LT3048 Series - Low Noise Bias Generator in 2mm × 2mm DFN

LT3048 Series
Low Noise Bias Generator
in 2mm × 2mm DFN
FEATURES
DESCRIPTION
Generates Low Noise Bias Voltage from Single
Cell Li-Ion Battery
nn Output Current: Up to 40mA
nn Low Output Ripple and Noise: <500µV
P-P
nn Boost Regulator
nn 1MHz Operation (LT3048)
nn 2.2MHz Operation (LT3048-XX)
nn Integrated Schottky Diode
nn Low Dropout Linear Regulator
nn 1.235V Feedback Voltage (LT3048)
nn Low Noise: <120µV
RMS (10Hz to 100kHz)
nn 0.1% Load Regulation
nn Fixed 3.3V, 5V, 12V, 15V and Adjustable Output Options
nn Short-Circuit and Thermal Protection
nn Load Disconnect in Shutdown
nn Available in 2mm × 2mm DFN Package
The LT®3048 series generate low noise, low ripple bias
supplies from input voltages of 2.7V to 4.8V.
nn
The LT3048 includes a boost regulator and a LDO linear
regulator. The boost regulator provides power to the
linear regulator.
The boost regulator output voltage is regulated to 1.1V
above the LDO output, optimizing LDO ripple rejection and
transient response. Fixed frequency operation and current
mode control allow the use of very small inductors and
results in low, predictable output ripple.
The linear regulator in the LT3048 generates a programmable output and the LT3048-XX generate fixed output
voltages. High power supply ripple rejection combined
with a low noise internal reference results in less than
500µVP-P output ripple and noise.
The LT3048 is available in a 8-lead 2mm × 2mm DFN
package.
APPLICATIONS
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
Sensor Bias
nn Op Amp Supply
nn
TYPICAL APPLICATION
Efficiency
10µH
SW
1µF
VIN
70
4.7µF
BSTOUT
60
LDOIN
LT3048-15
LDOOUT
OFF ON
BYP
EN
GND
3048 TA01a
1nF
1µF
OUT
15V
VIN (V) IOUT (mA)
2.7
19
3.3
22
3.6
24
EFFICIENCY (%)
IN
2.7V TO 4.8V
80
50
40
30
LDOOUT = 15V
L = 10µH
DCR = 650mΩ
VIN = 2.7V
VIN = 3.3V
VIN = 3.6V
20
10
0
0
5
10
20
15
LOAD CURRENT (mA)
25
3048 TA01b
3048fa
For more information www.linear.com/LT3048
1
LT3048 Series
ABSOLUTE MAXIMUM RATINGS
(Note 1)
VIN...............................................................................6V
SW.............................................................................25V
BSTOUT.....................................................................23V
LDOIN........................................................................22V
LDOOUT.....................................................................22V
FB................................................................................6V
BYP.........................................................................±0.3V
EN................................................................................6V
Operating Junction Temperature Range (Note 2)
E-Grade............................................... –40°C to 125°C
I-Grade............................................... –40°C to 125°C
Maximum Junction Temperature........................... 125°C
Storage Temperature Range................... –65°C to 150°C
PIN CONFIGURATION
LT3048-XX
LT3048
TOP VIEW
TOP VIEW
SW 1
8 BSTOUT
SW 1
VIN 2
7 EN
VIN 2
GND 3
BYP 4
9
GND
6 LDOIN
GND 3
5 LDOOUT
BYP 4
DC PACKAGE
8-LEAD (2mm × 2mm) PLASTIC DFN
8 BSTOUT
9
GND
7 EN
6 LDOOUT
5 FB
DC PACKAGE
8-LEAD (2mm × 2mm) PLASTIC DFN
θJA = 102°C/W
EXPOSED PAD (PIN 9) IS GND, MUST BE SOLDERED TO PCB
θJA = 102°C/W
EXPOSED PAD (PIN 9) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
TAPE AND REEL
PART MARKING
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LT3048EDC#PBF
LT3048EDC#TRPBF
LGRR
8-Lead (2mm × 2mm) Plastic DFN
–40°C to 125°C
LT3048IDC#PBF
LT3048IDC#TRPBF
LGRR
8-Lead (2mm × 2mm) Plastic DFN
–40°C to 125°C
LT3048EDC-15#PBF
LT3048EDC-15#TRPBF
LGKK
8-Lead (2mm × 2mm) Plastic DFN
–40°C to 125°C
LT3048IDC-15#PBF
LT3048IDC-15#TRPBF
LGKK
8-Lead (2mm × 2mm) Plastic DFN
–40°C to 125°C
LT3048EDC-12#PBF
LT3048EDC-12#TRPBF
LGQQ
8-Lead (2mm × 2mm) Plastic DFN
–40°C to 125°C
LT3048IDC-12#PBF
LT3048IDC-12#TRPBF
LGQQ
8-Lead (2mm × 2mm) Plastic DFN
–40°C to 125°C
LT3048EDC-5#PBF
LT3048EDC-5#TRPBF
LGQR
8-Lead (2mm × 2mm) Plastic DFN
–40°C to 125°C
LT3048IDC-5#PBF
LT3048IDC-5#TRPBF
LGQR
8-Lead (2mm × 2mm) Plastic DFN
–40°C to 125°C
LT3048EDC-3.3#PBF
LT3048EDC-3.3#TRPBF
LGQS
8-Lead (2mm × 2mm) Plastic DFN
–40°C to 125°C
LT3048IDC-3.3t#PBF
LT3048IDC-3.3#TRPBF
LGQS
8-Lead (2mm × 2mm) Plastic DFN
–40°C to 125°C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
Consult LTC Marketing for information on nonstandard 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/
2
3048fa
For more information www.linear.com/LT3048
LT3048 Series
ELECTRICAL CHARACTERISTICS
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VIN = 3.6V, EN/UVLO = 3V, unless otherwise noted. Parameter applies
to all options unless specified.
