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LTC3851AEUD#TRPBF

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LTC3851A
1
3851afa
Typical applicaTion
FeaTures
applicaTions
DescripTion
Synchronous
Step-Down Switching
Regulator Controller
The LTC
®
3851A is a high performance synchronous
step-down switching regulator controller that drives
an all N-channel synchronous power MOSFET stage. A
con stant frequency current mode architecture allows a
phase-lockable frequency of up to 750kHz.
OPTI-LOOP compensation allows the transient response
to be optimized over a wide range of output capacitance
and ESR values. The LTC3851A features a precision 0.8V
reference that is compatible with a wide 4V to 38V input
supply range.
The TK/SS pin ramps the output voltage during start-up.
Current foldback limits MOSFET heat dissipation during
short-circuit conditions. The MODE/PLLIN pin selects
among Burst Mode operation, pulse-skipping mode or
continuous inductor current mode at light loads and al-
lows the IC to be synchronized to an external clock. The
LTC3851A contains an improved PLL compared to the
LTC3851.
The LTC3851A-1 is a version with a power good output
signal instead of adjustable current limit.
High Efficiency Synchronous Step-Down Converter
n
Wide V
IN
Range: 4V to 38V Operation
n
R
SENSE
or DCR Current Sensing
n
±1% Output Voltage Accuracy
n
Phase-Lockable Fixed Frequency: 250kHz to 750kHz
n
Dual N-Channel MOSFET Synchronous Drive
n
Very Low Dropout Operation: 99% Duty Cycle
n
Adjustable Output Voltage Soft-Start or Tracking
n
Output Current Foldback Limiting
n
Output Overvoltage Protection
n
5V Internal Regulator
n
OPTI-LOOP
®
Compensation Minimizes C
OUT
n
Selectable Continuous, Pulse-Skipping or
Burst Mode
®
Operation at Light Loads
n
Low Shutdown I
Q
: 20µA
n
V
OUT
Range: 0.8V to 5.5V
n
Thermally Enhanced 16-Lead MSOP, 16-Lead Narrow
SSOP or 3mm × 3mm QFN Package
n
Automotive Systems
n
Telecom Systems
n
Industrial Equipment
n
Distributed DC Power Systems
Efficiency and Power Loss
vs Load Current
L, LT, LTC, LTM, Burst Mode, OPTI-LOOP, Linear Technology and the Linear logo are registered
trademarks and No R
SENSE
, UltraFast are trademarks of Linear Technology Corporation. All other
trademarks are the property of their respective owners. Protected by U.S. Patents including
5408150, 5481178, 5705919, 5929620, 6304066, 6498466, 6580258, 6611131.
I
LIM
RUN
TK/SS
I
TH
FREQ/PLLFLTR
V
IN
TG
SW
INTV
CC
MODE/PLLIN
BG
SENSE
+
SENSE
–
V
FB
GND
0.1µF
0.047µF
3.01k
LTC3851A
22µF
V
IN
4.5V TO 36V
V
OUT
3.3V
15A
3851A TA01a
0.68µH
30.1k
330pF
2200pF
0.1µF
330µF
×2
BOOST
15k
154k
48.7k
82.5k
0.1µF
4.7µF
LOAD CURRENT (mA)
10
70
EFFICIENCY (%)
POWER LOSS (mW)
75
80
85
90
100 1000 10000 100000
3851A TA01b
65
60
55
50
95
100
1000
100
10
10000
V
IN
= 12V
V
OUT
= 3.3V
EFFICIENCY
POWER LOSS
LTC3851A
2
3851afa
absoluTe MaxiMuM raTings
Input Supply Voltage (V
IN
) ......................... 40V to –0.3V
