This application note briefly describes the basic principle of e-paper so that the user can understand the necessity of an accurate VCOM voltage setting and how the STVM100 can be used for this purpose.
Electronic paper (e-paper) devices require precise setting of the common electrode voltage (VCOM) to prevent image artifacts like 'ghosting'. This document describes the general principles of electrophoretic display technology and explains why accurate VCOM calibration is necessary for high-quality images.
The note details how the STVM100 digital calibrator can replace traditional mechanical potentiometers. It provides a circuit example using an external resistive voltage divider and operational amplifier, controlled via an I2C interface to adjust VCOM in 128 steps. Additionally, it describes an auto-adjustment demonstration kit that facilitates calibration by reading target values from barcodes or manual input.
| Typical VCOM distribution range | -0.5 V to -2.5 V |
|---|---|
| Maximum error of auto-adjustment kit | 11 mV |
It allows the user to input the target value manually or by scanning a barcode on the e-paper PC board.
The test results show a maximum difference of 11 mV between the target voltage and the measured voltage.