Datasheet

ManualsBrandsLINEAR TECHNOLOGY ManualsPMICsPMIC - gate/half-bridge gate drivers Inductive, Capacitive Bipolar QFN 20 (4x4)

LT3572

3572fa

FEATURES

APPLICATIONS

DESCRIPTION

Dual Full-Bridge Piezo Driver

with 900mA Boost Converter

The LT

3572 is a highly integrated dual Piezo motor driver

capable of driving two Piezo motors at up to 40V from a

5V supply. Each Piezo driver can be independently turned

on or off along with the boost converter.

The boost regulator has a soft-start capability that limits the

inrush current at start-up. The boost regulator switching

frequency is set by an external resistor or the frequency can

be synchronized by an external clock. A PGOOD pin indicates

when the output of the boost converter is in regulation and

the Piezo drivers are allowed to start switching.

The LT3572 is available in a (4mm × 4mm) 20-pin QFN

package.

Dual Piezo Driver

■

2.7V to 10V Input Voltage Range

■

900mA Boost Converter

■

Dual Full-Bridge Piezo Drivers

■

Programmable Switching Frequency from

500kHz to 2.25MHz

■

Synchronizable Up to 2.5MHz

■

Soft-Start

■

Separate Enable for Each Piezo Driver and Boost

Converter

■

Available in a 4mm × 4mm 20-Pin QFN Package

■

Piezo Motor Drive

, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.

All other trademarks are the property of their respective owners.

SHDN

SHDNA

SHDNB

PWMA

PWMB

SYNC

PGOOD

3V TO 5V

10μH

GND

LT3572

10nF

4.7μF

15pF

10μF

OUT

30V

50mA

100k

576k

24.3k

3572 TA01a

OUTA

OUTB

42.2k

OUT

Response Driving Piezo Motor at 70kHz

OUTA

20V/DIV

OUTA

20V/DIV

PWMA

2V/DIV

2μs/DIV

3572 TA01b

TYPICAL APPLICATION

Summary of content (12 pages)

