LTC3672B-2
Monolithic Fixed-Output
400mA Buck Regulator with Dual
150mA LDOs in 2mm
×
2mm DFN
FEATURES
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DESCRIPTION
The LTC
®
3672B-2 is a triple power supply composed of
a 400mA synchronous buck regulator and two 150mA
low-dropout linear regulators (LDOs). Constant-frequency
2.25MHz operation is maintained down to very light loads.
The input supply range of 2.9V to 5.5V is especially well-
suited for single-cell Lithium-Ion and Lithium-Polymer
applications, and for powering low voltage ASICs from
3.3V or 5V rails.
The LTC3672B-2 regulates 1.2V at the buck output, 2.8V
at the LDO1 output, and 1.8V at the LDO2 output. Exter-
nal component count is minimal—all that is needed is a
single inductor, an input capacitor, and output capacitors
for each of the three outputs. Control loop compensation
is internal to the LTC3672B-2.
The LTC3672B-2 is available in a 2mm
×
2mm
×
0.75mm
8-Lead DFN package.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
Triple Output Supply From a Single 2.9V to 5.5V Input
Buck DC/DC: Fixed 1.2V Output, Up to 400mA
LDO1: Fixed 2.8V Output, Up to 150mA
LDO2: Fixed 1.8V Output, Up to 150mA
±2.5% Reference Accuracy
Constant-Frequency 2.25MHz Operation
Minimum External Component Count
Current Mode Operation for Excellent Line and Load
Transient Response
Internal Soft-Start for Each Output
Single Enable Pin Turns On/Shuts Down All Three
Outputs
Tiny 2mm
×
2mm
×
0.75mm DFN Package
APPLICATIONS
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DMB and DVB-H Cellphones
Handheld Products (PDA, PMP GPS)
,
Multivoltage Power for Digital Logic, I/O, FPGAs,
CPLDs, ASICs, CPUs, and RF Chipsets
TYPICAL APPLICATION
V
IN
2.9V TO 5.5V
4.7μH
2.2μF
V
IN
V
IN1
SW
4.7μF
GND
ENABLE
INPUT
BUCKOUT
V
OUT2
2.8V, UP TO 150mA
(SUBJECT TO DROPOUT
LIMITATIONS)
V
OUT3
1.8V
150mA
Buck DC/DC Efficiency vs Buck Load
100
95
V
OUT1
1.2V
400mA
90
EFFICIENCY (%)
85
80
75
70
65
60
0
50
100 150 200 250 300 350 400
I
LOAD
(mA)
3672B2 TA01b
V
IN
= 2.9V
LTC3672B-2
ENALL
LDO1
1μF
V
IN
= 3.6V
V
IN
= 5.5V
LDO2
3672B2 TA01
1μF
3672b2fa
1
LTC3672B-2
ABSOLUTE MAXIMUM RATINGS
(Notes 1, 3)
PIN CONFIGURATION
TOP VIEW
SW 1
GND 2
ENALL 3
BUCKOUT 4
9
8 V
IN
7 LDO2
6 LDO1
5 V
IN1
V
IN
............................................................... –0.3V to 6V
V
IN1
, BUCKOUT, ENALL, SW,
LDO2 ..........–0.3V to the Lesser of (V
IN
+ 0.3V) or 6V
LDO1 ............ –0.3V to the Lesser of (V
IN1
+ 0.3V) or 6V
Junction Temperature ........................................... 125°C
Operating Temperature Range (Note 2)........ –40 to 85°C
Storage Temperature Range....................... –65 to 125°C
DC PACKAGE
8-LEAD (2mm 2mm) PLASTIC DFN
T
JMAX
= 125°C,
θ
JA
= 102°C/W,
θ
JC
= 20°C/W
EXPOSED PAD (PIN 9) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
LTC3672BEDC-2#PBF
TAPE AND REEL
LTC3672BEDC-2#TRPBF
PART MARKING
LDBH
PACKAGE DESCRIPTION
8-Lead (2mm
×
2mm) 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/
ELECTRICAL CHARACTERISTICS
SYMBOL
V
IN
V
UVLO
I
Q,VIN
PARAMETER
Input Voltage Range
V
IN
Undervoltage Lockout Threshold
Undervoltage Lockout Hysteresis
V
IN
Quiescent Current
All Outputs Enabled, No Load
Shutdown
V
IN1
Quiescent Current
All Outputs Enabled, No Load
Shutdown
ENALL Pin Logic Low Voltage
ENALL Pin Logic High Voltage
ENALL Pin Pulldown Resistance
Oscillator Frequency
Regulated Output Voltage
PMOS Switch Maximum Peak Current (Note 5)
Available Output Current
PMOS Switch On-Resistance
NMOS Switch On-Resistance
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= V
IN1
= 3.6V, unless otherwise noted.
