LINER LT3045 20v, 500ma, ultralow noise, ultrahigh psrr linear regulator Datasheet

LT3045
20V, 500mA, Ultralow Noise,
Ultrahigh PSRR Linear Regulator
Features
Description
Ultralow RMS Noise: 0.8µVRMS (10Hz to 100kHz)
nn Ultralow Spot Noise: 2nV/√Hz at 10kHz
nn Ultrahigh PSRR: 76dB at 1MHz
nn Output Current: 500mA
nn Wide Input Voltage Range: 1.8V to 20V
nn Single Capacitor Improves Noise and PSRR
nn 100µA SET Pin Current: ±1% Initial Accuracy
nn Single Resistor Programs Output Voltage
nn High Bandwidth: 1MHz
nn Programmable Current Limit
nn Low Dropout Voltage: 260mV
nn Output Voltage Range: 0V to 15V
nn Programmable Power Good
nn Fast Start-Up Capability
nn Precision Enable/UVLO
nn Parallelable for Lower Noise and Higher Current
nn Internal Current Limit with Foldback
nn Minimum Output Capacitor: 10µF Ceramic
nn Reverse-Battery and Reverse-Current Protection
nn 12-Lead MSOP and 10-Lead 3mm × 3mm DFN Packages
The LT®3045 is a high performance low dropout linear
regulator featuring LTC’s ultralow noise and ultrahigh
PSRR architecture for powering noise sensitive applications. Designed as a precision current reference followed
by a high performance voltage buffer, the LT3045 can be
easily paralleled to further reduce noise, increase output
current and spread heat on the PCB.
nn
Applications
RF Power Supplies: PLLs, VCOs, Mixers, LNAs, PAs
Very Low Noise Instrumentation
nn High Speed/High Precision Data Converters
nn Medical Applications: Imaging, Diagnostics
nn Precision Power Supplies
nn Post-Regulator for Switching Supplies
nn
nn
The device supplies 500mA at a typical 260mV dropout
voltage. Operating quiescent current is nominally 2.2mA
and drops to <<1µA in shutdown. The LT3045’s wide
output voltage range (0V to 15V) while maintaining unitygain operation provides virtually constant output noise,
PSRR, bandwidth and load regulation, independent of the
programmed output voltage. Additionally, the regulator
features programmable current limit, fast start-up capability and programmable power good to indicate output
voltage regulation.
The LT3045 is stable with a minimum 10µF ceramic output
capacitor. Built-in protection includes reverse-battery
protection, reverse-current protection, internal current
limit with foldback and thermal limit with hysteresis. The
LT3045 is available in thermally enhanced 12-Lead MSOP
and 10-Lead 3mm × 3mm DFN packages.
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Analog
Devices, Inc. Patents pending. All other trademarks are the property of their respective owners.
Typical Application
LT3045
IN
4.7µF*
100µA
EN/UV
200k
110
100
–
+
90
VOUT
3V
IOUT(MAX)
500mA
OUT
PG
OUTS
SET
GND
ILIM
PGFB
4.7µF
30.1k
249Ω
80
70
60
VIN = 5V
RSET = 30.1k
CSET = 4.7µF
COUT = 10µF
IL = 500mA
50
10µF
402k
*OPTIONAL, SEE
APPLICATIONS
INFORMATION
PSRR (dB)
VIN
5V ±5%
Power Supply Ripple Rejection
120
40
30
49.9k
3045 TA01a
20
10
100
1k
10k 100k
FREQUENCY (Hz)
1M
10M
3045 TA01b
3045fa
For more information www.linear.com/LT3045
1
LT3045
Absolute Maximum Ratings
(Note 1)
IN Pin Voltage..........................................................±22V
EN/UV Pin Voltage...................................................±22V
IN-to-EN/UV Differential..........................................±22V
PG Pin Voltage (Note 10)................................–0.3V, 22V
ILIM Pin Voltage (Note 10)................................–0.3V, 1V
PGFB Pin Voltage (Note 10)............................–0.3V, 22V
SET Pin Voltage (Note 10)...............................–0.3V, 16V
SET Pin Current (Note 7)..................................... ±20mA
OUTS Pin Voltage (Note 10)............................–0.3V, 16V
OUTS Pin Current (Note 7).................................. ±20mA
OUT Pin Voltage (Note 10)..............................–0.3V, 16V
OUT-to-OUTS Differential (Note 14)........................ ±1.2V
IN-to-OUT Differential..............................................±22V
IN-to-OUTS Differential............................................±22V
Output Short-Circuit Duration........................... Indefinite
Operating Junction Temperature Range (Note 9)
E-Grade, I-Grade................................ –40°C to 125°C
H-Grade,............................................ –40°C to 150°C
Storage Temperature Range............... –65°C to 150°C
Lead Temperature (Soldering, 10 Sec)
MSE Package .................................................... 300°C
Pin Configuration
TOP VIEW
TOP VIEW
IN
1
10 OUT
IN
2
9 OUTS
EN/UV
3
PG
4
ILIM
5
11
GND
IN
IN
IN
EN/UV
PG
ILIM
8 GND
7 SET
6 PGFB
DD PACKAGE
10-LEAD (3mm × 3mm) PLASTIC DFN
TJMAX = 150°C, θJA = 34°C/W, θJC = 5.5°C/W
EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB
Order Information
1
2
3
4
5
6
13
GND
12
11
10
9
8
7
OUT
OUT
OUTS
GND
SET
PGFB
MSE PACKAGE
12-LEAD PLASTIC MSOP
TJMAX = 150°C, θJA = 33°C/W, θJC = 8°C/W
EXPOSED PAD (PIN 13) IS GND, MUST BE SOLDERED TO PCB
http://www.linear.com/product/LT3045#orderinfo
LEAD FREE FINISH
TAPE AND REEL
PART MARKING*
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LT3045EDD#PBF
LT3045EDD#TRPBF
LGYP
10-Lead (3mm × 3mm) Plastic DFN
–40°C to 125°C
LT3045IDD#PBF
LT3045IDD#TRPBF
LGYP
10-Lead (3mm × 3mm) Plastic DFN
–40°C to 125°C
LT3045HDD#PBF
LT3045HDD#TRPBF
LGYP
10-Lead (3mm × 3mm) Plastic DFN
–40°C to 150°C
LT3045EMSE#PBF
LT3045EMSE#TRPBF
3045
12-Lead Plastic MSOP
–40°C to 125°C
LT3045IMSE#PBF
LT3045IMSE#TRPBF
3045
12-Lead Plastic MSOP
–40°C to 125°C
LT3045HMSE#PBF
LT3045HMSE#TRPBF
3045
12-Lead Plastic MSOP
–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.
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/. Some packages are available in 500 unit reels through
designated sales channels with #TRMPBF suffix.
3045fa
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For more information www.linear.com/LT3045
LT3045
Electrical Characteristics
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C.
PARAMETER
CONDITIONS
MIN
Input Voltage Range
l
Minimum IN Pin Voltage ILOAD = 500mA, VIN UVLO Rising
VIN UVLO Hysteresis
(Note 2)
l
2
1.78
75
Output Voltage Range
VIN > VOUT
l
0
SET Pin Current (ISET)
VIN = 2V, ILOAD = 1mA, VOUT = 1.3V
2V < VIN < 20V, 0V < VOUT < 15V, 1mA < ILOAD < 500mA (Note 3)
l
99
98
Fast Start-Up Set Pin
Current
VPGFB = 289mV, VIN = 2.8V, VSET = 1.3V
Output Offset Voltage
VOS (VOUT – VSET)
(Note 4)
VIN = 2V, ILOAD = 1mA, VOUT = 1.3V
2V < VIN < 20V, 0V < VOUT < 15V, 1mA < ILOAD < 500mA (Note 3)
l
Line Regulation: ∆ISET
Line Regulation: ∆VOS
VIN = 2V to 20V, ILOAD = 1mA, VOUT = 1.3V
VIN = 2V to 20V, ILOAD = 1mA, VOUT = 1.3V (Note 4)
l
l
Load Regulation: ∆ISET
Load Regulation: ∆VOS
ILOAD = 1mA to 500mA, VIN = 2V, VOUT = 1.3V
ILOAD = 1mA to 500mA, VIN = 2V, VOUT = 1.3V (Note 4)
Change in ISET with VSET
Change in VOS with VSET
Change in ISET with VSET
Change in VOS with VSET
VSET = 1.3V to 15V, VIN = 20V, ILOAD = 1mA
VSET = 1.3V to 15V, VIN = 20V, ILOAD = 1mA (Note 4)
VSET = 0V to 1.3V, VIN = 20V, ILOAD = 1mA
VSET = 0V to 1.3V, VIN = 20V, ILOAD = 1mA (Note 4)
Dropout Voltage
ILOAD = 1mA, 50mA
TYP
100
100
MAX
20
V
2
V
mV
15
V
101
102
µA
µA
2
–1
–2
UNITS
mA
1
2
mV
mV
0.5
0.5
±2
±3
nA/V
µV/V
l
3
0.1
0.5
nA
mV
l
l
l
l
30
0.03
150
0.3
400
0.6
600
2
nA
mV
nA
mV
220
275
330
mV
mV
220
280
350
mV
mV
260
350
450
mV
mV
4
5.5
7
25
mA
mA
mA
mA
mA
l
ILOAD = 300mA (Note 5)
l
ILOAD = 500mA (Note 5)
l
GND Pin Current
VIN = VOUT(NOMINAL)
(Note 6)
ILOAD = 10µA
ILOAD = 1mA
ILOAD = 50mA
ILOAD = 100mA
ILOAD = 500mA
2.2
2.4
3.5
4.3
15
Output Noise Spectral
Density (Notes 4, 8)
ILOAD = 500mA, Frequency = 10Hz, COUT = 10µF, CSET = 0.47µF, VOUT = 3.3V
ILOAD = 500mA, Frequency = 10Hz, COUT = 10µF, CSET = 4.7µF, 1.3V ≤ VOUT ≤ 15V
ILOAD = 500mA, Frequency = 10kHz, COUT = 10µF, CSET = 0.47µF, 1.3V ≤ VOUT ≤ 15V
ILOAD = 500mA, Frequency = 10kHz, COUT = 10µF, CSET = 0.47µF, 0V ≤ VOUT < 1.3V
500
70
2
5
nV/√Hz
nV/√Hz
nV/√Hz
nV/√Hz
Output RMS Noise
(Notes 4, 8)
ILOAD = 500mA, BW = 10Hz to 100kHz, COUT = 10µF, CSET = 0.47µF, VOUT = 3.3V
ILOAD = 500mA, BW = 10Hz to 100kHz, COUT = 10µF, CSET = 4.7µF, 1.3V ≤ VOUT ≤ 15V
ILOAD = 500mA, BW = 10Hz to 100kHz, COUT = 10µF, CSET = 4.7µF, 0V ≤ VOUT < 1.3V
2.5
0.8
1.8
µVRMS
µVRMS
µVRMS
6
nARMS
l
l
l
l
Reference Current RMS BW = 10Hz to 100kHz
Output Noise (Notes 4, 8)
Ripple Rejection
1.3V ≤ VOUT ≤ 15V
VIN – VOUT = 2V (Avg)
(Notes 4, 8)
VRIPPLE = 500mVP-P, fRIPPLE = 120Hz, ILOAD = 500mA, COUT = 10µF, CSET = 4.7µF
VRIPPLE = 150mVP-P, fRIPPLE = 10kHz, ILOAD = 500mA, COUT = 10µF, CSET = 0.47µF
VRIPPLE = 150mVP-P, fRIPPLE = 100kHz, ILOAD = 500mA, COUT = 10µF, CSET = 0.47µF
VRIPPLE = 150mVP-P, fRIPPLE = 1MHz, ILOAD = 500mA, COUT = 10µF, CSET = 0.47µF
VRIPPLE = 80mVP-P, fRIPPLE = 10MHz, ILOAD = 500mA, COUT = 10µF, CSET = 0.47µF
117
90
77
76
53
dB
dB
dB
dB
dB
Ripple Rejection
0V ≤ VOUT < 1.3V
VIN – VOUT = 2V (Avg)
(Notes 4, 8)
VRIPPLE = 500mVP-P, fRIPPLE = 120Hz, ILOAD = 500mA, COUT = 10µF, CSET = 0.47µF
VRIPPLE = 50mVP-P, fRIPPLE = 10kHz, ILOAD = 500mA, COUT = 10µF, CSET = 0.47µF
VRIPPLE = 50mVP-P, fRIPPLE = 100kHz, ILOAD = 500mA, COUT = 10µF, CSET = 0.47µF
VRIPPLE = 50mVP-P, fRIPPLE = 1MHz, ILOAD = 500mA, COUT = 10µF, CSET = 0.47µF
VRIPPLE = 50mVP-P, fRIPPLE = 10MHz, ILOAD = 500mA, COUT = 10µF, CSET = 0.47µF
104
85
72
64
54
dB
dB
dB
dB
dB
EN/UV Pin Threshold
EN/UV Trip Point Rising (Turn-On), VIN = 2V
EN/UV Pin Hysteresis
EN/UV Trip Point Hysteresis, VIN = 2V
l
1.18
1.24
130
1.32
V
mV
3045fa
For more information www.linear.com/LT3045
3
LT3045
Electrical Characteristics
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C.
