71M6511 Datasheet, PDF (79/95 Pages) Teridian Semiconductor Corporation – Single-Phase Energy Meter IC

71M6511/71M6511H
Single-Phase Energy Meter IC
DATA SHEET
AUGUST 2007
Connecting LCDs
The 71M6511 has a LCD controller on-chip capable of controlling static or multiplexed LCDs. Figure 33 shows the basic
connection for a LCD.
71M6511
LCD
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Figure 33: Connecting LCDs
Figure 34 shows how 5V LCDs can be operated even when a 5V supply is not available. Setting the I/O RAM register
LCD_BSTEN to 1 starts the on-chip boost circuitry that will output an AC frequency on the VDRV pin. Using a small coupling
capacitor, two general-purpose diodes and a reservoir capacitor, a 5VDC voltage is generated which can be fed back into the
VLCD pin of the 71M6511. The LCD drivers are enabled with the I/O register LCD_ON; I/O register LCD_FS is used to adjust
contrast, and LCD_MODE selects the operation mode (LCD type).
LCD_BSTEN
V3P3
V3P3
71M6511
VDRV
VLCD
5VDC
5V LCD
Contrast LCD_FS
ON/OFF _{LCD_EN}
LCD type LCD_MODE
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Figure 34: LCD Boost Circuit
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