CONDITIONS
l
MIN
2.9
TYP
1.7
12
MAX
5.5
2
100
400
1
5
1
0.4
UNITS
V
V
mV
μA
μA
μA
μA
V
V
MΩ
V
IN
Rising
(Note 4)
V
BUCKOUT
= 1.3V
V
ENALL
= 0V
260
I
Q,VIN1
2.3
V
ENALL
= 0V
l
l
V
IL
V
IH
R
ENALL
f
OSC
V
BUCKOUT
I
MAXP
I
OUT,BUCK
R
P,BUCK
R
N,BUCK
1.2
5.5
1.8
2.25
1.2
800
0.6
0.7
2.7
1.23
1100
Synchronous Buck Regulator
MHz
V
mA
mA
Ω
Ω
3672b2fa
l
1.17
550
400
2
LTC3672B-2
ELECTRICAL CHARACTERISTICS
SYMBOL
R
PD,BUCKOUT
R
PD,SW
t
SS,BUCK
V
LDO1
PARAMETER
SW Pulldown Resistance in Shutdown
Soft-Start Time
Regulated Output Voltage
Line Regulation with Respect to V
IN
Load Regulation
Available Output Current
Short-Circuit Output Current
V
DROP1
t
SS,LDO1
R
PD,LDO1
V
LDO2
Dropout Voltage (Note 6)
Soft-Start Time
Output Pulldown Resistance in Shutdown
Regulated Output Voltage
Line Regulation with Respect to V
IN
Load Regulation
Available Output Current
Short-Circuit Output Current
V
DROP2
t
SS,LDO2
R
PD,LDO2
Dropout Voltage (Note 6)
Soft-Start Time
Output Pulldown Resistance in Shutdown
I
LDO2
= 150mA
LDO2 Output, I
LDO2
= 1mA
I
LDO2
= 1mA, V
IN
= 2.9V to 5.5V
I
LDO2
= 1mA to 150mA
150
450
290
0.1
10
400
l
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= V
IN1
= 3.6V, unless otherwise noted.
CONDITIONS
V
ENALL
= 0V
MIN
TYP
10
10
0.2
LDO1 Output, I
LDO1
= 1mA
I
LDO1
= 1mA, V
IN
= V
IN1
= 2.9V to 5.5V
I
LDO1
= 1mA to 150mA
150
440
I
LDO1
= 150mA
135
0.1
10
1.755
1.8
0.6
–0.1
1.845
250
l
MAX
UNITS
kΩ
kΩ
ms
BUCKOUT Pulldown Resistance in Shutdown V
ENALL
= 0V
LDO Regulator 1
2.73
2.8
1
–0.1
2.87
V
mV/V
mV/mA
mA
mA
mV
ms
kΩ
V
mV/V
mV/mA
mA
mA
mV
ms
kΩ
LDO Regulator 2
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 LTC3672B-2 is guaranteed to meet performance specifications
from 0°C to 85°C. Specifications over the –40°C to 85°C operating
temperature range are assured by design, characterization and correlation
with statistical process controls.
Note 3:
This IC includes overtemperature protection that is intended
to protect the device during momentary overload conditions. Junction
temperature will exceed 125°C when overtemperature protection is active.
Continuous operation above the specified maximum operating junction
temperature may impair device reliability.
Note 4:
Dynamic supply current is higher due to the gate charge delivered
to the buck regulator’s internal MOSFET switches at the switching
frequency.
Note 5:
The current limit features of this part are intended to protect the
IC from short term or intermittent fault conditions. Continuous operation
above the specified maximum specified pin current rating may result in
device degradation or failure.
Note 6:
Dropout voltage is the minimum input to output voltage differential
needed to maintain regulation at a specified output current. When LDO1 is
in dropout, its output voltage will be equal to: V
IN1
– V
DROP1
. When LDO2
is in dropout, its output voltage will be equal to: V
IN
– V
DROP2
.
3672b2fa
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LTC3672B-2
TYPICAL PERFORMANCE CHARACTERISTICS
V
IN
Quiescent Current
vs V
IN
Voltage
500
SW PIN NOT SWITCHING
130°C
90°C
I
VIN
(μA)
25°C
I
VIN1
(μA)
300
3
130°C
5
T
A
= 25°C unless otherwise specified.
