TS2509

3A / 500KHz PWM Buck Converter

4/9

Version: A09

Function Descriptions

PWM Control

The TS2509 consists of DC/DC converters that employ a pulse-width modulation (PWM) system. In converters of the

TS2509, the pulse width varies in a range from 0 to 100%, according to the load current. The ripple voltage produced

by the switching can easily be removed through a filter because the switching frequency remains constant. Therefore,

these converters provide a low-ripple power over broad ranges of input voltage and load current.

Setting the Output Voltage

Application circuit item shows the basic application circuit with TS2509 adjustable output version. The external resistor

sets the output voltage according to the following equation:

(EL CAP) Resistor select for output voltage setting

(MLCC) Resistor select for output voltage setting

R2

R1

R2

R1

5V

1.3K

6.8K

5V

7.5K

39K

3.3V

1.5K

4.7K

3.3V

15K

47K

2.5V

2.2K

4.7K

2.5V

22K

47K

1.8V

2K

2.5K

1.8V

27K

33K

1.5V

2.2K

2K

1.5V

30K

27K

1.2V

3K

1.5K

1.2V

30K

15K

1V

10K

2.5K

1V

56K

13K

Inductor Selection

For most designs, the operate with inductors of 10µH to 22µH. The inductor value can be derived from the following

equation:

1.8V

2.5V

3.3V

5V

L1 Value

10~15uH

10~15uH

15~22uH

15~22uH

Where is inductor Ripple Current. Large value inductors lower ripple current and small value inductors result in high

ripple currents. Choose inductor ripple current approximately 15% of the maximum load current 3A, ΔIL=0.4A. The DC

current rating of the inductor should be at least equal to the maximum load current plus half the ripple current to

prevent core saturation (3A+0.2A).

Input Capacitor Selection

(EL CAP)

This capacitor should be located close to the IC using short leads and the voltage rating should be approximately 1.5

times the maximum input voltage. The RMS current rating requirement for the input capacitor of a buck regulator is

approximately 1⁄2 the DC load current. A low ESR input capacitor sized for maximum RMS current must be used. A

220µF low ESR capacitor for most applications is sufficient.

(MLCC)

A 22µF MLCC or two 10uF MLCC capacitors for most applications is sufficient.