LT3150
Fast Transient Response,
Low Input Voltage, Very Low Dropout
Linear Regulator Controller
FEATURES
s
s
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DESCRIPTIO
s
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Fast Transient Response Optimized with
Ceramic Output Capacitors
FET R
DS(ON)
Defines Dropout Voltage
±1%
Reference Tolerance Over Temperature
Multifunction LDO Shutdown Pin with Latchoff
Fixed Frequency 1.4MHz Boost Converter Generates
MOSFET Gate Drive
Internally Compensated Boost Converter Uses Tiny
Capacitors and Inductor
Independent Boost Converter Shutdown Control
Permits LDO Output Voltage Supply Sequencing
16-Lead SSOP Package
The LT
®
3150 drives a low cost external N-channel MOSFET
as a source follower to produce a fast transient response,
very low dropout voltage linear regulator. Selection of the
N-channel MOSFET R
DS(ON)
allows dropout voltages below
300mV for low V
IN
to low V
OUT
applications.
The LT3150 includes a fixed frequency boost regulator
that generates gate drive for the N-channel MOSFET. The
internally compensated current mode PWM architecture
combined with the 1.4MHz switching frequency permits
the use of tiny, low cost capacitors and inductors.
The LT3150’s transient load performance is optimized
with ceramic output capacitors. A precision 1.21V refer-
ence accommodates low voltage supplies.
Protection includes a high side current limit amplifier that
activates a fault timer circuit. A multifunction shutdown
pin provides either current limit time-out with latchoff,
overvoltage protection or thermal shutdown. Independent
shutdown control of the boost converter provides on/off
and sequencing control of the LDO output voltage.
APPLICATIO S
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Microprocessor, ASIC and I/O Supplies
Very Low Dropout Input-to-Output Conversion
Logic Termination Supplies
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATIO
MBR0520L
1.8V to 1.5V, 4A Very Low Dropout Linear Regulator
(Typical Dropout Voltage = 65mV at I
OUT
= 4A)
+
C1
4.7µF
6.19k
1%
1.37k
1%
LT3150
V
IN2
SW
FB1
V
IN1
SHDN2 SHDN1
I
POS
SWGND
I
NEG
GND
GATE
GND
FB2
COMP
L1
10µH
50mV/DIV
5.1Ω
Si4410
243Ω
1%
50pF
1020Ω
1%
+
C
IN
220µF
2.5V
×2
V
IN
1.8V
2A/DIV
V
OUT
1.5V
4A
3150 TA02
1.5k
6800pF
2.2µF
×10
X5R CERAMIC
0805 CASE
C
IN
: PANASONIC SP SERIES EEFUE0E221R 20%
C1: AVX TAJA475M020R 20V 20%
L1: MURATA LQH32CN100K11 OR SUMIDA CDRH3D16100
3150 TA01
U
Transient Response for
0.1A to 4A Output Load Step
20µs/DIV
3150f
U
U
1
LT3150
ABSOLUTE
(Note 1)
AXI U
RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW
SW
SWGND
V
IN1
SHDN2
V
IN2
GND
NC
FB2
1
2
3
4
5
6
7
8
16 FB1
15 GND
14 SHDN1
13 I
POS
12 I
NEG
11 GATE
10 NC
9
COMP
V
IN1
, SHDN1 Voltage .............................................. 10V
SW Voltage .............................................. – 0.4V to 36V
FB1 Voltage ................................................ V
IN1
+ 0.3V
Current into FB1, FB2 Pin ....................................
±1mA
V
IN2
, I
POS
, I
NEG
....................................................... 22V
SHDN2 .................................................................... V
IN2
Operating Ambient Temperature Range ..... 0°C to 70°C
Junction Temperature (Note 2) ........................... 125°C
Storage Temperature Range ................ – 65°C to 150°C
Lead Temperature (Soldering, 10 sec)................. 300°C
ORDER PART
NUMBER
LT3150CGN
GN PART
MARKING
3150
GN PACKAGE
16-LEAD PLASTIC SSOP
T
JMAX
= 125°C,
θ
JA
= 130°C/W,
θ
JC
= 40°C/W
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
The
q
denotes specifications which apply over the full operating temperature range, otherwise specifications are at T
A
= 25°C.
V
IN1
= 1.5V, V
SHDN1
= V
IN1
, V
IN2
= 12V, GATE = 6V, I
POS
= I
NEG
= 5V, V
SHDN2
= 0.75V unless otherwise noted.
