LT3095
Dual-Channel Low Noise
Bias Generators
FEATURES
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DESCRIPTION
The
LT
®
3095
generates two low noise bias supplies from
a common input voltage ranging from 3V to 20V. Each
channel includes a fixed frequency, peak current-mode
step-up switching regulator and a low noise, single-
resistor-programmable 50mA linear regulator. The linear
regulator’s high power supply ripple rejection (PSRR)
combined with its low noise performance results in less
than 100µV
P-P
output ripple and noise.
Each boost regulator adjusts its output voltage to 2V above
the corresponding linear regulator’s output voltage, opti-
mizing power dissipation, PSRR and transient response.
This tracking scheme, along with internal boost regulator
frequency compensation and integrated Schottky diodes,
minimizes external component count and simplifies system
design. Each linear regulator includes internal current limit
and thermal limit protection circuitry.
The LT3095 switching frequency is externally program-
mable with a single resistor from 450kHz to 2MHz. A
SYNC pin allows synchronization to an external clock. The
LT3095 is available in a thermally enhanced, low profile
(0.75mm) 24-lead 3mm × 5mm QFN package.
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.
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Generates Two Independent Low Noise Bias Supplies
Boost Regulator:
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Wide Input Voltage Range: 3V to 20V
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Adjustable Switching Frequency: 450kHz to 2MHz
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Synchronizable to External Clock
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950mA Power Switches
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Integrated Schottky Diodes
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Internal Frequency Compensation
Linear Regulator:
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Wide Output Voltage Range: 1V to 20V
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SET Pin Reference Current: 50µA
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Low Noise: 4µV
RMS
(10Hz to 100kHz)
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High Frequency PSRR: 72dB at 1MHz
Independent Precision-Threshold Enable Pins
Symmetric Pinout Simplifies PCB Layout
Thermally Enhanced 3mm × 5mm 24-Lead
QFN Package
APPLICATIONS
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Noise-Sensitive USB Powered Applications
Data Conversion, Industrial Supplies, RF
Instrumentation Amplifiers
TYPICAL APPLICATION
V
IN
3V to 7V
2.2µF
6.8µH
EN1
SW1
GND
10µF
BSTOUT1
V
OUT1
5V, 50mA
2.2µF
1µF
100k
0.1µF
GND
LDOIN1
OUT1
SET1
INTV
CC
LT3095
BSTOUT2
LDOIN2
OUT2
SET2
RT
SYNC
GND
3095 TA01a
Output Ripple
IN
EN2
SW2
GND
10µF
10µH
V
BSTOUT
20mV/DIV
V
OUT2
15V, 50mA
2.2µF
300k
100k
1µF
V
OUT
50µV/DIV
V
IN
= 5V
V
OUT
= 15V
I
LOAD
= 50mA
f
OSC
= 1MHz
20MHz BW
1µs/DIV
3095 G03
3095fa
For more information
www.linear.com/LT3095
1
LT3095
ABSOLUTE MAXIMUM RATINGS
(Note 1)
PIN CONFIGURATION
TOP VIEW
SW1
SW2
20 GND
19 BSTOUT2
18 SYNC
25
GND
17 RT
16 GND
15 LDOIN2
14 GND
13 OUT2
9 10 11 12
SET1
EN1
EN2
SET2
IN, SET1, SET2 ........................................................24V
SW1, SW2, ................................................................24V
OUT1, OUT2 ...................................................24V, –0.3V
EN1, EN2 .. .....................................................24V, –0.3V
LDOIN1, LDOIN2, BSTOUT1, BSTOUT2.....................24V
RT, SYNC ....................................................................6V
Operating Junction Temperature (Note 2)
E-Grade, I-Grade ................................ –40°C to 125°C
MP-Grade .......................................... –55°C to 125°C
Storage Temperature Range .................. –65°C to 150°C
IN
24 23 22 21
GND 1
BSTOUT1 2
NC 3
INTV
CC
4
GND 5
LDOIN1 6
GND 7
OUT1 8
UDD PACKAGE
24-LEAD (3mm
×
5mm) PLASTIC QFN
T
JMAX
= 125°C,
θ
JA
= 38°C/W,
θ
JC
= 5.0°C/W
EXPOSED PAD (PIN 25) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
(http://www.linear.com/product/LT3095#orderinfo)
LEAD FREE FINISH
LT3095EUDD#PBF
LT3095IUDD#PBF
LT3095MPUDD#PBF
TAPE AND REEL
LT3095EUDD#TRPBF
LT3095IUDD#TRPBF
LT3095MPUDD#TRPBF
PART MARKING
LGRQ
LGRQ
LGRQ
PACKAGE DESCRIPTION
24-Lead (3mm x 5mm) Plastic QFN
24-Lead (3mm x 5mm) Plastic QFN
24-Lead (3mm x 5mm) Plastic QFN
TEMPERATURE RANGE
–40°C to 125°C
–40°C to 125°C
–55°C to 125°C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
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.
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C, V
IN
= 5V, SYNC = 0V unless otherwise noted.
