FEATURES
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LT3667
40V 400mA Step-Down
Switching Regulator with
Dual Fault Protected LDOs
DESCRIPTION
The
LT
®
3667
is a monolithic triple power supply composed
of a 400mA buck switching regulator and two 200mA low
dropout linear regulators (LDOs).
The buck regulator includes a high efficiency switch, a
boost diode, and the necessary oscillator, control and
logic circuitry. Current mode topology is used for fast
transient response and good loop stability. Low ripple
Burst Mode operation maintains high efficiency at low
output currents while keeping output ripple below 15mV
in a typical application.
Each LDO supplies 200mA of output current with a typical
dropout voltage of 340mV, and each LDO has an accurate
resistor programmable current limit.
Internal protection circuitry includes reverse-battery
protection, current limiting, thermal limiting and reverse
current protection.
The LT3667 is available in a thermally-enhanced 16-Lead
MSOP and a 24-Pin 3mm x 5mm QFN package with ex-
posed pad for low thermal resistance.
L,
LT, LTC, LTM, Burst Mode, Linear Technology and the Linear logo are registered trademarks
of Linear Technology Corporation. All other trademarks are the property of their respective
owners.
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Triple Output Supply from a Single Input Requires
Only One Inductor
I
Q
= 50μA at 12V
IN
to 5V, 3.3V and 2.5V with No Load
Buck Regulator:
Low Ripple (<15mV
P-P
) Burst Mode Operation
®
400mA Output with Internal Power Switch
4.3V to 40V Input Operation Range (60V Max)
Dual Low Dropout Linear Regulators
200mA Outputs with Programmable Current Limits
1.6V to 45V Input Range
Fault Protected to ±45V
Adjustable 250kHz to 2.2MHz Switching Frequency
Synchronizable Between 300kHz and 2.2MHz
Programmable Undervoltage Lockout
Power Good Indicators
Available in a Thermally-Enhanced 16-Lead MSOP
and 24-Lead (3mm
×
5mm) QFN Packages
APPLICATIONS
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Automotive Battery Regulation
Power for Portable Instrumentation
Industrial Supplies
Fault-Protected Sensor Supply
TYPICAL APPLICATION
V
IN
6V TO 40V
TRANSIENT
TO 60V
No-Load Supply Current
4.7µF
UVLO1 IN1
100
BOOST
SW
DA
FB1
LT3667
BD
IN2
IN3
OUT3
499k
FB2
158k
FB3
158k
3667 TA01a
0.22µF 22µH
931k
294k
22µF
90
SUPPLY CURRENT (µA)
5V
200mA
80
70
60
50
40
30
20
10
2.2µF
0
5
10
25
20
15
INPUT VOLTAGE (V)
30
35
ON OFF
EN
PG
RT
174k
22pF
2.5V
100mA
4.7µF
OUT2
340k
3.3V
100mA
EN2/ILIM2 GND EN3/ILIM3
3667 TA01b
3667fb
For more information
www.linear.com/LT3667
1
LT3667
ABSOLUTE MAXIMUM RATINGS
(Notes 1, 2)
FB2, FB3 Voltage .....................................................±45V
OUT2, OUT3 Voltage ...............................................±45V
IN2, IN3 (QFN) Voltage............................................±45V
OUT2 – IN2 Differential Voltage ..............................±45V
OUT3 – IN3/BD Differential Voltage (MSOP)...........±45V
OUT3 – IN3 Differential Voltage (QFN) ....................±45V
IN1, EN, UVLO1 (QFN) Voltage (Note 3) ....................60V
IN1 Reverse Voltage...............................................–0.3V
EN Pin Current .......................................................–1mA
IN3/BD (MSOP) Voltage ............................................30V
BD (QFN) Voltage ......................................................30V