PAGE 1
LT3572 Dual Full-Bridge Piezo Driver with 900mA Boost Converter FEATURES ■ ■ ■ ■ ■ ■ ■ ■ DESCRIPTION 2.7V to 10V Input Voltage Range 900mA Boost Converter Dual Full-Bridge Piezo Drivers Programmable Switching Frequency from 500kHz to 2.25MHz Synchronizable Up to 2.
PAGE 2
LT3572 PIN CONFIGURATION VOUT Voltage .............................................................40V OUTA, OUTA, OUTB, OUTB Voltage ...........................40V SW Voltage ...............................................................42V RT, SS, SYNC ..............................................................2V FB ...............................................................................3V All Other Pins ............................................................
PAGE 3
LT3572 ELECTRICAL CHARACTERISTICS The ● denotes the speciﬁcations which apply over the full operating temperature range, otherwise speciﬁcations are at TA = 25°C. VIN = 5V, VSHDNA= VSHDNB = VSHDN = 5V, unless otherwise noted. PARAMETER CONDITIONS MIN PWMA Pin Threshold TYP 0.3 PWMB Pin Threshold 0.3 MAX UNITS 1.5 V 1.5 V PGOOD Rising Threshold (Note 3) ● 1.12 1.16 1.19 V PGOOD Falling Threshold (Note 4) ● 1.01 1.04 1.065 V 1 3 kΩ 500 2.25 575 2.
PAGE 4
LT3572 TYPICAL PERFORMANCE CHARACTERISTICS Feedback Pin Voltage vs Temperature Oscillator Frequency vs Temperature 1.25 2.5 SS Pin Current vs Temperature 8 RT = 13k 7 1.23 1.22 1.21 SS PIN CURRENT (μA) 2.0 FREQUENCY (MHz) FEEDBACK VOLTAGE (V) 1.24 1.5 RT = 35k 1.0 6 5 4 3 2 0.5 1 0 0 –50 –25 25 50 75 100 125 150 TEMPERATURE (°C) 0 3572 G01 1.6 VSHDN = 5V 9 SHDN PIN CURRENT (μA) 3.5 QUIESCENT CURRENT (mA) SW Current Limit vs Temperature 10 2.5 2.0 1.5 1.0 1.4 8 7 6 5 VSHDN = 2.
PAGE 5
LT3572 PIN FUNCTIONS SW (Pin 1): Switch Node. This pin connects to the collector of an internal NPN power switch. VIN (Pin 2): Input Supply Pin. This pin must be locally bypassed with a capacitor. SYNC (Pin 3): Synchronization Pin. This pin is used to synchronize the internal oscillator to an external signal. The synchronizing range is 15% above the free running frequency set by the RT pin up to 2.5MHz. If not used, this pin must be tied to GND. SHDNB (Pin 12): Shutdown Pin. Tie to 1.
PAGE 6
LT3572 BLOCK DIAGRAM 8 7 VOUT 10 PWMA 11 SHDN 12 SHDNA SHDNB VIN START-UP/ INTERNAL BIAS A6 2 Q2 18 L1 OUTA SW A4 + Q3 S Q1 Q A2 1 R – 19 R4 D1 Q4 + OUTA A3 Q5 R5 – GND 5 GND 9 GND 20 + Q6 17 OUTB OSCILLATOR VOUT GND 21 R1 A1 FB – RC A5 Q7 1.225V CC SS Q10 C1 13 R2 14 C2 – Q8 16 OUTB 95%/85% A7 + Q9 PWMB 6 RT 4 SYNC 3 PGOOD 15 R3 3572 F01 Figure 1.
PAGE 7
LT3572 OPERATION Switching Regulator The LT3572 uses a constant frequency, current mode, control scheme to provide excellent line and load regulation for the output drivers. Operation can be best understood by referring to the Block Diagram in Figure 1. A pulse from the oscillator sets the RS ﬂip-ﬂop, A4, and turns on the internal NPN bipolar power switch, Q1. Current in Q1 and the external inductor, L1, begins to increase.
PAGE 8
LT3572 APPLICATIONS INFORMATION Duty Cycle 10000 DC = SWITCHING FREQUENCY (kHz) The typical maximum duty cycle of the LT3572 is 95% at 1MHz. This maximum duty cycle reduces as the switching frequency is increased. The duty cycle for a given application is given by: VOUT + VD – VIN VOUT + VD – VCESAT where VD is the diode forward drop, typically 0.5V and VCESAT is, in the worst case, 310mV at 0.8A.
PAGE 9
LT3572 APPLICATIONS INFORMATION 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. 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.
PAGE 10
LT3572 APPLICATIONS INFORMATION of several ceramic capacitor manufacturers. Consult the manufacturers for detailed information on their entire selection of ceramic parts. used. These diodes are rated to handle an average forward current of 0.5A. For higher efﬁciency, use a diode with better thermal characteristics such as the On Semiconductor MBRM140 (a 40V diode). Table 2. Ceramic Capacitor Manufacturers Taiyo Yuden (408) 573-4150 www.t-yuden.com AVX (803) 448-9411 www.avxcorp.
PAGE 11
LT3572 PACKAGE DESCRIPTION UF Package 20-Lead Plastic QFN (4mm × 4mm) (Reference LTC DWG # 05-08-1710 Rev A) 0.70 p0.05 4.50 p 0.05 3.10 p 0.05 2.00 REF 2.45 p 0.05 2.45 p 0.05 PACKAGE OUTLINE 0.25 p0.05 0.50 BSC RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED 0.75 p 0.05 4.00 p 0.10 R = 0.05 TYP R = 0.115 TYP 19 20 0.40 p 0.10 PIN 1 TOP MARK (NOTE 6) 1 2.45 p 0.10 4.00 p 0.10 PIN 1 NOTCH R = 0.20 TYP OR 0.
PAGE 12
LT3572 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LT1160 Half-/Full-Bridge N-Channel MOSFET Driver VIN: 10V to 15V, VOUT(MAX) = 60V, 24-Lead SO Package LT3469 Piezo Microactuator Driver with Boost Regulator VIN: 2.5V to 16V, VOUT = 35V Maximum, 40mA Current Limit for Piezo Microactuator LT3479 3A, Full Featured DC/DC Converter with Soft-Start and Inrush Current Protection VIN: 2.5V to 24V, VOUT(MAX) = 40V, IQ = Analog/PWM, ISD < 1μA, DFN, TSSOP Packages LT3580 42V, 2A, 2.