SN74AUP1G79_17 Datasheet, PDF (17/45 Pages) Texas Instruments – SN74AUP1G79 Low-Power Single Positive-Edge-Triggered D-Type Flip-Flop

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9 Applications, Implementation, and Layout
SN74AUP1G79
SCES592I – JULY 2004 – REVISED SEPTEMBER 2017
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
A rotary quadrature encoder is a simple, infinitely-turning knob that outputs two out-of-phase square waves as it
is turned and is often used in electronics as a method of human interface. One signal will lead the other in phase
depending on which direction the knob is turned. The SN74AUP1G79 can be used to determine which direction
the knob is being turned without the need for a microcontroller or other complex monitoring system by connecting
the outputs of the knob to the D and CLK inputs of the SN74AUP1G79 as shown in Figure 7. It is important to
note that the CLK input will control when the direction signal changes, as shown in Figure 8.
9.2 Typical Application
QINA
Quadrature
Encoder
QINB
SN74AUP1G79
0.8-3.6V
1D
2 CLK
VCC 5
0.1 F
3 GND
Q4
DIR
Figure 7. Typical Application Diagram
QINA
tpd
tpd
QINB
DIR
Figure 8. Timing Diagram for Quadrature Encoder Application
9.2.1 Design Requirements
The SN74AUP1G79 device uses CMOS technology and has balanced output drive. Take care to avoid bus
contention because it can drive currents that would exceed maximum limits.
9.2.2 Detailed Design Procedure
1. Recommended Input conditions
– Rise time and fall time specifications. See Δt/ΔV in Recommended Operating Conditions.
– Specified high and low levels. See V_IH and V_IL in Recommended Operating Conditions.
– Inputs are overvoltage tolerant, which allows them to go as high as 3.6 V at any valid V_CC
2. Recommended output conditions
– Load currents must not exceed 20 mA on the output and 50 mA total for the part
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