The LM3914N from Texas Instruments is a monolithic dot\/bar display driver that senses analog voltage levels and drives 10 LEDs, providing a linear analog display, in an 18-pin PDIP package. Key specifications: 10 LED driver outputs with individually regulated current; bar or dot display mode externally selectable; expandable to displays of 100 steps by chaining multiple LM3914s; internal adjustable voltage reference from 1.2 V to 12 V; operates with single supply of less than 3 V; inputs operate down to ground; output current programmable from 2 mA to 30 mA; no multiplex switching or interaction between outputs; input withstands plus or minus 35 V without damage or false outputs; LED driver outputs are current-regulated open-collectors; outputs can interface with TTL or CMOS logic; internal 10-step voltage divider is floating and can be referenced to a wide range of voltages; indication non-linearity typically 0.5 percent; 0 to 70 degrees C operating temperature; supply voltage 3 V to 15 V; LED supply up to 25 V. The N suffix denotes 18-lead PDIP package. NOTE: This product is no longer in production; new designs should consider alternatives.<\/p>","protected":false},"excerpt":{"rendered":"
The LM3914N from Texas Instruments is a monolithic dot\/bar display driver that senses analog voltage levels and drives 10 LEDs, providing a linear analog display, in an 18-pin PDIP package. Key specifications: 10 LED driver outputs with individually regulated current; bar or dot display mode externally selectable; expandable to displays of 100 steps by chaining […]<\/p>\n","protected":false},"author":2,"featured_media":2906,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[13,56],"tags":[],"chip_brand":[138],"class_list":["post-1948","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-integrated-circuits-ics","category-mosfets","chip_brand-ti"],"acf":{"brief_explanation":"10-LED dot\/bar display driver, linear, adj Vref 1.2-12V, 2-30mA LED current, expandable 100 steps, PDIP-18, 3-15V, 0~70C, NRND","date_code":"","package_case":"PDIP-18 (NFK) (19.3 x 9.4 mm, 2.54mm pitch)","in_stock":5000,"datasheet":"https:\/\/www.ti.com\/product\/LM3914","price":"$2.80 (1K+ pcs)","product_introduction":"The LM3914N from Texas Instruments is a classic monolithic integrated circuit that senses analog voltage levels and drives 10 LEDs to provide a linear analog display. It is one of the most iconic and widely-used display driver ICs in the electronics industry, having been in continuous production since its introduction by National Semiconductor (now part of TI) in the early 1980s.\n\nThe LM3914 is fundamentally a 10-step linear voltmeter on a chip. It contains an input buffer, 10 precision comparators, a 10-step resistor divider, an adjustable voltage reference, and 10 current-regulated LED driver outputs. The only external components needed for a basic application are the 10 LEDs, one programming resistor (which sets the LED brightness), and a power supply.\n\nThe bar or dot display mode is selected by a single pin (pin 9). In bar mode, all LEDs up to the level corresponding to the input voltage are lit, creating a bar graph. In dot mode, only the single LED corresponding to the input voltage level is lit, creating a moving dot. The dot mode has a small overlap (about 1 mV) between adjacent segments to ensure that at least one LED is always lit, preventing ambiguous display states.\n\nThe internal voltage reference generates a nominal 1.25 V between the REF OUT (pin 7) and REF ADJ (pin 8) pins. Using two external resistors (R1 and R2), the reference voltage can be adjusted from 1.2 V to 12 V. The same resistor that sets the reference voltage also programs the LED current: LED current is approximately 10 times the current flowing out of the REF OUT pin. This elegant design means that a single resistor sets both the full-scale voltage and the LED brightness.\n\nThe floating 10-step voltage divider is a key feature. Both ends of the divider (RHI at pin 6 and RLO at pin 4) are accessible, allowing the display to span any voltage range, not just 0 to VREF. For example, an expanded-scale meter can display 4.5 V to 5.0 V full-scale by connecting RHI to 5.0 V and RLO to 4.5 V. The 10 LEDs then represent 50 mV steps, providing much finer resolution than a 0-5 V display.\n\nThe LM3914 can be cascaded (chained) to create displays with 20, 30, or more segments. In dot mode, pin 9 of the lower-voltage LM3914 is connected to pin 1 of the next higher LM3914, and special internal circuitry ensures that only one LED is lit across all cascaded devices. In bar mode, the outputs of multiple LM3914s operate independently.