BOOST Pin Voltage ...................................................50V
BOOST Pin Above SW Pin.........................................30V
RT Voltage ..................................................................2V
FB1 Voltage .................................................................6V
EN2/ILIM2, EN3/ILIM3 Voltage ...................................4V
PG Voltage ................................................................30V
PG1, PG2, PG3 Voltage (QFN) ...................................30V
SYNC Voltage (QFN) ...................................................6V
Operating Junction Temperature Range (Notes 4, 5)
E-, I-Grades ....................................... −40°C to 125°C
H-Grades ........................................... −40°C to 150°C
Storage Temperature Range .................. −65°C to 150°C
Lead Temperature (Soldering, 10 sec)
MSOP Package Only ......................................... 300°C
PIN CONFIGURATION
TOP VIEW
SW
DA
NC
24 23 22 21
TOP VIEW
SW
BOOST
EN
RT
IN3/BD
OUT3
FB3
FB1
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
DA
IN1
PG
EN3/ILIM3
EN2/ILIM2
IN2
OUT2
FB2
BOOST 1
SYNC 2
EN 3
RT 4
BD 5
IN3 6
OUT3 7
FB3 8
9 10 11 12
PG1
FB1
PG2
PG3
25
GND
20 IN1
19 UVLO1
18 PG
17 EN3/ILIM3
16 EN2/ILIM2
15 IN2
14 OUT2
13 FB2
NC
17
GND
MSE PACKAGE
16-LEAD PLASTIC MSOP
θ
JA
= 40°C/W
EXPOSED PAD (PIN 17) IS GND, MUST BE SOLDERED TO PCB
UDD PACKAGE
24-LEAD (3mm
×
5mm) PLASTIC QFN
θ
JA
= 46°C/W
EXPOSED PAD (PIN 25) IS GND, MUST BE SOLDERED TO PCB
2
3667fb
For more information
www.linear.com/LT3667
LT3667
ORDER INFORMATION
LEAD FREE FINISH
LT3667EMSE#PBF
LT3667IMSE#PBF
LT3667HMSE#PBF
LT3667EUDD#PBF
LT3667IUDD#PBF
LT3667HUDD#PBF
TAPE AND REEL
LT3667EMSE#TRPBF
LT3667IMSE#TRPBF
LT3667HMSE#TRPBF
LT3667EUDD#TRPBF
LT3667IUDD#TRPBF
LT3667HUDD#TRPBF
PART MARKING
3667
3667
3667
LGFH
LGFH
LGFH
PACKAGE DESCRIPTION
16-Lead Plastic MSOP
16-Lead Plastic MSOP
16-Lead Plastic MSOP
24-Lead (3mm
×
5mm) Plastic QFN
24-Lead (3mm
×
5mm) Plastic QFN
24-Lead (3mm
×
5mm) Plastic QFN
TEMPERATURE RANGE
–40°C to 125°C
–40°C to 125°C
–40°C to 150°C
–40°C to 125°C
–40°C to 125°C
–40°C to 150°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/
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN1
= 12V unless otherwise noted. (Note 4)
PARAMETER
V
IN1
Undervoltage Lockout (Note 6)
V
IN1
Overvoltage Lockout
V
IN2
Undervoltage Lockout (Note 6)
UVLO1 Threshold Voltage
UVLO1 Pin Hysteresis
UVLO1 Pin Current
Quiescent Current from IN1
Quiescent Current from IN2
Quiescent Current from IN1 + IN2
Quiescent Current from IN3
EN Pin Current
EN Input Threshold
Power Good Pins PG (MSOP), PG1, PG2, PG3 (QFN)
Leakage Current
Output Voltage Low
Threshold as % of V
FB
(FB1, FB2, FB3)
PG1 Threshold Hysteresis
PG2/PG3 Threshold Hysteresis
V
PG
= 5V, V
PG1/2/3
= 5V
I
PG
= 40µA, I
PG1/2/3
= 40µA
Pin Voltage Falling
Pin Voltage Rising
Measured at FB1 Pin
Measured at FB2/FB3 Pin
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ELECTRICAL CHARACTERISTICS
CONDITIONS
V
IN2
= 0V, V
IN3
= 0V
V
IN1
= 3.5V, V
IN3
= 0V
Pin Voltage Falling
V
UVLO1
= 1V
V
EN
= 0.3V
V
EN
= 12V, V
IN2
= 0V, Not Switching
V
EN
= 0.3V
V
EN
= 12V, V
IN1
= 0V, V
IN2
= 5V
V
EN
= 0.3V, V
IN2
= 5V
V
EN
= 12V, V
IN2
= 5V, Not Switching
V
EN
= 0.3V, V
IN3
= 5V
V
EN
= 12V, V
IN3
= 5V
V
EN
= 12V
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MIN
