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LTC3851AIUD-1#PBF

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P21P22-P24P25-P27P28-P30
LTC3851A-1
1
3851a1fa
Typical applicaTion
FeaTures
applicaTions
DescripTion
Synchronous
Step-Down Switching
Regulator Controller
The LTC
®
3851A-1 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-1 features a precision 0.8V
reference and a power good indicator. A wide 4V to 38V
(40V absolute maximum) input supply range encompasses
most battery configurations and intermediate bus voltages.
The TK/SS pin ramps the output voltage during start-up and
shutdown with coincident or ratiometric tracking. Current
foldback limits MOSFET heat dissipation during short-
circuit conditions. The MODE/PLLIN pin selects among
Burst Mode operation, pulse-skipping mode or continu-
ous inductor current mode at light loads and allows the IC
to be synchronized to an external clock. The LTC3851A-1
contains an improved PLL compared to the LTC3851-1.
The LTC3851A-1 is identical to the LTC3851A except that
the I
LIM
pin is replaced by PGOOD.
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
Power Good Output Voltage Monitor
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
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
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.
PGO0D
RUN
TK/SS
I
TH
FREQ/PLLFLTR
V
IN
INTV
CC
TG
SW
INTV
CC
MODE/PLLIN
BG
SENSE
+
SENSE
–
V
FB
GND
0.047µF
0.1µF
4.7µF
3.01k
LTC3851A-1
22µF
V
IN
4.5V TO 38V
V
OUT
3.3V
15A
3851A1 TA01a
0.68µH
330pF
2200pF
0.1µF
0.1µF
330µF
×2
BOOST
15k
154k
48.7k
30.1k
82.5k
100k
LOAD CURRENT (mA)
10
70
EFFICIENCY (%)
POWER LOSS (mW)
75
80
85
90
100 1000 10000 100000
3851A1 TA01b
65
60
55
50
95
100
1000
100
10
10000
V
IN
= 12V
V
OUT
= 3.3V
EFFICIENCY
POWER LOSS
LTC3851A-1
2
3851a1fa
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, PGOOD ........ 6V to –0.3V
TK/SS ...................................................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)
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
PGOOD
TOP VIEW
17
GND
MSE PACKAGE
16-LEAD PLASTIC MSOP
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
+
PGOOD
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
LTC3851AEMSE-1#PBF LTC3851AEMSE-1#TRPBF 3851A1 16-Lead Plastic MSOP –40°C to 125°C
LTC3851AIMSE-1#PBF LTC3851AIMSE-1#TRPBF 3851A1 16-Lead Plastic MSOP –40°C to 125°C
LTC3851AHMSE-1#PBF LTC3851AHMSE-1#TRPBF 3851A1 16-Lead Plastic MSOP –40°C to 150°C
LTC3851AMPMSE-1#PBF LTC3851AMPMSE-1#TRPBF 3851A1 16-Lead Plastic MSOP –55°C to 150°C
LTC3851AEUD-1#PBF LTC3851AEUD-1#TRPBF LFQB
16-Lead (3mm × 3mm) Plastic QFN
–40°C to 125°C
LTC3851AIUD-1#PBF LTC3851AIUD-1#TRPBF LFQB
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)
MSE .................................................................. 300°C
LTC3851A-1
3
3851a1fa
elecTrical characTerisTics
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
Main Control Loops
V
IN
Input Operating Voltage Range 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
25
50
mA
µA
UVLO Undervoltage Lockout on INTV
CC
V
INTVCC
Ramping Down 3.25 V
UVLO Hys UVLO Hysteresis 0.4 V
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
V
FB
= 0.7V, V
SENSE
= 3.3V (H-Grade, MP-Grade)
l
l
40
35
53 65
70
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 Transition 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
INTV
CC
Linear Regulator
V
INTVCC
Internal V
CC
Voltage 6V < V
IN
< 38V 4.8 5 5.2 V
V
LDO
INT INTV
CC
Load Regulation I
CC
= 0mA to 50mA 0.5 %
The l denotes the specifications which apply over the specified operating
junction 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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LTC3851AIUD-1#PBF

Mfr. #:
Buy LTC3851AIUD-1#PBF
Manufacturer:
Analog Devices / Linear Technology
Description:
Switching Voltage Regulators 40Vin Synchronous Step-Down Switching Controller
Lifecycle:
New from this manufacturer.
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