TheSN54/74LS47 are Low Power Schottky BCD to 7-Segment Decoder /Driversconsisting of NAND gates, input buffers and seven AND-OR-INVERTgates. They offer active LOW, high sink current outputs for driving indicators directly. Seven NAND gates and one driver are connected in pairs tomake BCD data and its complement available to the seven decoding AND-OR-INVERT gates. The remaining NAND gate and three input buffers providelamp test, blanking input/ripple-blanking output and ripple-blanking input.
The SN74LS47N feature active-low outputs designed for driving common-anode LEDs or incandescent indicators directly.
Feature
- '46A, '47A, 'LS47 feature
- Open-Collector Outputs Drive Indicators Directly
- Lamp-Test Provision
- Leading/Trailing Zero Suppression
- '48, 'LS48 feature
- Internal Pull-Ups Eliminate Need for External Resistors
- Lamp-Test Provision
- Leading/Trailing Zero Suppression
- 'LS49 feature
- Open-Collector Outputs
- Blanking Input
- All Circuit Types Feature Lamp Intensity Modulation Capability
The '46A, '47A, and 'LS47 feature active-low outputs designed for driving, common-anode LEDs or incandescent indicators directly. The '48, 'LS48, and 'LS49 feature active-high outputs for driving lamp buffers or common-cathode LEDs. All of the circuits except 'LS49 have full ripple-blanking input/output controls and a lamp test input. The 'LS49 circuit incorporates a direct blanking input. Segment identification and resultant displays are shown below. Display patterns for BCD input counts above 9 are unique symbols to authenticate input conditions.
The '46A, '47A, '48, 'LS47, and 'LS48 circuits incorporate automatic leading and/or trailing-edge zero-blanking control (RBI\ and RBO\). Lamp test (LT\) of these types may be performed at any time when the BI\/RBO\ node is at a high level. All types (including the '49 and 'LS49) contain an overriding blanking input (BI\), which can be used to control the lamp intensity by pulsing or to inhibit the outputs. Inputs and outputs are entirely compatible for use with TTL logic outputs.
The SN54246/SN74246 and '247 and the SN54LS247/SN74LS247 and 'LS248 compose the 6 and the 9 with tails and were designed to offer the designer a choice between two indicator fonts.
