LCD circuits

Figure 9 is a detailed schematic of Figure 8s concept. The resonance loop is comprised of Q4 and the CMOS inverter based oscillator. The amplitude loop centers around the LT1375 switching regulator. Figure 10 shows waveforms. Traces A and B are Q2 and Q1 gate drives, respectively. Resultant Q1 and Q2 drain responses are traces C and D...

The circuit in Figure 1 provides ±18 to ±20V adjustable LCD bias voltages with 1% tracking accuracy. The circuit operates from a single 4.2 to 2.5V Li-ion cell for portable monochrome LCD applications. The circuit comprises two blocks: a negative-bias supply using the LT1611 inverting switching regulator and a positive-bias supply using the LT1636 rail-to-rail op amp. The LT1611 converts the Li-ion battery input voltage to a negative output voltage...

The 2 line x 16 character LCD modules are available from a wide range of manufacturers and should all be compatible with the HD44780. The one I used to test this circuit was a Powertip PC-1602F and an old Philips LTN211F-10 which was extracted from a Poker Machine! The diagram to the right, shows the pin numbers for these devices. When viewed from the front, the left pin is pin 14 and the right pin is pin 1...

The circuit in Figure 1 is a dual, grounded-lamp backlight inverter that operates from an input of 9V to 24V, delivers current from 0mA to 9mA per CCFL and has a dimming ratio greater than 100:1. The LT1768 in the circuit is a 350kHz fixed frequency, current mode, pulse width modulator that provides the lamp-current control function...

The resistor between basis and collector (around 47k) is to be individually set according transistor characteristics. Without PIC in socket at the collector should be 2.5 V...

This is a project that I started back late 2003 when I just starting to learn PIC programming. I wanted to building something that actually did somthing useful. This project is based on a PIC16F84. I actually came up with this idea and then after doing some searching I found that a few people had the same idea. But, I wanted to build my own that I could call mine, developed by me. The whole idea is, I have several GPS units with no display and I wanted an easy way to see my position...

This configuration is so successful that it works well in many designs with many µCs and µPs, from the tiny MC68HC705K1 to a DSP56156. Using this design with displays ranging from 4½§2 to 40½§4 characters/line produces no perceptible flicker. By cascading shift registers and adjusting the software accordingly, you can also use this shift-register interface with the ISD (San Jose, CA) sound-recorder chips or with any device that uses an 8-, 10-, 12-, or 16-bit bus interface...

The LCDs reduced size and power requirements allow much smaller product size, a highly desirable feature. CRT replacement requires a 10W to 20W inverter to drive the CCFL (cold cathode fluorescent lamp) that illuminates the LCD. Additionally, the inverter must provide the wide dimming range associated with CRTs, and it must have safety features to prevent catastrophic failures...

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The LT®1316, a micropower step-up DC/DC converter with peak switch current control, meets these needs. The device draws 33mA quiescent current and contains a 0.6W, 30V switch that can be programmed for a maximum peak current between 30mA and 600mA with an external resistor. It also has a low-battery detector that remains active in shutdown, where quiescent current drops to 3mA. The two circuit examples below illustrate how the LT1316s current limit function allows realization of difficult converter circuits...

Seven- or 14-segment LED displays are readily available at low cost and in many sizes. However, their relatively high power requirements and limited readability in direct sunlight restrict their use in battery-powered, portable devices. LCD modules driven by HD44780-compatible controllers offer simple interface characteristics, low power consumption, and good readability. However, their cost is relatively high, and their large dimensions sometimes preclude their use in small enclosures...

The circuit in Figure 1 saves I/O pins. It uses an 8051 µC, and only four I/O pins (P1.0 to P1.3) drive the LCD, instead of the 11 pins other displays require. Data transfers in a serial mode through the P1.0 port of the µC. The µC interfaces to Pin 2 of IC1, a 74HCT4094 8-bit shift register. Serial data advances on every clock pulse and transfers to the shift register. The register converts the serial data to parallel data, available on the output pins Q0 to Q7. The P1.1 port of the µC provides the clock...

There are many applications which use a microcontroller in combination with a Liquid Crystal Display. The normal method to control a LCD panel is to connect it to a special LCD driver device, which receives the display data from a microcontroller. A cheaper solution is to drive the LCD directly from the microcontroller. With the flexibility of a COP8 microcontroller the multiplexed LCD direct drive is possible. This application note shows a way how to drive a three way multiplexed LCD with up to 36 segments using a 28-pin COP800 device...

This application note interfaces a midrange PICmicro device to a Hitachi LM032L LCD character display module, with a two line by twenty character display. LCD modules are useful for displaying text information from a system. In large volume applications, the use of custom LCD displays becomes economical. The routines provided should be a good starting point for users whose applications implement a custom LCD. This source code should be compatible with the PIC16C5X devices, after modifications for the special function register initialization, but has not been verified on those devices...

The circuits in Figures 2 and 3 draw an extra 2 mA or so from the 5V supply--a drain that could limit the circuits` use in designs that require extremely long-life battery operation. For most designs, however, another 2 mA or so won`t be noticeable. You have a choice of several bias circuits, depending on your system`s exact configuration...