MM5480 LED Display Driver Y General Description Y The MM5480 is a monolithic MOS integrated circuit utilizing N-channel metal gate low threshold, enhancement mode and ion-implanted depletion mode devices. It utilizes the MM5451 die packaged in a 28-pin package making it ideal for a 3(/2 digit display. The MM5480 is designed to drive common anode-separate cathode LED displays. A single pin controls the LED display brightness by setting a reference current through a variable resistor connected either to VDD or to a separate supply of 11V maximum. Y Y Y Applications Y Y Y Y Features Y Y Y Continuous brightness control Serial data input No load signal required Wide power supply operation TTL compatibility Alphanumeric capability 3(/2 digit displays COPSTM microcontrollers or microprocessor displays Industrial control indicator Relay driver Digital clock, thermometer, counter, voltmeter Instrumentation readouts Block Diagram TL/F/6138 – 1 FIGURE 1 Connection Diagram Dual-In-Line Package Order Number MM5480N See NS Package Number N28B TL/F/6138 – 2 Top View FIGURE 2 COPSTM microcontrollers is a trademark of National Semiconductor Corporation. C1995 National Semiconductor Corporation TL/F/6138 RRD-B30M105/Printed in U. S. A. MM5480 LED Display Driver February 1995 Absolute Maximum Ratings Power Dissipation at 25§ C Molded DIP Package, Board Mount Molded DIP Package, Socket Mount If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/Distributors for availability and specifications. Voltage at Any Pin VSS b 0.3V to VSS a 12V b 65§ C to a 150§ C Storage Temperature 2.4W* 2.1W** Junction Temperature 150§ C Lead Temperature (Soldering, 10 sec.) 300§ C *Molded DIP Package, Board Mount, iJA e 52§ C/W, Derate 19.2 mW/§ C above 25§ C. **Molded DIP Package, Socket Mount, iJA e 58§ C/W, Derate 17.2 mW/§ C above 25§ C. Electrical Characteristics TA e b25§ C to a 85§ C, VDD e 4.75V to 11.0V, VSS e 0V unless otherwise specified Symbol Parameter Conditions VDD Power Supply IDD Power Supply Current Excluding Output Loads VIL Input Voltage Logical ‘‘0’’ Level g 10 mA Input Bias VIH Input Voltage Logical ‘‘1’’ Level 4.75V s VDD s 5.25V Min b 0.3 VDD l 5.25V Brightness Input Current (Note 2) IOH Output Sink Current (Note 3) Segment OFF VOUT e 3.0V IOL Output Sink Current (Note 3) Segment ON VOUT e 1V Brightness Input e 0 mA Brightness Input e 100 mA Brightness Input e 750 mA Brightness Input Voltage (Pin 13) OM Output Matching (Note 1) Max 4.75 IBR VIBR Typ Input Current e 750 mA Units 11 V 7 mA 0.8 V 2.2 VDD V VDD b 2 VDD V 0 0.75 mA 10.0 mA 10.0 4.0 25.0 mA mA mA 4.3 V g 20 % 0 2.0 15.0 2.7 3.0 AC Electrical Characteristics TA e b25§ C to a 85§ C, VDD e 5V g 0.5V Parameter Conditions Min fC Symbol Clock Input Frequency (Notes 5 and 6) DC Typ Max Units 500 th High Time 950 kHz ns tl Low Time 950 ns tDS Data Input Set-Up Time 300 ns tDH Data Input Hold Time 300 ns Note 1: Output matching is calculated as the percent variation from (IMAX a IMIN)/2. Note 2: With a fixed resistor on the brightness input pin some variation in brightness will occur from one device to another. Maximum brightness input current can be 2 mA as long as Note 3 and junction temperature equation are complied with. Note 3: Absolute maximum for each output should be limited to 40 mA. Note 4: The VOUT voltage should be regulated by the user. Note 5: AC input waveform specification for test purpose: tr s 20 ns, tf s 20 ns, f e 500 kHz, 50% g 10% duty cycle. Note 6: Clock input rise and fall times must not exceed 300 ns. 2 Functional Description There must be a complete set of 36 clocks or the shift registers will not clear. The MM5480 is specifically designed to operate 3(/2-digit alphanumeric displays with minimal interface with the display and the data source. Serial data transfer from the data source to the display driver is accomplished with 2 signals, serial data and clock. Using a format of a leading ‘‘1’’ followed by the 