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AY0438
32-Segment CMOS LCD Driver
FEATURES
* 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
PIN CONFIGURATION
40-Lead Dual In-line
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 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 40 39 38 37 36 35 34 33 32 31 30 29 28 27 26 25 24 23 22 21 CLOCK SEG 1 SEG 2 SEG 3 VSS DATA OUT DATA IN SEG 4 SEG 5 LCD BP SEG 6 SEG 7 SEG 8 SEG 9 SEG 10 SEG 11 SEG 12 SEG 13 SEG 14
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; decimals; 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 oscillator. The AY0438 is available in 40-lead dual in-line plastic and 44-lead PLCC packages. Unpackaged dice are also available.
44 PLCC
NC SEG 30 SEG 31 SEG 32 LOAD VDD CLOCK SEG 1 SEG 2 SEG 3 VSS 6 5 4 3 2 1 44 43 42 41 40
AY0438
SEG 29 SEG 28 SEG 27 SEG 26 SEG 25 SEG 24 SEG 23 SEG 22 SEG 21 SEG 20 SEG 19
7 8 9 10 11 12 13 14 15 16 17
AY0438
39 38 37 36 35 34 33 32 31 30 29
NC DATA OUT DATA IN SEG 4 SEG 5 LCD BP SEG 6 SEG 7 SEG 8 NC
(c) 1995 Microchip Technology Inc.
SEG 18 SEG 17 SEG 16 SEG 15 SEG 14 SEG 13 SEG 12 SEG 11 SEG 10 SEG 9 NC
18 19 20 21 22 23 24 25 26 27 28
DS70010I-page 1
AY0438
FIGURE 1: PIN DESCRIPTIONS
Pin # (PDIP Only) 1 2 3-29, 32, 33, 37-39 30 31 34 35 36 40 Name VDD Load Seg 1-32 BP LCD Data In Data Out VSS Clock Direction Input Output Output Input Input Output Ground Input Description Supply voltage Latch data from registers Direct drive outputs Backplane drive output Backplane drive input Data input to shift register Data output from shift register Ground System clock input
FIGURE 2: BLOCK DIAGRAM
Data in Clock Load 32-bit Static Shift Register Data out
FIGURE 3: BACKPLANE AND SEGMENT OUTPUT
32 Latches
SEG On
32 Segment Drivers 32 Outputs Backplane output
Backplane
LCD
LCD AC Generator
SEG Off
FIGURE 4: TIMING DIAGRAM
1/f CLOCK START Data in SEG 32 SEG 2 tDS Data out tPD Load tPW SEG 1 tDH 1 31 32
1.0
1.1
OPERATION:
Data In and Clock
enabled or visible, i.e. the output at Segment Output is 180 out-of-phase with the Backplane output (Figure 3).
The shift register shifts and outputs on the falling edge of the clock. Every clock falling edge does a logical left shift. As an example, if 32 clock pulses are supplied as in Figure 4, then the data input at the first clock will output at SEG 32, and the last data input (# 32) will output at SEG 1 when a LOAD signal is enabled (Figure 2). It is recommended that a complete 32 bit transfer be done every time the outputs are updated. A logic 1 at the Data In causes the corresponding segment to be
1.2
Load
A logic 1 at the Load input (Figure 2) causes the parallel load of the data in the shift register into the latches that control the segment drivers. If the Load signal is tied high, then the latches become transparent and the segment drivers are always connected to the shift registers.
DS70010I-page 2
(c) 1995 Microchip Technology Inc.
AY0438
1.3 LCD
LCD can be driven by an external signal or by connecting a capacitor between LCD 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 LCD input unconnected is not recommended. When driven by an external clock, the backplane output is in phase with the input clock. When cascading two AY0438 devices (Figure 6 and Figure 7), the backplane output can be generated using a capacitor to GND on the first AY0438. This backplane output can then be connected to the LCD input of the second AY0438. The backplane output of the second device is then used to drive the backplane of the LCD module.
FIGURE 5: OSCILLATOR FREQUENCY GRAPH (TYPICAL @ 25C)
140 Backplane Frequency (Hz) 120 100 80 60 40
0
20
40
60 CL (pF)
80
100
120
FIGURE 6: CASCADING TWO AY0438 DEVICES
Data in Data out Data in Clock Load
Clock Load
32-bit Static Shift Register
32-bit Static Shift Register
Data out
32 Latches
32 Latches
32 Segment Drivers LCD 1 to 32 Outputs Backplane output LCD
32 Segment Drivers 33 to 64 Outputs Backplane output
LCD AC Generator
LCD AC Generator
Clock Load
FIGURE 7: CASCADE TIMING DIAGRAM
1/f CLOCK START Data in SEG 64 SEG 2 tDS Data out tPD Load tPW SEG 1 tDH 1 63 64
(c) 1995 Microchip Technology Inc.
DS70010I-page 3
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.
