PCA2117DUGSSLASHDA datasheet(37/107 Pages) NXP

37 / 107 page

PCA2117

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Product data sheet

Rev. 4 — 8 April 2015

37 of 107

NXP Semiconductors

PCA2117

Automotive LCD driver for character displays

8.4 LCD voltage

8.4.1 VLCD pins

The PCA2117 has 3 VLCD pins:

VLCDIN — VLCD supply input

VLCDOUT — VLCD voltage output

VLCDSENSE — VLCD regulation circuitry input

The VLCD voltage can be generated on-chip or externally supplied.

8.4.2 External VLCD supply

When the external VLCD supply is selected, the VLCD voltage must be supplied to the pin

VLCDIN. The pins VLCDOUT and VLCDSENSE can be left unconnected or alternatively

connected to VLCDIN. The VLCD voltage is available at the row and column drives of the

device through the chosen bias system.

The internal charge pump must not be enabled, otherwise high internal currents may flow

as well as high currents via pin VDD2 and pin VLCDOUT. No internal temperature

compensation occurs on the externally supplied VLCD even if bit TCE is set logic 1 (see

Section 8.1.4.1). Also programming VLCDA[8:0] and VLCDB[8:0] has no effect on the

externally supplied VLCD.

8.4.3 Internal VLCD generation

When the internal VLCD generation is selected, the VLCD voltage is available on pin

VLCDOUT. The pins VLCDIN and VLCDSENSE must be connected to the pin VLCDOUT.

The Charge_pump_ctrl command (see Table 30 on page 24) controls the charge pump. It

can be enabled with the CPE bit. The multiplier setting can be configured with the

CPC[1:0] bits. The charge pump can generate a VLCD up to 4  VDD2.

8.4.3.1

VLCD programming

VLCD can be programmed by two bit-fields: VLCDA[8:0] and VLCDB[8:0]. VLCDA[8:0] is

programmed with the voltage for the character mode and VLCDB[8:0] with the voltage for

the icon mode.

The final value of VLCD is a combination of the programmed VLCDA[8:0] respectively

VLCDB[8:0] value and in addition the output of the temperature compensation block. The

system is exemplified in Figure 18.

PCA2117DUGS/DA Datasheet(PDF) 37 Page - NXP Semiconductors