MM5450/5451
LED Display Driver
General Description
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.
Features
•
•
•
•
•
•
•
•
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
Applications
•
•
•
•
Industrial control indicator
Relay driver
Digital clock, thermometer, counter, voltmeter
Instrumentation readouts
Ordering Information
Part Number
Standard
Pb-Free
MM5450BN MM5450YN
MM5451BN MM5451YN
MM5450BV MM5450YV
MM5451BV MM5451YV
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 PDIP
40-pin PDIP
44-pin PLCC
44-pin PLCC
____________________________________________________________________________________________________________
Block Diagram
VDD
BRIGHTNESS
CONTROL
19
20
OUT 34
24
OUT 1
18
35 OUTPUT BUFFERS
DATA ENABLE/OUT 35
(See Note 1)
SERIAL DATA
23
22
35 LATCHES
LOAD
35-BIT SHIFT
REGISTER
RESET
1
Note 1: Pin 23 is Data Enable in MM5450
Pin 23 is Output 35 in MM5451
RESET
(only available
in die form)
CLOCK
21
Figure 1.
SuperSwitcher and Super ßeta PNP are trademarks of Micrel, Inc.
Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (
408
) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
February 2006
M9999-021606
(408) 955-1690
Micrel, Inc.
MM5450/5451
Absolute Maximum Ratings
Voltage (any pin) ........................................V
SS
to V
SS
+ 12V
Power Dissipation
+25°C........................................................................1W
+85°C.................................................................560mW
Junction Temperature (T
J
) ....................................... +150°C
Storage Temperature (T
S
).........................–65°C to +150°C
Lead Temperature (soldering, 10sec.) ..................... +300°C
Operating Ratings
Supply voltage (V
DD
– V
SS
).......................... +4.75V to +11V
Ambient Temperature Range (T
A
) ............. –40°C to +85°C
Electrical Characteristics
4.5V
≤
V
DD
≤
11V, V
SS
= 0V; T
A
= 25°C,
bold
values indicate –40°C
≤
T
A
≤
+85°C, unless otherwise noted.
Symbol
Parameter
Power Supply Current
Data Input Voltage
V
L
V
H
Brightness Control Input Current
Output Sink Current
logic-0 level, ±10 µA input bias
logic-1 level, 4.75V
≤
V
DD
≤
5.25V
V
DD
> 5.25V
Note 2
segment off, V
OUT
= 3.0V
segment on, V
OUT
= 1.8V,
Note 3
brightness input = 0µA
brightness input = 100µA
brightness input = 750µA
Brightness Control Input Voltage
Output Matching
f
C
t
H
t
L
t
DS
t
DH
t
DES
Notes:
1. Output matching is calculated as the percent variation (I
MAX
+ I
MIN
) / 2.
2. With a fixed resistor on the brightness input pin, some variation in brightness will occur among devices.
3. See Figures 7, 8 and 9 for recommended operating conditions and limits. Absolute maximum for each output should be limited to 40mA.
4. V
OUT
should be regulated by user. See Figures 8 and 9 for allowable V
OUT
vs. I
OUT
operation.
5. AC input waveform specification for test purpose: t
R
≤
200ns, t
F
≤
20ns, f = 500kHz, 50% ±10% duty cycle.
6. Clock input rise and fall times must not exceed 300ns.
Condition
–25°C to +85°C, excluding output loads
–40°C to +85°C, excluding output loads
Min
Typ
Max
8.5
10
Units
mA
mA
V
V
V
mA
µA
µA
mA
mA
V
%
kHz
ns
ns
ns
ns
ns
–0.3
2.2
V
DD
–2
0
0.8
V
DD
V
DD
0.75
10
0
2.0
15
3.0
2.7
10
4
25
4.3
±20
500
input current = 750 µA
Note 1
Notes 5, 6
Notes 5, 6
Notes 5, 6
Clock Input Frequency
Clock Input High Time
Clock Input Low Time
Data Input Setup Time
Data Input Hold Setup Time
Data Enable Input Setup Time
Reset Pad Current
950
950
300
300
100
die
8
8
µA
February 2006
4
M9999-021606
(408) 955-1690
Micrel, Inc.
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.
The MIC37252 regulator is fully protected from damage
due to fault conditions. Current limiting is provided. This
limiting is linear; output current during overload
conditions is constant. Thermal shutdown disables the
device when the die temperature exceeds the maximum
safe operating temperature. Transient protection allows
device (and load) survival even when the input voltage
spikes above and below nominal. The output structure of
these regulators allows voltages in excess of the desired
output voltage to be applied without reverse current flow.
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.
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 pinout 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 V
OUT
. The
following equation can be used for calculations.
T
J
= (V
OUT
) (I
LED
) (No. of segments) (124°C/W) + T
A
where:
T
J
= junction temperature + 150°C max
V
OUT
= the voltage at the LED driver outputs
I
LED
= the LED current
124°C/W = thermal resistance of the package
T
A
= ambient temperature
The above equation was used to plot Figures 7–9.
February 2006
5
M9999-021606
(408) 955-1690
ARM技术
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