FIGURE 8: INTERFACING TO A LCD MODULE AND PIC16CXX DEVICE
AY0438
SEG1 SEG7 SEG6 SEG5 SEG A SEG F SEG G SEG E SEG D SEG C SEG B A FGB C E D LCD Backplane
PIC16CXX
RB0 RB1 RB2 Clock Data In Load
SEG4 SEG3 SEG2 SEG9-15 SEG19-23 SEG25-31
7 7 7
RB7 LCD
Backplane
EXAMPLE 1: EXAMPLE CODE ;************************************************************************* ;This program shows an interface between a PIC16CXX device ;and the AY0438 LCD controller to control a 7 Segment ;4 digit LCD module. ;The PIC16CXX interface to the AY0438 Hardware: ; ; PORTB bit 0 --> CLK ; PORTB bit 1 --> DATA IN ; PORTB bit 2 --> LOAD ; ;The LCD module is connected to the AY0438 as follows: ; Most Significant digit --> seg1 to seg7 ; 3rd Significant digit --> seg9 to seg15 ; 2nd Significant digit --> seg17 to seg 23 ; Least Significant digit --> seg25 to seg 31 ;
DS70010I-page 4
(c) 1995 Microchip Technology Inc.
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. ;In this example, a pushbutton connected to PORTB bit 7 ;is checked periodically to see if it has been pressed. If so, ;the LCD values in locations MSD to LSD are updated. ;************************************************************************* list p=16c71,f=inhx8m ; ; MSD equ 0x20 THRDSD equ 0x21 SCNDSD equ 0x22 LSD equ 0x23 count equ 0x24 temp equ 0x25 PORTB equ 0x06 #define CLK PORTB,0 #define DATAIN PORTB,1 #define LOAD PORTB,2 #define UPDATELCD PORTB,7 w equ 0 STATUS equ 0x03 C equ 0 RP0 equ 5 OPTION equ 0x81 RBPU equ 7 PCL equ 0x02 PCLATH equ 0x0A ; ; org 0 goto start org 0x10 ; ;This DecodeValue table must reside in page 0 for this program to work ; DecodeValue addwf PCL retlw B'00111111' ;decode for 0 retlw B'00000110' ;decode for 1 retlw B'01011011' ;decode for 2 retlw B'01001111' ;decode for 3 retlw B'01100110' ;decode for 4 retlw B'01101101' ;decode for 5
(c) 1995 Microchip Technology Inc.
DS70010I-page 5
AY0438
retlw retlw retlw retlw ; ; start clrf bsf movlw movwf bcf bcf 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 call Send8 ;serially output the seg values movf SCNDSD,w ;get 2nd significant digit call DecodeValue ;decode it call Send8 ;serially output it movf THRDSD,w ;get 3rd significant digit call DecodeValue ;decode it call Send8 movf MSD,w ;get Most significant value call DecodeValue ;decode it call Send8 ;serially send it bsf LOAD ;toggle the LOAD line bcf LOAD ;to enable the latches KeyReleased btfss UPDATELCD ;wait for key to be released goto KeyReleased goto wait ;repeat loop. ; ;Send8, sends the 8 bits in the W register Send8 movwf temp ;save in temp movlw .8 ;init count movwf count ;to 8 sendloop bcf DATAIN ;make sure DATAIN is low rrf temp ;rotate value through carry btfsc STATUS,C ;if bit clear then skip bsf DATAIN ;else set data bit bsf CLK ;toggle clock bcf CLK ; / decfsz count ;see if 8 done goto sendloop ;no then do all return ;else return end PORTB STATUS,RP0 B'11111000' PORTB OPTION,RBPU STATUS,RP0 ;set portb 0,1&2 as outputs ; / ; / ;enable pull-up for switch B'01111101' B'00000111' B'01111111' B'01101111' ;decode ;decode ;decode ;decode for for for for 6 7 8 9
DS70010I-page 6
(c) 1995 Microchip Technology Inc.
AY0438
2.0 ELECTRICAL CHARACTERISTICS
Maximum Ratings* VDD.............................................................................................................................................................. -0.3V to +12V Inputs (CLK, Data In, Load) ................................................................................................................. VCC to VDD +0.3V LCD Input ........................................................................................................................................ -0.3V to VDD +0.3V Power Dissipation.................................................................................................................................................250 mW Storage Temperature............................................................................................................................... -65C to +125C Operating Temperature Industrial.............................................................................................................. -40C to +85C * Exceeding these ratings could cause permanent damage to the device. This is a stress rating only and functional operation of this device at these conditions is not implied. Operating ranges are specified in Standard Conditions. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. Data labeled "typical" is presented for design guidance only and is not guaranteed.
