LT3572

9

3572fa

APPLICATIONS INFORMATION

PWM

The LT3572 can PWM the output drivers at a very high

frequency. The limitation on the frequency is determined

by the internal rise in die temperature that occurs when

driving the motor. The power delivered to the piezo motor

the PWM frequency. When any of these are increased the

power dissipated in the part increases causing the internal

die temperature to increase. Driving two 2.2nF capacitors

less than 80 kHz. The LT3572 can run at a higher frequency

needs to be lowered. A piezo motor has an associated

capacitance that cannot be reduced so the output voltage

run at a maxim frequency of 115 kHz. If a different motor is

used the maximum PWM frequency will need to be adjusted

inversely to the equivolent capacitance of the motor.

Inductor Selection

A 10μH inductor is recommended for most LT3572 ap-

plications. Choose an inductor that will handle at least

1A without saturating, and ensure that the inductor has a

losses. Table 1 lists several inductor manufacturers.

Table 1. Inductor Manufacturers

Sumida

(847) 956-0666

www.sumida.com

TDK

(847) 803-6100

www.tdk.com

Murata

(714) 852-2001

www.murata.com

FDK

(408) 432-8331

www.tdk.co.jp

Capacitor Selection

The small size of ceramic capacitors makes them ideal

for LT3572 applications. Only X5R or X7R types should

be used because they retain their capacitance over wider

voltage and temperature ranges than other types such as

Y5V or Z5U. A 4.7μF to 15μF output capacitor is sufficient

for stable transient response, however, more output ca-

transients.

Ceramic capacitors also make a good choice for the input

decoupling capacitor, which should be placed as close as

possible to the LT3572. A 1μF to 4.7μF input capacitor

is sufficient for most applications. Table 2 shows a list

1

2

3

4

5

15

14

13

12

11

R4

PWMB

PWMA

3572 BD LAYOUT

SHDN

SHDNA

SHDNB

FB

SS

C2

R2

R1

PGOOD

OUTB

OUTB

OUTA

OUTA

SW

SYNC

RT

GND

GND

C1

D1

L1

C3