PARAMETER
CONDITIONS
EN/UV Pin Current
VEN/UV = 0V, VIN = 20V
VEN/UV = 1.24V, VIN = 20V
VEN/UV = 20V, VIN = 0V
MIN
TYP
Quiescent Current in
VIN = 6V
Shutdown (VEN/UV = 0V) TJ ≤ 125°C (E/I-Grade)
TJ ≤ 150°C (H-Grade)
0.3
1
10
20
µA
µA
µA
850
l
l
±1
UNITS
15
0.03
8
l
MAX
µA
µA
µA
l
Internal Current Limit
(Note 12)
VIN = 2V, VOUT = 0V
VIN = 12V, VOUT = 0V
VIN = 20V, VOUT = 0V
Programmable
Current Limit
Programming Scale Factor: 2V < VIN < 20V (Note 11)
VIN = 2V, VOUT = 0V, RILIM = 300Ω
VIN = 2V, VOUT = 0V, RILIM = 1.5kΩ
PGFB Trip Point
PGFB Trip Point Rising
PGFB Hysteresis
PGFB Trip Point Hysteresis
7
mV
PGFB Pin Current
VIN = 2V, VPGFB = 300mV
25
nA
l
570
l
230
710
700
330
430
mA
mA
mA
l
l
450
90
150
500
100
550
110
mA • kΩ
mA
mA
l
291
300
309
mV
PG Output Low Voltage
IPG = 100µA
l
100
mV
PG Leakage Current
VPG = 20V
l
30
1
µA
Reverse Input Current
VIN = –20V, VEN/UV = 0V, VOUT = 0V, VSET = 0V
l
100
µA
Reverse Output Current
VIN = 0, VOUT = 5V, SET = Open
14
Minimum Load Required VOUT < 1V
(Note 13)
l
10
25
µA
µA
Thermal Shutdown
TJ Rising
Hysteresis
165
8
°C
°C
Start-Up Time
VOUT(NOM) = 5V, ILOAD = 500mA, CSET = 0.47µF, VIN = 6V, VPGFB = 6V
VOUT(NOM) = 5V, ILOAD = 500mA, CSET = 4.7µF, VIN = 6V, VPGFB = 6V
VOUT(NOM) = 5V, ILOAD = 500mA, CSET = 4.7µF, VIN = 6V, RPG1 = 50kΩ,
RPG2 = 700kΩ (with Fast Start-Up to 90% of VOUT)
55
550
10
ms
ms
ms
Thermal Regulation
10ms Pulse
–0.01
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 EN/UV pin threshold must be met to ensure device operation.
Note 3: Maximum junction temperature limits operating conditions. The
regulated output voltage specification does not apply for all possible
combinations of input voltage and output current, especially due to the
internal current limit foldback which starts to decrease current limit at
VIN – VOUT > 12V. If operating at maximum output current, limit the input
voltage range. If operating at the maximum input voltage, limit the output
current range.
Note 4: OUTS ties directly to OUT.
Note 5: Dropout voltage is the minimum input-to-output differential
voltage needed to maintain regulation at a specified output current. The
dropout voltage is measured when output is 1% out of regulation. This
definition results in a higher dropout voltage compared to hard dropout
— which is measured when VIN = VOUT(NOMINAL). For lower output
voltages, below 1.5V, dropout voltage is limited by the minimum input
voltage specification. For DFN package: Linear Technology is unable to
%/W
guarantee maximum dropout voltage specifications at high currents
due to production test limitations with Kelvin-sensing the package
pins. Please consult the Typical Performance Characteristics for curves
of dropout voltage as a function of output load current and temperature
measured in a typical application circuit.
Note 6: GND pin current is tested with VIN = VOUT(NOMINAL) and a current
source load. Therefore, the device is tested while operating in dropout. This
is the worst-case GND pin current. GND pin current decreases at higher
input voltages. Note that GND pin current does not include SET pin or ILIM
pin current but Quiescent current does include them.
Note 7: SET and OUTS pins are clamped using diodes and two 25Ω series
resistors. For less than 5ms transients, this clamp circuitry can carry
more than the rated current. Refer to Applications Information for more
information.
Note 8: Adding a capacitor across the SET pin resistor decreases output
voltage noise. Adding this capacitor bypasses the SET pin resistor’s
thermal noise as well as the reference current’s noise. The output noise
then equals the error amplifier noise. Use of a SET pin bypass capacitor
also increases start-up time.
3045fa
4
For more information www.linear.com/LT3045
LT3045
Electrical Characteristics
Note 9: The LT3045 is tested and specified under pulsed load conditions
such that TJ ≈ TA. The LT3045E is 100% tested at 25°C and performance
is guaranteed from 0°C to 125°C. Specifications over the –40°C to 125°C
operating temperature range are assured by design, characterization, and
correlation with statistical process controls. The LT3045I is guaranteed
over the full –40°C to 125°C operating temperature range. LT3045H is
100% tested at the 150°C operating junction temperature. High junction
temperatures degrade operating lifetimes. Operating lifetime is derated at
junction temperatures greater than 125°C.
Note 10: Parasitic diodes exist internally between the ILIM, PG, PGFB, SET,
OUTS, and OUT pins and the GND pin. Do not drive these pins more than
0.3V below the GND pin during a fault condition. These pins must remain at
a voltage more positive than GND during normal operation.
Note 11: The current limit programming scale factor is specified while the
internal backup current limit is not active. Note that the internal current
limit has foldback protection for VIN – VOUT differentials greater than 12V.
Note 12: The internal back-up current limit circuitry incorporates foldback
protection that decreases current limit for VIN – VOUT > 12V. Some level of
output current is provided at all VIN – VOUT differential voltages. Consult the
Typical Performance Characteristics graph for current limit vs VIN – VOUT.
Note 13: For output voltages less than 1V, the LT3045 requires a 10µA
minimum load current for stability.
Note 14: Maximum OUT-to-OUTS differential is guaranteed by design.
Typical Performance Characteristics
SET Pin Current
101.0
2.0
N = 3250
Offset Voltage (VOUT – VSET)
VIN = 2V
IL = 1mA
VOUT = 1.3V
1.5
OFFSET VOLTAGE (mV)
100.6
100.4
100.2
100.0
99.8
99.6
99.4
1.0
0.5
0
–0.5
–1.0
–1.5
99.2
98
0 25 50 75 100 125 150
TEMPERATURE (°C)
99
100
101
ISET DISTRIBUTION (µA)
3045 G01
Offset Voltage
3045 G02
SET Pin Current
IL = 1mA
100.8 V
OUT = 1.3V
2.0
100.6
100.4
150°C
125°C
25°C
–55°C
100.2
100.0
99.8
99.6
99.4
2
3045 G04
99.0
Offset Voltage (VOUT – VSET)
IL = 1mA
VOUT = 1.3V
1.5
1.0
150°C
125°C
25°C
–55°C
0.5
0
–0.5
–1.0
–1.5
99.2
–1
0
1
VOS DISTRIBUTION (mV)
0 25 50 75 100 125 150
TEMPERATURE (°C)
3045 G03
101.0
N = 3250
–2
–2.0
–75 –50 –25
102
OFFSET VOLTAGE (mV)
99.0
–75 –50 –25
SET PIN CURRENT (µA)
SET PIN CURRENT (µA)
SET Pin Current
VIN = 2V
IL = 1mA
VOUT = 1.3V
100.8
TJ = 25°C, unless otherwise noted.