PARAMETER
CONDITIONS
MIN
VIN Operating Range
TYP
2.7
MAX
4.8
UNITS
V
Boost Regulator
BSTOUT-LDOOUT Regulation Voltage
l
1
1.1
1.2
V
BSTOUT-VIN Regulation Voltage
LDOOUT < VIN
1.1
V
VIN Quiescent Current
Not Switching
EN ≤ 0.4V
475
0.1
600
1
µA
µA
Switching Frequency
LT3048
l
0.75
0.7
1.00
1.00
1.25
1.30
MHz
MHz
l
1.7
1.6
2.2
2.2
2.7
2.8
MHz
MHz
LT3048-XX
Maximum Duty Cycle
LT3048
LT3048-XX
93
86
95
90
Switch Current Limit
(Note 3)
300
400
Switch VCESAT
ISW = 200mA
Diode Forward Drop
IDIODE = 100mA
EN Voltage High
%
%
500
mA
220
mV
0.84
V
1.25
V
EN Voltage Low
0.4
V
µA
LDO Linear Regulator
LDO Quiescent Current
LT3048: Supplied by LDOIN
14
20
LT3048-XX: Supplied by BSTOUT
14
20
FB Pin Current
FB Regulation Voltage
60
LT3048: ILOAD = 100µA, FB = LDOOUT
LT3048: 100µA ≤ ILOAD ≤ 40mA
l
1.216
1.210
µA
nA
1.235
1.235
1.254
1.260
2
6
V
V
FB Load Regulation
LT3048: ∆ILOAD = 100µA to 40mA
LDOOUT Regulation Voltage
LT3048-15: ILOAD = 100µA
LT3048-15: 100µA ≤ ILOAD ≤ 40mA
l
14.775
14.625
15.00
15.00
15.225
15.375
V
V
LT3048-12: ILOAD = 100µA
LT3048-12: 100µA ≤ ILOAD ≤ 40mA
l
11.82
11.70
12.00
12.00
12.18
12.30
V
V
LT3048-5: ILOAD = 100µA
LT3048-5: 100µA ≤ ILOAD ≤ 40mA
l
4.925
4.875
5.00
5.00
5.075
5.125
V
V
LT3048-3.3: ILOAD = 100µA
LT3048-3.3: 100µA ≤ ILOAD ≤ 40mA
l
3.250
3.217
3.300
3.300
3.350
3.383
V
V
LT3048-15: ∆ILOAD = 100µA to 40mA
20
45
mV
LT3048-12: ∆ILOAD = 100µA to 40mA
20
45
mV
LT3048-5: ∆ILOAD = 100µA to 40mA
12
25
mV
LT3048-3.3: ∆ILOAD = 100µA to 40mA
9
18
mV
LDOOUT Load Regulation
mV
3048fa
For more information www.linear.com/LT3048
3
LT3048 Series
ELECTRICAL CHARACTERISTICS
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VIN = 3.6V, EN/UVLO = 3V, unless otherwise noted. Parameter applies
to all options unless specified.
