LM3914 Dot Bar Display Driver General Description The LM3914 is a monolithic integrated circuit that senses analog voltage levels and drives 10 LEDs providing a linear analog display A single pin changes the display from a moving dot to a bar graph Current drive to the LEDs is regulated and programmable eliminating the need for resistors This feature is one that allows operation of the whole system from less than 3V The circuit contains its own adjustable reference and accurate 10 step voltage divider The low bias current input buffer accepts signals down to ground or V yet needs no protection against inputs of 35V above or below ground The buffer drives 10 individual comparators referenced to the precision divider Indication non linearity can thus be held typically to 1 2 even over a wide temperature range Versatility was designed into the LM3914 so that controller visual alarm and expanded scale functions are easily added on to the display system The circuit can drive LEDs of many colors or low current incandescent lamps Many LM3914s can be chained to form displays of 20 to over 100 segments Both ends of the voltage divider are externally available so that 2 drivers can be made into a zero center meter The LM3914 is very easy to apply as an analog meter circuit A 1 2V full scale meter requires only 1 resistor and a single 3V to 15V supply in addition to the 10 display LEDs If the 1 resistor is a pot it becomes the LED brightness control The simplified block diagram illustrates this extremely simple external circuitry When in the dot mode there is a small amount of overlap or fade about 1 mV between segments This assures that at no time will all LEDs be OFF and thus any ambiguous display is avoided Various novel displays are possible 2004 National Semiconductor Corporation DS007970 Much of the display flexibility derives from the fact that all outputs are individual DC regulated currents Various effects can be achieved by modulating these currents The individual outputs can drive a transistor as well as a LED at the same time so controller functions including staging control can be performed The LM3914 can also act as a programmer or sequencer The LM3914 is rated for operation from 0 C to 70 C The LM3914N 1 is available in an 18 lead molded N package The following typical application illustrates adjusting of the reference to a desired value and proper grounding for accurate operation and avoiding oscillations Features Drives LEDs LCDs or vacuum fluorescents Bar or dot display mode externally selectable by user Expandable to displays of 100 steps Internal voltage reference from 1 2V to 12V Operates with single supply of less than 3V Inputs operate down to ground Output current programmable from 2 mA to 30 mA No multiplex switching or interaction between outputs Input withstands 35V without damage or false outputs LED driver outputs are current regulated open collectors n Outputs can interface with TTL or CMOS logic n The internal 10 step divider is floating and can be referenced to a wide range of voltages n n n n n n n n n n www national com LM3914 Dot Bar Display Driver February 2003 LM3914 Typical Applications 0V to 5V Bar Graph Meter 00797001 Note Grounding method is typical of all uses The 2 2 F tantalum or 10 F aluminum electrolytic capacitor is needed if leads to the LED supply are 6 or longer www national com 2 Storage Temperature Range If Military Aerospace specified devices are required please contact the National Semiconductor Sales Office Distributors for availability and specifications Soldering Information Dual In Line Package Soldering 10 seconds Power Dissipation Note 6 Molded DIP N 25V Voltage on Output Drivers 25V Reference Load Current 215 C Infrared 15 seconds 220 C See AN 450 Surface Mounting Methods and Their Effect on Product Reliability for other methods of soldering surface mount devices 35V Input Signal Overvoltage Note 4 Divider Voltage 260 C Plastic Chip Carrier Package Vapor Phase 60 seconds 1365 mW Supply Voltage 55 C to 150 C 100 mV to V 10 mA Electrical Characteristics Notes 2 4 Parameter Conditions Note 2 Min Typ Max Units COMPARATOR Offset Voltage Buffer and First Comparator 0V VRLO VRHI 12V ILED 1 mA 3 10 mV Offset Voltage Buffer and Any Other Comparator 0V VRLO VRHI 12V ILED 1 mA 3 15 mV Gain ILED VIN IL REF 2 mA ILED 10 mA Input Bias Current at Pin 5 0V VIN V 1 5V Input Signal Overvoltage No Change in Display 3 8 25 mA mV 100 nA 35 V 12 17 k 0 5 2 1 28 1 34 V 35 VOLTAGE DIVIDER Divider Resistance Total Pin 6 to 4 Accuracy Note 3 8 VOLTAGE REFERENCE Output Voltage 0 1 mA IL REF 4 mA V VLED 5V Line Regulation 3V V 18V 0 01 0 03 V Load Regulation 0 1 mA IL REF 4 mA V VLED 5V 0 4 2 Output Voltage Change with Temperature 0 C TA 70 C IL REF 1 mA V 5V 1 2 1 Adjust Pin Current 75 120 A mA OUTPUT DRIVERS LED Current V VLED 5V IL REF 1 mA LED Current Difference Between Largest and Smallest LED Currents VLED 5V LED Current Regulation 2V VLED 17V Dropout Voltage 10 13 ILED 2 mA 7 0 12 0 4 ILED 20 mA 1 2 3 ILED 2 mA 0 1 0 25 ILED 20 mA 1 3 ILED ON 20 mA VLED 5V ILED 2 mA 1 5 mA mA V Saturation Voltage ILED 2 0 mA IL REF 0 4 mA 0 15 0 4 V Output Leakage Each Collector Bar Mode Note 5 0 1 10 A Output Leakage Dot Mode Note 5 0 1 10 A 150 450 A V 5V IL REF 0 2 mA 2 4 4 2 mA V 20V IL REF 1 0 mA 6 1 9 2 mA Pins 10 18 Pin 1 60 SUPPLY CURRENT Standby Supply Current All Outputs Off 3 www national com LM3914 Absolute Maximum Ratings Note 1 LM3914 Electrical Characteristics Notes 2 4 Continued Note 1 Absolute Maximum Ratings indicate limits beyond which damage to the device may occur Operating Ratings indicate conditions for which the device is functional but do not guarantee specific performance limits Electrical Characteristics state DC and AC electrical specifications under particular test conditions which guarantee specific performance limits This assumes that the device is within the Operating Ratings Specifications are not guaranteed for parameters where no limit is given however the typical value is a good indication of device performance Note 2 Unless otherwise stated all specifications apply with the following conditions 3 VDC V 20 VDC VREF VRHI VRLO V 1 5V 0V VIN V 1 5V 3 VDC VLED V TA 25 C IL REF 0 2 mA VLED 3 0V pin 9 connected to pin 3 Bar Mode 0 015V VRLO 12VDC 0 015V VRHI 12 VDC For higher power dissipations pulse testing is used Note 3 Accuracy is measured referred to 10 000VDC at pin 6 with 0 …
View Full Document
Unlocking...