Overview
The LM3915N-1/NOPB from Texas Instruments is a versatile and highly integrated monolithic IC designed for driving LED displays in either bar or dot mode. This component is particularly suited for applications requiring the display of analog voltage levels, such as audio level indicators, power meters, and RF signal strength meters. The LM3915 is known for its ease of application, requiring minimal external components to set up a full-scale meter.
It operates with a single supply voltage ranging from 3V to 25V and can drive LEDs, LCDs, or vacuum fluorescent displays. The device features an internal voltage reference, a high-impedance input buffer, and current-regulated outputs, making it robust and reliable for various signal display needs.
Key Specifications
| Parameter | Min | Typ | Max | Units |
|---|---|---|---|---|
| Supply Voltage | 3 | - | 25 | V |
| Input Signal Range | 0 | - | 12 | V |
| Input Signal Overvoltage | -35 | - | 35 | V |
| Output Current per LED | 1 | - | 30 | mA |
| Internal Voltage Reference | 1.2 | 1.28 | 1.34 | V |
| Operating Temperature Range | 0 | - | 70 | °C |
| Storage Temperature Range | -55 | - | 150 | °C |
Key Features
- Bar or Dot Display Mode: Externally selectable by the user through the Mode Select pin (pin 9).
- Logarithmic Display: 3 dB/step, 30 dB range, making it suitable for signals with wide dynamic ranges such as audio levels and power meters.
- Internal Voltage Reference: Adjustable from 1.2V to 12V, providing a stable reference voltage for the display.
- Current Regulated Outputs: LED current is programmable from 1 mA to 30 mA, eliminating the need for external current limiting resistors.
- High Input Impedance Buffer: Accepts signals down to ground and up to within 1.5V of the positive supply, with input protection against ±35V overvoltage.
- Expandable Displays: Multiple LM3915s can be cascaded for displays up to 90 dB range.
- Direct Drive Capability: Can directly drive TTL or CMOS logic, and other display types like LCDs and vacuum fluorescents.
Applications
- Audio Level Indicators: Suitable for average or peak level indicators in audio equipment.
- Power Meters: Ideal for displaying power levels in various electrical systems.
- RF Signal Strength Meters: Used in communication equipment to display signal strength.
- Light Intensity and Vibration Displays: Can be used to display light intensity or vibration levels in industrial and scientific applications.
- Multi-Device Displays: Can be cascaded with other LM3915s or different models like LM3914 and LM3916 for extended-range displays).
Q & A
- What is the supply voltage range for the LM3915N-1/NOPB?
The supply voltage range is from 3V to 25V).
- How can the display mode be selected on the LM3915N-1/NOPB?
The display mode can be selected by the user through the Mode Select pin (pin 9). For bar mode, pin 9 should be connected to V+, and for dot mode, it should be left open or pulled below V+ by at least 200 mV).
- What types of displays can the LM3915N-1/NOPB drive?
The LM3915N-1/NOPB can drive LEDs, LCDs, and vacuum fluorescent displays).
- What is the range of the internal voltage reference?
The internal voltage reference is adjustable from 1.2V to 12V).
- Can the LM3915N-1/NOPB be cascaded for larger displays?
Yes, multiple LM3915s can be cascaded for displays up to 90 dB range).
- What is the operating temperature range of the LM3915N-1/NOPB?
The operating temperature range is from 0°C to 70°C).
- How is the LED current regulated in the LM3915N-1/NOPB?
The LED current is programmable from 1 mA to 30 mA and is regulated by an internal feedback loop, eliminating the need for external current limiting resistors).
- What is the input signal overvoltage protection of the LM3915N-1/NOPB?
The input can withstand ±35V without damage or false outputs).
- Can the LM3915N-1/NOPB directly drive logic circuits?
Yes, the LM3915N-1/NOPB can directly drive TTL or CMOS logic circuits).
- How does the LM3915N-1/NOPB handle AC signals?
The LM3915N-1/NOPB can display AC signals by applying them directly to the input, and it will respond to positive half-cycles only. It is recommended to use dot mode and run the LEDs at 30 mA for high enough average intensity).
