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/
I
LIM
MSE PACKAGE
16-LEAD PLASTIC MSOP
7
3851fb
2
LTC3851
ELECTRICAL CHARACTERISTICS
SYMBOL
V
IN
V
FB
I
FB
V
REFLNREG
V
LOADREG
PARAMETER
Operating Input 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
V
FB
= 0.7V, V
SENSE
= 3.3V, I
LIM
= 0V
V
FB
= 0.7V, V
SENSE
= 3.3V, I
LIM
= Float
V
FB
= 0.7V, V
SENSE
= 3.3V, I
LIM
= INTV
CC
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
4.8
l
l
l
l
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 15V, V
RUN
= 5V unless otherwise noted.
CONDITIONS
l
l
MIN
4
0.792
TYP
MAX
38
UNITS
V
V
nA
%/V
%
Main Control Loops
0.800
–10
0.002
0.01
0.808
–50
0.02
0.1
l
–0.01
2
3
1.2
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)
0.86
0.6
1.10
20
40
65
0.88
±1
1
1.25
130
30
50
75
2.6
1.5
2.4
1.1
25
25
25
25
30
30
90
5
0.5
0.90
±2
2
1.35
40
65
90
V
μA
μA
V
mV
mV
mV
mV
Ω
Ω
Ω
Ω
ns
ns
ns
ns
ns
ns
ns
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
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
INTV
CC
Linear Regulator
5.2
2
V
%
3851fb
3
LTC3851
ELECTRICAL CHARACTERISTICS
SYMBOL
f
NOM
f
LOW
f
HIGH
R
MODE/PLLIN
f
MODE
I
FREQ
PARAMETER
Nominal Frequency
Lowest Frequency
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
f
MODE
> f
OSC
f
MODE
< f
OSC
Oscillator and Phase-Locked Loop
R
FREQ
= 60k
R
FREQ
= 160k
R
FREQ
= 36k
480
220
710
500
250
750
100
250
750
–10
10
530
280
790
kHz
kHz
kHz
kΩ
kHz
kHz
μA
μA
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 15V, V
RUN
= 5V unless otherwise noted.
CONDITIONS
MIN
TYP
MAX
UNITS
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 is guaranteed to meet performance specifications
from 0°C to 85°C. Specifications over the –40°C to 85°C operating
temperature range are assured by design, characterization and correlation
with statistical process controls. The LTC3851I is guaranteed to meet
specifications over the –40°C to 125°C operating temperature range.
Note 3:
T
J
is calculated from the ambient temperature T
A
and power
dissipation P
D
according to the following formulas:
LTC3851GN: T
J
= T
A
+ (P
D
• 110°C/W)
LTC3851UD: T
J
= T
A
+ (P
D
• 68°C/W)
LTC3851MSE: T
J
= T
A
+ (P
D
• 40°C/W)
Note 4:
The LTC3851 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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