PARAMETER
CONDITIONS
LDOOUT Voltage Noise
BW = 10Hz to 100kHz
COUT = 1µF
LT3048: CBYP = 0nF, ILOAD = 40mA, LDOOUT = 1.235V
LT3048: CBYP = 1nF, ILOAD = 40mA, LDOOUT = 1.235V
38
25
µVRMS
µVRMS
LT3048-15: CBYP = 0nF, ILOAD = 24mA
LT3048-15: CBYP = 1nF, ILOAD = 24mA
250
60
µVRMS
µVRMS
LT3048-12: CBYP = 0nF, ILOAD = 31mA
LT3048-12: CBYP = 1nF, ILOAD = 31mA
225
60
µVRMS
µVRMS
LT3048-5: CBYP = 0nF, ILOAD = 40mA
LT3048:-5: CBYP = 1nF, ILOAD = 40mA
145
50
µVRMS
µVRMS
LT3048-3.3: CBYP = 0nF, ILOAD = 40mA
LT3048-3.3: CBYP = 1nF, ILOAD = 40mA
120
42
µVRMS
µVRMS
LT3048: fRIPPLE = 1.0MHz, ILOAD = 40mA
LT3048: fRIPPLE = 2.2MHz, ILOAD = 40mA
60
53
dB
dB
80
mA
Ripple Rejection
MIN
Current Limit
l
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 LT3048E 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
4
45
TYP
MAX
UNITS
LT3048I is guaranteed over the full –40°C to 125°C operating junction
temperature range. High junction temperatures degrade operating
lifetimes. Operating lifetime is derated at junction temperatures greater
than 125°C.
Note 3: Current limit guaranteed by design and/or correlation to static test.
Slope compensation reduces current limit at higher duty cycle.
3048fa
For more information www.linear.com/LT3048
LT3048 Series
TYPICAL PERFORMANCE CHARACTERISTICS
LT3048 FB Load Regulation
1.255
1.255
1.250
1.250
1.245
1.245
LT3048 Switching Frequency
1.3
FB VOLTAGE (V)
FB VOLTAGE (V)
1.260
SWITCHING FREQUENCY (MHz)
LT3048 FB Voltage
1.260
1.240
1.240
1.235
1.235
1.230
1.230
1.225
1.225
1.220
1.220
1.215
1.215
1.210
–50
–25
0
50
25
75
TEMPERATURE (°C)
100
1.210
125
0
5
10 15 20 25 30
LOAD CURRENT (mA)
35
LT3048 LDOOUT Noise
VIN = 3.6V
VOUT = 1.235V
L = 5.6μH
CBSTOUT = 4.7μF
CLDOOUT = 1μF
CBYP = 1nF
ILOAD = 40mA
50
40
30
LDOOUT = 15V
L = 10µH
DCR = 650mΩ
VIN = 2.7V
VIN = 3.3V
VIN = 3.6V
10
0
1M
3048 G04
LT3048-15 LDOOUT Voltage
0
5
10
20
15
LOAD CURRENT (mA)
15.0
14.9
14.8
14.7
25
0
5
10 15 20 25 30
LOAD CURRENT (mA)
14.9
14.8
14.7
–50
–25
0
25
50
75
TEMPERATURE (°C)
100
125
3048 G07
60
–50
50
–100
40
30
–150
–200
ILOAD
20
10
–250
–300
VIN = 3.6V
10µs/DIV
VOUT = 15V
L = 10µH
CLDOOUT = 1µF
CBYP = 1nF
ILOAD = 4mA TO 20mA
10000
3048 G08
For more information www.linear.com/LT3048
0
NOISE SPECTRAL DENSITY (nV/√Hz)
OUTPUT VOLTAGE DEVIATION (mV)
LDOOUT VOLTAGE (V)
15.0
VOUT
40
LT3048-15 LDOOUT Noise
70
LOAD CURRENT (mA)
15.1
0
35
3048 G06
LT3048-15 Transient Response
50
15.2
125
15.1
3048 G05
15.3
100
15.2
20
100k
0
50
25
75
TEMPERATURE (°C)
15.3
LDOOUT VOLTAGE (V)
EFFICIENCY (%)
NOISE SPECTRAL DENSITY (nV/√Hz)
10
1k
10k
FREQUENCY (Hz)
–25
LT3048-15 LDOOUT Load
Regulation
60
100
0.8
3048 G03
70
10
0.9
0.7
–50
40
80
100
0.01
1.0
LT3048-15 Efficiency
1000
0.1
1.1
3048 G02
3048 G01
1
1.2
1000
100
VIN = 3.6V
VOUT = 15V
L = 10μH
CBSTOUT = 4.7μF
CLDOOUT = 1μF
CBYP = 1nF
ILOAD = 24mA
10
1
0.1
10
100
1k
10k
FREQUENCY (Hz)
100k
1M
3048 G09
3048fa
5
LT3048 Series
TYPICAL PERFORMANCE CHARACTERISTICS
Operating Waveforms: DCM
LT3048-12 Efficiency
Operating Waveforms: CCM
80
70
VSW
5V/DIV
VSW
5V/DIV
EFFICIENCY (%)
