LM3916N

LM3916N - Dot/Bar Display Driver

Overview

The LM3916N is a monolithic integrated circuit designed to sense analog voltage levels and drive ten LEDs, LCDs, or vacuum fluorescent displays, creating an electronic version of a VU (Volume Unit) meter. This versatile IC provides a visual representation of analog signals, making it ideal for audio level indicators, power level meters, and other applications requiring proportional display output. The device features a single-pin control that toggles between bar graph and moving dot display modes, offering flexibility in display configuration.

With built-in regulated and programmable LED current drive, the LM3916N eliminates the need for external current-limiting resistors, simplifying circuit design. The fast response time makes it particularly suitable for real-time audio applications where immediate visual feedback is required. The entire display system can operate from a single power supply, further enhancing its ease of use in various electronic designs.

Features

• Drives LEDs, LCDs, or vacuum fluorescent displays
• Bar or dot display mode selectable via single pin
• Programmable LED current drive (no resistors required)
• Internal voltage reference from 1.2V to 12V
• Operates from single supply (3V to 25V)
• Fast response time for real-time audio applications
• Linear analog display scaling
• Input withstands ±35V without damage
• Low quiescent current drain (6mA typical)
• Cascadable for displays with more than 10 elements
• Directly replaces LM3914 in VU meter applications

Applications

• Audio VU meters and level indicators
• Power level meters for RF and audio equipment
• Battery voltage monitoring systems
• Analog signal strength indicators
• Industrial process control displays
• Automotive dashboard instrumentation
• Test and measurement equipment
• DIY electronics projects requiring visual feedback
• Audio recording studio equipment
• Musical instrument amplification systems

Electrical Characteristics

(TA = 25°C, V+ = 5V unless otherwise specified)

• Supply Voltage Range: 3V to 25V
• Supply Current: 6mA typical (no load)
• Reference Voltage: 1.28V typical (adjustable)
• Reference Voltage Range: 1.2V to 12V
• LED Current Range: 1mA to 30mA (programmable)
• Input Voltage Range: 0V to V+ - 1.5V
• Input Impedance: 30kΩ typical
• Comparator Threshold Accuracy: ±0.5dB typical
• Display Scaling: 3dB per step (logarithmic)
• Operating Temperature Range: 0°C to +70°C

Package Information

The LM3916N is available in an 18-pin PDIP (Plastic Dual In-line Package) with the following dimensions:

• Package Type: PDIP-18
• Length: 22.86mm (0.9 inches)
• Width: 6.35mm (0.25 inches)
• Height: 4.57mm (0.18 inches)
• Pin Spacing: 2.54mm (0.1 inches) between pins
• Row Spacing: 7.62mm (0.3 inches) between rows
• Material: Molded plastic
• Lead Material: Copper alloy
• Lead Finish: Matte tin
• Moisture Sensitivity Level (MSL): MSL 1 (Unlimited floor life at ≤30°C/85%RH)

Functional Description

The LM3916N operates as a precision analog-to-logarithmic display driver. The internal circuitry consists of ten comparators with precision voltage references, each comparator driving one display element. The reference ladder provides logarithmic (3dB/step) scaling specifically designed for audio VU meter applications, making it particularly suitable for sound level measurement.

The display mode (bar or dot) is selected by the MODE pin (Pin 9). When left open, the device operates in dot mode where only one LED is illuminated at a time. When connected to the supply voltage, the device operates in bar mode where all LEDs up to the input signal level remain illuminated.

The internal voltage reference can be used to set the full-scale display level and can be adjusted from 1.2V to 12V using external resistors. The LED current is set by a single resistor connected to the Iadj pin (Pin 7), with the current being approximately 10 times the current through this resistor.

Design Considerations

When designing with the LM3916N, several factors should be considered:

• Power Supply Decoupling: A 0.1μF ceramic capacitor should be placed close to the V+ pin to ensure stable operation.
• Input Signal Conditioning: For audio applications, proper rectification and smoothing of the AC signal is required before applying to the LM3916N.
• LED Selection: Standard LEDs with forward voltages up to 2.5V work well with the device at typical supply voltages.
• Heat Dissipation: When driving multiple LEDs at high currents, consider thermal management for both the IC and LEDs.
• Cascading: Multiple LM3916N devices can be cascaded for displays requiring more than 10 segments by connecting the REF OUT of one device to the REF IN of the next.

Typical Application Circuit

A basic VU meter application would include:

• Power supply connection with decoupling capacitor
• Signal input through a proper conditioning circuit
• Ten LEDs with anodes connected to the output pins and cathodes to ground
• Current-setting resistor between Pin 7 and ground
• Reference voltage divider network (if adjusting from default)
• Mode selection connection (either open or tied to V+)

Comparison with Similar Devices

The LM3916N differs from similar devices in the family:

• LM3914: Linear scaling (vs logarithmic in LM3916N)
• LM3915: Logarithmic scaling but with different step values
• LM3916N: Specifically optimized for audio VU meters with 3dB/step scaling