LM3310 datasheet(19/33 Pages) TI

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2S(RC + RO)CC

fPC =

fZC =

2SRCCC

t (s)

IL_AVG

ID_AVG

=IOUT_AVG

D*Ts

IL (A)

ID (A)

OUT

(a)

(b)

LM3310

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SNVS341E – AUGUST 2005 – REVISED MAY 2013

INTRODUCTION TO COMPENSATION (BOOST CONVERTER)

(a) Inductor current

(b) Diode current

Figure 48.

The LM3310 is a current mode PWM boost converter. The signal flow of this control scheme has two feedback

loops, one that senses switch current and one that senses output voltage.

To keep a current programmed control converter stable above duty cycles of 50%, the inductor must meet

certain criteria. The inductor, along with input and output voltage, will determine the slope of the current through

the inductor (see Figure 48 (a)). If the slope of the inductor current is too great, the circuit will be unstable above

duty cycles of 50%. A 10µH inductor is recommended for most 660 kHz applications, while a 4.7µH inductor may

be used for most 1.28 MHz applications. If the duty cycle is approaching the maximum of 85%, it may be

necessary to increase the inductance by as much as 2X. See INDUCTOR AND DIODE SELECTION for more

detailed inductor sizing.

The LM3310 provides a compensation pin (VC) to customize the voltage loop feedback. It is recommended that a

series combination of RC and CC be used for the compensation network, as shown in the Typical Application

Circuit. For any given application, there exists a unique combination of RC and CC that will optimize the

performance of the LM3310 circuit in terms of its transient response. The series combination of RC and CC

introduces a pole-zero pair according to the following equations:

(6)

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