LT3572 查看數據表（PDF） - Linear Technology

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LT3572

Dual Full-Bridge Piezo Driver with 900mA Boost Converter

Linear Technology 

LT3572

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

is propotional to VOUT2, the capacitance of the motor, and

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

with VOUT at 30V, the maximum PWM frequency should be

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

but either VOUT needs to be reduced or the capacitance

needs to be lowered. A piezo motor has an associated

capacitance that cannot be reduced so the output voltage

must be lowered. Since the power is proportional to VOUT2 a

reduction of VOUT to 25V from 30V will allow the LT3572 to

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

low DCR (copper-wire resistance) to minimize I2R power

losses. Table 1 lists several inductor manufacturers.

Table 1. Inductor Manufacturers

Sumida

(847) 956-0666

TDK

(847) 803-6100

Murata

(714) 852-2001

FDK

(408) 432-8331

www.sumida.com

www.tdk.com

www.murata.com

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-

pacitance can help limit the voltage droop on VOUT during

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

OUTA OUTB

D1

OUTA

OUTB

C1

L1

C3

SW 1

VIN 2

SYNC 3

RT 4

GND 5

15 PGOOD

C2

14 SS

GND

R2

13 FB

R1

12 SHDNB

11

SHDNA

CFF

PWMB

PWMA

SHDN

R4

VOUT

3572 BD LAYOUT

3572fa

9

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