IL
100mA/DIV
60
IL
100mA/DIV
50
40
30
VOUT = 12V
L = 10µH
DCR = 650mΩ
VIN = 2.7V
VIN = 3.3V
VIN = 3.6V
20
10
3048 G10
500ns/DIV
VIN = 3.6V
VOUT = 15V
L = 10µH
ILOAD = 20mA
12.3
12.2
12.2
12.1
12.0
12.9
12.7
0
5
10 15 20 25 30
LOAD CURRENT (mA)
35
12.0
11.9
–25
0
50
25
75
TEMPERATURE (°C)
3048 G13
LDOOUT VOLTAGE (V)
EFFICIENCY (%)
40
VOUT = 5V
L = 4.7µH
DCR = 350mΩ
VIN = 2.7V
VIN = 3.3V
VIN = 3.6V
20
10
0
0
5
10
15 20 25 30
LOAD CURRENT (mA)
35
1
10
100
1k
10k
FREQUENCY (Hz)
100k
LT3048-5 LDOOUT Voltage
5.125
5.100
5.100
5.075
5.075
5.050
5.025
5.000
4.975
4.950
5.050
5.025
5.0
4.975
4.950
4.925
4.925
4.900
4.900
0
5
10 15 20 25 30
LOAD CURRENT (mA)
1M
3048 G15
5.125
4.875
40
VIN = 3.6V
VOUT = 12V
L = 10μH
CBSTOUT = 4.7μF
CLDOOUT = 1μF
CBYP = 1nF
ILOAD = 31mA
10
0.1
125
LDOOUT VOLTAGE (V)
60
30
100
100
LT3048-5 LDOOUT
Load Regulation
70
30
1000
3048 G14
LT3048-5 Efficiency
50
25
LT3048-12 LDOOUT Noise
12.1
11.7
–50
40
10
20
15
LOAD CURRENT (mA)
10000
11.0
12.8
5
0
3048 G12
LT3048-12 LDOOUT Voltage
12.3
LDOOUT VOLTAGE (V)
LDOOUT VOLTAGE (V)
LT3048-12 LDOOUT
Load Regulation
0
3048 G11
500ns/DIV
NOISE SPECTRAL DENSITY (nV/√Hz)
VIN = 3.6V
VOUT = 15V
L = 2.2µH
ILOAD = 15mA
35
40
3048 G17
4.875
–50
–25
0
50
25
75
TEMPERATURE (°C)
100
125
3048 G18
3048 G16
6
3048fa
For more information www.linear.com/LT3048
LT3048 Series
TYPICAL PERFORMANCE CHARACTERISTICS
LT3048-5 LDOOUT Noise
3.38
60
3.36
100
VIN = 3.6V
VOUT = 5V
L = 4.7μH
CBSTOUT = 2.2μF
CLDOOUT = 1μF
CBYP = 1nF
ILOAD = 40mA
10
1
10
100
1k
10k
FREQUENCY (Hz)
40
30
VOUT = 3.3V
L = 3.3µH
DCR = 285mΩ
VIN = 2.7V
VIN = 3.3V
VIN = 3.6V
20
10
100k
0
1M
LDOOUT VOLTAGE (V)
50
1000
EFFICIENCY (%)
NOISE SPECTRAL DENSITY (nV/√Hz)
10000
0.1
LT3048-3.3 LDOOUT
Load Regulation
LT3048-3.3 Efficiency
0
5
10
15 20 25 30
LOAD CURRENT (mA)
3048 G19
35
3.34
3.32
3.30
3.28
3.26
3.24
3.22
40
0
5
10 15 20 25 30
LOAD CURRENT (mA)
35
40
3048 G21
3048 G20
LT3048-3.3 LDOOUT Voltage
LT3048-3.3 LDOOUT Noise
NOISE SPECTRAL DENSITY (nV/√Hz)
3.36
LDOOUT VOLTAGE (V)
LDOOUT Current Limit
90
10000
3.34
3.32
3.30
3.28
3.26
3.24
3.22
–50
–25
25
75
0
50
TEMPERATURE (°C)
100
80
1000
100
VIN = 3.6V
VOUT = 3.3V
L = 3.3μH
CBSTOUT = 2.2μF
CLDOOUT = 1μF
CBYP = 1nF
ILOAD = 40mA
10
1
0.1
125
70
CURRENT LIMIT (mA)
3.38
10
100
1k
10k
FREQUENCY (Hz)
60
50
40
30
20
10
100k
3048 G22
0
–50
1M
0
25
50
75
TEMPERATURE (°C)
–25
3048 G23
125
100
3048 G24
Boost Switch Current Limit
500
450
450
400
400
350
300
250
200
150
100
2.0
350
300
250
200
150
100
1.5
1.0
0.5
50
50
0
LT3048-XX Switching Frequency
2.5
FREQUENCY (MHz)
SWITCH CURRENT LIMIT (mA)
SWITCH CURRENT LIMIT (mA)
Boost Switch Current Limit
500
0
20
60
40
DUTY CYCLE (%)
80
100
3048 G25
0
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
3048 G26
0
–50 –25
0
25 50
75 100 125 150
TEMPERATURE (°C)
3048 G27
3048fa
For more information www.linear.com/LT3048
7
LT3048 Series
PIN FUNCTIONS
LT3048
LT3048-XX
SW (Pin 1): Boost Regulator Switch Node. This is the
collector of the internal power transistor and the anode
of the internal Schottky diode.
