2.2MHz) monolithic buck switching regulator that accepts
input voltages up to 36V. A high efficiency 0.5Ω switch is
included on the device along with a boost diode and the
necessary oscillator, control, and logic circuitry. Current
mode topology is used for fast transient response and good
loop stability. A SYNC pin allows the user to synchronize the
part to an external clock, and to choose between Low Ripple
Burst Mode operation and standard PWM operation.
The Low Ripple Burst Mode maintains high efficiency at
low output currents while keeping output ripple below
15mV in typical applications. Shutdown reduces input
supply current to less than 1μA while a resistor and
capacitor on the RUN/SS pin provide a controlled output
voltage ramp (soft-start). A power good flag signals when
V
OUT
reaches 90% of the programmed output voltage.
Protection circuitry senses the current in the power switch
and external Schottky catch diode to protect the LT3682
against short-circuit conditions. Frequency foldback and
thermal shutdown provide additional protection.
The LT3682 is available in a 12-Pin 3mm
×
3mm DFN with
exposed pad for low thermal resistance.
L,
LT, LTC and LTM are registered trademarks of Linear Technology Corporation. Burst Mode
is a trademark of Linear Technology Corporation. All other trademarks are the property of their
respective owners.
n
n
n
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n
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n
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Wide Input Range:
Operation from 3.6V to 36V
Overvoltage Lockout Protects Circuits through
60V Transients
1A Output Current
Low Ripple Burst Mode
®
Operation
I
Q
= 75μA at 12V
IN
to 3.3V
OUT
Output Ripple < 15mV
P-P
Adjustable Switching Frequency: 250kHz to 2.2MHz
Short-Circuit Protected
Synchronizable Between 300kHz and 2.2MHz
0.8V Feedback Reference Voltage
Output Voltage 0.8V to 20V
Soft-Start Capability
Power Good Flag
Small 12-Pin Thermally Enhanced 3mm
×
3mm
DFN Package
APPLICATIONS
n
n
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n
n
Automotive Battery Regulation
Automotive Entertainment Systems
Industrial Supplies
Power for Portable Products
Distributed Supply Regulation
TYPICAL APPLICATION
5V Step-Down Converter
V
IN
6.9V TO 36V
TRANSIENT TO 60V
V
IN
ON OFF
2.2μF
16.2k
40.2k
470pF
RUN/SS
V
C
R
T
PG
SYNC
GND
PGND
LT3682
SW
DA
FB
102k
f = 800kHz
3682 TA01
Efficiency
V
OUT
5V
0.9A, V
IN
6.9V
1A, V
IN
12V
EFFICIENCY (%)
100
V
OUT
= 5V
90
V
OUT
= 3.3V
BD
BOOST
0.22μF
10μH
80
70
536k
10μF
60
V
IN
= 12V
L = 10µH
f = 800 kHz
0
0.2
0.4
0.6
LOAD CURRENT (A)
0.8
1
3682 TA01b
50
3682f
1
LT3682
ABSOLUTE MAXIMUM RATINGS
(Note 1)
PIN CONFIGURATION
TOP VIEW
V
C
FB
PG
GND
BD
BOOST
1
2
3
4
5
6
13
12
V
IN
11
SYNC
10
R
T
9
RUN/SS
8
SW
7 DA
V
IN
, RUN/SS Voltage (Note 2) …….……………. ....60V
BOOST Pin Voltage …………………………..…….50V
BOOST Pin Above SW Pin …………………..……..30V
FB, R
T
, V
C
Voltage ......................................................5V
SYNC …………………………….………….……. 20V
BD and PG Voltage ..…….………………..……….. 30V
Operating Junction Temperature Range (Notes 3 and 6)
LT3682E ……………….………….. .
−40°C
to 125°C
LT3682I …………………………….
−40°C
to 125°C
Storage Temperature Range …………..