0
2
4
6 8 10 12 14 16 18 20
INPUT VOLTAGE (V)
3045 G05
–2.0
0
2
4
6 8 10 12 14 16 18 20
INPUT VOLTAGE (V)
3045 G06
3045fa
For more information www.linear.com/LT3045
5
LT3045
Typical Performance Characteristics
SET Pin Current
101.0
2.0
100.2
100.0
99.8
99.6
99.4
1.5
0.5
0
–0.5
99.0
–2.0
3
4.5 6 7.5 9 10.5 12 13.5 15
OUTPUT VOLTAGE (V)
0
1.5
8
2.0
1.5
1.0
0.08
0.06
0.04
ISET
0.02
3
4.5 6 7.5 9 10.5 12 13.5 15
OUTPUT VOLTAGE (V)
0
–75 –50 –25
Quiescent Current
3.0
VEN/UV = VIN
IL = 10µA
RSET = 33.2k
2.5
40
35
30
VIN = 20V
25
20
VIN = 2V
15
0
0 25 50 75 100 125 150
TEMPERATURE (°C)
3045 G09
VEN/UV = 0V
45
2.5
0.10
VOS
Quiescent Current
50
VIN = 2V
VEN/UV = VIN
3.5
IL = 10µA
RSET = 13k
3.0
QUIESCENT CURRENT (µA)
10
2.0
1.5
1.0
0.5
5
0
–75 –50 –25
0
–75 –50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
Quiescent Current
DROPOUT VOLTAGE (mV)
2.5
2.0
1.5
1.0
150°C
125°C
25°C
–55°C
0.5
0
2
4
6
8
10 12
OUTPUT VOLTAGE (V)
16
3045 G13
450
400
350
300
250
200
150
150°C
125°C
25°C
–55°C
100
50
14
4
6 8 10 12 14 16 18 20
INPUT VOLTAGE (V)
Dropout Voltage
500
RSET = 33.2k
450
3.0
2
3045 G12
Typical Dropout Voltage
500
VIN = 20V
VEN/UV = VIN
IL = 10µA
3.5
0
3045 G11
3045 G10
4.0
0
0 25 50 75 100 125 150
TEMPERATURE (°C)
DROPOUT VOLTAGE (mV)
QUIESCENT CURRENT (mA)
10
3045 G08
0.5
QUIESCENT CURRENT (mA)
0.12
2
Quiescent Current
0
0.14
12
4
3045 G07
4.0
0.16
14
QUIESCENT CURRENT (mA)
1.5
0.18
6
–1.0
99.2
0.20
V = 2.5V
18 ∆IIN= 1mA to 500mA
L
16 VOUT = 1.3V
150°C
125°C
25°C
–55°C
1.0
–1.5
0
IL = 1mA
VIN = 20V
Load Regulation
20
∆ISET (nA)
100.4
Offset Voltage (VOUT – VSET)
∆ VOS (mV)
SET PIN CURRENT (µA)
100.6
150°C
125°C
25°C
–55°C
OFFSET VOLTAGE (mV)
IL = 1mA
VIN = 20V
100.8
TJ = 25°C, unless otherwise noted.
0
0
RSET = 33.2k
400
IL = 400mA
350
300
IL = 500mA
250
200
IL = 1mA
150
100
50
50 100 150 200 250 300 350 400 450 500
OUTPUT CURRENT (mA)
3045 G14
0
–75 –50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
3045 G15
3045fa
6
For more information www.linear.com/LT3045
LT3045
Typical Performance Characteristics
GND Pin Current
22
VIN = 5V
RSET = 33.2k
18
18
GND PIN CURRENT (mA)
IL = 500mA
12
10
IL = 300mA
8
6
IL = 100mA
4
2
0
–75 –50 –25
16
14
12
10
8
6
150°C
125°C
25°C
–55°C
4
2
IL = 1mA
0
0 25 50 75 100 125 150
TEMPERATURE (°C)
0
1.30
1.00
0.75
0.50
0 25 50 75 100 125 150
TEMPERATURE (°C)
1.26
1.24
VIN = 2V
1.22
VIN = 10V
1.5
150°C
125°C
25°C
–55°C
1.0
0.5
0
0
2
4
6 8 10 12 14 16 18 20
ENABLE PIN VOLTAGE (V)
3045 G22
EN/UV PIN CURRENT (µA)
EN/UV PIN CURRENT (µA)
4.5
2.0
3 4 5 6 7
INPUT VOLTAGE (V)
8
10
VIN = 10V
140
125
110
VIN = 2V
95
80
50
–75 –50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
0 25 50 75 100 125 150
TEMPERATURE (°C)
3045 G21
Negative Enable Pin Current
0
–10
VIN = 2V
8
7
6
5
VIN = 20V
4
3
2
1
0
9
155
3045 G20
9
2.5
2
65
1.18
–75 –50 –25
VIN = 20V
3.0
1
170
EN/UV Pin Current
3.5
0
185
10
4.0
RL = 330Ω
RL = 3.3kΩ
EN/UV Pin Hysteresis
1.28
EN/UV Pin Current
5.0
RL = 33Ω
4
200
3045 G19
5.5
6
3045 G18
1.20
RISING UVLO
FALLING UVLO
RL = 11Ω
8
0
EN/UV PIN HYSTERESIS (mV)
1.75
0
–75 –50 –25
10
EN/UV Turn-On Threshold
1.32
TURN-ON THRESHOLD (V)
INPUT UVLO THRESHOLD (V)
Minimum Input Voltage
1.25
RL = 6.6Ω
12
3045 G17
2.00
0.25
14
2
50 100 150 200 250 300 350 400 450 500
OUTPUT CURRENT (mA)
3045 G16
1.50
RSET = 33.2k
16
EN/UV PIN CURRENT (µA)
GND PIN CURRENT (mA)
14
VIN = 4.3V
RSET = 33.2k
20
16
GND Pin Current
18
GND PIN CURRENT (mA)
GND Pin Current
20
TJ = 25°C, unless otherwise noted.
–20
–30
–40
–50
–60
–70
–80
–90
0
2
4
6 8 10 12 14 16 18 20
ENABLE PIN VOLTAGE (V)
3045 G23
VIN = 2V
150°C
125°C
25°C
–55°C
–100
–20 –18 –16 –14 –12 –10 –8 –6 –4 –2
ENABLE PIN VOLTAGE (V)
0
3045 G24
3045fa
For more information www.linear.com/LT3045
7
LT3045
Typical Performance Characteristics
Input Pin Current
Internal Current Limit
0.3
1000
150°C
125°C
25°C
–55°C
900
Internal Current Limit
600
RILIM = 0Ω
VOUT = 0V
500
0.2
0.1
CURRENT LIMIT (mA)
800
CURRENT LIMIT (mA)
INPUT CURRENT (µA)
VIN = 2V
TJ = 25°C, unless otherwise noted.
700
600
500
400
300
200
100
0
–20 –18 –16 –14 –12 –10 –8 –6 –4 –2
ENABLE PIN VOLTAGE (V)
3045 G25
Internal Current Limit
CURRENT LIMIT (mA)
CURRENT LIMIT (mA)
800
700
600
500
400
150°C
125°C
25°C
–55°C
100
0
RILIM = 300Ω
VOUT = 0V
500
400
300
100
2 4 6 8 10 12 14 16 18 20
INPUT-TO-OUTPUT DIFFERENTIAL (V)
100
308
500
400
300
2.5VIN
5VIN
10VIN
50 100 150 200 250 300 350 400 450 500
OUTPUT CURRENT (mA)
3045 G31
VIN = 12V
60
20
0
–75 –50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
0 25 50 75 100 125 150
TEMPERATURE (°C)
3045 G30
PGFB Hysteresis
8
VIN = 2V
7
306
PGFB HYSTERESIS (mV)
600
VIN = 2.5V
80
PGFB Rising Threshold
PGFB RISING THRESHOLD (mV)
ILIM PIN CURRENT (uA)
120
3045 G29
VILIM = 0V
900 RSET = 13k
0
140
310
700
RILIM = 1.5k
VOUT = 0V
40
VIN = 2.5V
VIN = 12V
0
–75 –50 –25
ILIM Pin Current
100
160
600
1000
200
180
700
3045 G28
0
Programmable Current Limit
200
200
800
0 25 50 75 100 125 150
TEMPERATURE (°C)
3045 G27
CURRENT LIMIT (mA)
900
800
0
0
–75 –50 –25
Programmable Current Limit
RILIM = 0Ω
200
200
0 25 50 75 100 125 150
TEMPERATURE (°C)
1000
300
300
3045 G26
1000
900
400
100
VIN = 2.5V
VIN = 12V
0
–75 –50 –25
0
VIN = 20V
RILIM = 0Ω
VOUT = 0V
304
302
300
298
296
294
6
5
4
3
2
1
292
290
–75 –50 –25
VIN = 2V
0 25 50 75 100 125 150
TEMPERATURE (°C)
3045 G32
0
–75 –50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
3045 G33
3045fa
8
For more information www.linear.com/LT3045
LT3045
Typical Performance Characteristics
PG Output Low Voltage
ISET During Start-Up with Fast
Start-Up Enabled
PG Pin Leakage Current
100
50
VIN = 2V
VPGFB = 290mV
IPG = 100µA
80
70
30
60
IPG (nA)
35
25
20
40
30
10
20
5
10
0.5
3045 G35
ISET During Start-Up with Fast
Start-Up Enabled
12
VPGFB = 290mV
VSET = 1.3V
OUTPUT SINK CURRENT (mA)
ISET (mA)
2.5
2.0
1.5
1.0
0.5
0
2
10
6
4
2
VOUT Forced Above VOUT(NOMINAL)
0
5
4
100
5
6
7 8 9 10 11 12 13 14 15
OUTPUT VOLTAGE (V)
3045 G40
2
Power Supply Ripple Rejection
110
80
80
70
60
100
70
60
50
VIN = 5V
RSET = 30.1k
COUT = 10µF
IL = 500mA
10
COUT = 10µF
COUT = 22µF
100
90
20
0 25 50 75 100 125 150
TEMPERATURE (°C)
3045 G39
90
40
4
3
3045 G38
CSET = 4.7µF
CSET = 0.47µF
110
30
0
4
120
50
2
5
Power Supply Ripple Rejection
IIN when VEN = 0V
IOUT when VEN = 0V
IIN when VEN = VIN
IOUT when VEN = VIN
VIN = 5V
RSET = 33.2k
VOUT – VSET > 5mV
0
–75 –50 –25
20
120
PSRR (dB)
CURRENT (mA)
6
10
15
VOUT – VSET (mV)
PSRR (dB)
VIN = 5V
RSET = 33.2k
6
1
3045 G37
8
150°C
125°C
25°C
–55°C
8
0
4 6 8 10 12 14 16 18 20
VIN-TO-VSET DIFFERENTIAL (V)
Output Overshoot Recovery
Current Sink
7
VIN = 5V
RSET = 33.2k
0 25 50 75 100 125 150
TEMPERATURE (°C)
3045 G36
Output Overshoot Recovery
Current Sink
3.5
0
0
–75 –50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
3045 G34
3.0
1.5
1.0
0
–75 –50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
VIN = 2.5V
VPGFB = 290mV
VSET = 1.3V
2.0
50
15
0
–75 –50 –25
2.5
ISET (mA)
40
3.0
VPG = 2V
VPGFB = 310mV
90
OUTPUT SINK CURRENT (mA)
45
VPG (mV)
TJ = 25°C, unless otherwise noted.