\n\nThe LM3914N is the PDIP-18 package version, popular for prototyping and educational applications. The through-hole package allows easy breadboard use and hand soldering. The LM3914 is also available in PLCC-20 (LM3914FN) for surface-mount applications.\n\nIMPORTANT: TI has designated the LM3914 as not recommended for new designs (NRND), and the product is no longer in production. However, it remains widely available from distributors and second-source manufacturers. For new designs, alternatives include the LM3914 from other manufacturers, discrete LED driver solutions with MCU control, or integrated LED driver ICs with I2C\/SPI interfaces.","working_principle":"The LM3914N operates as a linear 10-step analog-to-LED display converter with an internal voltage reference and precision resistor divider.\n\nInput Buffer: The signal input at pin 5 (SIG) enters a high-impedance buffer amplifier that presents very low input bias current (25 nA typical). The buffer accepts input voltages from ground (0 V) up to VCC - 1.5 V, and is protected against overvoltage up to plus or minus 35 V. The buffer output drives the non-inverting inputs of all 10 comparators simultaneously.\n\nPrecision Resistor Divider: The internal resistor string consists of 10 equal-value resistors connected in series between the RHI (pin 6) and RLO (pin 4) pins. The total resistance is approximately 10 kOhm (1 kOhm per step). The voltage at each tap of the divider provides the reference voltage for one comparator. Because the resistors are monolithically integrated and laser-trimmed, their matching is very precise (typically 0.5 percent non-linearity), ensuring even spacing between LED thresholds.\n\nComparator Array: Each of the 10 comparators compares the buffered input voltage (at the non-inverting input) with the voltage at its respective divider tap (at the inverting input). When the input voltage exceeds the tap voltage, the comparator output activates its corresponding LED driver. In bar mode, all comparators with tap voltages below the input are activated, lighting all LEDs up to the current level. In dot mode, only the comparator corresponding to the highest activated tap is allowed to drive its LED, with adjacent comparators inhibited by the mode control logic.\n\nMode Pin Logic: Pin 9 (MODE) controls the display mode and the dot-mode carry function. When pin 9 is connected to VCC (pin 3), the chip is in bar mode: all comparators below the input level drive their LEDs. When pin 9 is left open, the chip is in dot mode: only one LED is lit. When pin 9 is pulled low by an external signal (such as the output of a higher LM3914 in a cascaded chain), the current LED is forced off to implement the dot-mode carry.\n\nVoltage Reference: The internal bandgap reference generates a nominal 1.25 V between REF OUT (pin 7) and REF ADJ (pin 8). The reference voltage is set by external resistors R1 and R2: VREF = 1.25 x (1 + R2\/R1) + IADJ x R2, where IADJ is typically 75 uA. The current flowing through R1 and R2 is also the programming current for the LED drivers: each lit LED draws approximately 10 times the reference current. For example, if the reference load is 1 mA, each LED draws approximately 10 mA.\n\nLED Current Regulation: Each LED driver is a current-regulated open-collector NPN transistor. The current through each lit LED is held constant regardless of the LED supply voltage (VLED) from about 2 V to 17 V. This eliminates the need for individual LED series resistors. The LED current matching between outputs is typically within 0.12 mA at 2 mA and 1.2 mA at 20 mA.\n\nCascading: Multiple LM3914s can be chained to create displays with more than 10 segments. In dot mode, pin 9 of the lower-voltage device connects to pin 1 of the higher-voltage device. When an LED in the higher device lights, the current through pin 1 pulls pin 9 of the lower device below VLED, which activates comparator C2 internally, turning off LED 10 of the lower device. This ensures only one LED is lit across all cascaded devices.","pin_description":"
| Pin<\/th> | Name<\/th> | Type<\/th> | Description<\/th><\/tr><\/thead> | ||||||||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1<\/td> | LED1<\/td> | Output<\/td> | LED driver output 1 (lowest threshold); open-collector current-regulated output; sinks current through LED 1 when the input voltage exceeds the first divider tap; the LED cathode connects here, anode to VLED through the LED; current is regulated by the reference programming resistor<\/td><\/tr> | ||||||||||||||||||||||||||||||||||||
