REF LEVEL

0.000 dB

0.0 deg

100

1k

START 50.000 Hz

10k

STOP 50 000.000 Hz

/DIV

10.000 dB

45.000 deg

0

GAIN

PHASE

REF LEVEL

0.000 dB

0.0 deg

100

1k

START 50.000 Hz

10k

STOP 50 000.000 Hz

/DIV

10.000 dB

45.000 deg

0

GAIN

PHASE

LM5576, LM5576-Q1

SNVS447I – JANUARY 2007 – REVISED APRIL 2013

www.ti.com

Figure 18. Error Amplifier Gain and Phase

The overall loop can be predicted as the sum (in dB) of the modulator gain and the error amp gain.

Figure 19. Overall Loop Gain and Phase

If a network analyzer is available, the modulator gain can be measured and the error amplifier gain can be

configured for the desired loop transfer function. If a network analyzer is not available, the error amplifier

compensation components can be designed with the guidelines given. Step load transient tests can be

performed to verify acceptable performance. The step load goal is minimum overshoot with a damped response.

C6 can be added to the compensation network to decrease noise susceptibility of the error amplifier. The value

of C6 must be sufficiently small since the addition of this capacitor adds a pole in the error amplifier transfer

function. This pole must be well beyond the loop crossover frequency. A good approximation of the location of

18

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