SYMBOL PARAMETER
V
IN
I
IN
V
EN1,2
Input Voltage Supply Range
V
IN
Pin Supply Current
V
TRIP
(off to on)
Enable Threshold Hysteresis
Enable Pin Current
V
EN
= 5V
V
EN1
= V
EN2
= 5.0V, V
IN
= 5V (Not Switching)
V
EN1
= V
EN2
= 0.3V, V
IN
= 20V (Shutdown)
V
EN1,2
Rising
l
ELECTRICAL CHARACTERISTICS
CONDITIONS
l
IN
MIN
3
TYP
3.25
1.6
MAX
20
5
5
1.35
135
5
UNITS
V
mA
μA
V
mV
μA
1.12
110
1.23
125
1
2
3095fa
For more information
www.linear.com/LT3095
LT3095
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C, V
IN
= 5V, SYNC = 0V unless otherwise noted.
SYMBOL PARAMETER
INTV
CC
INTV
CC
Voltage
INTV
CC
Under Voltage Lockout
INTV
CC
Under Voltage Lockout
Hysteresis
Boost Regulator
BOOST
(V
LDOIN
– V
OUT
) Differential Regulation
Voltage
Boost Maximum Duty Cycle
Switch Pin Leakage Current
Boost Switch Peak Current Limit
Switch V
CESAT
OSC
Oscillator Frequency
V
EN1
= V
EN2
= 5V, V
OUT
= 10V, I
LOAD
= 0mA
f
OSC
= 1MHz
Switch OFF, V
SW
= 12V
(Note 3)
I
SW
= 400mA
RT = 210k, V
IN
= 5V
RT = 100k, V
IN
= 5V
RT = 44.5k, V
IN
= 5V
V
SYNC
= 0V to 1.5V pulse
V
SYNC
= 5V
f
OSC
= 1MHz, 50% duty cycle
V
OUT
= 10V, I
LOAD
= 0mA
V
OUT
= 1V to 20V, I
LOAD
= 0mA to 50mA
Offset Voltage (V
OUT
– V
SET
)
LDO Voltage Regulation: ΔI
SET
LDO Voltage Regulation: ΔV
OS
(Note 5)
LDO Load Regulation: ΔI
SET
LDO Load Regulation: ΔV
OS
(Note 4)
LDOIN Supply Current
Ripple Rejection
3V < V
OUT
< 20V, I
LOAD
= 50mA
LDO Output Noise Voltage
LDO Output Current Limit
V
OUT
= 10V, I
LOAD
= 0mA
V
OUT
= 3V to 20V, I
LOAD
= 0mA
V
OUT
= 1V to 20V, I
LOAD
= 0mA
V
OUT
= 10V, I
LOAD
= 0mA to 50mA
V
OUT
= 10V, I
LOAD
= 0mA to 50mA
I
LOAD
= 0mA
f
RIPPLE
= 450kHz, C
SET
= 0.1µF, C
OUT
= 2.2µF, I
LOAD
= 50mA
f
RIPPLE
= 1MHz, C
SET
= 0.1µF, C
OUT
= 2.2µF, I
LOAD
= 50mA
f
RIPPLE
= 2MHz, C
SET
= 0.1µF, C
OUT
= 2.2µF, I
LOAD
= 50mA
V
OUT
= 5V, I
LOAD
= 50mA, C
SET
= 0.47µF, C
OUT
= 2.2µF,
BW = 10Hz to 100KHz.
V
OUT
= 1V to 20V
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l
l
l
l
l
l
l
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ELECTRICAL CHARACTERISTICS
CONDITIONS
V
EN1
= V
EN2
= 5V
V
EN1
= V
EN2
= 5V, INTV
CC
Rising
V
EN1
= V
EN2
= 5V
l
MIN
2.25
TYP
2.7
2.4
300
MAX
2.55
UNITS
V
V
mV
1.85
90
2
2.15
V
%
0.01
0.8
0.47
0.95
1.85
20
15
0.8
49.5
49
–1
1.1
50
50
0.15
–60
–50
100
–6
450
73
72
71
4
55
70
0.95
250
0.5
1
2
1
1.1
0.53
1.05
2.15
80
20
1.3
50.5
51
1
–100
150
µA
A
mV
MHz
MHz
MHz
%
µA
V
µA
µA
mV
nA
µV
nA
mV
µA
dB
SYNC Duty Cycle Range
SYNC Pin Input Current
SYNC Threshold
LDO Linear Regulator
LDO
SET Pin Current
µV
RMS
mA
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. Absolute Maximum Ratings are those values
beyond which the life of a device may be impaired.
Note 2:
The LT3095E 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
LT3095I is guaranteed over the full –40°C to 125°C operating junction
temperature range. The LT3095MP is 100% tested over the –55°C to
125°C operating junction temperature range.
Note 3:
The boost peak current limit is measured in a low frequency test
mode. In operation at high frequencies, the inductor current may exceed
this value due to delays in the control circuitry.
Note 4:
Linear Technology
®
is unable to guarantee maximum load
regulation due to production test limitations with Kelvin-sensing the
package pins. Please consult the Typical Performance Characteristics for
curves of output regulation as a function of load current.
