Here, in the article “BCD-To-7-Segment LCD Display Driver” you will learn about 7 segment lcd display IC, it’s key parameter and its application.
Description of BCD-To-7-Segment LCD Display Driver
Liquid crystal displays are activated by a AC signal across a selected display segment; this feature is included in the function block of the 7-segment LCD driver illustrated in figure 1. In addition to the standard BCD input, there is also a display frequency input terminal. Two functions can be performed by this terminal. When this driver IC is used to drive LED or other displays, this terminal, when in the 0 state, causes the selected 7-segment outputs to be in the 1 state, and when the display frequency input is 1, the select outputs will be 0. In the usual use with LCD, however, the input to the terminal will be a square wave ranging in frequency from 30 to 100 Hz. The selected segments of the display will have a square-wave output across them is 1800 out of the phase with the display frequency input.
In addition to the 7-segment output, there is also a display frequency output which provides the level-shifted, high-amplitude display frequency necessary for driving the common electrode in liquid crystal displays (LCD). Note that positive and negative power-supply voltages are required.
Key Parameters
The electrical characteristics are essentially the same as those of particular digital IC family.
- Maximum power dissipation: 500 mW at -40 to 600 is typical for high-voltage CMOS ICs.
- Quiescent current: Maximum current drawn when IC is not operating. 5 mA for high-voltage CMOS with +/- 5V power supply.
- Propagation delay time: The time required from input to output. Maximum is 1300 ns for +\- power supply and high voltage CMOS.
- Noise margin: The noise voltage with regard to power-supply voltage. 1V noise margin at 5V power supply is typical for high-voltage CMOS ICs.
Applications
This IC can drive most liquid crystal displays. It is used in auto dashboard displays, panel meters, wall and table clocks, calculators, etc.
Representative Part Number: Hughes H 0437
Comments
A variety of LCD drivers is available, including those containing a storage latch function, those able to accept any 4-bit number and displaying the letters L, H, B, A and the minus sign. In LCD wristwatches, the decoder and display driver function is part of the watch IC.