TPS62100, TPS62101, TPS62102, TPS62103

MULTIMODE LOW POWER BUCK CONVERTER

SLUS446B – MAY 2000 – REVISED DECEMBER 2000

10

POST OFFICE BOX 655303

APPLICATION INFORMATION

f – Frequency – Hz

1

10

100

1 k

10 k

100 k

1 M

10 M

100 M

–50

0

50

100

150

200

Gain

Phase

–50

0

50

100

150

200

–100

–100

Figure 1. Error Amplifier Gain Phase Response

loop compensation and the TPS6210X series of converters

Feedback-loop compensation in the data sheet examples assumes that the output-filter capacitor is a

mulit-layer ceramic (MLC) type. With this type of output capacitor, the ESR zero will be too high in frequency

to use as part of the compensation network. This can complicate the loop compensation, especially in the

higher-switching frequency versions where error-amplifier bandwidth must be taken into consideration. A

typical PWM- and output-filter response plot is shown in Figure 2. Note the lightly-loaded circuit has a pair of

complex poles that cause the gain peaking and rapid-phase shift near the L-C resonant frequency.

The strategy that has been the best to date for designing a compensator for this circuit has been to use: