8.2.1.3 Application Curves

Time (200

sec/div)

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

Tx Pulse

Rx Pulse

 = 311.5s = 5.3cm

Figure 8-2. Log_Out Response for Ultrasonic

Distance Measurement

Frequency (Hz)

-25

-22.5

-20

-17.5

-15

-12.5

-10

-7.5

-5

-2.5

0

100k

1M

10M

-25

-22.5

-20

-17.5

-15

-12.5

-10

-7.5

-5

-2.5

0

-4.33dB

Figure 8-3. Band-Pass Filter Frequency Response

8.3 Power Supply Recommendations

The LOG300 contains two supply pins. The analog power supply pin (VCC) and the frequency detect block

supply pin (Freq_Supply). Both pins can be biased at any voltage between 3V to 5.25V with respect to the

AGND. While both these pins are connected to different circuitry internally, TI recommends to connect both of

these pins to the same potential. Provide separate decoupling capacitors, resistors, and ferrite beads to these

supply pins (see Section 8.4.2) to maintain sufficient immunity against cross coupling.

The LOG300 is sensitive to the noise coupling through the supply pins. Use a low-pass filter on the supply line

with a cutoff frequency less than the incoming frequency signal.

For example if the incoming signal is 100kHz, and the band-pass filter has been tuned to achieve a center

frequency of 100kHz, design a RC filter on the supply with a cut off frequency of at least 10kHz. For a higher

signal frequency the RC values start diminishing to smaller values and hence the cut off frequency can be

parked to any appropriate value.

An external band-pass filter if used between the LNA and the LOG detector block, along with a low-pass filter on

the supply pins provides enough power-supply rejection to keep Log_Out unaffected.

www.ti.com

LOG300

SLOSEB7A – SEPTEMBER 2024 – REVISED OCTOBER 2024

Copyright © 2024 Texas Instruments Incorporated

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Product Folder Links: LOG300