Buck Regulated Output
vs Temperature
1.23
BUCK REGULATED OUTPUT (V)
1.22
1.21
BUCK AT NO LOAD
1.20
1.19
1.18
1.17
–50 –25
BUCK AT 400mA LOAD
V
IN
= 3.6V
V
IN1
Quiescent Current
vs V
IN1
Voltage
V
IN
= V
IN1
400
4
90°C
200
–45°C
2
–45°C
25°C
1
100
0
2.5
3.0
3.5
4.0
V
IN
(V)
4.5
5.0
5.5
0
2.5
3.0
3.5
3672B2 G01
4.0
4.5
V
IN1
(V)
5.0
5.5
0
25 50 75 100 125 150
TEMPERATURE (°C)
3672B2 G03
3672B2 G02
LDO1 Regulated Output
vs Temperature
2.87
V = V
IN1
= 3.6V
2.86
IN
2.85
2.84
2.83
2.82
LDO1 AT NO LOAD
2.81
2.80
LDO1 AT 150mA LOAD
2.79
2.78
2.77
2.76
2.75
2.74
2.73
–50 –25 0
25 50 75 100 125 150
TEMPERATURE ( C)
3672B2 G04
LDO2 Regulated Output
vs Temperature
1.845
LDO2 REGULATED OUTPUT (V)
1.830
1.815
LDO2 AT NO LOAD
1.800
1.785
1.770
1.755
–50 –25
LDO2 AT 150mA LOAD
BUCK OUTPUT (V)
V
IN
= 3.6V
1.23
1.22
1.21
Buck Regulated Output
vs V
IN
Input Voltage
BOTH LDOs UNLOADED
LD01 REGULATED OUTPUT (V)
BUCK AT NO LOAD
1.20
1.19
1.18
1.17
2.5
BUCK AT 400mA LOAD
0
25 50 75 100 125 150
TEMPERATURE (°C)
3672B2 G05
3.0
3.5
4.0
4.5
5.0
V
IN
INPUT VOLTAGE (V)
5.5
3672B2 G06
LDO1 Regulated Output
vs V
IN1
Input Voltage
2.87
BUCK AND LDO2 UNLOADED
2.86
V
IN
= V
IN1
2.85
2.84
2.83
2.82
2.81
I
LDO1
= 0mA
2.80
2.79
I
LDO1
= 150mA
2.78
2.77
2.76
2.75
2.74
2.73
2.5
3.0
3.5
4.0
4.5
5.0
V
IN1
INPUT VOLTAGE (V)
1.85
1.84
1.83
LDO2 OUTPUT (V)
1.82
1.81
1.80
1.79
1.78
1.77
1.76
5.5
LDO2 Regulated Output Voltage
vs V
IN
Input Voltage
BUCK AND LDO1 UNLOADED
LDO1 OUTPUT (V)
I
LDO2
= 0mA
I
LDO2
= 150mA
1.75
2.5
3.0
3672b2 G07
3.5
4.0
4.5
5.0
V
IN
INPUT VOLTAGE (V)
5.5
3672B2 G08
3672b2fa
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LTC3672B-2
TYPICAL PERFORMANCE CHARACTERISTICS
V
IN1
– LDO1 Dropout Voltage
vs Load
200
V
IN
= V
IN1
DROPOUT VOLTAGE (mV)
350
300
DROPOUT VOLTAGE (mV)
150
25 C
100
–45 C
50
25 C
250
200
150
–45 C
100
50
0
0
25
50
75
100
LDO1 LOAD (mA)
125
150
0
0
25
50
75
100
LDO2 LOAD (mA)
125
150
90 C
90 C
LDO1 SHORT-CIRCUIT CURRENT (mA)
T
A
= 25°C unless otherwise specified.
V
IN
– LDO2 Dropout Voltage
vs Load
500
LDO1 Short-Circuit Current vs V
IN1
90 C
–45 C
25 C
300
400
200
100
V
IN
= V
IN1
0
2.5
3.0
3.5
4.0
4.5
V
IN1
(V)
5.0
5.5
3672B2 G09
3672B2 G10
3672B2 G11
LDO2 Short-Circuit Current vs V
IN
600
LDO2 SHORT CIRCUIT CURRENT (mA)
500
400
300
200
100
0
2.5
–45°C
25°C
90°C
3.0
3.5
4.0
V
IN
(V)
4.5
5.0
5.5
FREQUENCY (MHz)
2.6
2.5
2.4
2.3
2.2
2.1
Buck Oscillator Frequency
vs Temperature
V
IN
= 5.5V
V
IN
= 4.2V
V
IN
= 3.6V
V
IN
= 2.9V
2.0
1.9
–50 –30 –10 10 30 50 70 90 110 130
TEMPERATURE (°C)
3672B2 G13
3672B2 G12
PMOS Switch Maximum
Peak Current vs Temperature
PMOS SWITCH MAX PEAK CURRENT (mA)
1000
PMOS ON-RESISTANCE (mΩ)
900
800
900
700
600
500
400
300
200
100
Buck PMOS Switch On-Resistance
vs Temperature
130°C
90°C
25°C
–45°C
800
700
V
IN
= 2.9V
V
IN
= 3.6V
V
IN
= 5.5V
600
–50 –30 –10 10 30 50 70 90 110 130
TEMPERATURE (°C)
3672B2 G14
0
2.5
3.0
3.5
4.0
V
IN
(V)
4.5
5.0
5.5
3672B2 G15
3672b2fa
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