SP6126 Просмотр технического описания (PDF) - Signal Processing Technologies

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SP6126

High-Voltage, Step Down Controller in TSOT6

Signal Processing Technologies 

Loop Compensation Example 1- A converter

utilizing a SP6126 has a 6.8uH inductor and

a 22uF/5mΩ ceramic capacitor. Determine

whether Type-III compensation is needed.

From equation (2) fESRZERO = 1.45MHz. From

equation (3) fDBPOLE = 13 kHz. Since the

condition specified in (1) is not met, Type-III

compensation has to be used by adding

external components RZ and CZ. Using

equation (4) CZ is calculated 61.2pF (use 62

pF). Following the guideline given in table 1,

a 2kΩ RZ should be used.

The steps followed in example 1 were used

to compensate the typical application circuit

shown on page 1. Satisfactory frequency

response of the circuit, seen in figure 2,

validates the above procedure.

GENERAL OVERVIEW

Loop Compensation Example 2- A converter

utilizing a SP6126 has a 6.8uH inductor and

a 150uF, 82mΩ Aluminum Electrolytic

capacitor. Determine whether Type-III

compensation is needed.

From equation (2) fESRZERO = 13kHz. From

equation (3) fDBPOLE = 5 kHz. Since the

condition specified in (1) is not met, Type-III

compensation has to be used by adding

external components RZ and CZ. Using

equation (4) CZ is calculated 160pF (use

150 pF). Since fESRZERO ÷ fDBPOLE is

approximately 3, RZ has to be set at 30kΩ.

Figure 2- Satisfactory frequency response of typical application circuit shown on page

1. Crossover frequency fc is 80kHz with a corresponding phase margin of 65 degrees.

Mar 29-07 RevD

SP6126: TSOT-6 PFET Buck Controller

5

 2007 Sipex Corporation

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