Datasheet

ManualsBrandsMICROCHIP TECHNOLOGY ManualsPMICsPMIC - display driver LCD 32 segments 16 characters Parallel 25 µA PLCC 44

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

1995 Microchip Technology Inc. DS70010I-page 1

FEATURES

• Drives up to 32 LCD segments of arbitrary conﬁg-

uration

• CMOS process for: wide supply voltage range,

low- power operation, high-noise immunity, wide

temperature range

• CMOS and TTL-compatible inputs

• Electrostatic discharge protection on all pins

• Cascadable

• On-chip oscillator

• Requires only three control lines

APPLICATIONS

• Industrial displays

• Consumer product displays

• Telecom product displays

• Automotive dashboard displays

DESCRIPTION

The AY0438 is a CMOS integrated device that drives a

liquid crystal display, usually under microprocessor

control. The part acts as a smart peripheral that drives

up to 32 LCD segments. It needs only three control

lines due to its serial input construction. It latches the

data to be displayed and relieves the microprocessor

from the task of generating the required waveforms.

The AY0438 can drive any standard or custom parallel

drive LCD display, whether it be ﬁeld effect or dynamic

scattering; 7-, 9-, 14- or 16-segment characters; deci-

mals; leading + or -; or special symbols. Several

AY0438 devices can be cascaded. The AC frequency

of the LCD waveforms can either be supplied by the

user or generated by attaching a capacitor to the LCD

input, which controls the frequency of an internal oscil-

lator.

The AY0438 is available in 40-lead dual in-line plastic

and 44-lead PLCC packages. Unpackaged dice are

also available.

PIN CONFIGURATION

CLOCK

SEG 1

SEG 2

SEG 3

V

SS

DATA OUT

DATA IN

SEG 4

SEG 5

LCDΦ

BP

SEG 6

SEG 7

SEG 8

SEG 9

SEG 10

SEG 11

SEG 12

SEG 13

SEG 14

VDD

LOAD

SEG 32

SEG 31

SEG 30

SEG 29

SEG 28

SEG 27

SEG 26

SEG 25

SEG 24

SEG 23

SEG 22

SEG 21

SEG 20

SEG 19

SEG 18

SEG 17

SEG 16

SEG 15

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NC

DATA OUT

DATA IN

SEG 4

SEG 5

LCDΦ

BP

SEG 6

SEG 7

SEG 8

NC

SEG 29

SEG 28

SEG 27

SEG 26

SEG 25

SEG 24

SEG 23

SEG 22

SEG 21

SEG 20

SEG 19

NC

SEG 30

SEG 31

SEG 32

LOAD

V

DD

CLOCK

SEG 1

SEG 2

SEG 3

V

SS

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NC

SEG 9

SEG 10

SEG 11

SEG 12

SEG 13

SEG 14

SEG 15

SEG 16

SEG 17

SEG 18

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40-Lead Dual In-line

44 PLCC

AY0438

AY0438

AY0438

32-Segment CMOS LCD Driver

Summary of content (11 pages)

PAGE 1
AY0438 32-Segment CMOS LCD Driver • Drives up to 32 LCD segments of arbitrary configuration • CMOS process for: wide supply voltage range, low- power operation, high-noise immunity, wide temperature range • CMOS and TTL-compatible inputs • Electrostatic discharge protection on all pins • Cascadable • On-chip oscillator • Requires only three control lines APPLICATIONS • • • • Industrial displays Consumer product displays Telecom product displays Automotive dashboard displays PIN CONFIGURATION 40-Lead Dual
PAGE 2
AY0438 FIGURE 1: PIN DESCRIPTIONS Pin # (PDIP Only) Name Direction Description 1 VDD - Supply voltage 2 Load Input Latch data from registers 3-29, 32, 33, 37-39 Seg 1-32 Output Direct drive outputs 30 BP Output Backplane drive output 31 LCDΦ Input Backplane drive input 34 Data In Input Data input to shift register 35 Data Out Output Data output from shift register 36 VSS Ground Ground 40 Clock Input System clock input FIGURE 2: BLOCK DIAGRAM Data in Clock Load FIGURE
PAGE 3
AY0438 1.3 LCDφ FIGURE 5: OSCILLATOR FREQUENCY GRAPH (TYPICAL @ 25°C) LCDφ can be driven by an external signal or by connecting a capacitor between LCDφ and ground (GND), which will enable the on-chip oscillator required to generate the backplane output voltage. Figure 5 shows the relationship between capacitance value and output frequency. Leaving the LCDφ input unconnected is not recommended. When driven by an external clock, the backplane output is in phase with the input clock.
PAGE 4
AY0438 1.4 General 1.5 In order to avoid any race conditions, the Data In and Load signals should not be changed during a falling edge of the Clock. Figure 4 and Figure 7 show a typical timing diagram for a 32 segment and 64 segment LCD module. Interfacing to a LCD Module and PIC16CXX Device Figure 8 shows a typical layout of an AY0438 connected to a LCD module and interfaced to a PIC16CXX family device. Example 1 lists code used to program the PIC16CXX device. This code was complied using MPASM.
PAGE 5
AY0438 ;The DP are not connected, but can be connected to seg8, 16, 24 & 32. ;For each digit, the segments are connected as: ; Seg A --> seg(8*n + 1) ; Seg B --> seg(8*n + 2) ; Seg C --> seg(8*n + 3) ; Seg D --> seg(8*n + 4) ; Seg E --> seg(8*n + 5) ; Seg F --> seg(8*n + 6) ; Seg G --> seg(8*n + 7) ;where n = 0, 1, 2 and 3 for MSD, 3rdSD, 2ndSD and LSD respectively. ;The firmware uses the values in registers: ; MSD, THRDSD, SCNDSD and LSD to determine the values to be ;pulsed to the AY0438.
PAGE 6
AY0438 retlw retlw retlw retlw B'01111101' B'00000111' B'01111111' B'01101111' ;decode ;decode ;decode ;decode for for for for 6 7 8 9 clrf bsf movlw movwf bcf bcf PORTB STATUS,RP0 B'11111000' PORTB OPTION,RBPU STATUS,RP0 ;set portb 0,1&2 as outputs ; / ; / ;enable pull-up for switch ; ; start wait btfsc UPDATELCD ;see if update switch is low goto wait ;no then wait bcf LOAD ;make sure load is disabled movf LSD,w ;get least significant value clrf PCLATH ;PCH = 0 call DecodeValue ;decode the value c
PAGE 7
AY0438 2.0 ELECTRICAL CHARACTERISTICS Maximum Ratings* VDD.............................................................................................................................................................. -0.3V to +12V Inputs (CLK, Data In, Load) ................................................................................................................. VCC to VDD +0.3V LCDΦ Input .............................................................................................................
PAGE 8
AY0438 NOTES: DS70010I-page 8  1995 Microchip Technology Inc.
PAGE 9
AY0438 AY0438 Product Identification System To order or to obtain information, e.g., on pricing or delivery, please use the listed part numbers, and refer to the factory or the listed sales offices. PART NO.
PAGE 10
Note the following details of the code protection feature on PICmicro® MCUs. • • • • • • The PICmicro family meets the specifications contained in the Microchip Data Sheet. Microchip believes that its family of PICmicro microcontrollers is one of the most secure products of its kind on the market today, when used in the intended manner and under normal conditions. There are dishonest and possibly illegal methods used to breach the code protection feature.
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