Topside Driver Voltage (BOOST) ................ 46V to –0.3V
Switch Voltage (SW) ..................................... 40V to –5V
INTV
CC
, (BOOST – SW), RUN ...................... 6V to –0.3V
TK/SS, I
LIM
...........................................INTV
CC
to –0.3V
SENSE
+
, SENSE
–
.......................................... 6V to –0.3V
MODE/PLLIN, FREQ/PLLFLTR ..............INTV
CC
to –0.3V
I
TH
, V
FB
Voltages .......................................... 3V to –0.3V
(Note 1)
GN PACKAGE
16-LEAD PLASTIC SSOP NARROW
1
2
3
4
5
6
7
8
TOP VIEW
16
15
14
13
12
11
10
9
MODE/PLLIN
FREQ/PLLFLTR
RUN
TK/SS
I
TH
FB
SENSE
–
SENSE
+
SW
TG
BOOST
V
IN
INTV
CC
BG
GND
I
LIM
T
JMAX
= 125°C, θ
JA
= 110°C/W
1
2
3
4
5
6
7
8
MODE/PLLIN
FREQ/PLLFLTR
RUN
TK/SS
I
TH
FB
SENSE
–
SENSE
+
16
15
14
13
12
11
10
9
SW
TG
BOOST
V
IN
INTV
CC
BG
GND
I
LIM
TOP VIEW
MSE PACKAGE
16-LEAD PLASTIC MSOP
17
GND
T
JMAX
= 125°C, θ
JA
= 35°C/W TO 40°C/W
EXPOSED PAD (PIN 17) IS GND,
MUST BE SOLDERED TO PCB
16 15 14 13
5 6 7 8
TOP VIEW
17
GND
UD PACKAGE
16-LEAD (3mm × 3mm) PLASTIC QFN
9
10
11
12
4
3
2
1RUN
TK/SS
I
TH
FB
BOOST
V
IN
INTV
CC
BG
FREQ/PLLFLTR
MODE/PLLIN
SW
TG
SENSE
–
SENSE
+
I
LIM
GND
T
JMAX
= 125°C, θ
JA
= 68°C/W, θ
JC
= 4.2°C/W
EXPOSED PAD (PIN 17) IS GND,
MUST BE SOLDERED TO PCB
pin conFiguraTion
orDer inForMaTion
LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE
LTC3851AEGN#PBF LTC3851AEGN#TRPBF 3851A 16-Lead Plastic SSOP –40°C to 125°C
LTC3851AIGN#PBF LTC3851AIGN#TRPBF 3851A 16-Lead Plastic SSOP –40°C to 125°C
LTC3851AEMSE#PBF LTC3851AEMSE#TRPBF 3851A 16-Lead Plastic MSOP –40°C to 125°C
LTC3851AIMSE#PBF LTC3851AIMSE#TRPBF 3851A 16-Lead Plastic MSOP –40°C to 125°C
LTC3851AHMSE#PBF LTC3851AHMSE#TRPBF 3851A 16-Lead Plastic MSOP –40°C to 150°C
LTC3851AMPMSE#PBF LTC3851AMPMSE#TRPBF 3851A 16-Lead Plastic MSOP –55°C to 150°C
LTC3851AEUD#PBF LTC3851AEUD#TRPBF LFPZ
16-Lead (3mm × 3mm) Plastic QFN
–40°C to 125°C
LTC3851AIUD#PBF LTC3851AIUD#TRPBF LFPZ
16-Lead (3mm × 3mm) Plastic QFN
–40°C to 125°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
Consult LTC Marketing for information on non-standard lead based finish parts.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/
INTV
CC
Peak Output Current ..................................50mA
Operating Junction Temperature Range (Notes 2, 3)
E-Grade, I-Grade ................................ –40°C to 125°C
H-Grade ............................................. –40°C to 150°C
MP-Grade .......................................... –55°C to 150°C
Storage Temperature Range .................. –65°C to 150°C
Lead Temperature (Soldering, 10 sec)
GN/MSE ............................................................300°C
LTC3851A
3
3851afa
elecTrical characTerisTics
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
Main Control Loops
V
IN
Operating Input Voltage Range
l
4 38 V
V
FB
Regulated Feedback Voltage I
TH
= 1.2V (Note 4) 0°C to 85°C
I
TH
= 1.2V (Note 4) –40°C to 125°C
I
TH
= 1.2V (Note 4) –40°C to 150°C
