both RoHS compliant and non-compliant versions

Functional Description

The CA3162E operates on the dual-slope integration principle, which provides inherent noise rejection and excellent accuracy. The conversion cycle consists of two phases:

1. Input Integration Phase: The input signal is integrated for a fixed time period (1000 clock cycles for 4Hz mode, 42 clock cycles for 96Hz mode).
2. Reference Integration Phase: A reference voltage of opposite polarity is integrated until the integrator output returns to zero.

The time required for the reference integration phase is proportional to the input voltage, providing the digital representation of the analog input.

Display Multiplexing

The device outputs BCD data for each digit sequentially, along with digit select strobes. When used with the CA3161E decoder/driver, this enables a multiplexed 3-digit display with minimal external components. The multiplexing occurs at a rate fast enough to appear continuous to the human eye.

Special Functions

The CA3162E includes several special functions to enhance usability:

• Hold Input: When activated, stops new conversions while maintaining the last valid reading on the display.
• Overrange Detection: Automatically detects inputs exceeding +999mV or more negative than -99mV, displaying "EEE" or "-" respectively.
• Auto-Zero: Internal circuitry automatically compensates for offset voltages.

Design Considerations

Power Supply

While the CA3162E can operate from a single +5V supply, proper bypassing is essential for optimal performance. A 0.1μF ceramic capacitor should be placed as close as possible to the V+ pin, with a larger electrolytic capacitor (10μF or greater) for bulk storage.

Input Considerations

The differential input allows for flexible measurement configurations. For best results:

• Keep input leads short to minimize noise pickup
• Use shielded cables for long signal runs
• Ensure common-mode voltage remains within specified limits

Reference Voltage

The internal bandgap reference provides excellent stability, but for applications requiring higher accuracy, an external reference can be used by connecting to the appropriate pin.

Conclusion

The CA3162E represents a complete, high-performance solution for 3-digit digital measurement applications. Its integration of critical functions (A/D conversion, reference, timing, and display multiplexing) into a single package significantly reduces component count and board space requirements while maintaining excellent measurement accuracy. The availability of an extended temperature version (CA3162AE) makes this device suitable for a wide range of commercial, industrial, and military applications.