LM2901VDR2G Quad Differential Comparator: Datasheet, Pinout, and Application Circuit Design

The LM2901VDR2G is a widely-used, industry-standard quad differential comparator from ON Semiconductor, designed to operate from a single power supply or dual supplies over a wide voltage range. This highly versatile component is essential in numerous electronic applications, from simple voltage detection to complex analog-to-digital interfaces. Its key strength lies in its low power consumption and ability to function with a wide range of supply voltages, making it suitable for both battery-powered and industrial equipment.

Datasheet Overview and Key Specifications

A thorough review of the datasheet is critical for proper implementation. The LM2901VDR2G features four independent precision voltage comparators. Key absolute maximum ratings and electrical characteristics include:

Wide Supply Voltage Range: From 2V to 36V with a single supply, or ±1V to ±18V in a split-supply configuration.

Low Supply Current Drain: Typically 0.8 mA per comparator, independent of the supply voltage.

Low Input Bias Current: Typically 25 nA.

Low Input Offset Voltage: Typically 2 mV.

Common-Mode Input Voltage Range: Includes ground (0V), allowing it to sense signals near the negative rail.

Differential Input Voltage Range: Equal to the supply voltage.

Output Voltage Swing: Compatible with TTL, MOS, and CMOS logic systems when using a pull-up resistor.

Pinout Configuration

The LM2901VDR2G is available in a standard SOIC-14 package. The pinout is as follows:

Pins 1, 7, 8, 14: Outputs 1 through 4 (OUT A, OUT B, OUT C, OUT D)

Pins 2, 6, 9, 13: Inverting Inputs 1 through 4 (-IN A, -IN B, -IN C, -IN D)

Pins 3, 5, 10, 12: Non-Inverting Inputs 1 through 4 (+IN A, +IN B, +IN C, +IN D)

Pin 4: VCC+ (Positive Supply Voltage)

Pin 11: GND (Ground / Negative Supply Voltage)

Application Circuit Design: A Basic Voltage Monitor

A fundamental application is a window comparator circuit used for under-voltage and over-voltage monitoring. This design utilizes two of the four comparators.

Design Example: 12V Battery Monitor

Objective: Create a circuit that lights an LED when a 12V battery voltage falls below 11V or rises above 13V.

Components: LM2901VDR2G, three resistors (to create two voltage references), two LEDs (or one bicolor LED with additional resistors).

Circuit Operation:

1. A resistive voltage divider from the battery creates a stable reference voltage (e.g., 2.5V).

2. Two other dividers create the lower threshold (11V equivalent) and upper threshold (13V equivalent) signals, which are connected to the inverting input of one comparator and the non-inverting input of the other, respectively.

3. The actual battery voltage, scaled down by another divider, is fed to the opposite inputs of the comparators.

4. When the scaled battery voltage drops below the lower threshold, the output of the first comparator goes low, triggering the first LED.

5. When the scaled battery voltage rises above the upper threshold, the output of the second comparator goes high, triggering the second LED.

6. The outputs are open-collector, requiring pull-up resistors to VCC or to a logic supply voltage for the output stage to function correctly. This is a critical design aspect of using this IC.

Design Considerations:

Hysteresis: To prevent output oscillation when the input voltage is near the trigger point, adding positive feedback to create hysteresis is highly recommended. This involves adding a feedback resistor from the output back to the non-inverting input.

Noise Immunity: Bypass capacitors (e.g., 0.1µF) placed close to the VCC and GND pins are essential for stabilizing the supply and improving noise immunity.

Output Loading: Ensure the current through the output pull-up resistor and any connected load (like an LED) does not exceed the IC's maximum output sink current capability.

ICGOODFIND: The LM2901VDR2G stands as a fundamental building block in analog circuit design. Its robustness, wide supply voltage range, and open-collector outputs provide designers with exceptional flexibility for voltage level detection, interfacing between analog and digital domains, and motor control applications. A deep understanding of its datasheet parameters and the implementation of hysteresis are paramount for creating stable and reliable circuits in real-world environments.

Keywords: Quad Differential Comparator, Open-Collector Output, Wide Supply Voltage, Window Comparator Circuit, Hysteresis Design.