SP6122ACUSLASHTR datasheet(9/19 Pages) SIPEX

9 / 19 page

Rev. 7/16/03

SP6122 Low Voltage, Micro 8, PFET, Buck Controller

SP6122

VCC

FFLAG

VOUT

ENABLE

PDRV

GND

ISET

ISENSE

FFLAG

VOUT

1.00k

STPS2L25U

ENABLE

CIN

47µF

Ceramic

VIN

+3.3V

2.2µH

+1.9V

CEN

4.7nF

GND

COUT

470µF

6.5k

12.5k

+ C1

4.7µF

Ceramic

VOUT

PMOS

PDS6375

Figure 1. SP6122 Evaluation Board Application Schematic

As an SP6122 application example, we will

use the circuit from the SP6122 Evaluation

Board Manual. This evaluation board uses

the Sipex SP6122ACU, 1.25V adjustable

PFET controller to realize a 3.3V to 1.9V

step down converter. The board is opti-

mized for 1A – 4A operation and has an

DS(ON) over current trip threshold of about

7A. The body of the applications section

contains:

• Data for the Evaluation Board

• Guidelines for Component Selection

• Features and Protection

• Layout Guidelines

• Introduction to the “Buck Cad Calculator”

Spreadsheet

Data For Evaluation Board

The SP6122 is engineered for size and mini-

mum pin count, yet has a very accurate 2.0%

reference over line, load and temperature.

Figure 2 data shows a typical SP6122 Evalu-

ation Board Efficiency plot, with efficiencies to

88% and output currents to 4A. Load Regula-

tion plot in Figure 3 shows an essentially flat

response of only 3mV change for up to 4A

load. Figure 4 Line Regulation illustrates a

1.90V output that varies only 4mV or 0.2% for

an input voltage change from 3.0V to 5.5V.

While data on individual power supply boards

may vary, the capability of the SP6122 of

achieving high accuracy over load and line

shown here is quite impressive and desirable

for accurate power supply design.

012

345

ILOAD (A)

Figure 2. SP6122 Efficiency with V

IN = 3.3V,

OUT = 1.9V.

APPLICATION INFORMATION

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