SYMBOL
PARAMETER
V
IN1
Minimum Operating Voltage
V
IN1
Maximum Operating Voltage
V
FB1
I
Q1
FB1 Reference Voltage
FB1 Input Bias Current
V
IN1
Quiescent Current
V
IN1
Quiescent Current in Shutdown
FB1 Reference Line Regulation
Switching Frequency
Maximum Duty Cycle
Switch Current Limit
Switch V
CESAT
Switch Leakage Current
SHDN1 Input Voltage High
SHDN1 Input Voltage Low
SHDN1 Input Bias Current
Linear Regulator Controller
I
Q2
V
FB2
V
IN2
Quiescent Current
FB2 Reference Voltage
q
q
q
CONDITIONS
MIN
TYP
0.9
MAX
1.1
10
1.255
80
4.5
0.5
1.0
0.2
1.9
UNITS
V
V
V
nA
mA
µA
µA
%/V
MHz
%
mA
Boost Switching Regulator
1.20
1.23
27
3
0.01
0.01
0.02
Current Flows into Pin
V
SHDN1
= 1.5V
V
SHDN1
= 0V, V
IN1
= 2V
V
SHDN1
= 0V, V
IN1
= 5V
1.5V
≤
V
IN1
≤
10V
q
q
q
1
82
550
1.4
86
800
300
0.01
(Note 3)
I
SW
= 300mA
V
SW
= 5V
350
1
0.3
1
V
SHDN1
= 3V, Current Flows into Pin
V
SHDN1
= 0V, Current Flows into Pin
5
1.203
1.198
25
0.01
12
1.210
1.210
0.01
–0.6
50
0.1
19
1.217
1.222
0.03
–4
FB2 Line Regulation
FB2 Input Bias Current
10V
≤
V
IN2
≤
20V
FB2 = V
FB2
, Current Flows out of Pin
q
q
2
U
mV
µA
V
V
µA
µA
mA
V
V
%/V
µA
3150f
W
U
U
W W
W
LT3150
ELECTRICAL CHARACTERISTICS
The
q
denotes specifications which apply over the full operating temperature range, otherwise specifications are at T
A
= 25°C.
V
IN1
= 1.5V, V
SHDN1
= V
IN1
, V
IN2
= 12V, GATE = 6V, I
POS
= I
NEG
= 5V, V
SHDN2
= 0.75V unless otherwise noted.
SYMBOL
A
VOL
V
OL
V
OH
PARAMETER
Large-Signal Voltage Gain
GATE Output Swing Low (Note 4)
GATE Output Swing High
I
POS
+ I
NEG
Supply Current
Current Limit Threshold Voltage
q
CONDITIONS
V
GATE
= 3V to 10V
I
GATE
= 0mA
I
GATE
= 0mA
3V
≤
I
POS
≤
20V
q
q
q
q
MIN
69
V
IN2
– 1.6
0.3
42
37
TYP
84
2.5
V
IN2
– 1
0.625
50
50
– 0.20
MAX
3
UNITS
dB
V
V
1
58
63
– 0.50
8.0
– 23
0.25
2.20
1.240
150
mA
mV
mV
%/V
µA
µA
V
V
V
mV
Current Limit Threshold Voltage
Line Regulation
SHDN2 Sink Current
SHDN2 Source Current
SHDN2 Low Clamp Voltage
SHDN2 High Clamp Voltage
SHDN2 Threshold Voltage
SHDN2 Threshold Hysteresis
3V
≤
I
POS
≤
20V
Current Flows Into Pin
Current Flows Out of Pin
q
q
q
q
q
q
q
2.5
–8
1.50
1.18
50
5.0
– 15
0.1
1.85
1.21
100
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of the device may be impaired.
Note 2:
T
J
is calculated from the ambient temperature T
A
and power
dissipation P
D
according to the following formula:
T
J
= T
A
+ (P
D
• 130°C/W)
Note 3:
Switch current limit is guaranteed by design and/or correlation to
static test.
Note 4:
The V
GS(th)
of the external MOSFET must be greater than
3V – V
OUT
.