VIN = 5V
RSET = 30.1k
30 CSET = 0.47µF
IL = 500mA
20
10
100
1k
10k 100k
FREQUENCY (Hz)
40
1k
10k 100k
FREQUENCY (Hz)
1M
10M
3045 G41
1M
10M
3045 G42
3045fa
For more information www.linear.com/LT3045
9
LT3045
Typical Performance Characteristics
Power Supply Ripple Rejection
as a Function of Error Amplifier
Input Pair
Power Supply Ripple Rejection
140
120
120
100
90
80
10
100
70
60
VIN = 5V
RSET = 30.1k
COUT = 10µF
CSET = 0.47µF
1k
10k 100k
FREQUENCY (Hz)
1M
20
10M
40
10
100
10
1k
10k 100k
FREQUENCY (Hz)
1M
0
10M
0.8
0.6
0.4
7
6
5
4
3
2
1
0.2
0.1
1
10
SET PIN CAPACITANCE (µF)
3045 G46
1.4
1.2
1.0
0.8
0.6
0.4
0
100
Noise Spectral Density
1M
10M
3045 G49
1.5
3
4.5 6 7.5 9 10.5 12 13.5 15
OUTPUT VOLTAGE (V)
3045 G48
Noise Spectral Density
OUTPUT NOISE (nV/√Hz)
10
0
3045 G47
1000
1 V = 5V
IN
RSET = 33.2k
COUT = 10µF
ILOAD = 500mA
0.1
10
100
1k
10k 100k
FREQUENCY (Hz)
1.6
0.2
0
0.01
50 100 150 200 250 300 350 400 450 500
LOAD CURRENT (mA)
VIN = VOUT + 2V
COUT = 10µF
CSET = 4.7µF
ILOAD = 500mA
1.8
RMS OUTPUT NOISE (µVRMS)
RMS OUTPUT NOISE (µVRMS)
1.0
Noise Spectral Density
1000
1000
100
100
10
5
2.0
VIN = 5V
COUT = 10µF
RSET = 33.2k
ILOAD = 500mA
8
1.2
100
1
2
3
4
INPUT–TO–OUTPUT DIFFERENTIAL (V)
Integrated RMS Output Noise
(10Hz to 100kHz)
9
VIN = 5V
RSET = 33.2k
1.6 COUT = 10µF
CSET = 4.7µF
1.4
CSET = 0.047µF
CSET = 0.47µF
CSET = 1µF
CSET = 4.7µF
CSET = 22µF
0
3045 G45
Integrated RMS Output Noise
(10Hz to 100kHz)
1.8
0
IL = 500mA
RSET = 30.1k
COUT = 10µF
CSET = 0.47µF
100kHz
500kHz
1MHz
2MHz
20
3045 G44
2.0
RMS OUTPUT NOISE (µVRMS)
50
VOUT ≥ 1.3V
0.6V < VOUT < 1.3V
VOUT ≤ 0.6V
30
Integrated RMS Output Noise
(10Hz to 100kHz)
OUTPUT NOISE (nV/√Hz)
60
30
40
3045 G43
0
70
COUT = 10µF
1 V = 5V
IN
RSET = 33.2k
COUT = 22µF
CSET = 4.7µF
ILOAD = 500mA
0.1
10
100
1k
10k 100k
1M
FREQUENCY (Hz)
10M
3045 G50
OUTPUT NOISE (nV/√Hz)
20
80
50
IL = 500mA
IL = 300mA
IL = 100mA
IL = 50mA
IL = 1mA
40
80
90
PSRR (dB)
PSRR (dB)
PSRR (dB)
100
Power Supply Ripple Rejection
100
VIN = VOUT + 2V
IL = 500mA
COUT = 10µF
CSET = 0.47µF
110
60
TJ = 25°C, unless otherwise noted.
IL = 500mA
IL = 300mA
IL = 100mA
IL = 10mA
IL = 1mA
10
1 V = 5V
IN
RSET = 33.2k
CSET = 4.7µF
COUT = 10µF
0.1
10
100
1k
10k 100k
FREQUENCY (Hz)
1M
10M
3045 G51
3045fa
10
For more information www.linear.com/LT3045
LT3045
Typical Performance Characteristics
Noise Spectral Density as
a Function of Error Amplifier
Input Pair
TJ = 25°C, unless otherwise noted.
Output Noise: 10Hz to 100kHz
Load Transient Response
OUTPUT NOISE (nV/√Hz)
1000
VOUT ≥ 1.3V
0.6V < VOUT < 1.3V
VOUT ≤ 0.6V
100
OUTPUT
CURRENT
500mA/DIV
5µV/DIV
VIN = 5V
RSET = 33.2k
COUT = 10µF
CSET = 4.7µF
IL = 500mA
10
1 V =V
IN
OUT + 2V
IL = 500mA
COUT = 10µF
CSET = 4.7µF
0.1
10
100
1k
10k 100k
FREQUENCY (Hz)
OUTPUT
VOLTAGE
20mV/DIV
3042 G53
1ms/DIV
1M
20µs/DIV
VIN = 5V
RSET = 33.2k
COUT = 10µF
CSET = 0.47µF
LOAD STEP = 10mA TO 500mA
10M
3045 G52
Start-Up Time with and
without Fast Start-Up Circuitry for
Large CSET
Line Transient Response
3042 G54
Input Supply Ramp-Up and
Ramp-Down
500mV/DIV
INPUT VOLTAGE
OUTPUT WITH
FAST START–UP
(SET AT 90%)
INPUT
VOLTAGE
500mV/DIV
2V/DIV
OUTPUT
VOLTAGE
1mV/DIV
OUTPUT WITHOUT
FAST START–UP
5µs/DIV
VIN = 4.5V TO 5V
RSET = 33.2k
COUT = 10µF
CSET = 0.47µF
IL = 500mA
3042 G55
VIN = 5V
RSET = 33.2k
COUT = 10µF
CSET = 4.7µF
RL = 6.6Ω
100ms/DIV
PULSE EN/UV
2V/DIV
OUTPUT VOLTAGE
3042 G56
50ms/DIV
3042 G57
VIN = 0V TO 5V
VEN/UV = VIN
RSET = 33.2k
COUT = 10µF
CSET = 0.47µF
RL = 6.6Ω
3045fa
For more information www.linear.com/LT3045
11
LT3045
Pin Functions
(DFN/MSOP)
IN (Pins 1, 2/Pins 1, 2, 3): Input. These pins supply power
to the regulator. The LT3045 requires a bypass capacitor
at the IN pin. In general, a battery’s output impedance
rises with frequency, so include a bypass capacitor in
battery-powered applications. While a 4.7µF input bypass
capacitor generally suffices, applications with large load
transients may require higher input capacitance to prevent
input supply droop. Consult the Applications Information
section on the proper use of an input capacitor and its effect
on circuit performance, in particular PSRR. The LT3045
withstands reverse voltages on IN with respect to GND,
OUTS and OUT. In the case of a reversed input, which occurs if a battery is plugged-in backwards, the LT3045 acts
as if a diode is in series with its input. Hence, no reverse
current flows into the LT3045 and no negative voltage
appears at the load. The device protects itself and the load.
EN/UV (Pin 3/Pin 4): Enable/UVLO. Pulling the LT3045’s
EN/UV pin low places the part in shutdown. Quiescent
current in shutdown drops to less than 1µA and the output voltage turns off. Alternatively, the EN/UV pin can set
an input supply undervoltage lockout (UVLO) threshold
using a resistor divider between IN, EN/UV and GND. The
LT3045 typically turns on when the EN/UV voltage exceeds
1.24V on its rising edge, with a 130mV hysteresis on its
falling edge. The EN/UV pin can be driven above the input
voltage and maintain proper functionality. If unused, tie
EN/UV to IN. Do not float the EN/UV pin.
PG (Pin 4/Pin 5): Power Good. PG is an open-collector
flag that indicates output voltage regulation. PG pulls low
if PGFB is below 300mV. If the power good functionality is not needed, float the PG pin. A parasitic substrate
diode exists between PG and GND pins of the LT3045; do
not drive PG more than 0.3V below GND during normal
operation or during a fault condition.
ILIM (Pin 5/Pin 6): Current Limit Programming Pin.
Connecting a resistor between ILIM and GND programs
the current limit. For best accuracy, Kelvin connect this
resistor directly to the LT3045’s GND pin. The programming scale factor is nominally 150mA•kΩ. The ILIM pin
sources current proportional (1:500) to output current;
therefore, it also serves as a current monitoring pin with
a 0V to 300mV range. If the programmable current limit
functionality is not needed, tie ILIM to GND. A parasitic
substrate diode exists between ILIM and GND pins of the
LT3045; do not drive ILIM more than 0.3V below GND
during normal operation or during a fault condition.
PGFB (Pin 6/Pin 7): Power Good Feedback. The PG pin
pulls high if PGFB increases beyond 300mV on its rising
edge, with 7mV hysteresis on its falling edge. Connecting an external resistor divider between OUT, PGFB and
GND sets the programmable power good threshold with
the following transfer function: 0.3V • (1 + RPG2/RPG1).
As discussed in the Applications Information section,
PGFB also activates the fast start-up circuitry. Tie PGFB
to IN if power good and fast start-up functionalities are
not needed, and if reverse input protection is additionally
required, tie the anode of a 1N4148 diode to IN and its
cathode to PGFB. See the Typical Applications section for
details. A parasitic substrate diode exists between PGFB
and GND pins of the LT3045; do not drive PGFB more
than 0.3V below GND during normal operation or during
a fault condition.
SET (Pin 7/Pin 8): SET. This pin is the inverting input of
the error amplifier and the regulation set-point for the
LT3045. SET sources a precision 100µA current that
flows through an external resistor connected between SET
and GND. The LT3045’s output voltage is determined by
VSET = ISET • RSET. Output voltage range is from zero to
15V. Adding a capacitor from SET to GND improves noise,
PSRR and transient response at the expense of increased
start-up time. For optimum load regulation, Kelvin connect
the ground side of the SET pin resistor directly to the load.
A parasitic substrate diode exists between SET and GND
pins of the LT3045; do not drive SET more than 0.3V below
GND during normal operation or during a fault condition.
GND (Pin 8, Exposed Pad Pin 11/Pin 9, Exposed Pad
Pin 13): Ground. The exposed backside is an electrical
connection to GND. To ensure proper electrical and thermal performance, solder the exposed backside to the PCB
ground and tie it directly to the GND pin.
3045fa
12
For more information www.linear.com/LT3045
LT3045
Pin Functions
OUTS (Pin 9/Pin 10): Output Sense. This pin is the noninverting input to the error amplifier. For optimal transient
performance and load regulation, Kelvin connect OUTS
directly to the output capacitor and the load. Also, tie the
GND connections of the output capacitor and the SET pin
capacitor directly together. A parasitic substrate diode exists between OUTS and GND pins of the LT3045; do not
drive OUTS more than 0.3V below GND during normal
operation or during a fault condition.
OUT (Pin 10/Pins 11, 12): Output. This pin supplies
power to the load. For stability, use a minimum 10µF
output capacitor with an ESR below 20mΩ and an ESL
below 2nH. Large load transients require larger output
capacitance to limit peak voltage transients. Refer to the
Applications Information section for more information
on output capacitance. A parasitic substrate diode exists
between OUT and GND pins of the LT3045; do not drive
OUT more than 0.3V below GND during normal operation
or during a fault condition.