SW (Pin 1): Boost Regulator Switch Node. This is the
collector of the internal power transistor and the anode
of the internal Schottky diode.
VIN (Pin 2): Input Supply. Provides operating current to
the boost regulator. Bypass to ground.
VIN (Pin 2): Input Supply. Provides operating current to
the boost regulator. Bypass to ground.
GND (Pin 3): Ground. This pin must be soldered to PCB
ground. The exposed pad must also be soldered to PCB
ground.
GND (Pin 3): Ground. This pin must be soldered to PCB
ground. The exposed pad must also be soldered to PCB
ground.
BYP (Pin 4): Bypass. Add an optional capacitor from
LDOOUT to BYP to reduce noise at LDOOUT; otherwise
leave BYP unconnected. A capacitor also soft-starts the
linear regulator.
BYP (Pin 4): Bypass. Add an optional capacitor from
LDOOUT to BYP to reduce noise at LDOOUT; otherwise
leave BYP unconnected. A capacitor also soft-starts the
linear regulator.
FB (Pin 5): The LT3048 regulates the FB pin to 1.25V.
Connect the feedback resistor divider tap to this pin.
LDOOUT (Pin 5): LDO Linear Regulator Output. This pin
is regulated to a fixed voltage. Bypass to ground with a
minimum of 1μF.
LDOOUT (Pin 6): LDO Linear Regulator Output. This pin
is programmed by the feedback resistor divider. Bypass
to ground with a minimum of 1μF.
LDOIN (Pin 6): LDO Linear Regulator Input. Normally
connected to BSTOUT. Bypass to ground.
EN (Pin 7): Enable. Logic input to enable the boost and
linear regulator.
EN (Pin 7): Enable. Logic input to enable the boost and
linear regulator.
BSTOUT (Pin 8): Boost Regulator Output. This pin is connected to the internal Schottky diode and is regulated to
1.1V above LDOOUT. Bypass to ground.
BSTOUT (Pin 8): Boost Regulator Output. This pin is connected to the internal Schottky diode and is regulated to
1.1V above LDOOUT. Bypass to ground.
GND (Exposed Pad Pin 9): The internal boost power switch
is connected to the exposed pad. Tie to ground.
GND (Exposed Pad Pin 9): The internal boost power switch
is connected to the exposed pad. Tie to ground.
8
3048fa
For more information www.linear.com/LT3048
LT3048 Series
LT3048 BLOCK DIAGRAMS
L1
IN
C2
C1
2
1
VIN
8
BSTOUT
SW
Q2
+
1.1V
LDOOUT
OUT
6
ON OFF 7
EN
C4
OSC
C3
Q1
– + +
BYP
R1
4
A1
FB
5
R2
VC
+
1.235V
GND
3, 9
3048 F01a
Figure 1a. LT3048 Block Diagram
L1
IN
C2
C1
2
1
VIN
8
6
BSTOUT
SW
LDOIN
Q2
+
1.1V
LDOOUT
OUT
5
ON OFF 7
EN
C4
OSC
C3
Q1
– + +
BYP
4
A1
VC
+
GND
3, 9
3048 F01b
Figure 1b. LT3048-XX Block Diagram
3048fa
For more information www.linear.com/LT3048
9
LT3048 Series
OPERATION
The LT3048 combines a boost regulator with a low dropout linear regulator to produce a programmable output
from a lower input voltage. The LT3048-15, LT3048-12,
LT3048-5, LT3048-3.3 regulate to 15V, 12V, 5V and 3.3V,
respectively. With EN below 0.4V, all circuits are turned
off, Q2 disconnects the load from the input, and current
consumption is less than 1µA. Driving EN high enables the
oscillator and all bias circuits including voltage reference
and regulation amplifiers.
The boost regulator uses peak current mode operation,
providing cycle-by-cycle current regulation and limiting,
fast transient response, and good stability. The error amplifier, A1, regulates BSTOUT (and LDOIN) to 1.1V above
LDOOUT or VIN, whichever is higher.
