XD3914

XD3914 is a monolithic integrated circuit capable of sensing analog voltage levels and driving 10 LEDs to provide a linear analog display. The display mode can be switched from moving dot to bar graph via a single pin. LED drive current is controlled and programmable, eliminating the need for resistors. This feature allows the entire system to operate at voltages below 3V. The circuit contains an internally adjustable reference source and a precision 10-step voltage divider. A low bias current input buffer accepts signals as low as ground or V-, and requires no protection for inputs 30V above or below ground. The buffer drives 10 independent comparators referenced to the precision voltage divider. As a result, display nonlinearity is typically held within 2% even over a wide temperature range. The XD3914 is designed for versatility, allowing controller functions, visual alarms, and scale expansion to be easily added to the display system. The circuit can drive LEDs of various colors or low-current incandescent lamps. Multiple XD3914s can be "cascaded" to form displays ranging from 20 to over 100 segments. Both ends of the voltage divider are externally accessible, enabling two drivers to be combined into a zero-center meter. The XD3914 is very easy to use as an analog meter circuit. A 1.2V full-scale meter requires only 1 resistor and a 3V to 15V supply (in addition to the 10 display LEDs). If this resistor is a potentiometer, it becomes an LED brightness control. A simplified block diagram illustrates this extremely simple external circuitry. In dot mode, a small amount of overlap or "fade" (approximately 1mV) exists between segments, ensuring that all LEDs are never simultaneously "off" and preventing any ambiguous display. A wide variety of novel display modes is possible. Much of the display flexibility stems from all outputs being independent DC regulated current sources. Various effects can be achieved by modulating these currents. Each output can simultaneously drive a transistor and an LED, enabling controller functions including "sequencing" control. The XD3914 can also be used as a programmer or sequential controller. The XD3914 operates over a temperature range of -40°C to +85°C and is available in a DIP18 package.

Key features

• Drives LED, LCD, or vacuum fluorescent displays
• User-selectable bar or dot display mode via external configuration
• Expandable to 100-step display
• Internal voltage reference ranging from 1.2V to 12V
• Single-supply operation below 3V
• Input operable down to ground
• Output current programmable from 2 mA to 30 mA
• No multiplexing or inter-output interference
• Input withstands ±30V without damage or false output
• LED drive outputs: current-regulated, open-collector
• Outputs compatible with TTL or CMOS logic
• Internal 10-step divider is floating, referenceable to a wide voltage range