L1

D1

Q1

10 PF

100 PF

10 PH

1k

2.15k

Si2343

LM3475

EN

GND

PGATE

FB

1

2

3

4

5

1 nF

LM3475

www.ti.com

SNVS239C – OCTOBER 2004 – REVISED OCTOBER 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 LM3475 employs a hysteretic control architecture; which provides excellent load transient response and

efficiency even at light loads, as compared to its PWM architectures. No external compensation is required which

results in a simple design and low component count. A typical schematic is described in the next section.

8.2 Typical Application

Figure 10. Full Demo Board Schematic

8.2.1 Design Requirements

To properly size the components for the application, the designer needs the following parameters: input voltage

range, output voltage, output current range, and required switching frequency. These four main parameters affect

the choices of component available to achieve a proper system behavior. Although hysteretic control is a simple

control scheme, the operating frequency and other performance characteristics depend on external conditions

and components. If the inductance, output capacitance, ESR, VIN, or Cff is changed, there will be a change in

the operating frequency and possibly output ripple. Therefore, care must be taken to select components which

will provide the desired operating range.

8.2.2 Detailed Design Procedure

Table 1. Bill of Materials

DESIGNATOR

DESCRIPTION

PART NUMBER

VENDOR

10 µF, 16 V, X5R

EMK325BJ106MN

TAIYO YUDEN

100 µF, 6 V, Ta

TPSY107M006R0100

AVX

1 nF, 25 V, X7R

VJ1206Y102KXXA

Vishay

D1

Schottky, 20 V, 2 A

CMSH2-20L

Central Semiconductor

L1

10 µH, 3.1 A

CDRH103R100

Sumida

Q1

30 V, 2.5 A

Si2343

Vishay

1 k

Ω, 0805, 1%

CRW08051001F

Vishay

2.15 k

Ω, 0805, 1%

CRCW08052151F

Vishay

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