40
0.95
TYP
4
42
4
1
75
1
0.01
13
0.01
38
0.01
40
0.01
25
0.6
MAX
4.3
44
4.3
1.05
30
1
30
1
80
1
90
1
60
2
1.1
UNITS
V
V
V
V
mV
nA
µA
µA
µA
µA
µA
µA
µA
µA
µA
V
µA
V
%
%
mV
mV
0.3
0.1
0.2
88
108
90
110
30
20
1
0.3
92
112
3667fb
For more information
www.linear.com/LT3667
3
LT3667
ELECTRICAL CHARACTERISTICS
PARAMETER
Switching Regulator
Switching Frequency
R
T
= 37.4k
R
T
= 102k
R
T
= 487k
5% Duty Cycle, V
IN
= 5V, V
FB1
= 0V
90% Duty Cycle, V
IN
= 5V, V
FB1
= 0V
I
SW
= 200mA
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The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN1
= 12V unless otherwise noted. (Note 4)
CONDITIONS
MIN
1.8
0.8
220
600
450
420
TYP
2.0
0.94
243
120
750
550
300
500
0.05
900
0.04
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MAX
2.1
1.1
275
170
950
750
650
2
4
2.5
16
1.212
1.224
20
0.005
0.5
2.2
UNITS
MHz
MHz
kHz
ns
mA
mA
mV
mA
µA
mV
µA
V
mA
V
mV
nA
%/V
V
V
MHz
V
mV
mV
mV
%/V
mV
mV
mV
mV
mV
mV
mV
mV
µA
mA
mA
µA
µA
µA
nA
nA
dB
Minimum Switch Off-Time
Switch Current Limit (Note 7)
Switch V
CESAT
DA Pin Current to Stop Switching
Switch Leakage Current
Boost Schottky Diode Forward Voltage
Boost Schottky Diode Reverse Leakage
Minimum Boost Voltage (Note 8)
BOOST Pin Current
Feedback Voltage (FB1)
I
SW
= 200mA, V
BOOST
= 15V
V
SW
= 0V
I
BOOSTDIODE
= 50mA, V
IN
= NC, V
BOOST
= 0V
V
REVERSE
= 12V, V
IN
= NC
1.7
10
1.188
1.176
1.2
1.2
0.1
0.001
1.2
0.3
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FB1 Pin Bias Current
Reference Voltage Line Regulation
SYNC High Level Input Voltage
SYNC Low Level Input Voltage
SYNC Input Frequency
Each LDO Regulator
Minimum Input Voltage
Feedback Voltage (FB2/FB3)
Load Regulation (Note 12)
Reference Voltage Line Regulation (Note 12)
Dropout Voltage (Notes 9, 10), V
IN
= V
OUT(NOMINAL)
Pin Voltage = 1.2V
4.2V < V
IN1
< 40V
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I
LOAD
= 200mA
V
IN
= 2.2V, I
LOAD
= 1mA
2.2V < V
IN
< 15V, 1mA < I
LOAD
< 200mA
V
IN
= 2.2V, I
LOAD
= 1mA to 200mA
2.2V < V
IN2,3
< 45V
I
LOAD
= 1mA
I
LOAD
= 1mA
I
LOAD
= 50mA
I
LOAD
= 50mA
I
LOAD
= 100mA
I
LOAD
= 100mA
I
LOAD
= 200mA
I
LOAD
= 200mA
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1.6
792
784
800
0.2
0.005
70
2.2
808
816
5
0.01
165
210
300
400
400
450
650
750
90
2
10
20
1
2
±40
±40
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230
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280
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340
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GND Pin Current, V
IN
= V
OUT(NOMINAL)
+ 0.6V
(Notes 10, 11)
I
LOAD
= 0mA
I
LOAD
= 50mA
I
LOAD
= 200mA
40
1
5
13
0.2
1.2
Quiescent Current I
IN2
with LDO2 Disabled
V
IN1
= 0V, V
IN2
= 12V, V
EN2/ILIM2
= 2V
Quiescent Current I
IN3
with LDO3 Disabled (QFN)
V
IN1
= 16V, V
IN3
= 12V, V
EN3/ILIM3
= 2V
Quiescent Current I
IN3/BD
with LDO3 Disabled (MSOP) V
IN1
= 16V, V
IN3/BD
= 12V, V
EN3/ILIM3
= 2V
FB2 Pin Bias Current (Note 12)
FB3 Pin Bias Current (Note 12)
Ripple Rejection (Note 12)
V
IN2
= 12V
V
IN3
= 12V
V
IN
– V
OUT
= 2V (Avg), V
RIPPLE
= 0.5V
P-P
,
f
RIPPLE
= 120Hz, I
LOAD
=200mA
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–3
60
85
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3667fb
For more information
www.linear.com/LT3667
LT3667
ELECTRICAL CHARACTERISTICS
PARAMETER
Reverse Output Current (Note 13)
Input Reverse Leakage Current LDO2
