MIC3263YML datasheet(22/32 Pages) MICREL

22 / 32 page

Micrel, Inc.

MIC3263

January 2010

M9999-012110

-200

1.E+02

1.E+03

-150

-100

-50

100

1.E+04

1.E+05

1.E+06

Freq

Gain

Phase

26db

-40

-20

100

1.E+02

1.E+03

1.E+04

1.E+05

1.E+06

Freq

Gain

Phase

Fco=1.6kHz

This example illustrates the RHPZ at 162kHz.

details the

−90° phase shift due to the RHPZ.

in (GVC)

The goal is to make the loop transfer function T(fCO)

crossover well before the RHPZ.

Chose a

Figure 16

Figure 16. Control-to-Output Ga

RHPZ

or less; chose

From the plot and or calculation, the magnitude of:---

f= 16kHz

(16kHz) = 26db

⎛⎞

⎜⎟

⎝⎠

1.8V

H(s) = 20Log

= -24db

29V

From:

T(s) = G

(s) * G

(s) * H(s)

T(16kHz) = G

(16kHz) + 26db - 24db = 0

→

(16kHz) = -2db

0.8v/v

e error amplifier’s zero at

nF. The location of the

RO affects the phase boost in the loop transfer function.

If fZERO were closer to 16kHz the phase boost would be

less and vise versa.

Figure 17. Error Amp Gain and Phase (in Example 1)

Figure 18. Loop Gain and Phase (in Example 1)

Therefore R4 = 15kΩ. Next set th

about 5kHz. Therefore C2 = 2.2

fZE

-100

() ≅

0.8 = g

Z IIR

g * R

-80

-60

-40

-20

1.E+02

1.E+03

1.E+04

1.E+05

1.E+06

Freq

Midband Gain

Fzero

Gain

Phase

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