3045fa
For more information www.linear.com/LT3045
13
LT3045
Block Diagram
VIN
EN/UV
CIN
IN
CURRENT
REFERENCE
2mA
100µA
–
+
ENABLE
COMPARATOR
+
–
+
V
–
FAST START-UP
1.24V
–
300mV
INPUT
UVLO
V
+
–
–
COUT
INTERNAL CURRENT
LIMIT
–
+
RPG
GND
215Ω
+
–
300mV
+
V
PG
VOUT
RL
1.5V
PROGRAMMABLE
CURRENT LIMIT
SET-TO-OUTS
PROTECTION
CLAMP
RPG2
QPWR
OUT
V
INPUT UVLO
CURRENT LIMIT
THERMAL SHDN
DROPOUT
FAST START-UP
DISABLE LOGIC
PGFB
QP
+
–
+
THERMAL
SHDN
–
+
+
QC
DRIVER
OUTPUT OVERSHOOT
RECOVERY
BIAS
PROGRAMMABLE
POWER GOOD
V
ERROR
AMPLIFIER
SET
RSET
OUTS
CSET
–
300mV
ILIM
RILIM
RPG1
3045 BD
3045fa
14
For more information www.linear.com/LT3045
LT3045
Applications Information
The LT3045 is a high performance low dropout linear
regulator featuring LTC’s ultralow noise (2nV/√Hz at
10kHz) and ultrahigh PSRR (76dB at 1MHz) architecture
for powering noise sensitive applications. Designed as a
precision current source followed by a high performance
rail-to-rail voltage buffer, the LT3045 can be easily paralleled to further reduce noise, increase output current and
spread heat on the PCB. The device additionally features
programmable current limit, fast start-up capability and
programmable power good.
The LT3045 is easy to use and incorporates all of the protection features expected in high performance regulators.
Included are short-circuit protection, safe operating area
protection, reverse battery protection, reverse current
protection, and thermal shutdown with hysteresis.
Output Voltage
The LT3045 incorporates a precision 100µA current source
flowing out of the SET pin, which also ties to the error
amplifier’s inverting input. Figure 1 illustrates that connecting a resistor from SET to ground generates a reference
voltage for the error amplifier. This reference voltage is
simply the product of the SET pin current and the SET
pin resistor. The error amplifier’s unity-gain configuration
produces a low impedance version of this voltage on its
noninverting input, i.e. the OUTS pin, which is externally
tied to the OUT pin.
The LT3045’s rail-to-rail error amplifier and current reference allows for a wide output voltage range from 0V (using a 0Ω resistor) to VIN minus dropout — up to 15V. A
PNP-based input pair is active for 0V to 0.6V output and an
VIN
5V ±5%
LT3045
IN
100µA
4.7µF
–
+
EN/UV
OUT
PGFB
VOUT, 3.3V
IOUT(MAX), 500mA
OUTS
SET
GND ILIM
10µF
PG
Table 1. 1% Resistor for Common Output Voltages
VOUT (V)
RSET (kΩ)
2.5
24.9
3.3
33.2
5
49.9
12
121
15
150
The benefit of using a current reference compared with
a voltage reference as used in conventional regulators is
that the regulator always operates in unity gain configuration, independent of the programmed output voltage. This
allows the LT3045 to have loop gain, frequency response
and bandwidth independent of the output voltage. As a
result, noise, PSRR and transient performance do not
change with output voltage. Moreover, since none of the
error amp gain is needed to amplify the SET pin voltage
to a higher output voltage, output load regulation is more
tightly specified in the hundreds of microvolts range and
not as a fixed percentage of the output voltage.
Since the zero TC current source is highly accurate, the
SET pin resistor can become the limiting factor in achieving high accuracy. Hence, it should be a precision resistor.
Additionally, any leakage paths to or from the SET pin
create errors in the output voltage. If necessary, use high
quality insulation (e.g., Teflon, Kel-F); moreover, cleaning of all insulating surfaces to remove fluxes and other
residues may be required. High humidity environments
may require a surface coating at the SET pin to provide
a moisture barrier.
Minimize board leakage by encircling the SET pin with a
guard ring operated at a potential close to itself — ideally
tied to the OUT pin. Guarding both sides of the circuit
board is recommended. Bulk leakage reduction depends
3045 F01
0.47µF
NPN-based input pair is active for output voltages greater
than 1.3V, with a smooth transition between the two input
pairs from 0.6V to 1.3V output. While the NPN-based input
pair is designed to offer the best overall performance, refer
to the Electrical Characteristics Table for details on offset
voltage, SET pin current, output noise and PSRR variation
with the error amp input pair. Table 1 lists many common
output voltages and their corresponding 1% RSET resistors.
33.2k
Figure 1. Basic Adjustable Regulator
3045fa
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15
LT3045
Applications Information
on the guard ring width. Leakages of 100nA into or out of
the SET pin creates a 0.1% error in the reference voltage.
Leakages of this magnitude, coupled with other sources
of leakage, can cause significant errors in the output voltage, especially over wide operating temperature range.
Figure 2 illustrates a typical guard ring layout technique.
VIN
IN
LT3045
100µA
CIN
EN/UV
PGFB
OUT
PG
1
10
2
9
3
11
VOUT
IOUT(MAX): 500mA
OUTS
SET
OUT
DEMO BOARD
PCB LAYOUT
ILLUSTRATES
4-TERMINAL
CONNECTION
TO COUT
GND
COUT
ILIM
8
4
7
5
6
SET
RSET
CSET
3045 F02
3045 F03
Figure 2. DFN Guard Ring Layout
Figure 3. COUT and CSET Connections for Best Performance
Since the SET pin is a high impedance node, unwanted
signals may couple into the SET pin and cause erratic
behavior. This is most noticeable when operating with a
minimum output capacitor at heavy load currents. Bypassing the SET pin with a small capacitance to ground
resolves this issue — 10nF is sufficient.
the GND side of CSET directly to the GND side of COUT,
as well as keep the GND sides of CIN and COUT reasonably close. Refer to the LT3045 demo board manual for
more information on the recommended layout that meets
these requirements. While the LT3045 is robust enough
not to oscillate if the recommended layout is not followed,
depending on the actual layout, phase/gain margin, noise
and PSRR performance may degrade.
For applications requiring higher accuracy or an adjustable output voltage, the SET pin may be actively driven
by an external voltage source capable of sinking 100µA.
Connecting a precision voltage reference to the SET pin
eliminates any errors present in the output voltage due
to the reference current and SET pin resistor tolerances.
Output Sensing and Stability
The LT3045’s OUTS pin provides a Kelvin sense connection
to the output. The SET pin resistor’s GND side provides a
Kelvin sense connection to the load’s GND side.
Additionally, for ultrahigh PSRR, the LT3045 bandwidth
is made quite high (~1MHz), making it very close to a
typical 10µF (1206 case size) ceramic output capacitor’s
self-resonance frequency (~1.6MHz). Therefore, it is very
important to avoid adding extra impedance (ESR and
ESL) outside the feedback loop. To that end, as shown in
Figure 3, minimize the effects of PCB trace and solder
inductance by tying the OUTS pin directly to COUT and
Stability and Output Capacitance
The LT3045 requires an output capacitor for stability.
Given its high bandwidth, LTC recommends low ESR and
ESL ceramic capacitors. A minimum 10µF output capacitance with an ESR below 20mΩ and an ESL below 2nH is
required for stability.
Given the high PSRR and low noise performance attained
using a single 10µF ceramic output capacitor, larger values
of output capacitor only marginally improves the performance because the regulator bandwidth decreases with
increasing output capacitance — hence, there is little to
be gained by using larger than the minimum 10µF output
capacitor. Nonetheless, larger values of output capacitance
do decrease peak output deviations during a load transient.
Note that bypass capacitors used to decouple individual
components powered by the LT3045 increase the effective
output capacitance.
3045fa
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LT3045
Applications Information
X5R and X7R dielectrics result in more stable characteristics and are thus more suitable for LT3045. The X7R
dielectric has better stability across temperature, while
the X5R is less expensive and is available in higher values.
Nonetheless, care must still be exercised when using
X5R and X7R capacitors. The X5R and X7R codes only
specify operating temperature range and the maximum
capacitance change over temperature. While capacitance
change due to DC bias for X5R and X7R is better than
Y5V and Z5U dielectrics, it can still be significant enough
to drop capacitance below sufficient levels. As shown in
Figure 6, capacitor DC bias characteristics tend to improve
as component case size increases, but verification of
expected capacitance at the operating voltage is highly
recommended. Due to its good voltage coefficient in small
case sizes, LTC recommends using Murata’s GJ8 series
ceramic capacitors.
20
BOTH CAPACITORS ARE 16V,
1210 CASE SIZE, 10µF
0
CHANGE IN VALUE (%)
X5R
–20
–40
–60
Y5V
–80
–100
0
2
4
14
6
12
8 10
DC BIAS VOLTAGE (V)
16
3045 F04
Figure 4. Ceramic Capacitor DC Bias Characteristics
40
BOTH CAPACITORS ARE 16V,
1210 CASE SIZE, 10µF
20
CHANGE IN VALUE (%)
Give extra consideration to the type of ceramic capacitors
used. 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 temperature characteristic codes of Z5U, Y5V,
X5R and X7R. The Z5U and Y5V dielectrics are good for
providing high capacitance in the small packages, but they
tend to have stronger voltage and temperature coefficients
as shown in Figure 4 and Figure 5. When used with a 5V
regulator, a 16V 10µF Y5V capacitor can exhibit an effective
value as low as 1µF to 2µF for the DC bias voltage applied
over the operating temperature range.
X5R
0
–20
–40
Y5V
–60
–80
–100
–50
–25
0
25
75
50
TEMPERATURE (°C)
100
125
3045 F05
Figure 5. Ceramic Capacitor Temperature Characteristics
20
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 upon
it, similar to how a piezoelectric microphone works. For a
ceramic capacitor, this stress can be induced by mechanical
vibrations within the system or due to thermal transients.
LT3045 applications in high vibration environments have
three distinct piezoelectric noise generators: ceramic
output, input, and SET pin capacitors. However, due to
LT3045’s very low output impedance over a wide frequency range, negligible output noise is generated using
CHANGE IN VALUE (%)
0
High Vibration Environments
–20
–40
–60
–80
–100
MURATA: 25V,10%,
X7R/X5R, 10µF CERAMIC
1
5
10
15
DC BIAS (V)
25
20
3045 F06
GRM SERIES, 0805, 1.45mm THICK
GRM SERIES, 1206, 1.8mm THICK
GRM SERIES, 1210, 2.2mm THICK
GJ8 SERIES, 1206, 1.9mm THICK
Figure 6. Capacitor Voltage Coefficient for Different Case Sizes
3045fa
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17
LT3045
Applications Information
a ceramic output capacitor. Similarly, due to LT3045’s
ultrahigh PSRR, negligible output noise is generated
using a ceramic input capacitor. Nonetheless, given the
high SET pin impedance, any piezoelectric response
from a ceramic SET pin capacitor generates significant
output noise – peak-to-peak excursions of hundreds of
µVs. However, due to the SET pin capacitor’s high ESR
and ESL tolerance, any non-piezoelectrically responsive
(tantalum, electrolytic, or film) capacitor can be used at
the SET pin – although electrolytic capacitors tend to
have high 1/f noise. In any case, use of a surface mount
capacitor is highly recommended.