−65°C
to 150°C
DD PACKAGE
12-LEAD (3mm 3mm) PLASTIC DFN
θ
JA
= 43°C/W
EXPOSED PAD (PIN 13) IS PGND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
LT3682EDD#PBF
LT3682IDD#PBF
TAPE AND REEL
LT3682EDD#TRPBF
LT3682IDD#TRPBF
PART MARKING*
LFDW
LFDW
PACKAGE DESCRIPTION
12-Lead (3mm
×
3mm) Plastic DFN
12-Lead (3mm
×
3mm) Plastic DFN
TEMPERATURE RANGE
–40°C to 125°C
–40°C to 125°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
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/
ELECTRICAL CHARACTERISTICS
PARAMETER
Minimum Operating Voltage
V
IN
Overvoltage Lockout
Quiescent Current from V
IN
The
l
denotes specifications which apply over the full operating temperature
range, otherwise specifications are at T
A
= 25°C, V
IN
= 10V, V
RUN
/SS = 10V, V
BD
= 3.3V unless otherwise noted. (Note 3)
CONDITIONS
V
BD
= 3.3V
V
BD
< 3.0V
V
RUN/SS
= 0.2V
V
RUN/SS
= 10V, V
BD
= 3.3V, Not Switching
V
RUN/SS
= 10V, V
BD
= 0V, Not Switching
V
RUN/SS
= 0.2V
V
RUN/SS
= 10V, V
BD
= 3.3V, Not Switching
V
RUN/SS
= 10V, V
BD
= 0V, Not Switching
l
l
l
l
MIN
TYP
3.4
3.4
MAX
3.6
4.3
41
0.5
60
160
0.5
100
5
3
808
812
80
0.005
UNITS
V
V
V
μA
μA
μA
μA
μA
μA
V
mV
mV
nA
%/V
μS
V/V
36
39
0.01
35
90
0.01
55
0
2.8
Quiescent Current from BD Pin
l
Minimum BD Pin Voltage
Feedback Voltage
FB Pin Bias Current (Note 4)
FB Voltage Line Regulation
Error Amp g
m
Error Amp Voltage Gain
FB Pin Voltage = 800mV
3.6V < V
IN
< 36V
I
VC
=
±1.5μA
l
l
792
780
800
800
5
0.001
430
1300
3682f
2
LT3682
ELECTRICAL CHARACTERISTICS
PARAMETER
V
C
Source Current
V
C
Sink Current
V
C
Pin to Switch Current Gain
V
C
Switching Threshold
V
C
Clamp Voltage
Switching Frequency
R
RT
= 8.06kΩ
R
RT
= 29.4kΩ
R
RT
= 158kΩ
l
The
l
denotes specifications which apply over the full operating temperature
range, otherwise specifications are at T
A
= 25°C, V
IN
= 10V, V
RUN
/SS = 10V, V
BD
= 3.3V unless otherwise noted. (Note 3)
CONDITIONS
MIN
TYP
50
50
1.25
0.5
1.98
0.9
225
1.45
1.18
1.25
V
SW
= 0V, V
IN
= 60V
I
BSD
= 50mA
V
SW
= 10V, V
BD
= 0
l
MAX
UNITS
μA
μA
A/V
0.6
2
2.2
1
250
130
1.7
1.4
460
1.6
0.01
720
0.1
1.7
10.5
12
0.7
2.42
1.1
275
210
2
1.66
1.95
1
850
1
2.5
17.5
20
0.2
V
V
MHz
MHz
kHz
ns
A
A
mV
A
μA
mV
μA
V
mA
μA
V
V
μA
μA
V
mV
mV
MHz
Minimum Switch Off-Time
Switch Current Limit (Note 7)
Switch V
CESAT
DA Pin Current to Stop OSC
Switch Leakage Current
Boost Schottky Diode Voltage Drop
Boost Schottky Diode Reverse Leakage
Minimum Boost Voltage (Note 5)
BOOST Pin Current
RUN/SS Pin Current
RUN/SS Input Voltage High
RUN/SS Input Voltage Low
PG Leakage Current
PG Sink Current
PG Threshold as % of V
FB
PG Threshold Hysteresis
SYNC Threshold Voltage
SYNC Input Frequency
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 the device
reliability and lifetime.
Note 2:
Absolute Maximum Voltage at V
IN
and RUN/SS pins is 60V for
nonrepetitive 1 second transients, and 36V for continuous operation.
Note 3:
The LT3682E is guaranteed to meet performance specifications from
0°C to 125°C junction temperature. Specifications over the
−40°C
to 125°C
operating junction temperature range are assured by design, characterization
and correlation with statistical process controls. The LT3682I is guaranteed
over the full
−40°C
to 125°C operating junction temperature range.
V
PG
= 5V
V
PG
= 0.4V
Measured at FB pin. FB Pin Voltage Rising
Measured at FB Pin
I
SW
= 0.5A
V
RUN/SS
= 10V
SYNC = 0V
SYNC = 3.3V or Clocked
I
SW
= 1A
2.5
0.1
l
1
92%
800
2.2
100
88%
300
0.3
1000
90%
12
550
Note 4:
Bias current flows out of the FB pin.
Note 5:
This is the minimum voltage across the boost capacitor needed to
guarantee full saturation of the switch.
Note 6:
This IC includes over-temperature protection that is intended
to protect the device during momentary overload conditions. Junction
temperature will exceed the maximum operating junction temperature
when over-temperature protection is active. Continuous operation above
the specified maximum operating junction temperature may impair device
reliability.
Note 7:
Current limit guaranteed by design and/or correlation to static test.
Slope compensation reduces current limit at higher duty cycles.
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