LMV822MM datasheet(21/37 Pages) TI1

21 / 37 page

LMV821-N, LMV822-N, LMV822-N-Q1

LMV824-N, LMV824-N-Q1

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SNOS032G – AUGUST 1999 – REVISED NOVEMBER 2013

(5)

Notice that R3 could also be calculated as 0.707 of Ra or R2.

The circuit was implemented and its cutoff frequency measured. The cutoff frequency measured at 2.92 kHz.

The circuit also showed good repeatability. Ten different LMV822 samples were placed in the circuit. The

corresponding change in the cutoff frequency was less than a percent.

TRI-LEVEL VOLTAGE DETECTOR

The tri-level voltage detector of Figure 44 provides a type of window comparator function. It detects three

different input voltage ranges: Min-range, Mid-range, and Max-range. The output voltage (VO) is at VCC for the

Min-range. VO is clamped at GND for the Mid-range. For the Max-range, VO is at Vee. Figure 45 shows a VO vs.

VI oscilloscope photo per the circuit of Figure 44.

Its operation is as follows: VI deviating from GND, causes the diode bridge to absorb IIN to maintain a clamped

condition (VO= 0V). Eventually, IIN reaches the bias limit of the diode bridge. When this limit is reached, the

clamping effect stops and the op amp responds open loop. The design equation directly preceding Figure 45,

shows how to determine the clamping range. The equation solves for the input voltage band on each side GND.

The mid-range is twice this voltage band.

Figure 44. Tri-level Voltage Detector

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Product Folder Links: LMV821-N LMV822-N LMV822-N-Q1 LMV824-N LMV824-N-Q1

LMV822MM Datasheet(PDF) 21 Page - Texas Instruments