EXPOSED PAD (PIN 17) IS GND, MUST BE SOLDERED TO PCB
UD PACKAGE
16-LEAD (3mm 3mm) PLASTIC QFN
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
ORDER INFORMATION
LEAD FREE FINISH
LTC3851EMSE-1#PBF
LTC3851IMSE-1#PBF
LTC3851EUD-1#PBF
LTC3851IUD-1#PBF
TAPE AND REEL
LTC3851EMSE-1#TRPBF
LTC3851IMSE-1#TRPBF
LTC3851EUD-1#TRPBF
LTC3851IUD-1#TRPBF
PART MARKING*
38511
38511
LDNT
LDNT
PACKAGE DESCRIPTION
16-Lead Plastic MSOP
16-Lead Plastic MSOP
16-Lead (3mm
×
3mm) Plastic QFN
16-Lead (3mm
×
3mm) Plastic QFN
TEMPERATURE RANGE
–40°C to 85°C
–40°C to 125°C
–40°C to 85°C
–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/
TG
TOP VIEW
38511fa
2
LTC3851-1
ELECTRICAL CHARACTERISTICS
SYMBOL
V
IN
V
FB
I
FB
V
REFLNREG
V
LOADREG
PARAMETER
Input Operating Voltage Range
Regulated Feedback Voltage
Feedback Current
Reference Voltage Line Regulation
Output Voltage Load Regulation
I
TH
= 1.2V (Note 4)
(Note 4)
V
IN
= 6V to 38V (Note 4)
(Note 4)
Measured in Servo Loop,
ΔI
TH
= 1.2V to 0.7V
(Note 4)
Measured in Servo Loop,
ΔI
TH
= 1.2V to 1.6V
g
m
g
m
GBW
I
Q
Transconductance Amplifier g
m
Transconductance Amp Gain Bandwidth
Input DC Supply Current
Normal Mode
Shutdown
Undervoltage Lockout on INTV
CC
UVLO Hysteresis
Feedback Overvoltage Lockout
SENSE Pins Current
Soft-Start Charge Current
RUN Pin On Threshold
RUN Pin On Hysteresis
Maximum Current Sense Threshold
TG Driver Pull-Up On-Resistance
TG Driver Pull-Down On-Resistance
BG Driver Pull-Up On-Resistance
BG Driver Pull-Down On-Resistance
TG Transition Time
Rise Time
Fall Time
BG Transition Time
Rise Time
Fall Time
Top Gate Off to Bottom Gate On Delay
Bottom Switch-On Delay Time
Bottom Gate Off to Top Gate On Delay
Top Switch-On Delay Time
Minimum On-Time
Internal V
CC
Voltage
INTV
CC
Load Regulation
Nominal Frequency
Lowest Frequency
V
FB
= 0.7V, V
SENSE
= 3.3V
TG High
TG Low
BG High
BG Low
(Note 6)
C
LOAD
= 3300pF
C
LOAD
= 3300pF
(Note 6)
C
LOAD
= 3300pF
C
LOAD
= 3300pF
C
LOAD
= 3300pF Each Driver
(Note 6)
C
LOAD
= 3300pF Each Driver
(Note 6)
(Note 7)
6V < V
IN
< 38V
I
CC
= 0mA to 50mA
R
FREQ
= 60k
R
FREQ
= 160k
480
220
4.8
l
l
l
The
l
denotes the specifications which apply over the full operating
junction temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 15V, V
RUN
= 5V unless otherwise noted.
CONDITIONS
MIN
4
0.792
0.800
–10
0.002
0.01
TYP
MAX
38
0.808
–50
0.02
0.1
UNITS
V
V
nA
%/V
%
Main Control Loops
l
–0.01
2
3
1
20
3.25
0.4
–0.1
%
mmho
MHz
mA
μA
V
V
I
TH
= 1.2V, Sink/Source = 5μA (Note 4)
I
TH
= 1.2V
(Note 5)
V
RUN
= 5V
V
RUN
= 0V
V
INTVCC
Ramping Down
Measured at V
FB
V
TK/SS
= 0V
V
RUN
Rising
l
l
35
UVLO
UVLO Hys
V
OVL
I
SENSE
I
TK/SS
V
RUN
V
RUNHYS
V
SENSE(MAX)
TG R
UP
TG R
DOWN
BG R
UP
BG R
DOWN
TG t
r
TG t
f
BG tr
BG tf
TG/BG t
1D
BG/TG t
2D
t
ON(MIN)
V
INTVCC
V
LDO
INT
f
NOM
f
LOW
0.86
0.6
1.10
40
0.88
±1
1
1.25
130
50
2.6
1.5
2.4
1.1
25
25
25
25
30
30
90
5
0.5
500
250
0.90
±2
2
1.35
65
V
μA
μA
V
mV
mV
Ω
Ω
Ω
Ω
ns
ns
ns
ns
ns
ns
ns
INTV
CC
Linear Regulator
5.2
V
%
530
280
kHz
kHz
38511fa
Oscillator and Phase-Locked Loop
3
LTC3851-1
ELECTRICAL CHARACTERISTICS
SYMBOL
f
HIGH
R
MODE/PLLIN
f
MODE
I
FREQ
PARAMETER
Highest Frequency
MODE/PLLIN Input Resistance
MODE/PLLIN Minimum Input Frequency V
MODE
= External Clock
MODE/PLLIN Maximum Input Frequency V
MODE
= External Clock
Phase Detector Output Current
Sinking Capability
Sourcing Capability
PGOOD Voltage Low
PGOOD Leakage Current
PGOOD Trip Level
f
MODE
> f
OSC
f
MODE
< f
OSC
I
PGOOD
= 2mA
V
PGOOD
= 5V
V
FB
with Respect to Set Regulated Voltage
V
FB
Ramping Negative
V
FB
Ramping Positive
–12
8
–10
10
The
l
denotes the specifications which apply over the full operating
junction temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 15V, V
RUN
= 5V unless otherwise noted.
CONDITIONS
R
FREQ
= 36k
MIN
710
TYP
750
100
250
750
–10
10
0.1
0.3
±1
–8
12
MAX
790
UNITS
kHz
kΩ
kHz
kHz
μA
μA
V
μA
%
%
PGOOD Output
V
PGL
I
PGOOD
V
PG
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 LTC3851E-1 is guaranteed to meet performance specifications
from 0°C to 85°C. Specifications over the –40°C to 85°C operating
junction temperature range are assured by design, characterization and
correlation with statistical process controls. The LTC3851I-1 is guaranteed
over the –40°C to 125°C operating junction temperature range.
Note 3:
T
J
is calculated from the ambient temperature T
A
and power
dissipation P
D
according to the following formulas:
LTC3851MSE-1: T
J
= T
A
+ (P
D
• 90°C/W)
LTC3851UD-1: T
J
= T
A
+ (P
D
• 68°C/W)
Note 4:
The LTC3851-1 is tested in a feedback loop that servos V
ITH
to a
specified voltage and measures the resultant V
FB
.
Note 5:
Dynamic supply current is higher due to the gate charge being
delivered at the switching frequency. See Applications Information.
Note 6:
Rise and fall times are measured using 10% and 90% levels. Delay
times are measured using 50% levels.
Note 7:
The minimum on-time condition is specified for an inductor
peak-to-peak ripple current ~40% of I
MAX
(see Minimum On-Time
Considerations in the Applications Information section).
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