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 In-line VDD LOAD SEG 32 SEG 31 1 2 3 4 40 39 38 37 CLOCK SEG 1 SEG 2 SEG 3 SEG 30 SEG 29 SEG 28 SEG 27 5 6 7 8 36 35 34 33 VSS DATA OUT DATA IN SEG 4 SEG 26 SEG 25 9 10 32 31 SEG 5 LCDΦ SEG 24 SEG 23 SEG 22 SEG 21 11 12 13 14 30 29 28 27 BP SEG 6 SEG 7 SEG 8 SEG 20 SEG 19 SEG 18 SEG 17 15 16 17 18 26 25 24 23 SEG 9 SEG 10 SEG 11 SEG 12 SEG 16 SEG 15 19 20 22 21 SEG 13 SEG 14 AY0438 FEATURES DESCRIPTION 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 LCDΦ BP SEG 6 SEG 7 SEG 8 NC 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 The AY0438 is available in 40-lead dual in-line plastic and 44-lead PLCC packages. Unpackaged dice are also available. NC SEG 30 SEG 31 SEG 32 LOAD VDD CLOCK SEG 1 SEG 2 SEG 3 VSS 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. 44 PLCC 6 5 4 3 2 1 44 43 42 41 40 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. 1995 Microchip Technology Inc. DS70010I-page 1 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 3: BACKPLANE AND SEGMENT OUTPUT 32-bit Static Shift Register Data out SEG On 32 Latches 32 Segment Drivers LCDΦ Backplane 32 Outputs Backplane output LCD AC Generator SEG Off FIGURE 4: TIMING DIAGRAM 1/f CLOCK 1 32 31 START Data in SEG 32 SEG 2 SEG 1 tDS tDH Data out tPD Load tPW 1.0 OPERATION: 1.1 Data In and Clock 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 DS70010I-page 2 enabled or visible, i.e. the output at Segment Output is 180° out-of-phase with the Backplane output (Figure 3). 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. 1995 Microchip Technology Inc. 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. 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 LCDφ input of the second AY0438. The backplane output of the second device is then used to drive the backplane of the LCD module. Backplane Frequency (Hz) 140 120 100 80 60 40 0 20 40 60 80 100 120 CL (pF) FIGURE 6: CASCADING TWO AY0438 DEVICES Data in Clock Load 32-bit Static Shift Register Data out Data in Clock Load 32 Latches 32 Latches 32 Segment Drivers LCDΦ 32 Segment Drivers 1 to 32 Outputs LCD AC Generator Backplane output Data out 32-bit Static Shift Register LCDΦ 33 to 64 Outputs LCD AC Generator Backplane output Clock Load FIGURE 7: CASCADE TIMING DIAGRAM 1/f CLOCK 1 64 63 START Data in SEG 64 SEG 2 SEG 1 tDS tDH Data out tPD Load 1995 Microchip Technology Inc. tPW 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 PIC16CXX RB0 Clock RB1 Data In RB2 Load SEG4 SEG3 SEG2 SEG A SEG F SEG G SEG E SEG D SEG C SEG B LCD Backplane A F G B C E D 7 7 SEG9-15 7 SEG19-23 SEG25-31 RB7 Backplane LCDΦ 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 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 1995 Microchip Technology Inc. DS70010I-page 5 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 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 DS70010I-page 6 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 LCDΦ Input ........................................................................................................................................ -0.3V to VDD +0.3V Power Dissipation.................................................................................................................................................250 mW Storage Temperature............................................................................................................................... -65˚C to +125˚C Operating Temperature Industrial.............................................................................................................. -40˚C to +85˚C * 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 = 40°C to +85°C Characteristics Sym Min Typ Max Units Conditions Supply Voltage VDD +3.0 — +8.5 V Supply Current IDD — 25 60 µA LCDΦ OSC < 15 kHz — 13 30 µA LCDΦ OSC < 100 Hz V VIH 0.5 VDD — VDD Clock VIL1 0 — 0.1 VDD V 3.0V ≤ VDD ≤ 8.5V Data, VIL2 0 — 0.1 VDD V 3.0V ≤ VDD ≤ 8.5V Load IL — 0.01 ±10 µA VIN = 0V and +5.0V CI — — 5.0 pF VDD = +5.0V VOH 0.8 VDD — VDD V IOH = -100 µA VOL 0 — 0.1 VDD V IOL = 100 µA VIN 0.9 VDD — VDD V LCDΦ Input Low Level VIL 0 — 0.1 VDD V LCDΦ Input Leakage IL — — 10 µA Input High Level Input Low Level Input Leakage Current Input Capacitance Segment Output Voltage LCDΦ Input High Level VIN = 0V and +5.0V VDD = +5.0V TABLE 3: AC CHARACTERISTICS Characteristics Sym Min Typ Max Units Conditions f DC — 1.5 MHz 50% duty cycle Data Set-up Time tDS 150 — — nsec Data Hold Time tDH 50 — — nsec Load Pulse Width tPW 175 — — nsec Data Out Prop. Delay tPD — — 500 nsec Clock Rate 1995 Microchip Technology Inc. Data change to Clk falling edge CL = 55 pF DS70010I-page 7 AY0438 NOTES: DS70010I-page 8 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 = = = Plastic DIP PLCC Die in Waffle Pack Temperature Range: I = = 0˚C to +70˚C 40˚C to +85˚C 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. Your local Microchip sales office. 2. The Microchip Corporate Literature Center U.S. FAX: (602) 786-7277 3. 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 1995 Microchip Technology Inc. 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. 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. 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