LT3572
Dual Full-Bridge Piezo Driver
with 900mA Boost Converter
FEATURES
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■
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DESCRIPTION
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.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
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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
APPLICATIONS
■
Piezo Motor Drive
TYPICAL APPLICATION
Dual Piezo Driver
V
IN
3V TO 5V
10μH
V
OUT
30V
50mA
SW
V
OUT
FB
OUTA
LT3572
OUTA
3572 TA01a
Response Driving Piezo Motor at 70kHz
100k
4.7μF
V
IN
SHDN
SHDNA
SHDNB
PWMA
PWMB
SYNC
PGOOD
RT
15pF
576k
10μF
24.3k
V
OUTA
20V/DIV
V
OUTA
20V/DIV
OUTB
GND
OUTB
42.2k
SS
10nF
PWMA
2V/DIV
2μs/DIV
3572 TA01b
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LT3572
ABSOLUTE MAXIMUM RATINGS
(Note 1)
PIN CONFIGURATION
TOP VIEW
OUTA
OUTA
OUTB
OUTB
15 PGOOD
14 SS
21
13 FB
12 SHDNB
11 SHDNA
6
PWMB
7
PWMA
8
V
OUT
9 10
GND
SHDN
GND
SW 1
V
IN
2
SYNC 3
RT 4
GND 5
V
OUT
Voltage .............................................................40V
OUTA,
OUTA,
OUTB,
OUTB
Voltage ...........................40V
SW Voltage ...............................................................42V
RT, SS, SYNC ..............................................................2V
FB ...............................................................................3V
All Other Pins ............................................................10V
Maximum Junction Temperature........................... 125°C
Operating Temperature Range (Note 2).... –40°C to 85°C
Storage Temperature Range................... –65°C to 125°C
20 19 18 17 16
UF PACKAGE
20-LEAD (4mm 4mm) PLASTIC QFN
T
JMAX
= 125°C,
θ
JA
= 37°C/W
EXPOSED PAD (PIN 21) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
LT3572EUF#PBF
TAPE AND REEL
LT3572EUF#TRPBF
PART MARKING
3572
PACKAGE DESCRIPTION
20-Lead (4mm
×
4mm) Plastic DFN
TEMPERATURE RANGE
–40°C to 85°C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
Consult LTC Marketing for information on non-standard lead based finish parts.
For more information on lead free part marking, go to:
http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to:
http://www.linear.com/tapeandreel/
The
●
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 5V, V
SHDNA
= V
SHDNB
= V
SHDN
= 5V, unless otherwise noted.
PARAMETER
Minimum Operating Voltage
V
IN
Quiescent Current
V
IN
Shutdown Current
SHDN
Pin Threshold
SHDNA
Pin Threshold
SHDNB
Pin Threshold
SHDN
Pin Bias Current
SHDNA
Pin Bias Current
SHDNB
Pin Bias Current
V
SHDN
= 5V, V
SHDNA
= 0V, V
SHDNB
= 0V
V
SHDN
= 0V, V
SHDNA
= 0V, V
SHDNB
= 0V
V
SHDN
= 0V, V
SHDNA
= 5V, V
SHDNB
= 0V
V
SHDN
= 0V, V
SHDNA
= 0V, V
SHDNB
= 0V
V
SHDN
= 0V, V
SHDNA
= 0V, V
SHDNB
= 5V
V
SHDN
= 0V, V
SHDNA
= 0V, V
SHDNB
= 0V
V
FB
= 1.3V
V
SHDN
= V
SHDNA
= V
SHDNB
= 0V
0.3
0.3
0.3
8
0.1
8
0.1
8
0.1
CONDITIONS
●
ELECTRICAL CHARACTERISTICS
MIN
TYP
2.5
3.4
0
MAX
2.7
4
1
1.5
1.5
1.5
15
1
15
1
15
1
UNITS
V
mA
μA
V
V
V
μA
μA
μA
μA
μA
μA
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LT3572
ELECTRICAL CHARACTERISTICS
PARAMETER
PWMA Pin Threshold
PWMB Pin Threshold
PGOOD
Rising Threshold
PGOOD
Falling Threshold
PGOOD
Resistance
Switching Frequency
Maximum Duty Cycle
Synchronization Frequency
SYNC Pin Thresholds
SS Current
FB Pin Voltage
FB Pin Voltage Line Regulation
FB Pin Bias Current
SW Current Limit
SW V
CESAT
SW Leakage Current
OUTx Rise Time
OUTx Fall Time
V
IN
= 2.5V to 10V
V
FB
= 1.225V (Note 6)
(Note 7)
I
SW
= 800mA
SW = 40V
C = 2.2nF, V
OUT
= 30V (Note 8)
C = 2.2nF, V
OUT
= 30V (Note 8)
0.9
●
The
●
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 5V, V
SHDNA
= V
SHDNB
= V
SHDN
= 5V, unless otherwise noted.
