PCF2119X_10 Datasheet, PDF (11/83 Pages) NXP Semiconductors – LCD controllers/drivers Single-chip LCD controller and driver

NXP Semiconductors
PCF2119x
LCD controllers/drivers
Remarks:
• Values producing more than 6.5 V at operating temperature are not allowed.
Operation above this voltage may damage the device. When programming the
operating voltage the temperature coefficient of V_LCDOUT must be taken into account.
• Values below 2.2 V are below the specified operating range of the chip and are
therefore not allowed.
When the LCD supply voltage is generated on-chip, the V_LCD pins should be decoupled to
V_SS with a suitable capacitor. The generated V_LCDOUT is independent of V_DD and is
temperature compensated.
In Equation 2 the internal charge pump is not considered. However, if the supplied voltage
to V_DD2 and V_DD3 is below the required V_LCD it is necessary to use the internal charge
pump. The multiplication factor has to be set such, that V_DD2 and V_DD3 (which are equal)
multiplied with the programmed multiplication factor exceeds the required V_LCD under all
circumstances (i.e. at low temperatures and along with the temperature compensation -
see Section 10.2.3.4). If still a higher multiplication factor is chosen, V_LCD will not increase
(it is set by Equation 2) but the current that can be delivered will be higher. Also current
consumption increases (see Section 16.6).
When the V_LCD generator and the direct mode are switched off, an external voltage may
be supplied at connected pins V_LCDIN and V_LCDOUT. V_LCDIN and V_LCDOUT may be higher or
lower than V_DD2.
In direct mode (see Icon_ctl instruction, Section 10.2.3.3) the internal V_LCD generator is
turned off and the V_LCDOUT output voltage is directly connected to V_DD2. This reduces the
current consumption depending on V_DD2 value and LCD liquid properties.
The V_LCD generator ensures that, as long as V_DD2 and V_DD3 are in the valid range (2.2 V
to 4 V), the required peak voltage V_LCD = 6.5 V can be generated at any time.
8.5 LCD bias voltage generator
The intermediate bias voltages for the LCD display are also generated on-chip. This
removes the need for an external resistive bias chain and significantly reduces the system
current consumption. The optimum value of V_LCD depends on the multiplex rate, the LCD
threshold voltage (V_th) and the number of bias levels. Using a 5-level bias scheme for the
1:18 multiplex rate allows V_LCD < 5 V for most LCD liquids.
The intermediate bias levels for the different multiplex rates are shown in Table 6. These
bias levels are automatically set to the given values when switching to the corresponding
multiplex rate.
PCF2119X
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 7 — 15 November 2010
© NXP B.V. 2010. All rights reserved.
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