LMP7709MTSLASHNOPB datasheet(25/41 Pages) TI1

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= (1 +

)(1 +

)

f =

RP + R1//RF

= 1 +

f = 0

fZ =

í(RC + R1//RF + RP) C

fP =

íRCC

= (1 +

)(

)

1 + s(RC + R1//RF + RP)C

1 + sRCC

LMP7707, LMP7708, LMP7709

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SNOSAW5B – JUNE 2007 – REVISED MARCH 2013

Figure 58. LMP7707 with Lead-Lag Compensation for Inverting Configuration

The inverse feedback factor of the circuit in Figure 58 is:

(13)

The pole of the inverse feedback function is located at:

(14)

The zero of the inverse feedback function is located at:

(15)

The low frequency inverse feedback factor is given by:

(16)

The high frequency inverse feedback factor is given by:

(17)

From these formulas, we can tell that

1. The 1/F's zero is located at a lower frequency compared to 1/F's pole.

2. The intersection point of 1/F and the open loop gain G is determined by the choice of resistor values for RP

and RC if the values of R1 and RF are set before compensation.

3. This procedure results in the creation of a pole-zero pair, the positions of which are interdependent.

4. This pole-zero pair is used to:

–

Raise the 1/F value to a greater value in the region immediately to the left of its intercept with the A

function in order to meet the Gmin requirement.

–

Achieve the preceding with no additional loop phase delay.

5. The location of the 1/F zero is determined by the following conditions:

–

The value of 1/F at low frequency.

–

The value of 1/F at the intersection point.

–

The location of 1/F pole.

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