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/
3851afa
2
TG
LTC3851A
elecTrical characTerisTics
SYMBOL
V
IN
V
FB
PARAMETER
Operating Input Voltage Range
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
(Note 4)
V
IN
= 6V to 38V (Note 4)
(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)
(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)
g
m
g
m
GBW
I
Q
UVLO
UVLO Hys
V
OVL
I
SENSE
I
TK/SS
V
RUN
V
RUNHYS
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
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)
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)
l
l
l
l
l
l
l
l
l
l
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.
CONDITIONS
l
l
l
l
l
MIN
4
0.792
0.788
0.788
0.788
TYP
MAX UNITS
38
V
V
V
V
V
nA
%/V
%
%
%
%
mmho
MHz
mA
µA
V
V
12.5
±2
2
1.35
40
45
65
70
95
100
%
µA
µA
V
mV
mV
mV
mV
mV
mV
mV
Ω
Ω
Ω
Ω
ns
ns
ns
ns
ns
ns
ns
3851afa
Main Control Loops
0.800
0.808
0.812
0.812
0.812
–50
0.02
0.1
0.2
–0.01
–0.1
–0.2
2
3
1.2
25
3.25
0.4
V
FB
with Respect to Set Regulated Voltage V
FB
Ramping
Positive (OV)
V
TK/SS
= 0V
V
RUN
Rising
l
I
FB
V
REFLNREG
V
LOADREG
Feedback Current
Reference Voltage Line Regulation
Output Voltage Load Regulation
–10
0.002
0.01
I
TH
= 1.2V, Sink/Source = 5µA (Note 4)
I
TH
= 1.2V (Note 8)
(Note 5)
V
RUN
= 5V
V
RUN
= 0V
V
INTVCC
Ramping Down
7.5
50
10
±1
0.6
1.10
20
15
40
35
65
60
1
1.22
120
30
53
80
2.2
1.2
2.1
1.1
25
25
25
25
30
30
90
V
SENSE(MAX)
Maximum Current Sense Threshold
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)
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 C
LOAD
= 3300pF Each Driver
Switch-On Delay Time
(Note 6)
Minimum On-Time
(Note 7)
3
LTC3851A
elecTrical characTerisTics
SYMBOL
V
INTVCC
V
LDO
INT
f
NOM
f
LOW
f
HIGH
f
MODE
I
FREQ
PARAMETER
Internal V
CC
Voltage
INTV
CC
Load Regulation
Nominal Frequency
Lowest Frequency
Highest Frequency
MODE/PLLIN Minimum Input Frequency
MODE/PLLIN Maximum Input Frequency
Phase Detector Output Current
Sinking Capability
Sourcing Capability
INTV
CC
Linear Regulator
6V < V
IN
< 38V
I
CC
= 0mA to 50mA
R
FREQ
= 60k
R
FREQ
= 160k
R
FREQ
= 36k
V
MODE
= External Clock
V
MODE
= External Clock
f
MODE
> f
OSC
f
MODE
< f
OSC
460
205
690
4.8
5
0.5
500
235
750
100
250
750
–90
75
5.2
2
540
265
810
V
%
kHz
kHz
kHz
kΩ
kHz
kHz
µA
µA
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.
CONDITIONS
MIN
TYP
MAX UNITS
Oscillator and Phase-Locked Loop
R
MODE/PLLIN
MODE/PLLIN Input Resistance
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 LTC3851A is tested under pulsed load conditions such that
T
A
≈ T
J
. The LTC3851AE is guaranteed to meet performance specifications
from 0°C to 85°C junction temperature. Specifications over the –40°C
to 125°C operating junction temperature range are assured by design,
characterization and correlation with statistical process controls. The
LTC3851AI is guaranteed to meet specifications over the –40°C to 125°C
operating junction temperature range, the LTC3851AH is guaranteed
over the –40°C to 150°C operating junction temperature range and the
LTC3851AMP is tested and guaranteed over the –55°C to 150°C operating
junction temperature range. High junction temperatures degrade operating
lifetimes; operating lifetime is derated for junction temperatures greater
than 125°C. Note that the maximum ambient temperature consistent with
these specifications is determined by specific operating conditions in
conjunction with board layout, the rated package thermal impedance and
other environmental factors.
Note 3:
T
J
is calculated from the ambient temperature T
A
and power
dissipation P
D
according to the following formulas:
LTC3851AGN: T
J
= T
A
+ (P
D
• 110°C/W)
LTC3851AUD: T
J
= T
A
+ (P
D
• 68°C/W)
LTC3851AMSE: T
J
= T
A
+ (P
D
• 40°C/W)
Note 4:
The LTC3851A 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. Rise and fall times are assured by
design, characterization and correlation with statistical process controls.
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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