| 2<\/td> | V-<\/td> | Power<\/td> | Negative supply \/ ground; connects to circuit ground; all LED driver current returns through this pin; important: all signal grounds, reference grounds, and bottom of the resistor divider should connect to this pin at a single point to avoid ground-loop errors<\/td><\/tr> | ||||||||||||||||||||||||||||||||||||
| 3<\/td> | V+<\/td> | Power<\/td> | Positive supply voltage; 3 V to 15 V (max 25 V absolute); bypass with 2.2 uF tantalum or 10 uF electrolytic capacitor to pin 2 if LED supply leads are long; the IC draws only a few mA from this pin, as most LED current comes from the separate VLED supply<\/td><\/tr> | ||||||||||||||||||||||||||||||||||||
| 4<\/td> | RLO<\/td> | Reference<\/td> | Resistor divider low end; the bottom of the internal 10-step voltage divider connects here; set this to the lowest voltage to be displayed (typically 0 V for a 0-to-VREF display); for expanded-scale meters, set to the minimum display voltage; bypass with 0.001-0.1 uF capacitor in noisy environments<\/td><\/tr> | ||||||||||||||||||||||||||||||||||||
| 5<\/td> | SIG<\/td> | Input<\/td> | Signal input; the analog voltage to be displayed; high input impedance (25 nA bias current); accepts signals from ground to VCC-1.5 V; protected against overvoltage to plus or minus 35 V (with current limit of plus or minus 3 mA); for higher voltage tolerance, add a 39 kOhm series resistor (allows plus or minus 100 V inputs)<\/td><\/tr> | ||||||||||||||||||||||||||||||||||||
| 6<\/td> | RHI<\/td> | Reference<\/td> | Resistor divider high end; the top of the internal voltage divider connects here; set this to the voltage that lights LED 10 (full-scale); typically connected to REF OUT (pin 7) for a 0-to-VREF display; for expanded-scale meters, connect to the maximum display voltage<\/td><\/tr> | ||||||||||||||||||||||||||||||||||||
| 7<\/td> | REF OUT<\/td> | Reference<\/td> | Reference voltage output; nominal 1.25 V above REF ADJ (pin 8); the current drawn from this pin sets the LED brightness (LED current approximately 10x reference current); connect programming resistors R1 and R2 between REF OUT, REF ADJ, and ground to set both the reference voltage and LED current; VREF = 1.25 x (1 + R2\/R1)<\/td><\/tr> | ||||||||||||||||||||||||||||||||||||
| 8<\/td> | REF ADJ<\/td> | Reference<\/td> | Reference voltage adjust; the bottom of the internal reference amplifier; connect R1 from pin 7 to pin 8 and R2 from pin 8 to ground; the reference voltage is developed across R1 and R2; the adjust pin current is approximately 75 uA flowing out of the pin<\/td><\/tr> | ||||||||||||||||||||||||||||||||||||
| 9<\/td> | MODE<\/td> | Input<\/td> | Mode select; connect to V+ (pin 3) for bar mode; leave open for dot mode; for cascading in dot mode, connect pin 9 of the lower device to pin 1 (LED1 output) of the next higher device; in dot mode, pulling this pin low forces all LEDs off; the pin 9 voltage is sensed by internal comparators C1 and C2 for mode and carry control<\/td><\/tr> | ||||||||||||||||||||||||||||||||||||
| 10<\/td> | LED10<\/td> | Output<\/td> | LED driver output 10 (highest threshold); open-collector current-regulated output; sinks current through LED 10 when the input voltage exceeds the tenth divider tap; in dot mode cascading, this output is disabled when a higher device lights its LED1<\/td><\/tr> | ||||||||||||||||||||||||||||||||||||
| 11<\/td> | LED9<\/td> | Output<\/td> | LED driver output 9; same characteristics as LED1<\/td><\/tr> | ||||||||||||||||||||||||||||||||||||
| 12<\/td> | LED8<\/td> | Output<\/td> | LED driver output 8; same characteristics as LED1<\/td><\/tr> | ||||||||||||||||||||||||||||||||||||
| 13<\/td> | LED7<\/td> | Output<\/td> | LED driver output 7; same characteristics as LED1<\/td><\/tr> | ||||||||||||||||||||||||||||||||||||
| 14<\/td> | LED6<\/td> | Output<\/td> | LED driver output 6; same characteristics as LED1<\/td><\/tr> | ||||||||||||||||||||||||||||||||||||
| 15<\/td> | LED5<\/td> | Output<\/td> | LED driver output 5; same characteristics as LED1<\/td><\/tr> | ||||||||||||||||||||||||||||||||||||
| 16<\/td> | LED4<\/td> | Output<\/td> | LED driver output 4; same characteristics as LED1<\/td><\/tr> | ||||||||||||||||||||||||||||||||||||
| 17<\/td> | LED3<\/td> | Output<\/td> | LED driver output 3; same characteristics as LED1<\/td><\/tr> | ||||||||||||||||||||||||||||||||||||
| 18<\/td> | LED2<\/td> | Output<\/td> | LED driver output 2; same characteristics as LED1<\/td><\/tr><\/tbody><\/table>","application_scenarios":"
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