Regulating 1.1V between LDOIN and LDOOUT allows the
linear regulator to provide good transient response and
ripple rejection, while maintaining good efficiency. This
regulation loop also minimizes total power dissipation
in fault conditions. If the output is overloaded, the linear
regulator will enter current limit, LDOOUT voltage will
decrease. By reducing the boost regulator output voltage,
the voltage across Q2 will be reduced, limiting dissipation
in Q2. Thermal shutdown provides additional protection.
APPLICATIONS INFORMATION
Capacitor Selection
Inductor Selection
A 4.7μF ceramic capacitor should be sufficient for the
boost regulator output bypass. Low ESR (equivalent
series resistance) ceramic capacitors should be used
at the outputs of the regulator to minimize the output
ripple voltage. Use only X5R or X7R dielectrics, as these
materials retain their capacitance over wider voltage and
temperature ranges better than other dielectrics.
A 5.6μH inductor will suffice for most LT3048 applications.
See Table 2 for recommended inductor values. Smaller
value inductors can be used at the cost of reduced maximum
load current. Figure 2 shows the maximum load current as
a function of output voltage. The inductor’s RMS current
rating must be greater than the maximum input current.
To keep efficiency high, the DCR (series resistance) should
be minimized. Table 3 lists several vendors.
Table 1. Ceramic Capacitor Manufacturers
MANUFACTURER
PHONE
WEB
Table 2. Recommended Inductor Values
Taiyo Yuden
(408) 573-4150
www.t-yuden.com
PART #
INDUCTANCE
AVX
(803) 448-9411
www.avxcorp.com
LT3048
5.6μH
www.murata.com
LT3048-15
10μH
LT3048-12
10μH
LT3048-5
4.7μH
LT3048-3.3
3.3μH
Murata
(714) 852-2001
FB Resistor Network
The output voltage is programmed with a resistor divider
between the output and FB pin. Choose the 1% resistors
according to:
 V

R1= R2  OUT − 1
 1.235V 
R2 should be 200k or less to avoid bias current errors.
10
Table 3. Inductor Manufacturers
VENDOR
URL
Coilcraft
www.coilcraft.com
Sumida
www.sumida.com
Toko
www.toko.com
Würth Elektronik
www.we-online.com
3048fa
For more information www.linear.com/LT3048
LT3048 Series
APPLICATIONS INFORMATION
45
L = 5.6µH
DCR = 120mΩ
VIN = 2.7V
VIN = 3.3V
VIN = 3.6V
40
LOAD CURRENT (mA)
35
30
C1
C2
GUARANTEED
25
20
15
L1
10
5
0
0
2
4
6 8 10 12 14 16 18 20 22
LDOOUT VOLTAGE (V)
C4
C3
3048 F02
Figure 2. LT3048 Typical and Guaranteed Load
Current vs. Output Voltage
Reducing Output Noise With A Bypass Capacitor
The LT3048 relies on the power supply rejection of the
linear regulator to reduce switching regulator noise at
LDOOUT. The linear regulator also contributes thermal
noise to the output. The thermal noise can be reduced,
and transient response improved, by adding a capacitor
between LDOOUT and BYP. A typical value is 1nF. This
capacitor increases start-up time of the regulator.
Recommended PCB Layout
Figure 3 shows the recommended layout for LT3048 circuits. Most important is careful placement of the BSTOUT
bypass capacitor C2. High frequency AC current flows in a
loop formed by C2, internal power transistor Q1 and boost
diode D2. Keep this loop small. Also be sure to place an
unbroken ground plane below this loop, on the highest
copper layer below the surface. This prevents the AC loop
from coupling to LDOOUT and other nearby circuitry. Keep
the SW node as small as possible.
LDO Stability and Output Capacitance
The LT3048 linear regulator requires an output capacitor
for stability. It is designed to be stable with most low
ESR capacitors (typically ceramic, tantalum or low ESR
electrolytic). A minimum output capacitor of 1μF with an
ESR of 1Ω or less is recommended to prevent oscillations. Larger values of output capacitance decrease peak
3048 F03
Figure 3. Recommended PCB Layout
deviations and provide improved transient response for
larger load current changes. Bypass capacitors, used to
decouple individual components powered by the LT3048,
increase the effective output capacitor value.
