MM5451 Datasheet PDF - Micrel
Part Number | MM5451 | |
Description | LED Display Driver | |
Manufacturers | Micrel | |
Logo | ||
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MM5450/5451
LED Display Driver
Micrel
General Description
Features
The MM5450 and MM5451 LED display drivers are monolithic
MOS IC’s fabricated in an N-Channel, metal-gate process.
The technology produces low-threshold, enhancement-mode,
and ion-implanted depletion-mode devices.
A single pin controls the LED display brightness by setting a
reference current through a variable resistor connected to
the supply.
Applications
• Continuous brightness control
• Serial data input
• No load signal requirement
• Enable (on MM5450)
• Wide power supply operation
• TTL compatibility
• 34 or 35 outputs, 15mA capability
• Alphanumeric capability
• Industrial control indicator
• Relay driver
• Digital clock, thermometer, counter, voltmeter
• Instrumentation readouts
Ordering Information
Part Number
MM5450BN
MM5451BN
MM5450BV
MM5451BV
Junction Temp. Range
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
Package
40-pin Plastic DIP
40-pin Plastic DIP
44-pin PLCC
44-pin PLCC
Block Diagram
BRIGHTNESS
CONTROL
19
OUT 34
VDD
20 24
OUT 1
18
35 OUTPUT BUFFERS
DATA ENABLE/OUT 35 23
(See Note 1)
22
SERIAL DATA
21
CLOCK
35 LATCHES
LOAD
35-BIT SHIFT
REGISTERS
RESET
Note 1: Pin 23 is Data Enable in MM5450
Pin 23 is Output 35 in MM5451
Figure 1.
RESET
(only available
1 in die form) 870 01
Micrel, Inc. • 1849 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 944-0970 • http://www.micrel.com
May 2000
1 MM5450/5451
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MM5450/5451
Functional Description
The MM5450 and MM5451 were designed to drive either 4- or
5-digit alphanumeric LED displays with the added benefit of
requiring minimal interface with the display or data source.
Data is transferred serially via 2 signals; clock and serial data.
Data transfer without the added inconvenience of an external
load signal is accomplished by using a format of a leading “1”
followed by the allowed 35 data bits. These 35 data bits are
latched after the 36th has been transferred. This scheme
provides non multiplexed, direct drive to the LED display.
Characters currently displayed (thus, data output) changes
only if the serial data bits differ from those previously transferred.
Control of the output current for LED displays provides for the
display brightness. To prevent oscillations, a 1nF capacitor
should be connected to pin 19, brightness control.
The block diagram is shown in Figure 1. For the MIC5450, the
DATA ENABLE is a metal option and is used instead of the
35th output. The output current is typically 20-times greater
that the current into pin 19, which is set by an external variable
resistor.
There is an external reset connection shown which is available
on unpackaged (die) only. Figure 2 illustrates the die pad
locations for bonding in “chip on board” applications.
Figure 5 shows the input data format. A leading “1” is followed
by 35 bits of data. After the 36th had been transferred, a LOAD
signal is generated synchronously with the clock high state.
This loads the 35 bits of data into the latches. The low side of
the clock is used to generate a RESET signal which clears all
shift registers for the next set of data. All shift registers are
static master-slave, with no clear for the master portion of the
first register, allowing continuous operation.
Micrel
There must be a complete set of 36 clocks or the shift registers
will not clear.
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 3 and 4 show the pin-out of the MIC5450 and MIC5451.
Bit 1 is the first bit following the start bit and it will appear on
pin 18. A logical “1” at the input will turn on the appropriate
LED.
Figure 5 shows the timing relationships between data, clock
and DATA ENABLE. A maximum clock frequency of 0.5MHz
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 = (VOUT) (ILED) (No. of segments) (124°C/W) + TA
where:
TJ = junction temperature + 150°C max
V = the voltage at the LED driver outputs
OUT
ILED = the LED current
124°C/W = thermal resistance of the package
TA = ambient temperature
The above equation was used to plot Figures 7–9.
CLOCK
CLOCK
DATA
LOAD
(INTERNAL)
RESET
(INTERNAL)
May 2000
DATA
DATA ENABLE
1
START BIT 1
300 nS MIN
Figure 5.
100 nS MIN
36 37
BIT 35 BIT 36
Figure 6. Input Data Format
5
MM5450/5451
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Part DetailsOn this page, you can learn information such as the schematic, equivalent, pinout, replacement, circuit, and manual for MM5451 electronic component. |
Information | Total 8 Pages | |
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Download | [ MM5451.PDF Datasheet ] |
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