I
TH
= 1.2V (Note 4) –55°C to 150°C
l
l
l
l
0.792
0.788
0.788
0.788
0.800 0.808
0.812
0.812
0.812
V
V
V
V
I
FB
Feedback Current (Note 4) –10 –50 nA
V
REFLNREG
Reference Voltage Line Regulation V
IN
= 6V to 38V (Note 4) 0.002 0.02 %/V
V
LOADREG
Output Voltage Load Regulation (Note 4) Measured in Servo Loop,
∆I
TH
= 1.2V to 0.7V
(Note 4) Measured in Servo Loop,
∆I
TH
= 1.2V to 0.7V (H-Grade, MP-Grade)
l
l
0.01
0.1
0.2
%
%
(Note 4) Measured in Servo Loop,
∆I
TH
= 1.2V to 1.6V
(Note 4) Measured in Servo Loop,
∆I
TH
= 1.2V to 1.6V (H-Grade, MP-Grade)
l
l
–0.01
–0.1
–0.2
%
%
g
m
Transconductance Amplifier g
m
I
TH
= 1.2V, Sink/Source = 5µA (Note 4) 2 mmho
g
m
GBW Transconductance Amp Gain Bandwidth I
TH
= 1.2V (Note 8) 3 MHz
I
Q
Input DC Supply Current
Normal Mode
Shutdown
(Note 5)
V
RUN
= 5V
V
RUN
= 0V
1.2
25
50
mA
µA
UVLO Undervoltage Lockout on INTV
CC
V
INTVCC
Ramping Down 3.25 V
UVLO Hys UVLO Hysteresis 0.4 V
V
OVL
Feedback Overvoltage Lockout V
FB
with Respect to Set Regulated Voltage V
FB
Ramping
Positive (OV)
7.5 10 12.5 %
I
SENSE
SENSE Pins Current ±1 ±2 µA
I
TK/SS
Soft-Start Charge Current V
TK/SS
= 0V 0.6 1 2 µA
V
RUN
RUN Pin On—Threshold V
RUN
Rising
l
1.10 1.22 1.35 V
V
RUNHYS
RUN Pin On—Hysteresis 120 mV
V
SENSE(MAX)
Maximum Current Sense Threshold V
FB
= 0.7V, V
SENSE
= 3.3V, I
LIM
= 0V
V
FB
= 0.7V, V
SENSE
= 3.3V, I
LIM
= 0V (H-/MP-Grade)
V
FB
= 0.7V, V
SENSE
= 3.3V, I
LIM
= Float
V
FB
= 0.7V, V
SENSE
= 3.3V, I
LIM
= Float (H-/MP-Grade)
V
FB
= 0.7V, V
SENSE
= 3.3V, I
LIM
= INTV
CC
V
FB
= 0.7V, V
SENSE
= 3.3V, I
LIM
= INTV
CC
(H-/MP-Grade)
l
l
l
l
l
l
20
15
40
35
65
60
30
53
80
40
45
65
70
95
100
mV
mV
mV
mV
mV
mV
TG R
UP
TG Driver Pull-Up On-Resistance TG High 2.2 Ω
TG R
DOWN
TG Driver Pull-Down On-Resistance TG Low 1.2 Ω
BG R
UP
BG Driver Pull-Up On-Resistance BG High 2.1 Ω
BG R
DOWN
BG Driver Pull-Down On-Resistance BG Low 1.1 Ω
TG t
r
TG t
f
TG Transition Time
Rise Time
Fall Time
(Note 6)
C
LOAD
= 3300pF
C
LOAD
= 3300pF
25
25
ns
ns
BG tr
BG tf
BG T
ransition Time
Rise Time
Fall Time
(Note 6)
C
LOAD
= 3300pF
C
LOAD
= 3300pF
25
25
ns
ns
TG/BG t
1D
Top Gate Off to Bottom Gate On Delay
Bottom Switch-On Delay Time
C
LOAD
= 3300pF Each Driver
(Note 6)
30 ns
BG/TG t
2D
Bottom Gate Off to Top Gate On Delay Top
Switch-On Delay Time
C
LOAD
= 3300pF Each Driver
(Note 6)
30 ns
t
ON(MIN)
Minimum On-Time (Note 7) 90 ns
The l denotes the specifications which apply over the specified operating
temperature range, otherwise specifications are at T
A
= 25°C (Note 2). V
IN
= 15V, V
RUN
= 5V unless otherwise noted.
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LTC3851AEUD#TRPBF

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Buy LTC3851AEUD#TRPBF
Manufacturer:
Analog Devices / Linear Technology
Description:
Switching Voltage Regulators Synchronous Step-Down Switching Regulator Controller
Lifecycle:
New from this manufacturer.
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