Stability and Input Capacitance
The LT3045 is stable with a minimum 4.7µF IN pin capacitor.
LTC recommends using low ESR ceramic capacitors. In
cases where long wires connect the power supply to the
LT3045’s input and ground terminals, the use of low value
input capacitors combined with a large load current can
result in instability. The resonant LC tank circuit formed by
the wire inductance and the input capacitor is the cause
and not because of LT3045’s instability.
The self-inductance, or isolated inductance, of a wire
is directly proportional to its length. The wire diameter,
however, has less influence on its self-inductance. For
example, the self-inductance of a 2-AWG isolated wire
with a diameter of 0.26" is about half the inductance of a
30-AWG wire with a diameter of 0.01". One foot of 30-AWG
wire has 465nH of self-inductance.
Several methods exist to reduce a wire’s self-inductance.
One method divides the current flowing towards the LT3045
between two parallel conductors. In this case, placing the
wires further apart reduces the inductance; up to a 50%
reduction when placed only a few inches apart. Splitting
the wires connect two equal inductors in parallel. However,
when placed in close proximity to each other, their mutual inductance adds to the overall self inductance of the
wires — therefore a 50% reduction is not possible in such
cases. The second and more effective technique to reduce
the overall inductance is to place the forward and return
current conductors (the input and ground wires) in close
proximity. Two 30-AWG wires separated by 0.02" reduce
the overall inductance to about one-fifth of a single wire.
If a battery mounted in close proximity powers the LT3045,
a 4.7µF input capacitor suffices for stability. However, if a
distantly located supply powers the LT3045, use a larger
value input capacitor. Use a rough guideline of 1µF (in
addition to the 4.7µF minimum) per 6" of wire length.
The minimum input capacitance needed to stabilize the
application also varies with the output capacitance as well
as the load current. Placing additional capacitance on the
LT3045’s output helps. However, this requires significantly
more capacitance compared to additional input bypassing.
Series resistance between the supply and the LT3045 input
also helps stabilize the application; as little as 0.1Ω to 0.5Ω
suffices. This impedance dampens the LC tank circuit at
the expense of dropout voltage. A better alternative is to
use a higher ESR tantalum or electrolytic capacitor at the
LT3045 input in parallel with a 4.7µF ceramic capacitor.
PSRR and Input Capacitance
For applications utilizing the LT3045 for post-regulating
switching converters, placing a capacitor directly at
the LT3045 input results in ac current (at the switching
frequency) to flow near the LT3045. This relatively highfrequency switching current generates a magnetic field
that couples to the LT3045 output, thereby degrading its
effective PSRR. While highly dependent on the PCB, the
switching pre-regulator, the input capacitance, amongst
other factors, the PSRR degradation can be easily over
30dB at 1MHz. This degradation is present even if the
LT3045 is de-soldered from the board, because it effectively degrades the PSRR of the PC board itself. While
negligible for conventional low PSRR LDOs, LT3045’s
ultrahigh PSRR requires careful attention to higher order
parasitics in order to extract the full performance offered
by the regulator.
To mitigate the flow of high-frequency switching current
near the LT3045, the LT3045 input capacitor can be entirely
removed -- as long as the switching converter’s output
capacitor is located more than an inch away from the
LT3045. Magnetic coupling rapidly decreases with increasing distance. Nonetheless, if the switching pre-regulator
is placed too far away (conservatively more than a couple
inches) from the LT3045, with no input capacitor present,
as with any regulator, the LT3045 input will oscillate at the
3045fa
18
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LT3045
Applications Information
parasitic LC resonance frequency. Besides, it is generally a
very common (and a preferred) practice to bypass regulator input with some capacitance. So this option is fairly
limited in its scope and not the most palatable solution.
To that end, LTC recommends using the LT3045 demo
board layout for achieving the best possible PSRR performance. The LT3045 demo board layout utilizes magnetic
field cancellation techniques to prevent PSRR degradation
caused by this high-frequency current flow—while utilizing
the input capacitor.
Filtering High Frequency Spikes
For applications where the LT3045 is used to post-regulate
a switching converter, its high PSRR effectively suppresses any “noise” present at the switcher’s switching
frequency — typically 100kHz to 4MHz. However, the very
high frequency (hundreds of MHz) “spikes” — beyond the
LT3045’s bandwidth — associated with the switcher’s
power switch transition times will almost directly pass
through the LT3045. While the output capacitor is partly
intended to absorb these spikes, its ESL will limit its ability
at these frequencies. A ferrite bead or even the inductance
associated with a short (e.g. 0.5”) PCB trace between the
switcher’s output and the LT3045’s input can serve as an
LC-filter to suppress these very high frequency spikes.
Output Noise
The LT3045 offers many advantages with respect to noise
performance. Traditional linear regulators have several
sources of noise. The most critical noise sources for a
traditional regulator are its voltage reference, error amplifier,
noise from the resistor divider network used for setting
output voltage and the noise gain created by this resistor
divider. Many low noise regulators pin out their voltage
reference to allow for noise reduction by bypassing the
reference voltage.
Unlike most linear regulators, the LT3045 does not use a
voltage reference; instead, it uses a 100µA current reference. The current reference operates with typical noise
current level of 20pA/√Hz (6nARMS over a 10Hz to 100kHz
bandwidth). The resultant voltage noise equals the current
noise multiplied by the resistor value, which in turn is RMS
summed with the error amplifier’s noise and the resistor’s
own noise of √4kTR — whereby k = Boltzmann’s constant
1.38 • 10–23J/K and T is the absolute temperature.
One problem that conventional linear regulators face is
that the resistor divider setting the output voltage gains up
the reference noise. In contrast, the LT3045’s unity-gain
follower architecture presents no gain from the SET pin
to the output. Therefore, if a capacitor bypasses the SET
pin resistor, then the output noise is independent of the
programmed output voltage. The resultant output noise
is then set just by the error amplifier’s noise — typically
2nV/√Hz from 10kHz to 1MHz and 0.8µVRMS in a 10Hz to
100kHz bandwidth using a 4.7µF SET pin capacitor. Paralleling multiple LT3045s further reduces noise by √N, for
N parallel regulators.
Refer to the Typical Performance Characteristics section
for noise spectral density and RMS integrated noise over
various load currents and SET pin capacitances.
Set Pin (Bypass) Capacitance: Noise, PSRR, Transient
Response and Soft-Start
In addition to reducing output noise, using a SET pin bypass
capacitor also improves PSRR and transient performance.
Note that any bypass capacitor leakage deteriorates the
LT3045’s DC regulation. Capacitor leakage of even 100nA
is a 0.1% DC error. Therefore, LTC recommends the use
of a good quality low leakage ceramic capacitor.
Using a SET pin bypass capacitor also soft-starts the output
and limits inrush current. The RC time constant, formed
by the SET pin resistor and capacitor, controls soft-start
time. Ramp-up rate from 0 to 90% of nominal VOUT is:
tSS ≈ 2.3 • RSET • CSET (Fast Start-Up Disabled)
Fast Start-Up
For ultralow noise applications that require low 1/f noise
(i.e. at frequencies below 100Hz), a larger value SET pin
capacitor is required, up to 22µF. While this would normally
significantly increase the regulator’s start-up time, the
LT3045 incorporates fast start-up circuitry that increases
the SET pin current to about 2mA during start-up.
As shown in the Block Diagram, the 2mA current source
remains engaged while PGFB is below 300mV, unless the
3045fa
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19
LT3045
Applications Information
regulator is in current limit, dropout, thermal shutdown
or input voltage is below minimum VIN.
If fast start-up capability is not used, tie PGFB to IN or to
OUT for output voltages above 300mV. Note that doing
so also disables power good functionality.
ENABLE/UVLO
The EN/UV pin is used to put the regulator into a micropower shutdown state. The LT3045 has an accurate
1.24V turn-on threshold on the EN/UV pin with 130mV
of hysteresis. This threshold can be used in conjunction
with a resistor divider from the input supply to define an
accurate undervoltage lockout (UVLO) threshold for the
regulator. The EN/UV pin current (IEN) at the threshold from
the Electrical Characteristics table needs to be considered
when calculating the resistor divider network:
 R 
VIN(UVLO) =1.24V • 1+ EN2  +IEN •REN2
 REN1 
The EN/UV pin current (IEN) can be ignored if REN1 is less
than 100k. If unused, tie EN/UV pin to IN.
Programmable Power Good
As illustrated in the Block Diagram, power good threshold is user programmable using the ratio of two external
resistors, RPG2 and RPG1:
 R 
VOUT(PG _ THRESHOLD) = 0.3V • 1+ PG2  +IPGFB •RPG2
 RPG1 
If the PGFB pin increases above 300mV, the open-collector
PG pin de-asserts and becomes high impedance. The
power good comparator has 7mV hysteresis and 5µs of
deglitching. The PGFB pin current (IPGFB) from the Electrical
Characteristics table must be considered when determining
the resistor divider network. The PGFB pin current (IPGFB)
can be ignored if RPG1 is less than 30k. If power good
functionality is not used, float the PG pin. Please note that
programmable power good and fast start-up capabilities
are disabled for output voltages below 300mV.
Externally Programmable Current Limit
The ILIM pin’s current limit threshold is 300mV. Connecting
a resistor from ILIM to GND sets the maximum current
flowing out of the ILIM pin, which in turn programs the
LT3045’s current limit. With a 150mA • kΩ programming
scale factor, the current limit can be calculated as follows:
Current Limit =
150mA •kΩ
RILIM
For example, a 1kΩ resistor programs the current limit
to 150mA and a 2kΩ resistor programs the current limit
to 75mA. For good accuracy, Kelvin connect this resistor
to the LT3045’s GND pin.
In cases where IN-to-OUT differential is greater than 12V,
the LT3045’s foldback circuitry decreases the internal
current limit. As a result, internal current limit may override the externally programmed current limit level to keep
the LT3045 within its safe-operating-area (SOA). See the
Internal Current Limit vs Input-to-Output Differential graph
in the Typical Performance Characteristics section.
As shown in the Block Diagram, the ILIM pin sources current
proportional (1:500) to output current; therefore, it also
serves as a current monitoring pin with a 0V to 300mV
range. If external current limit or current monitoring is
not used, tie ILIM to GND.
Output Overshoot Recovery
During a load step from full load to no load (or light
load), the output voltage overshoots before the regulator
responds to turn the power transistor OFF. Given that there
is no load (or very light load) present at the output, it takes
a long time to discharge the output capacitor.
As illustrated in the Block Diagram, the LT3045 incorporates
an overshoot recovery circuitry that turns on a current
sink to discharge the output capacitor in the event OUTS
is higher than SET. This current is typically about 4mA.
No load recovery is disabled for input voltages less than
2.5V or output voltages less than 1.5V.
