+ L1 -

- L2 +

+ L1 -

- L2 +

+

-

+

-

a

b

PWM COMPARATOR

¦

Q1

Q2

x10

R3

30k

R4

140k

R5

R6

RAMP

GENERATOR

1.4MHz

OSCILLATOR

Q

R

s

R

0.05

CURRENT LIMIT

COMPARATOR

DRIVER

+

-

-

+

R1

EXTERNAL

R2

EXTERNAL

(OPTIONAL)

1 SW

2 GND

5

3 NFB

4

N

SHDN

SHUTDOWN

FF

R

THERMAL

SHUTDOWN

LM2611

SNOS965J – JUNE 2001 – REVISED DECEMBER 2015

www.ti.com

7 Detailed Description

7.1 Overview

The LM2611 consists of a current mode controller with an integrated primary switch and integrated current

sensing circuitry. The feedback is connected to the internal error amplifier and a type II/III internal compensation

scheme is used. A ramp generator provides some slope compensation to the system. SHDN pin is a logic input

designed to shut down the converter.

7.2 Functional Block Diagram

7.3 Feature Description

7.3.1 Cuk Converter

Figure 13. Operating Cycles of a Cuk Converter

The LM2611 is a current mode, fixed frequency PWM switching regulator with a

−1.23-V reference that makes it

ideal for use in a Cuk converter. The Cuk converter inverts the input and can step up or step down the absolute

value. Using inductors on both the input and output, the Cuk converter produces very little input and output

current ripple. This is a significant advantage over other inverting topologies such as the buck-boost and flyback.

The operating states of the Cuk converter are shown in Figure 13. During the first cycle, the transistor switch is

(D).

8

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