Input Reverse Leakage Current LDO3 (QFN)
Internal Current Limit (Note 12)
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN1
= 12V unless otherwise noted. (Note 4)
CONDITIONS
V
OUT2
= 1.2V, V
IN1
= V
IN2
= V
IN3
= 0V
V
OUT3
= 1.2V, V
IN1
= V
IN2
= V
IN3
= 0V
V
IN2
= –45V, V
IN1
= V
IN3
= V
OUT2
= 0V
V
IN3
= –45V, V
IN1
= V
IN2
= V
OUT3
= 0V
V
IN2
= 2.2V, V
OUT2
= 0V, EN2/ILIM2 Pin Grounded
∆V
OUT2
= –5%
V
IN3
= 2.2V, V
OUT3
= 0V, EN3/ILIM3 Pin Grounded
∆V
OUT3
= –5%
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MIN
TYP
5
5
MAX
40
40
300
300
UNITS
µA
µA
µA
µA
mA
mA
mA
mA
300
220
300
220
9.5
47
48.45
176
0.9
10
51
51
197
1
10.5
55
53.55
230
1.2
Externally Programmed Current Limit
R
EN/ILIM
= 31.6k, V
OUT2/3
= 5V, V
IN2/3
≥ 5.6V
R
EN/ILIM
= 6.19k, V
OUT2/3
= 5V, V
IN2/3
≥ 5.6V
R
EN/ILIM
= 6.19k, V
OUT2/3
= 5V, 5.6V ≤ V
IN2/3
≤ 15V
R
EN/ILIM
= 1.54k, V
OUT2/3
= 5V, 5.6V ≤ V
IN2/3
≤ 15V
V
EN/ILIM
Rising
mA
mA
mA
mA
V
LDO Disable Threshold
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:
Positive currents flow into pins, negative currents flow out of pins.
Minimum and maximum values refer to absolute values.
Note 3:
Absolute maximum voltage at the IN1, UVLO1 and EN pins is 60V
for nonrepetitive 1 second transients, and 40V for continuous operation.
Note 4:
The LT3667E 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
LT3667I is guaranteed over the full −40°C to 125°C operating junction
temperature range. The LT3667H is guaranteed over the full −40°C to
150°C operating junction temperature range.
Note 5:
This IC includes overtemperature protection that is intended
to protect the device during momentary overload conditions. Junction
temperature will exceed the maximum operating junction temperature
when overtemperature protection is active. Continuous operation above
the specified maximum operating junction temperature may impair device
reliability.
Note 6:
This is the voltage necessary to keep the internal bias circuitry in
regulation.
Note 7:
Current limit guaranteed by design and/or correlation to static test.
Slope compensation reduces current limit at higher duty cycles.
Note 8:
This is the minimum voltage across the boost capacitor needed to
guarantee full saturation of the switch.
Note 9:
Dropout voltage is the minimum input-to-output voltage
differential needed for an LDO to maintain regulation at a specified output
current. When an LDO is in dropout, its output voltage will be equal to
V
IN
– V
DROP
.
Note 10:
To satisfy minimum input voltage requirements, the LT3667 is
tested and specified for these conditions with an external resistor divider
(80.6k bottom, 422k top) which sets V
OUT
to 5V. The external resistor
divider adds 9.93μA of DC load on the output. This external current is not
factored into GND pin current.
Note 11:
GND pin current is tested with V
IN
= V
OUT(NOMINAL)
+ 0.6V and a
current source load. GND pin current increases in dropout.
Note 12:
The LT3667 is tested and specified for these conditions with FB2
(FB3) pin connected to the OUT2 (OUT3) pin.
Note 13:
Reverse output current is tested with the IN2 (IN3) pin grounded
and the OUT2 (OUT3) pin forced to the rated output voltage. This current
flows into the OUT2 (OUT3) pin and out of the GND pin.
3667fb
For more information
www.linear.com/LT3667
5
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