CONDITIONS
MIN
0.3
0.3
(Note 3)
(Note 4)
RT = 75.0kΩ
RT = 13.0kΩ
RT = 75.0kΩ
RT = 13.0kΩ
(Note 5)
●
●
●
●
●
●
●
TYP
MAX
1.5
1.5
UNITS
V
V
V
V
kΩ
kHz
MHz
%
%
1.12
1.01
425
1.9
95
85
575
0.3
1.16
1.04
1
500
2.25
1.19
1.065
3
575
2.6
2500
1.5
4.5
1.225
0.01
50
1.3
310
0.2
1.255
0.05
200
1.7
450
5
120
120
kHz
V
μA
V
%/V
nA
A
mV
μA
ns
ns
1.195
Note 1:
Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2:
The LT3572 is guaranteed to meet specified performance from
0°C to 70°C operating junction temperature. Specifications over the
–40°C to 85°C operating junction temperature range are assured by
design, characterization and correlation with statistical process controls.
Note 3:
Rising threshold voltage on FB pin that pulls
PGOOD
low.
Note 4:
Falling threshold voltage on FB pin that causes a high impedance
on
PGOOD.
Note 5:
Minimum pulse width is 100ns. Maximum off pulse width is 100ns.
Note 6:
Current flows into the pin.
Note 7:
Current limit guaranteed by design and/or correlation to static test.
Note 8:
OUTx refers to OUTA,
OUTA,
OUTB,
OUTB.
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LT3572
TYPICAL PERFORMANCE CHARACTERISTICS
Feedback Pin Voltage vs
Temperature
1.25
2.5
Oscillator Frequency vs
Temperature
RT = 13k
8
7
SS Pin Current vs Temperature
1.24
FEEDBACK VOLTAGE (V)
FREQUENCY (MHz)
2.0
SS PIN CURRENT (μA)
6
5
4
3
2
1
1.23
1.5
RT = 35k
1.22
1.0
1.21
0.5
1.20
–50 –25
0
25 50
75 100 125 150
TEMPERATURE (°C)
3572 G01
0
–50 –25
0
25 50
75 100 125 150
TEMPERATURE (°C)
3572 G02
0
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
3572 G03
Quiescent Current vs Temperature
4.0
3.5
QUIESCENT CURRENT (mA)
3.0
2.5
2.0
1.5
1.0
0.5
0
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
3572 G04
SHDN
Pin Current vs Temperature
10
9
SHDN PIN CURRENT (μA)
8
7
6
5
4
3
2
1
0
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
3572 G05
SW Current Limit vs Temperature
1.6
1.4
PEAK CURRENT (A)
1.2
1.0
0.8
0.6
0.4
0.2
0
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
3572 G06
V
SHDN
= 5V
V
SHDN
= 2.5V
SW Saturation Voltage vs
Temperature
0.50
SWITCH SATURATION VOLTAGE (V)
0.45
0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
3572 G07
Start-Up
I
IN
200mA/DIV
I
SW
= 800mA
V
OUT
20V/DIV
V
OUTA
20V/DIV
I
SW
= 400mA
PGOOD
5V/DIV
200μs/DIV
3572 G08
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LT3572
PIN FUNCTIONS
SW (Pin 1):
Switch Node. This pin connects to the col-
lector of an internal NPN power switch.
V
IN
(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.
RT (Pin 4):
Frequency Set Pin. Place a resistor to GND
to set the internal frequency. The range of oscillation is
500kHz to 2.25MHz.
GND (Pins 5, 9, 20):
Ground.
PWMB (Pin 6):
Logic Input for the Driver. A high signal
on this input sets OUTB high and
OUTB
low.
PWMA (Pin 7):
Logic Input for the Driver. A high signal
on this input sets OUTA high and
OUTA
low.
V
OUT
(Pin 8):
Output for the Switching Regulator and the
Input Supply for the Drivers.
SHDN
(Pin 10):
Shutdown Pin. Tie to 1.5V or more to
enable the switcher. Pull low to disable the switcher.
SHDNA
(Pin 11):
Shutdown Pin. Tie to 1.5V or more to
enable OUTA and
OUTA.
Pull low to place OUTA and
OUTA
in a high impedance state.
SHDNB
(Pin 12):
Shutdown Pin. Tie to 1.5V or more to
enable OUTB and
OUTB.
Pull low to place OUTB and
OUTB
in a high impedance state.
FB (Pin 13):
Feedback Pin. The LT3572 regulates this pin
to 1.225V. Connect the feedback resistors to this pin to
set the output voltage for the switching regulator.
SS (Pin 14):
Soft-Start Pin. Place a soft-start capacitor
here. A capacitor on the soft-start pin slowly ramps the
current limit of the part from 0A to 1.3A.
PGOOD
(Pin 15):
This pin is an open-drain output that
pulls low when the FB pin is within 95% of its regulation
value.
OUTB
(Pin 16):
The Output Driver. This node switches
between V
OUT
and GND and is inverted from OUTB.
OUTB (Pin 17):
The Output Driver. This node switches
between V
OUT
and GND.
OUTA (Pin 18):
The Output Driver. This node switches
between V
OUT
and GND .
OUTA
(Pin 19):
The Output Driver. This node switches
between V
OUT
and GND and is inverted from OUTA.
Exposed Pad (Pin 21):
Ground. The Exposed Pad of the
package provides both electrical contact to ground and
good thermal contact to the printed circuit board. The
Exposed Pad must be soldered to the circuit board for
proper operation.
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