Give consideration to the use of ceramic capacitors as
they are manufactured with a variety of dielectrics, each
with different behavior across temperature and applied
voltage. The most common dielectrics used are specified
with EIA codes of Z5U, Y5V, X5R and X7R. Typical voltage and temperature coefficients are shown in Figures 4
and 5. The X5R and X7R dielectrics have more stable
characteristics and are most suitable for use as the output
capacitor. The X7R type has better stability across temperature, while the X5R is less expensive and is available
in higher values. Care still must be exercised when using
X5R and X7R capacitors; the codes only specify operating
temperature range and maximum capacitance change
over temperature. Capacitance change due to DC bias
with X5R and X7R capacitors can be significant enough
to drop capacitor values below appropriate levels. Capacitor DC bias characteristics tend to improve as case size
increases, but expected capacitance at operating voltage
should be verified.
3048fa
For more information www.linear.com/LT3048
11
LT3048 Series
APPLICATIONS INFORMATION
Wide Input Voltage Applications
40
The LT3048 can be used in wide input voltage applications. The input supply voltage to the LT3048 must be
between 2.7V and 4.8V and capable of at least 10mA.
The inductor can run off a separate voltage supply (PVIN).
This technique allows the output to be powered from 1V
to 23V (see Figure 6).
CHANGE IN VALUE (%)
20
X5R
0
–20
–40
Y5V
–60
–80
BOTH CAPACITORS ARE 16V,
1210 CASE SIZE, 10µF
–100
–50 –25
50
25
75
0
TEMPERATURE (°C)
100
125
3048 F04
Figure 4. Ceramic Capacitor Temperature Characteristics
20
SW
IN
2.7V TO 4.8V
1µF
VIN
BSTOUT
4.7µF
OUT
5V
LDOUT
301k
LT3048
1nF
FB
BOTH CAPACITORS ARE 16V,
1210 CASE SIZE, 10µF
0
CHANGE IN VALUE (%)
5.6µH
PVIN
1V TO 23V
100k
OFF ON
X5R
EN
GND
BYP
1µF
3048 F06
–20
–40
Figure 6. Connecting the Inductor to a Separate Voltage Supply
–60
Y5V
–80
–100
0
2
4
6
8
10
12
DC BIAS VOLTAGE (V)
14
16
3048 F05
Figure 5. Ceramic Capacitor DC Bias Characteristics
Voltage and temperature coefficients are not the only
sources of problems. Some ceramic capacitors have a
piezoelectric response. A piezoelectric device generates
voltage across its terminals due to mechanical stress. In a
ceramic capacitor, the stress can be induced by vibrations
in the system or thermal transients.
12
3048fa
For more information www.linear.com/LT3048
LT3048 Series
APPLICATIONS INFORMATION
LT3048
LT3048 Efficiency
70
5.6µH
WE-LHMI4020
SW
BSTOUT
VIN
1µF
60
4.7µF
LDOUT
301k
LT3048
1nF
FB
OUT
5V
30mA
100k
OFF ON
BYP
EN
50
EFFICIENCY (%)
IN
2.7V TO 4.8V
1µF
GND
40
30
VOUT = 5V
L = 5.6µH
DCR = 120mΩ
VIN = 2.7V
VIN = 3.3V
VIN = 3.6V
20
3048 TA2a
10
0
0
5
10
20
15
LOAD CURRENT (mA)
25
30
3048 TA02b
LT3048-15
80
10µH
LPS3008-103MLB
SW
1µF
70
4.7µF
BSTOUT
VIN
LDOIN
LT3048-15
LDOOUT
OFF ON
60
BYP
EN
1nF
GND
3048 TA03a
OUT
15V
1µF
VIN (V) IOUT (mA)
2.7
19
3.3
22
3.6
24
EFFICIENCY (%)
IN
2.7V TO 4.8V
LT3048-15: Efficiency
50
40
30
LDOOUT = 15V
L = 10µH
DCR = 650mΩ
VIN = 2.7V
VIN = 3.3V
VIN = 3.6V
20
10
0
5
0
10
20
15
LOAD CURRENT (mA)
25
3048 TA03b
LT3048-12
80
10µH
LPS3008-103MR
SW
1µF
70
4.7µF
BSTOUT
VIN
LDOIN
LT3048-12
LDOOUT
OFF ON
60
BYP
EN
GND
3048 TA04a
1nF
OUT
12V
1µF
VIN (V) IOUT (mA)
2.7
25
3.3
29
3.6
30
EFFICIENCY (%)
IN
2.7V TO 4.8V
LT3048-12: Efficiency
50
40
30
VOUT = 12V
L = 10µH
DCR = 650mΩ
VIN = 2.7V
VIN = 3.3V
VIN = 3.6V
20
10
0
0
5
10
20
15
LOAD CURRENT (mA)
25
30
3048 TA04b
3048fa
For more information www.linear.com/LT3048
13
LT3048 Series
PACKAGE DESCRIPTION
Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings.