35 data bits allows data transfer without an additional load signal. The 35 data bits are latched after the 36th bit is complete, thus providing non-multiplexed, direct drive to the display. Outputs change only if the serial data bits differ from the previous time. Display brightness is determined by control of the output current for LED displays. A 0.001 mF ceramic or mica disc capacitor should be connected to brightness control, pin 13, to prevent possible oscillations. A block diagram is shown in Figure 1 . The output current is typically 20 times greater than the current into pin 13, which is set by an external variable resistor. There is an internal limiting resistor of 400X nominal value. When the chip first powers ON an internal power ON reset signal is generated which resets all registers and all latches. The START bit and the first clock return the chip to its normal operation. Figure 5 shows the Output Data Format for the 5480. Because it uses only 23 of the possible 35 outputs, 12 of the bits are ‘Don’t Cares’. Figure 3 shows the timing relationships between data and clock. A maximum clock frequency of 0.5 MHz is assumed. For applications where a lesser number of outputs are used, it is possible to either increase the current per output, or operate the part at higher than 1V VOUT. The following equation can be used for calculations. Tj e (VOUT) (ILED) (No. of segments) (iJA) a TA where: Tj e junction temperature, 150§ C max. VOUT e the voltage at the LED driver outputs ILED e the LED current iJA e thermal coefficient of the package TA e ambient temperature iJA (Socket Mount) e 58§ C/W iJA (Board Mount) e 52§ C/W Figure 4 shows the input data format. A start bit of logical ‘‘1’’ precedes the 35 bits of data. At the 36th clock a LOAD signal is generated synchronously with the high state of the clock, which loads the 35 bits of the shift registers into the latches. At the low state of the clock a RESET signal is generated which clears all the shift registers for the next set of data. The shift registers are static master-slave configuration. There is no clear for the master portion of the first shift register, thus allowing continuous operation. TL/F/6138 – 3 FIGURE 3 TL/F/6138 – 4 FIGURE 4. Input Data Format START 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 5451 START X 1 2 3 4 5 6 7 X X X 8 9 10 11 X X X X 12 13 14 15 16 17 X 18 X X 19 20 21 22 23 X 5480 FIGURE 5. Output Data Format 3 Functional Description (Continued) I19 e DV 1k FIGURE 6. Typical Application of Constant Current Brightness Control TL/F/6138 – 5 TL/F/6138 – 6 FIGURE 7. Brightness Control Varying the Duty Cycle Basic 3(/2-Digit Interface Safe Operating Area TL/F/6138 – 7 TL/F/6138 – 8 4 5 MM5480 LED Display Driver Physical Dimensions inches (millimeters) Dual-In-Line Package (N) Order Number MM5480N NS Package Number N28B LIFE SUPPORT POLICY NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein: 1. Life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body, or (b) support or sustain life, and whose failure to perform, when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury to the user. National Semiconductor Corporation 1111 West Bardin Road Arlington, TX 76017 Tel: 1(800) 272-9959 Fax: 1(800) 737-7018 2. A critical component is any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness. National Semiconductor Europe Fax: (a49) 0-180-530 85 86 Email: cnjwge @ tevm2.nsc.com Deutsch Tel: (a49) 0-180-530 85 85 English Tel: (a49) 0-180-532 78 32 Fran3ais Tel: (a49) 0-180-532 93 58 Italiano Tel: (a49) 0-180-534 16 80 National Semiconductor Hong Kong Ltd. 13th Floor, Straight Block, Ocean Centre, 5 Canton Rd. Tsimshatsui, Kowloon Hong Kong Tel: (852) 2737-1600 Fax: (852) 2736-9960 National Semiconductor Japan Ltd. Tel: 81-043-299-2309 Fax: 81-043-299-2408 National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications. 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