TABLE 2: DC CHARACTERISTICS
VDD = +5V unless otherwise noted, TA = 40C to +85C Characteristics Supply Voltage Supply Current Input High Level Input Low Level Input Leakage Current Input Capacitance Segment Output Voltage LCD Input High Level LCD Input Low Level LCD Input Leakage Clock Data, Load Sym VDD IDD VIH VIL1 VIL2 IL CI VOH VOL VIN VIL IL Min +3.0 -- -- 0.5 VDD 0 0 -- -- 0.8 VDD 0 0.9 VDD 0 -- Typ -- 25 13 -- -- -- 0.01 -- -- -- -- -- -- Max +8.5 60 30 VDD 0.1 VDD 0.1 VDD 10 5.0 VDD 0.1 VDD VDD 0.1 VDD 10 Units V A A V V V A pF V V V V A VIN = 0V and +5.0V VDD = +5.0V 3.0V VDD 8.5V 3.0V VDD 8.5V VIN = 0V and +5.0V VDD = +5.0V IOH = -100 A IOL = 100 A LCD OSC < 15 kHz LCD OSC < 100 Hz Conditions
TABLE 3: AC CHARACTERISTICS
Characteristics Clock Rate Data Set-up Time Data Hold Time Load Pulse Width Data Out Prop. Delay Sym f tDS tDH tPW tPD Min DC 150 50 175 -- Typ -- -- -- -- -- Max 1.5 -- -- -- 500 Units MHz nsec nsec nsec nsec CL = 55 pF Conditions 50% duty cycle Data change to Clk falling edge
(c) 1995 Microchip Technology Inc.
DS70010I-page 7
AY0438
NOTES:
DS70010I-page 8
(c) 1995 Microchip Technology Inc.
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.
X /XX
Package: P L S I = = = = = Plastic DIP PLCC Die in Waffle Pack 0C to +70C 40C to +85C
Temperature Range: Device:
32 Segment LCD Driver
Sales and Support
Products supported by a preliminary Data Sheet may possibly have an errata sheet describing minor operational differences and recommended workarounds. To determine if an errata sheet exists for a particular device, please contact one of the following: 1. 2.
3.
Your local Microchip sales office. The Microchip Corporate Literature Center U.S. FAX: (602) 786-7277
The Microchip's Bulletin Board, via your local CompuServe number (CompuServe membership NOT required).
Please specify which device, revision of silicon and Data Sheet (include Literature #) you are using. For latest version information and upgrade kits for Microchip Development Tools, please call 1-800-755-2345 or 1-602-786-7302.
DS70010I-page 9
(c) 1995 Microchip Technology Inc.
Note the following details of the code protection feature on PICmicro(R) 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. All of these methods, to our knowledge, require using the PICmicro microcontroller in a manner outside the operating specifications contained in the data sheet. The person doing so may be engaged in theft of intellectual property. Microchip is willing to work with the customer who is concerned about the integrity of their code. Neither Microchip nor any other semiconductor manufacturer can guarantee the security of their code. Code protection does not mean that we are guaranteeing the product as "unbreakable". Code protection is constantly evolving. We at Microchip are committed to continuously improving the code protection features of our product.
* * *
If you have any further questions about this matter, please contact the local sales office nearest to you.
Information contained in this publication regarding device applications and the like is intended through suggestion only and may be superseded by updates. It is your responsibility to ensure that your application meets with your specifications. No representation or warranty is given and no liability is assumed by Microchip Technology Incorporated with respect to the accuracy or use of such information, or infringement of patents or other intellectual property rights arising from such use or otherwise. Use of Microchip's products as critical components in life support systems is not authorized except with express written approval by Microchip. No licenses are conveyed, implicitly or otherwise, under any intellectual property rights.
Trademarks The Microchip name and logo, the Microchip logo, FilterLab, KEELOQ, microID, MPLAB, PIC, PICmicro, PICMASTER, PICSTART, PRO MATE, SEEVAL and The Embedded Control Solutions Company are registered trademarks of Microchip Technology Incorporated in the U.S.A. and other countries. dsPIC, ECONOMONITOR, FanSense, FlexROM, fuzzyLAB, In-Circuit Serial Programming, ICSP, ICEPIC, microPort, Migratable Memory, MPASM, MPLIB, MPLINK, MPSIM, MXDEV, PICC, PICDEM, PICDEM.net, rfPIC, Select Mode and Total Endurance are trademarks of Microchip Technology Incorporated in the U.S.A. Serialized Quick Turn Programming (SQTP) is a service mark of Microchip Technology Incorporated in the U.S.A. All other trademarks mentioned herein are property of their respective companies. (c) 2002, Microchip Technology Incorporated, Printed in the U.S.A., All Rights Reserved.
Printed on recycled paper.
Microchip received QS-9000 quality system certification for its worldwide headquarters, design and wafer fabrication facilities in Chandler and Tempe, Arizona in July 1999. The Company's quality system processes and procedures are QS-9000 compliant for its PICmicro(R) 8-bit MCUs, KEELOQ(R) code hopping devices, Serial EEPROMs and microperipheral products. In addition, Microchip's quality system for the design and manufacture of development systems is ISO 9001 certified.
2002 Microchip Technology Inc.
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03/01/02
2002 Microchip Technology Inc.

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