LMV331M5X datasheet(16/38 Pages) TI1

16 / 38 page

LMV331-N, LMV339-N, LMV393-N

SNOS018H – AUGUST 1999 – REVISED DECEMBER 2014

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8.2 Typical Applications

8.2.1 Squarewave Oscillator

Figure 20. Squarewave Oscillator

8.2.1.1 Design Requirements

Comparators are ideal for oscillator applications. This square wave generator uses the minimum number of

components. The output frequency is set by the RC time constant of the capacitor C1 and the resistor in the

negative feedback R4. The maximum frequency is limited only by the large signal propagation delay of the

comparator in addition to any capacitive loading at the output, which would degrade the output slew rate.

8.2.1.2 Detailed Design Procedure

Figure 21. Squarewave Oscillator Timing Thresholds

To analyze the circuit, assume that the output is initially high. For this to be true, the voltage at the inverting input

Vc has to be less than the voltage at the non-inverting input Va. For Vc to be low, the capacitor C1 has to be

discharged and will charge up through the negative feedback resistor R4. When it has charged up to value equal

to the voltage at the positive input Va1, the comparator output will switch.

Va1 will be given by:

(9)

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LMV331M5X 数据表(PDF) 16 Page - Texas Instruments