The ‘LS48 translates four lines of BCD () input data into the 7-segment numeral code and provides seven corre- sponding outputs having pull-up resistors. Jameco Part no.: ; Manufacturer: Major Brands; Manufacturer no.: 74LS Texas Instruments [ KB ]; Data Sheet (current) [ KB ]; Representative. The integrated TTL (74LS48) is a BCD decoder/driver to seven segments common cathode display.
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The CO signal is a symmetrical square- wave at one-tenth of the CLK input frequency, and is useful in cascading B counters. Figure 3 shows how to connect the ripple-blanking terminals to give 74la48 zero suppression on the first three digits of a four-digit display.
Basic method of cascading B ICs without zero suppression.
Figure 4 shows the functional diagram and pin notations of the device, which can use any power source in the 5V to 15V range. If trailing-zero suppression is required, the direction of ripple-blanking feedback must be reversed with the RBI terminal of the LSD grounded and its RBO terminal wired to the RBI terminal of the next least-significant stage, and so on.
This feature enables the IC to act as a universal unit that can drive common-cathode or common-anode LED or liquid-crystal seven-segment displays with equal ease, as shown in Figures 10 to Driving a gas discharge readout with a B. Functional diagram and pin notations of the B decade counter with seven-segment display driver. The B has four input control terminals, and three auxiliary output terminals.
This procedure is repeated on all except the LSD, which does not require zero suppression.
The rest of this article describes a few of the most popular of these devices. Figure 15 shows the basic circuit connections to be used when cascading stages. Figure 14 shows the functional diagram and pin notations of the B. The 74LS47 has active-low outputs designed for driving a common-anode LED display via external current-limiting resistors Rxas shown in Figure 2.
Learning Electronics Need to brush up on your electronics principles? Driving a fluorescent readout with a B. 744ls48 each case, Rx determines the operating segment current of the display, and Ry determines the base current of the transistor. Some of these devices have integral ripple-blanking facilities, others have built-in data latches, and a few even have built-in decade counter stages, etc.
74LS48 BCD to 7-segment Decoder Driver IC | Warefab
These multi-part series may be just what you need! Note in the cases of Figures 6 and 7 that an NPN buffer transistor must be interposed between each output drive segment and the input segment of the display. Driving a gas discharge readout.
The IC does not incorporate a data latch and has no facility for ripple blanking. Figure 11 shows the basic way of using the B to drive a seven-segment LCD, and Figures 12 and 13 show it used to drive other types of seven-segment displays. 74lss48 practice, however, it is far better to use a B IC for this particular application.
Using Seven-Segment Displays — Part 2
When the not-LATCH terminal is pulled low, the BCD input signals that are present at the moment of transition are latched into memory and fed in decoded form to 74lz48 seven-segment outputs until the not-LATCH pin returns to the high state.
Series Using 7-Segment Displays All articles in this series: The B can be used to drive most popular types of seven-segment displays. In Figure 12Rx sets the segment current of the display and Ry sets the base current of the transistor 10mA maximum.
Figures 6, 7 74lss48, and 8 show how to modify the above circuit to drive LED common-anode displays, gas discharge displays, and low-brightness fluorescent displays, respectively. If cascaded B ICs are required to give automatic leading-zero suppression, the basic Figure 17 circuit must be modified as shown in Figure 18 to provide ripple-blanking operation. Finally, the LE latch enable terminal pin 5 enables the IC to give either direct or latched decoding operation.
The display can be blanked at any time by driving the BL terminal to the logic-1 level.
A current-limiting resistor Rx must be wired in series with each display segment and must have its value chosen to limit the segment current below 25mA. A special two-part feature on how to use seven-segment alphanumeric displays. They have integral ripple-blanking facilities, but do not incorporate data latches.