3045fa
20
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LT3045
Applications Information
VIN
5V ±5%
If OUTS is externally held above SET, the current sink
turns ON in an attempt to restore OUTS to its programmed
voltage. The current sink remains ON until the external
circuitry releases OUTS.
LT3045
IN
100µA
10µF
–
+
EN/UV
OUT
PGFB
20mΩ
OUTS
SET
GND ILIM
PG
VOUT
3.3V
IOUT(MAX)
1A
LT3045
IN
100µA
–
+
EN/UV
OUT
PGFB
20mΩ
OUTS
SET
GND ILIM
PG
10µF
3045 F07
16.5k
Direct Paralleling for Higher Current
10µF
0.47µF
Higher output current is obtained by paralleling multiple
LT3045s. Tie all SET pins together and all IN pins together.
Connect the OUT pins together using small pieces of PCB
trace (used as a ballast resistor) to equalize currents in
the LT3045s. PCB trace resistance in milliohms/inch is
shown in Table 2.
Table 2. PC Board Trace Resistance
WEIGHT (oz)
10mil WIDTH
20mil WIDTH
1
54.3
27.1
2
27.1
13.6
Trace resistance is measured in mΩ/in.
The small worst-case offset of 2mV for each paralleled
LT3045 minimizes the required ballast resistor value.
Figure 7 illustrates that two LT3045s, each using a 20mΩ
PCB trace ballast resistor, provide better than 20% accurate
output current sharing at full load. The two 20mΩ external
resistors only add 10mV of output regulation drop with a
1A maximum current. With a 3.3V output, this only adds
0.3% to the regulation accuracy. As has been discussed
previously, tie the OUTS pin directly to the output capacitor.
Figure 7. Parallel Devices
More than two LT3045s can also be paralleled for even
higher output current and lower output noise. Paralleling
multiple LT3045s is also useful for distributing heat on the
PCB. For applications with high input-to-output voltage
differential, an input series resistor or resistor in parallel
with the LT3045 can also be used to spread heat.
PCB Layout Considerations
Given the LT3045’s high bandwidth and ultrahigh PSRR,
careful PCB layout must be employed to achieve full device
performance. Figure 8 shows a recommended layout that
delivers full performance of the regulator. Refer to the
LT3045’s DC2491A demo board manual for further details.
Figure 8. Recommended DFN Layout
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21
LT3045
Applications Information
Thermal Considerations
Table 3. Measured Thermal Resistance for DFN Package
The LT3045 has internal power and thermal limiting circuits that protect the device under overload conditions.
The thermal shutdown temperature is nominally 165°C
with about 8°C of hysteresis. For continuous normal
load conditions, do not exceed the maximum junction
temperature (125°C for E- and I-grades). It is important to
consider all sources of thermal resistance from junction to
ambient. This includes junction-to-case, case-to-heat sink
interface, heat sink resistance or circuit board-to-ambient
as the application dictates. Additionally, consider all heat
sources in close proximity to the LT3045.
The undersides of the DFN and MSOP packages have
exposed metal from the lead frame to the die attachment.
Both packages allow heat to directly transfer from the die
junction to the PCB metal to limit maximum operating
junction temperature. The dual-in-line pin arrangement
allows metal to extend beyond the ends of the package
on the topside (component side) of the PCB.
For surface mount devices, heat sinking is accomplished
by using the heat spreading capabilities of the PCB and its
copper traces. Copper board stiffeners and plated throughholes can also be used to spread the heat generated by
the regulator.
Tables 3 and 4 list thermal resistance as a function of copper
area on a fixed board size. All measurements were taken
in still air on a 4 layer FR-4 board with 1oz solid internal
planes and 2oz top/bottom planes with a total board thickness of 1.6mm. The four layers were electrically isolated
with no thermal vias present. PCB layers, copper weight,
board layout and thermal vias affect the resultant thermal
resistance. For more information on thermal resistance
and high thermal conductivity test boards, refer to JEDEC
standard JESD51, notably JESD51-7 and JESD51-12.
Achieving low thermal resistance necessitates attention
to detail and careful PCB layout.
COPPER AREA
TOP SIDE*
BOTTOM SIDE
BOARD AREA
THERMAL
RESISTANCE
2500mm2
2500mm2
2500mm2
34°C/W
1000mm2
2500mm2
2500mm2
34°C/W
225mm2
2500mm2
2500mm2
35°C/W
100mm2
2500mm2
2500mm2
36°C/W
*Device is mounted on topside
Table 4. Measured Thermal Resistance for MSOP Package
COPPER AREA
TOP SIDE*
BOTTOM SIDE
BOARD AREA
THERMAL
RESISTANCE
2500mm2
2500mm2
2500mm2
33°C/W
1000mm2
2500mm2
2500mm2
33°C/W
225mm2
2500mm2
2500mm2
34°C/W
100mm2
2500mm2
2500mm2
35°C/W
*Device is mounted on topside
Calculating Junction Temperature
Example: Given an output voltage of 3.3V and input voltage
of 5V ± 5%, output current range from 1mA to 500mA,
and a maximum ambient temperature of 85°C, what is the
maximum junction temperature?
The LT3045’s power dissipation is:
IOUT(MAX) • (VIN(MAX) – VOUT) + IGND • VIN(MAX)
where:
IOUT(MAX) = 500mA
VIN(MAX) = 5.25V
IGND (at IOUT = 500mA and VIN = 5.25V) = 12.5mA
thus:
PDISS = 0.5A • (5.25V – 3.3V) + 12.5mA • 5.25V = 1W
Using a DFN package, the thermal resistance is in the
range of 34°C/W to 36°C/W depending on the copper area.
Therefore, the junction temperature rise above ambient
approximately equals:
1W • 35°C/W = 35°C
The maximum junction temperature equals the maximum ambient temperature plus the maximum junction
temperature rise above ambient:
TJMAX = 85°C + 35°C = 120°C
22
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3045fa
LT3045
Typical Applications
Overload Recovery
Protection Features
Like many IC power regulators, the LT3045 incorporates
safe-operating-area (SOA) protection. The SOA protection
activates at input-to-output differential voltages greater
than 12V. The SOA protection decreases the current limit
as the input-to-output differential increases and keeps
the power transistor inside a safe operating region for
all values of input-to-output voltages up to the LT3045’s
absolute maximum ratings. The LT3045 provides some
level of output current for all values of input-to-output differentials. Refer to the Current Limit curves in the Typical
Performance Characteristics section. When power is first
applied and input voltage rises, the output follows the input
and keeps the input-to-output differential low to allow the
regulator to supply large output current and start-up into
high current loads.
The LT3045 incorporates several protection features for
battery-powered applications. Precision current limit and
thermal overload protection protect the LT3045 against
overload and fault conditions at the device’s output. For
normal operation, do not allow the junction temperature
to exceed 125°C (E-grade, I-grade) or 150°C (H-grade).
Due to current limit foldback, however, at high input voltages a problem can occur if the output voltage is low and
the load current is high. Such situations occur after the
removal of a short-circuit or if the EN/UV pin is pulled high
after the input voltage has already turned ON. The load
line in such cases intersects the output current profile at
two points. The regulator now has two stable operating
points. With this double intersection, the input power
supply may need to be cycled down to zero and brought
back up again to make the output recover. Other linear
regulators with foldback current limit protection (such as
the LT1965 and LT1963A) also exhibit this phenomenon,
so it is not unique to the LT3045.
The LT3045 also incorporates reverse input protection
whereby the IN pin withstands reverse voltages of up to
–20V without causing any input current flow and without
developing negative voltages at the OUT pin. The regulator
protects both itself and the load against batteries that are
plugged-in backwards.
To protect the LT3045’s low noise error amplifier, the SETto-OUTS protection clamp limits the maximum voltage
between SET and OUTS with a maximum DC current of
20mA through the clamp. So for applications where SET
is actively driven by a voltage source, the voltage source
must be current limited to 20mA or less. Moreover, to limit
the transient current flowing through these clamps during
a transient fault condition, limit the maximum value of the
SET pin capacitor (CSET) to 22µF.
In circuits where a backup battery is required, several
different input/output conditions can occur. The output
voltage may be held up while the input is either pulled to
GND, pulled to some intermediate voltage, or left opencircuit. In all of these cases, the reverse current protection
circuitry prevents current flow from output to the input.
Nonetheless, due to the OUTS-to-SET clamp, unless the
SET pin is floating, current can flow to GND through the
SET pin resistor as well as up to 15mA to GND through
the output overshoot recovery circuitry. This current flow
through the output overshoot recovery circuitry can be
significantly reduced by placing a Schottky diode between
OUTS and SET pins, with its anode at the OUTS pin.
