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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74ls4 to brush up 74os48 your electronics principles? Learning Electronics Need to brush up on your electronics principles? Basic method of cascading B ICs without zero suppression. 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 the seven-segment outputs until the not-LATCH pin returns 74ld48 the high state.
The not-BL pin 4 terminal is also normally tied high, but blanks turns off all seven segments when pulled low. Method of applying leading-zero suppression to the first three digits of a four-digit display using 74LS47 ICs.
Figure 1 shows the functional diagrams and pin designations of these devices, each of which is housed in a pin DIL package. They have integral ripple-blanking facilities, but do not incorporate data latches. The B can be used to drive most popular types of seven-segment displays.
Driving a fluorescent readout with a B. 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.
The B is very easy to use, and has only three input control 74ls8 of these, the not-LT pin 3 pin is normally tied high, but turns on all seven segments of the display when pulled low.
The rest of this article describes a few of the most popular of these devices. Basic way of using the B to drive a seven-segment common-cathode LED display. 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. 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.
Driving a gas discharge readout. The B has four input control terminals, and three auxiliary output terminals. The segment output currents are internally limited to about 5mA at 10V or 10mA at 15V. The opening episode of this special feature explained the basic operating and usage principles of seven-segment alphanumeric displays.
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.
Figure 5 shows the basic connections for driving a common-cathode LED display. The display can be blanked at any time by driving the BL terminal to the logic-1 level.
These multi-part series may be just what you need! In each case, Rx determines the operating segment current of the display, and Ry determines the base current of 74sl48 transistor. Series Using 7-Segment Displays All articles in this series: This procedure is repeated on all except the LSD, which does not require zero suppression.
Finally, the LE latch enable terminal pin 5 enables the IC to give either direct or latched decoding operation. Figures 6, 7and 8 show how to modify the above circuit to drive LED common-anode displays, gas discharge displays, and low-brightness fluorescent displays, respectively. 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.
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.
Figure 15 shows the basic circuit connections to be used when cascading stages. 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 A special two-part feature on how to use seven-segment alphanumeric displays. In Figure 12Rx sets the segment current of the display and Ry sets the base current of the transistor 10mA maximum. In practice, however, it is far better to use a B IC for this particular application.
Way of using the B to drive a seven-segment LCD. Driving a gas discharge readout with a B. The LT terminal drives all display outputs on when the terminal is driven to logic 0 with the RBO terminal open or at logic 1. Enabling the display can be connected directly to the outputs of the IC without the use of external current-limiting resistors. Figure 3 shows how to connect the ripple-blanking terminals to give leading zero suppression on the first three digits of a four-digit display.
Figure 14 shows the functional diagram and pin notations of the B.
Driving a low-brightness fluorescent readout. The IC does not incorporate a data latch and has no facility for ripple blanking. Way of using the B to drive a common-cathode or b common-anode seven-segment LED displays.
Functional diagram and pin notations of the B decade counter with seven-segment display driver. Figure 4 shows the functional diagram and pin notations of the device, which can use any power source in the 5V to 15V range. The CO signal is a symmetrical square- wave at one-tenth of the CLK input frequency, and is useful in cascading B counters. Method of modifying the Figure 17 circuit to give automatic leading-zero suppression.
The 74LS47 has active-low outputs designed for driving a common-anode LED display via external current-limiting resistors Rxas shown in Figure 2.