LMP8602MASLASHNOPB datasheet(22/42 Pages) TI1

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C2 =

C =

C2 =

C1 =

R1Z0

C =

R1Zo

C1 =

(K2

1)Q

R1Z0

LMP8601, LMP8601-Q1

LMP8602, LMP8602-Q1

LMP8603, LMP8603-Q1

SNOSAR2H – SEPTEMBER 2008 – REVISED APRIL 2016

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Product Folder Links: LMP8601 LMP8601-Q1 LMP8602 LMP8602-Q1 LMP8603 LMP8603-Q1

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Feature Description (continued)

For instance, the value of Q can be set to 0.5

√2 to create a Butterworth response, to 1/√3 to create a Bessel

response, or a 0.5 to create a critically damped response. After the value of R2 has been found, the second and

last step of the design procedure is to calculate the required value of C to give the desired low-pass cut-off

frequency using:

(13)

For the gain = 2, the result is:

(14)

The gain = 5 results in:

(15)

The gain = 10 gives:

(16)

For C2 the value is calculated with:

(17)

For a gain = 2:

C2 = C1

(18)

Or for a gain = 5:

(19)

And for a gain = 10:

(20)

Note that the frequency response achieved using this procedure is only accurate if the cut-off frequency of the

second-order filter is much smaller than the intrinsic 60-kHz, low-pass filter. In other words, choose the frequency

response of the LMP860x or LMP860x-Q1 circuit so that the internal poles do not affect the external second-

order filter.

7.4 Device Functional Modes

7.4.1 Gain Adjustment

The gain of the LMP860x and LMP860x-Q1 is fixed; however, the overall gain may be adjusted as the signal

path between the two internal amplifiers is available on the A1 and A2 pins.

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