DC8 Package
8-Lead Plastic DFN (2mm × 2mm)
(Reference LTC DWG # 05-08-1939 Rev Ø)
Exposed Pad Variation AA
1.8 REF
0.90
REF
0.23
REF
0.85 ±0.05
2.60 ±0.05
PACKAGE
OUTLINE
0.335 REF
0.25 ±0.05
0.45 BSC
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED
2.00 ±0.05
(4 SIDES)
PIN 1 BAR
TOP MARK
(SEE NOTE 6)
2.00 SQ ±0.05
1.8 REF
5
8
0.23
0.335 REF
REF
0.55 ±0.05
PIN 1 NOTCH
R = 0.15
(DC8MA) DFN 0113 REV Ø
4
0.200 REF
0.75 ±0.05
1
0.23 ±0.05
0.45 BSC
BOTTOM VIEW—EXPOSED PAD
0.00 – 0.05
NOTE:
1. DRAWING IS NOT A JEDEC PACKAGE OUTLINE
2. DRAWING NOT TO SCALE
3. ALL DIMENSIONS ARE IN MILLIMETERS
4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE
5. EXPOSED PAD SHALL BE SOLDER PLATED
6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE
TOP AND BOTTOM OF PACKAGE
14
3048fa
For more information www.linear.com/LT3048
LT3048 Series
REVISION HISTORY
REV
DATE
DESCRIPTION
A
2/15
Clarified to Include All Fixed and Adjustable Output Options
PAGE NUMBER
1 − 16
3048fa
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection
of its circuits
as described
herein will not infringe on existing patent rights.
For more
information
www.linear.com/LT3048
15
LT3048 Series
TYPICAL APPLICATIONS
LT3048-5
70
4.7µH
LPS3008-472MR
60
SW
1µF
4.7µF
BSTOUT
VIN
50
LDOIN
LT3048-5
LDOOUT
OFF ON
1nF
BYP
EN
OUT
5V
1µF 40mA
EFFICIENCY (%)
IN
2.7V TO 4.8V
LT3048-5: Efficiency
40
30
VOUT = 5V
L = 4.7µH
DCR = 350mΩ
VIN = 2.7V
VIN = 3.3V
VIN = 3.6V
20
GND
3048 TA05a
10
0
0
5
10
15 20 25 30
LOAD CURRENT (mA)
35
40
3048 TA05b
LT3048-3.3
60
3.3µH
LPS3008-332MR
SW
1µF
BSTOUT
VIN
LDOIN
LT3048-3.3
LDOOUT
OFF ON
1nF
BYP
EN
50
4.7µF
OUT
3.3V
1µF 40mA
EFFICIENCY (%)
IN
2.7V TO 4.8V
LT3048-3.3: Efficiency
GND
40
30
VOUT = 3.3V
L = 3.3µH
DCR = 285mΩ
VIN = 2.7V
VIN = 3.3V
VIN = 3.6V
20
10
3048 TA06a
0
0
5
10
15 20 25 30
LOAD CURRENT (mA)
35
40
3048 TA06b
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
LT3460
300mA, 38V ISW, 1.3MHz, High Efficiency Step-Up
DC/DC Converter
VIN: 2.5V to 16V, VOUT(MAX) = 36V, IQ = 2mA, ISD < 1µA, SC70,
ThinSOT™ Package
LT3461/LT3461A
300mA, 38V ISW, 1.3MHz, High Efficiency Step-Up
DC/DC Converters
VIN: 2.5V to 16V, VOUT(MAX) = 38V, IQ = 2.8mA, ISD < 1µA, SC70,
ThinSOT Packages
LT3464
120mA, 38V ISW, High Efficiency Step-Up DC/DC
Converter with Integrated Schottky, Output Disconnect
VIN: 2.3V to 10V, VOUT(MAX) = 34V, IQ = 25µA, ISD < 1µA, ThinSOT
Package
LT1613
550mA ISW, 1.4MHz, High Efficiency Step-Up
DC/DC Converter
VIN: 0.9V to 10V, VOUT(MAX) = 34V, IQ = 3mA, ISD < 1µA, ThinSOT
Package
LT1761
20V, 100mA (IOUT) Low Noise LDO
VIN: 1.8V to 20V, VOUT(MIN) = 1.22V, IQ = 20µA, ISD < 1µA, ThinSOT
Package
LT3009
20V, 20mA (IOUT) Low Noise LDO
VIN: 1.6V to 20V, VOUT(MIN) = 0.6V, IQ = 3µA, ISD < 1µA, SC70,
2mm × 2mm DFN-6 Packages
16
3048fa
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
For more information www.linear.com/LT3048
(408) 432-1900 ● FAX: (408) 434-0507
●
www.linear.com/LT3048
LT 0215 REV A • PRINTED IN USA
 LINEAR TECHNOLOGY CORPORATION 2014