LM43602 datasheet(24/44 Pages) TI2

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FBB

FBT

OUT

LM43602-Q1

SNVSA83C – APRIL 2015 – REVISED OCTOBER 2017

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Product Folder Links: LM43602-Q1

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Typical Applications (continued)

8.2.1 Design Requirements

Detailed design procedure is described based on a design example. For this design example, use the

parameters listed in Table 3 as the input parameters.

Table 3. Design Example Parameters

DESIGN PARAMETER

VALUE

Input voltage VIN

12 V typical, range from 3.5 V to 36 V

Output voltage VOUT

3.3 V

Input ripple voltage

400 mV

Output ripple voltage

30 mV

Output current rating

2 A

Operating frequency

500 kHz

Soft-start time

10 ms

8.2.2 Detailed Design Procedure

8.2.2.1 Custom Design With WEBENCH® Tools

Click here to create a custom design using the LM43602-Q1 device with the WEBENCH® Power Designer.

1. Start by entering the input voltage (VIN), output voltage (VOUT), and output current (IOUT) requirements.

2. Optimize the design for key parameters such as efficiency, footprint, and cost using the optimizer dial.

3. Compare the generated design with other possible solutions from Texas Instruments.

The WEBENCH Power Designer provides a customized schematic along with a list of materials with real-time

pricing and component availability.

In most cases, these actions are available:

•

Run electrical simulations to see important waveforms and circuit performance

•

Run thermal simulations to understand board thermal performance

•

Export customized schematic and layout into popular CAD formats

•

Print PDF reports for the design, and share the design with colleagues

Get more information about WEBENCH tools at www.ti.com/WEBENCH.

8.2.2.2 Output Voltage Set-Point

The output voltage of the LM43602-Q1 device is externally adjustable using a resistor divider network. The

divider network is comprised of top feedback resistor RFBT and bottom feedback resistor RFBB. Equation 11 is

used to determine the output voltage of the converter:

(11)

Choose the value of the RFBT to be 100 kΩ to minimize quiescent current to improve light load efficiency in this

application. With the desired output voltage set to be 3.3 V and the VFB = 1.015 V, the RFBB value can be

calculated using Equation 11. The formula yields a value of 43.478 kΩ. Choose the closest available value of

43.2 kΩ for the RFBB. Refer to Adjustable Output Voltage for more details.

8.2.2.3 Switching Frequency

The default switching frequency of the LM43602-Q1 device is set at 500 kHz when RT pin is open circuit. The

switching frequency is selected as 500 kHz in this application for one less passive components. If other

frequency is desired, use Equation 12 to calculate the required value for RT.

RT(kΩ) = 40200 / Freq (kHz) – 0.6

(12)

For 500 kHz, the calculated RT is 79.8 kΩ, and standard value of 80.6 kΩ can also be used to set the switching

frequency at 500 kHz.

LM43602 Datasheet(PDF) 24 Page - Texas Instruments

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