MC14499DW Motorola, MC14499DW Datasheet - Page 3

• Manufacturer Part Number: MC14499DW
• Description: 7-Segment LED Display Decoder/Driver with Serial Interface
• Manufacturer: Motorola

display plus 4 bits for the decimal point — these latter four
bits are optional.
the four digits, as shown in Figure 1.
tive low. The sample and shift are accomplished on the fal-
ling clock edge, see Figure 2. Data are loaded from the shift
register to the latches when ENB goes high. While the shift
register is being loaded, the previous data are stored in the
latches.
pulses to load data; otherwise only 16 are required.
CASCADING
output of the shift register is switched to the decimal point
driver, see Figure 3. Therefore, to cascade n four–digit dis-
play drivers, a set–up is used which loads the 1111 cascad-
ing word:
MOTOROLA
The circuit accepts a 20–bit input, 16 bits for the four–digit
The input sequence is the decimal point code followed by
In order to enter data the enable input, ENB, must be ac-
If the decimal point is used, the system requires 20 clock
The circuit may be cascaded in the following manner.
If a 1111 word is loaded into the decimal point latch, the
1. ENB = active low.
2. Load 20 bits, the first four bits being 1, with 20 clock
3. ENB = high, to load the latch.
4. Repeat steps 1 to 3 (n – 1) times.
pulses.
CIRCUIT OPERATION
BIT NO.
20
DIGIT IV
19
18 17 16 15 14 13 12 11 10
DIGIT III
Figure 1. Input Sequence
DIGIT II
SHIFT
SCANNER
lator, which requires an external frequency–determining ca-
pacitor. The capacitor voltage varies between two trigger
levels at the oscillator frequency.
mended operating range of 200 to 800 Hz. For test purposes
this frequency may be increased up to 10 kHz.
scanner waveforms corresponding to the four digits — see
Figure 4.
SEGMENT DECODER
ure 5.
OUTPUT DRIVERS
TIME
5. (n x 20) bits can be loaded into n circuits, with 1111 as
The scanner frequency is determined by an on–chip oscil-
An external oscillator signal can be used, within the recom-
A divide by four counter provides four non–overlapping
The code used in these matrix decoders is shown in Fig-
There are two different drivers:
A typical application circuit is shown in Figure 6.
The segment and decimal point drivers; these are NPN
emitter followers with no current limiting devices.
The digit output buffers; these are short–circuit protected
CMOS devices.
9
decimal point word to continue the cascading.
DIGIT I
8
7
6
5
DECIMAL POINT
4
3
2
1
MC14499
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