CIN: VISHAY/SPRAGUE 595D226X0020C2T

CCUK: TAIYO YUDEN X5R LMK212BJ105MG

COUT: TAIYO YUDEN X5R JMK325BJ226MM

D: ON SEMICONDUCTOR MBR0520

L1: SUMIDA CLS62-220 or MURATA LZH3C220 (UNCOUPLED)

L1A

22PH

CCUK

2.2PF

COUT

22PF

L1B

22PH

VIN

12V

VOUT-5V

375mA

VDD

5V

D

CFF

1000pF

RFB1

29.4k

RFB2

10k

VIN

SW

NFB

GND

SHDN

LM2611A

1

2

3

4

5

CIN

22PF

LM2611

www.ti.com

SNOS965J – JUNE 2001 – REVISED DECEMBER 2015

8 Application and Implementation

NOTE

Information in the following applications sections is not part of the TI component

specification, and TI does not warrant its accuracy or completeness. TI’s customers are

responsible for determining suitability of components for their purposes. Customers should

validate and test their design implementation to confirm system functionality.

8.1 Application Information

The LM2611 is a Cuk controller with an integrated switch. The following section provides an approach to sizing

the components for the target application and shows some typical examples of applications to help the designer.

8.2 Typical Application

8.2.1 Cuk Converter With Integrated Switch

Figure 21. Typical Cuk Converter Implementation Using LM26211

8.2.1.1 Design Requirements

The first variables needed are the output voltage and the input voltage range (min to max). The input voltage

range ensures that the IC is suitable for the application and that the absolute maximum voltage are respected.

The expected maximum output current is also needed to verify that the IC can deliver the required current.

8.2.1.2 Detailed Design Procedure

The first components to choose are the power inductors. Typically a smaller inductance yields a smaller solution

footprint and lower cost but the higher ripple makes a smaller inductance not compatible with every application.

Due to the internal compensation, TI recommends a 10-µH to 22-µH inductor. Try to choose the inductors so that

the peak-to-peak ripple is lower than 0.3 A of the average current by using Equation 3 and Equation 5.

Using the maximum output current and the input voltage range, calculate the worst case peak current in the

switch using Equation 6. If the peak current is above the peak current limit for this part, consider increasing the

inductance and re-calculate. If the inductance is above 22 µH for each inductor, the designer will have to pay

special attention to stability over the extended range of operation (it's always a good practice to do so even if the

inductance is within the recommended range).

Using the desired output voltage, calculate the value of the feedback resistors. The reference voltage is 1.23 V.

Resistors of 50 k

Ω or less must be used due to the leakage at the NFB pin.

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