HD66727 Datasheet, PDF (61/97 Pages) Hitachi Semiconductor – Low-Power Dot-Matrix Liquid Crystal Display Controller/Driver with Key Scan Function

HD66727
When an Internal Booster and Internal Operational Amplifiers are Used
To supply LCD drive voltage using the internal booster, circuits should be connected as shown in Figure
34. Here, contrast can be adjusted through the CT bits of the contrast control instruction. Temperature can
be compensated either through the CT bits or by controlling the reference voltage for the booster (Vci pin)
using a thermistor.
Note that Vci is both a reference voltage and power supply for the booster; the reference voltage must
therefore be adjusted using an emitter-follower or a similar element so that sufficient current can be
supplied. In this case, Vci must be equal to or smaller than the V_CC level.
The HD66727 incorporates a voltage-follower operational amplifier for each of V1 to V5 to reduce current
flowing through the internal bleeder-resistors, which generate different levels of liquid-crystal drive
voltages. Thus, potential differences between V_CC and V1 and between V_EE and V5 must be 0.4V or greater.
Note that the OPOFF pin must be grounded when using the operational amplifiers.
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