Note 5:
For V
OUT
< 1.25V, the LT3095 is tested with a 30µA external
load. This load substitutes for an internal 30µA load which exists for
V
OUT
> 1.25V.
3095fa
For more information
www.linear.com/LT3095
3
LT3095
TYPICAL PERFORMANCE CHARACTERISTICS
Efficiency
80
70
60
EFFICIENCY (%)
50
40
30
20
10
0
0
10
f
SW
= 1MHz
V
OUT1
= 5V
V
OUT2
= 15V
I
LOAD1
= I
LOAD2
V
IN
= 5V
V
IN
= 3.3V
20
30
40
LOAD CURRENT (mA)
50
3095 G01
T
A
= 25°C, unless otherwise noted.
Transient Output Ripple
V
BSTOUT
20mV/DIV
V
BSTOUT
20mV/DIV
Transient Output Ripple
V
OUT
5mV/DIV
V
OUT
50µV/DIV
V
IN
= 5V
V
OUT
= 15V
I
LOAD
= 50mA
f
OSC
= 1MHz
350MHz BW
1µs/DIV
3095 G02
V
IN
= 5V
V
OUT
= 15V
I
LOAD
= 50mA
f
OSC
= 1MHz
20MHz BW
1µs/DIV
3095 G03
Linear Regulator Transient
Response
51.0
I
OUT
50mA/DIV
V
OUT1
10mV/DIV
V
OUT2
10mV/DIV
50.8
50.6
SET PIN CURRENT (µA)
50.4
50.2
50.0
49.8
49.6
49.4
49.2
SET Pin Current
V
OUT
= 10V
SET Pin Current Distribution
N = 10298
V
IN
= 5V
V
OUT1
= 5V
V
OUT2
= 15V
C
OUT
= 2.2µF
CH1 LOAD STEP = 1mA to 50mA
5µs/DIV
3095 G04
49.0
–75 –50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
3095 G05
49
49.5
50
50.5
I
SET
DISTRIBUTION (µA)
51
3095 G06
SET Pin Current
51.0
50.8
50.6
SET PIN CURRENT (µA)
SET PIN CURRENT (µA)
50.4
50.2
50.0
49.8
49.6
49.4
49.2
49.0
0
2
4
6 8 10 12 14 16 18 20
SET PIN VOLTAGE (V)
3095 G07
SET Pin Current
51.0
50.8
50.6
50.4
50.2
50.0
49.8
49.6
49.4
49.2
49.0
0
10
20
30
40
OUTPUT CURRENT (mA)
50
3095 G08
V
IN
= 5V
300
250
OFFSET VOLTAGE (µV)
200
150
100
50
Offset Voltage (V
OUT
– V
SET
)
V
OUT
= 10V
I
LOAD
= 0mA
0
–75 –50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
3095 G09
4
3095fa
For more information
www.linear.com/LT3095
LT3095
TYPICAL PERFORMANCE CHARACTERISTICS
Offset Voltage (V
OUT
– V
SET
)
100
I
LOAD
= 1mA
T
A
= 25°C, unless otherwise noted.
Offset Voltage Distribution
N = 10298
1
0
–1
OFFSET VOLTAGE (mV)
–2
–3
–4
–5
–6
–7
Offset Voltage (V
OUT
– V
SET
)
80
OFFSET VOLTAGE (µV)
60
40
20
0
0
2
4
6 8 10 12 14 16 18 20
OUTPUT VOLTAGE (V)
3095 G10
–1
–0.5
0
0.5
V
OS
DISTRIBUTION (mV)
1
3095 G11
–8
–40°C
25°C
125°C
0
10
20
30
40
OUTPUT CURRENT (mA)
50
3095 G12
LDO Current Limit
80
80.0
LDO Current Limit
V
OUT
= V
SET
– 200mV
TURN–ON THRESHOLD (V)
1.24
EN Turn-On Threshold
V
IN
= 5V
LDO CURRENT LIMIT (mA)
LDO CURRENT LIMIT (mA)
75
75.0
1.23
70
70.0
1.22
65
60
65.0
1.21
55
–75 –50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
3095 G13
60.0
0
2
4
6 8 10 12 14 16 18 20
OUTPUT VOLTAGE (V)
3095 G14
1.20
–75 –50 –25 0
25 50 75
TEMPERATURE (°C)
100 125
3095 G15
EN Pin Hysteresis
150
1.4
EN Pin Current
V
EN
= V
IN
= 5V
5
EN Pin Current
V
IN
= 5V
EN PIN HYSTERESIS (mV)
140
EN PIN CURRENT (µA)
1.2
EN PIN CURRENT (µA)
0 25 50 75 100 125 150
TEMPERATURE (°C)
3095 G17
4
130
1.0
3
120
0.8
2
110
0.6
1
100
–75 –50 –25 0
25 50 75
TEMPERATURE (°C)
100 125
3095 G16
0.4
–75 –50 –25
0
0
2
4
6 8 10 12 14 16 18 20
EN PIN VOLTAGE (V)
3095 G18
3095fa
For more information
www.linear.com/LT3095
5
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