3045fa
For more information www.linear.com/LT3045
23
LT3045
Typical Applications
12VIN to 3.3VOUT with 0.8µVRMS Integrated Noise
LT3045
IN
VIN
12V ±5%
4.7µF
100µA
–
+
EN/UV
200k
VOUT
3.3V
IOUT
200mA
OUT
PG
OUTS
GND
SET
ILIM
10µF
PGFB
453k
4.7µF
33.2k
750Ω
49.9k
3045 TA02
Low Noise CC/CV Lab Power Supply
LT3045
IN
VIN
4.7µF
Ultralow Noise Current Source for RF Biasing Applications
VIN
1.8V to 20V
100µA
OUT
PG
0.47µF
ROUT = R1 + RLOAD
EN/UV
PGFB
VOUT
OUTS
SET
100µA
4.7µF
–
+
EN/UV
LT3045
IN
GND
RSET
OUT
PGFB
OUTS
PG
ILIM
10µF
SET
GND
ILIM
VOUT(MAX): 15V
R1
I : 200mA
1Ω OUT
10µF
RLOAD
4.7µF
RIOUT
RSET
2k
3045 TA03
3045 TA04
VOUT(MAX) = 100μA • RSET
IOUT(MAX) =
150mA • kΩ
RIOUT
OUTPUT CURRENT NOISE = 0.8µVRMS/ROUT
INCREASE R1 (AND RSET) TO REDUCE CURRENT NOISE
3045fa
24
For more information www.linear.com/LT3045
LT3045
Typical Applications
Programming Undervoltage Lockout
VIN
4V Turn-ON
3.4V Turn-OFF
4.7µF
⎛ 110k ⎞
VIN(UVLO)RISING =1.24V • ⎜1+
⎟
⎝ 49.9k ⎠
LT3045
IN
100µA
PGFB
REN2
110k
PG
–
+
VOUT
3.3V
IOUT(MAX)
500mA
OUT
EN/UV
REN1
49.9k
OUTS
SET
10µF
GND ILIM
3045 TA05
0.47µF
33.2k
Ratiometric Tracking
LT3045
IN
100µA
–
+
EN/UV
PGFB
VIN
5.5V TO 20V
PG
LT3045
IN
EN/UV
0.1µF
PGFB
OUT
PG
OUTS
SET
0.1µF
GND
ILIM
10µF
VOUT
5V
OUTS
SET
100µA
10µF
OUT
16.9k
GND
10µF
ILIM
3045 TA06
VOUT
3.3V
MIN LOAD 200µA
33.2k
3045fa
For more information www.linear.com/LT3045
25
LT3045
Typical Applications
Ultralow 1/f Noise Reference Buffer
VIN
6V ±5%
LT3045
IN
100µA
4.7µF
–
+
EN/UV
PGFB
1,2
PG
6,7
LTC6655-5
OUTS
SET
3,4,5
VOUT = 5V
IOUT(MAX)
500mA
OUT
GND
10µF
ILIM
1k
3045 TA07
10µF
49.9k
4.7µF
Paralleling Multiple Devices Using ILIM (Current Monitor) to Cancel Ballast Resistor Drop
LT3045
IN
10µF
LT3045
100µA
EN/UV
VOUT = 3.3V
IOUT(MAX) = 1A
PGFB
OUT
PG
OUTS
SET
IN
100µA
–
+
GND
ILIM
+
–
VIN
5V ±5%
OUT
20mΩ
10µF
20mΩ
10µF
RILIM
287Ω
EN/UV
PGFB
PG
OUTS
ILIM
GND
SET
287Ω
3045 TA08
1µF
16.5k
N = NUMBER OF DEVICES IN PARALLEL
RCDC = CABLE (BALLAST RESISTOR) DROP CANCELLATION RESISTOR
RILIM = CURRENT LIMIT PROGRAMMING RESISTOR
RBALLAST = BALLAST RESISTOR
ILIM = OUTPUT CURRENT LIMIT
RCDC
5Ω
RILIM = 150mA • kΩ/ILIM – RCDC • N
= 287Ω (FOR 500mA ILIM PER REGULATOR)
RCDC = RBALLAST • 500/N
= 5Ω
3045fa
26
For more information www.linear.com/LT3045
LT3045
Typical Applications
Paralleling Multiple LT3045s for 2A Output Current
LT3045
IN
VIN
5V ±5%
22µF
LT3045
100µA
IN
100µA
–
+
200k
OUT
PG
OUT
20mΩ
OUTS
SET ILIM
GND
+
–
EN/UV
PGFB
20mΩ
10µF
EN/UV
PGFB
PG
OUTS
ILIM
10µF
GND
SET
453k
49.9k
VOUT = 3.3V
IOUT(MAX) = 2A
DROPOUT = 300mV
0.8µVRMS
4
= 0.4µVRMS
OUTPUT NOISE =
LT3045
IN
LT3045
100µA
100µA
–
+
PGFB
OUT
PG
OUT
20mΩ
OUTS
SET
GND
+
–
EN/UV
IN
ILIM
10µF
4.7µF
20mΩ
10µF
EN/UV
PGFB
PG
OUTS
ILIM
GND
SET
8.25k
3045 TA09
3045fa
For more information www.linear.com/LT3045
27
LT3045
Typical Applications
Low Noise Wheatstone Bridge Power Supply
LT1763 NOISE: 20µVRMS (10Hz TO 100kHz)
LT3045 NOISE: 0.8µVRMS (10Hz TO 100kHz)
LT3045
IN
VIN
5V ±5%
4.7µF
100µA
EN/UV
200k
–
+
OUT
PG
RESISTOR
TOLERANCE
BRIDGE PSRR
NOISE AT VBRIDGE
USING LT1763
NOISE AT VBRIDGE
USING LT3045
PERFECT
MATCHING
INFINITE
–
–
1%
40dB
200nVRMS
8nVRMS
5%
26dB
1000nVRMS
42.5nVRMS
VOUT: 3.3V AND IOUT(MAX): 500mA
R1
OUTS
SET
GND ILIM PGFB
10µF
R3
VBRIDGE
453k
+
R2
4.7µF
–
R4
49.9k
33.2k
3045 TA10
PGFB Disabled without Reverse Input Protection
LT3045
IN
VIN
4.7µF
PGFB Disabled with Reverse Input Protection
4.7µF
100µA
–
+
EN/UV
–
+
1N4148
OUT
PG
0.47µF
100µA
EN/UV
PGFB
OUT
VOUT
PGFB
OUTS
SET
LT3045
IN
VIN
GND
ILIM
PG
10µF
RSET
0.47µF
3045 TA11
VOUT
OUTS
SET
GND
ILIM
10µF
RSET
3045 TA12
3045fa
28
For more information www.linear.com/LT3045
LT3045
Package Description
Please refer to http://www.linear.com/product/LT3045#packaging for the most recent package drawings.
DD Package
10-Lead Plastic DFN (3mm × 3mm)
(Reference LTC DWG # 05-08-1699 Rev C)
0.70 ±0.05
3.55 ±0.05
1.65 ±0.05
2.15 ±0.05 (2 SIDES)
PACKAGE
OUTLINE
0.25 ±0.05
0.50
BSC
2.38 ±0.05
(2 SIDES)
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
3.00 ±0.10
(4 SIDES)
R = 0.125
TYP
6
0.40 ±0.10
10
1.65 ±0.10
(2 SIDES)
PIN 1 NOTCH
R = 0.20 OR
0.35 × 45°
CHAMFER
PIN 1
TOP MARK
(SEE NOTE 6)
0.200 REF
0.75 ±0.05
0.00 – 0.05
5
1
(DD) DFN REV C 0310
0.25 ±0.05
0.50 BSC
2.38 ±0.10
(2 SIDES)
BOTTOM VIEW—EXPOSED PAD
NOTE:
1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION OF (WEED-2).
CHECK THE LTC WEBSITE DATA SHEET FOR CURRENT STATUS OF VARIATION ASSIGNMENT
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
3045fa
For more information www.linear.com/LT3045
29
LT3045
Package Description
Please refer to http://www.linear.com/product/LT3045#packaging for the most recent package drawings.
MSE Package
12-Lead Plastic MSOP, Exposed Die Pad
(Reference LTC DWG # 05-08-1666 Rev G)
BOTTOM VIEW OF
EXPOSED PAD OPTION
2.845 ±0.102
(.112 ±.004)
5.10
(.201)
MIN
2.845 ±0.102
(.112 ±.004)
0.889 ±0.127
(.035 ±.005)
6
1
1.651 ±0.102
(.065 ±.004)
1.651 ±0.102 3.20 – 3.45
(.065 ±.004) (.126 – .136)
12
0.65
0.42 ±0.038
(.0256)
(.0165 ±.0015)
BSC
TYP
RECOMMENDED SOLDER PAD LAYOUT
0.254
(.010)
0.35
REF
4.039 ±0.102
(.159 ±.004)
(NOTE 3)
0.12 REF
DETAIL “B”
CORNER TAIL IS PART OF
DETAIL “B” THE LEADFRAME FEATURE.
FOR REFERENCE ONLY
7
NO MEASUREMENT PURPOSE
0.406 ±0.076
(.016 ±.003)
REF
12 11 10 9 8 7
DETAIL “A”
0° – 6° TYP
3.00 ±0.102
(.118 ±.004)
(NOTE 4)
4.90 ±0.152
(.193 ±.006)
GAUGE PLANE
0.53 ±0.152
(.021 ±.006)
DETAIL “A”
1.10
(.043)
MAX
0.18
(.007)
SEATING
PLANE
0.22 – 0.38
(.009 – .015)
TYP
1 2 3 4 5 6
0.650
(.0256)
BSC
NOTE:
1. DIMENSIONS IN MILLIMETER/(INCH)
2. DRAWING NOT TO SCALE
3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS.
MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS.
INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX
6. EXPOSED PAD DIMENSION DOES INCLUDE MOLD FLASH. MOLD FLASH ON E-PAD SHALL
NOT EXCEED 0.254mm (.010") PER SIDE.
0.86
(.034)
REF
0.1016 ±0.0508
(.004 ±.002)
MSOP (MSE12) 0213 REV G
3045fa
30
For more information www.linear.com/LT3045
LT3045
Revision History
REV
DATE
DESCRIPTION
A
10/17
Added H-grade options
PAGE NUMBER
Modified Quiescent Current in Shutdown specs
2, 23
4
Modified Note 9
5
Modified PGFB description
12
3045fa
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/LT3045
31
LT3045
Typical Application
Parallel Devices
LT3045
IN
VIN
5V ±5%
100µA
10µF
–
+
EN/UV
OUT
PGFB
20mΩ
OUTS
SET
GND ILIM
PG
10µF
VOUT
3.3V
IOUT(MAX)
1A
LT3045
IN
100µA
–
+
EN/UV
OUT
PGFB
20mΩ
OUTS
SET
GND ILIM
PG
10µF
3045 TA13
16.5k
0.47µF
Related Parts
PART NUMBER
DESCRIPTION
COMMENTS
LT1761
100mA, Low Noise LDO
300mV Dropout Voltage, Low Noise: 20µVRMS, VIN = 1.8V to 20V,
TSOT-23 Package
LT1763
500mA, Low Noise LDO
300mV Dropout Voltage, Low Noise: 20μVRMS, VIN = 1.8V to 20V,
4mm × 3mm DFN and SO-8 Packages
LT3042
200mA, Ultralow Noise and Ultrahigh PSRR LDO
0.8μVRMS Noise and 79dB PSRR at 1MHz, VIN = 1.8V to 20V, 350mV
Dropout Voltage, Programmable Current Limit and Power Good,
3mm × 3mm DFN and MSOP Packages
LT3055
500mA LDO with Diagnostics and Precision Current Limit
340mV Dropout Voltage, Low Noise: 25μVRMS, VIN = 1.8V to 45V,
4mm × 3mm DFN and MSOP Packages
LT3065
500mA Low Noise LDO with Soft-Start
300mV Dropout Voltage, Low Noise: 25μVRMS, VIN = 1.8V to 45V,
3mm × 3mm DFN and MSOP Packages
LT3080
1.1A, Parallelable, Low Noise, Low Dropout Linear Regulator
300mV Dropout Voltage (2-Supply Operation), Low Noise: 40μVRMS,
VIN: 1.2V to 36V, VOUT: 0V to 35.7V, Current-Based Reference with
1-Resistor VOUT Set; Directly Parallelable (No Op Amp Required),
Stable with Ceramic Capacitors; TO-220, DD-Pak, SOT-223, MSOP
and 3mm × 3mm DFN-8 Packages; LT3080-1 Version Has Integrated
Internal Ballast Resistor
LT3085
500mA, Parallelable, Low Noise, Low Dropout Linear
Regulator
275mV Dropout (2-Supply Operation), Low Noise: 40μVRMS, VIN: 1.2V
to 36V, VOUT: 0V to 35.7V, Current-Based Reference with 1-Resistor
VOUT Set, Directly Parallelable (No Op Amp Required), Stable with
Ceramic Capacitors; MS8E and 2mm × 3mm DFN-6 Packages
3045fa
32
LT 1017 REV A • PRINTED IN USA
www.linear.com/LT3045
For more information www.linear.com/LT3045
 LINEAR TECHNOLOGY CORPORATION 2016