SCAS291W MARCH 1993 – October 2016 SN54LVC138A , SN74LVC138A
PRODUCTION DATA.
- 1 Features
- 2 Applications
- 3 Description
- 4 Revision History
- 5 Pin Configuration and Functions
- 6 Specifications
- 7 Parameter Measurement Information
- 8 Detailed Description
- 9 Application and Implementation
- 10Power Supply Recommendations
- 11Layout
- 12Device and Documentation Support
- 13Mechanical, Packaging, and Orderable Information
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9 Application and Implementation
NOTE
Information in the following applications sections is not part of the TI component specification, and TI does not warrant its accuracy or completeness. TI’s customers are responsible for determining suitability of components for their purposes. Customers should validate and test their design implementation to confirm system functionality.
9.1 Application Information
The SN74LVC138A is useful as a scanning column selector for an LED Matrix display as it can be used for the low-side drive of the LED string. The decoder functionality ensures that no more than one output is pulled to a low-level logic voltage so that only a single column is enabled at any point in time.
9.2 Typical Application
Figure 3. LED Matrix Driver Application
9.2.1 Design Requirements
These devices use CMOS technology and have balanced output drive. Take care to avoid bus contention because it can drive currents that would exceed maximum limits. The high drive also creates fast edges into light loads, so routing and load conditions must be considered to prevent ringing.
9.2.2 Detailed Design Procedure
- Recommended Input Conditions
- For switch time specifications, see propagation delay times in Switching Characteristics—SN74LVC138A.
- For input voltage level specifications for control inputs, see VIH and VIL in Recommended Operating Conditions.
- Recommended Output Conditions
- Outputs must not be pulled above VCC or below GND.
9.2.3 Application Curve
Figure 4. Input High and Input Low Thresholds vs Supply Voltage