3150f
3
LT3150
TYPICAL PERFOR A CE CHARACTERISTICS
Boost Switching Regulator
Switch V
CESAT
vs Switch Current
700
600
500
T
A
= 25°C
SWITCHING FREQUENCY (MHz)
SHDN1 INPUT BIAS CURRENT (µA)
V
CESAT
(mV)
400
300
200
100
0
0
100
200 300 400 500
SWITCH CURRENT (mA)
600
700
Switch Current Limit vs Duty Cycle
1000
900
SWITCH CURRENT LIMIT (mA)
FB1 REFERENCE VOLTAGE (V)
800
70°C
700
600
500
400
300
200
10
20
30
40
50
60
DUTY CYCLE (%)
70
80
–40°C
25°C
Linear Regulator Controller
V
IN2
Quiescent Current
vs Temperature
19
18
17
16
15
V
IN
= 12V
14
V
IN
= 20V
13
12
V
IN
= 8V
11
10
9
8
7
6
5
–75 –50 –25 0 25 50 75 100 125 150 175
TEMPERATURE (°C)
3150 G06
V
IN2
QUIESCENT CURRENT (mA)
FB2 INPUT BIAS CURRENT (µA)
FB2 REFERENCE VOLTAGE (V)
4
U W
Oscillator Frequency
vs Temperature
2.00
1.75
1.50
1.25
1.00
0.75
0.50
0.25
0
–50
V
IN
= 1.5V
V
IN
= 5V
50
SHDN1 Input Bias Current
vs V
SHDN1
T
A
= 25°C
40
30
20
10
0
–25
0
25
50
TEMPERATURE (°C)
75
100
3150 G02
0
1
2
3
4
SHDN1 PIN VOLTAGE (V)
5
3150 G03
3150 G01
FB1 Reference Voltage
vs Temperature
1.25
1.24
VOLTAGE
1.23
1.22
1.21
1.20
–50
–25
0
25
50
TEMPERATURE (°C)
75
100
3150 G05
3150 G04
FB2 Reference Voltage
vs Temperature
1.222
1.220
1.218
1.216
1.214
1.212
1.210
1.208
1.206
1.204
1.202
1.200
1.198
–75 –50 –25 0 25 50 75 100 125 150 175
TEMPERATURE (°C)
3150 G07
FB2 Input Bias Current
vs Temperature
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
V
IN
= 20V
V
IN
= 12V
V
IN
= 8V
0
–75 – 50 –25 0 25 50 75 100 125 150 175
TEMPERATURE (°C)
3150 G08
3150f
LT3150
TYPICAL PERFOR A CE CHARACTERISTICS
FB2 Line Regulation
vs Temperature
0.030
0.025
0.020
0.015
0.010
0.005
0
–75 – 50 –25 0 25 50 75 100 125 150 175
TEMPERATURE (°C)
3150 G09
ERROR AMPLIFIER GAIN (dB) AND PHASE (DEG)
LARGE-SIGNAL VOLTAGE GAIN (dB)
FB2 LINE REGULATION (%/V)
Gate Output Swing Low
vs Temperature
3.00
2.75
I
LOAD
= 50mA
GATE OUTPUT SWING HIGH (V)
2.5
2.0
1.5
1.0
3.0
2.50
NO LOAD
2.25
2.00
1.75
1.50
1.25
1.00
–75 – 50 –25 0 25 50 75 100 125 150 175
TEMPERATURE (°C)
3150 G12
I
POS
+ I
NEG
SUPPLY CURRENT (µA)
GATE OUTPUT SWING LOW (V)
Current Limit Threshold Voltage
vs Temperature
CURRENT LIMIT THRESHOLD VOLTAGE (mV)
65
60
55
50
I
POS
= 20V
45
40
35
–75 – 50 –25 0 25 50 75 100 125 150 175
TEMPERATURE (°C)
3150 G15
CURRENT LIMIT THRESHOLD
VOLTAGE LINE REGULATION (%/V)
SHDN2 SINK CURRENT (µA)
I
POS
= 5V
I
POS
= 3V
U W
Linear Regulator Controller
Error Amplifier Large-Signal
Voltage Gain vs Temperature
120
115
110
105
100
95
90
85
80
75
70
–75 – 50 –25 0 25 50 75 100 125 150 175
TEMPERATURE (°C)
3150 G10
Gain and Phase vs Frequency
200
150
PHASE
100
GAIN
50
0
1k
10k
100k
1M
FREQUENCY (Hz)
10M
100M
3150 G11
Gate Output Swing High (V
IN2
–
V
GATE
) vs Temperature
1000
900
800
700
600
500
400
I
POS
+ I
NEG
Supply Current
vs Temperature
I
LOAD
= 50mA
I
POS
= I
NEG
= 5V
I
POS
= I
NEG
= 12V
I
POS
= I
NEG
= 20V
I
POS
= I
NEG
= 3V
NO LOAD
0.5
0
–75 – 50 –25 0 25 50 75 100 125 150 175
TEMPERATURE (°C)
3150 G13
300
–75 – 50 –25 0 25 50 75 100 125 150 175
TEMPERATURE (°C)
3150 G14
Current Limit Threshold Voltage
Line Regulation vs Temperature
0
7.5
7.0
– 0.1
6.5
6.0
5.5
5.0
4.5
4.0
3.5
3.0
– 0.5
–75 – 50 –25 0 25 50 75 100 125 150 175
TEMPERATURE (°C)
3150 G16
SHDN2 Sink Current
vs Temperature
– 0.2
– 0.3
– 0.4
2.5
–75 – 50 –25 0 25 50 75 100 125 150 175
TEMPERATURE (°C)
3150 G17
3150f
5
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