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
LTC3851AEMSE-1#PBF
LTC3851AIMSE-1#PBF
LTC3851AHMSE-1#PBF
LTC3851AMPMSE-1#PBF
LTC3851AEUD-1#PBF
LTC3851AIUD-1#PBF
TAPE AND REEL
LTC3851AEMSE-1#TRPBF
LTC3851AIMSE-1#TRPBF
LTC3851AHMSE-1#TRPBF
LTC3851AMPMSE-1#TRPBF
LTC3851AEUD-1#TRPBF
LTC3851AIUD-1#TRPBF
PART MARKING*
3851A1
3851A1
3851A1
3851A1
LFQB
LFQB
PACKAGE DESCRIPTION
16-Lead Plastic MSOP
16-Lead Plastic MSOP
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 125°C
–40°C to 125°C
–40°C to 150°C
–55°C to 150°C
–40°C to 125°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
3851a1fa
2
LTC3851A-1
elecTrical characTerisTics
SYMBOL
V
IN
V
FB
PARAMETER
Input Operating 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
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
Transconductance Amplifier g
m
Transconductance Amp Gain Bandwidth
Input DC Supply Current
Normal Mode
Shutdown
Undervoltage Lockout on INTV
CC
UVLO Hysteresis
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
V
FB
= 0.7V, V
SENSE
= 3.3V
V
FB
= 0.7V, V
SENSE
= 3.3V (H-Grade, 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)
C
LOAD
= 3300pF Each Driver
(Note 6)
(Note 7)
6V < V
IN
< 38V
I
CC
= 0mA to 50mA
4.8
l
l
l
l
l
l
l
l
l
l
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.
CONDITIONS
MIN
4
0.792
0.788
0.788
0.788
0.800
TYP
MAX
38
0.808
0.812
0.812
0.812
–50
0.02
0.1
0.2
–0.01
–0.1
–0.2
2
3
1
25
3.25
0.4
±1
V
TK/SS
= 0V
V
RUN
Rising
l
UNITS
V
V
V
V
V
nA
%/V
%
%
%
%
mmho
MHz
mA
µA
V
V
Main Control Loops
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
50
±2
2
1.35
65
70
µA
µA
V
mV
mV
mV
Ω
Ω
Ω
Ω
ns
ns
ns
ns
ns
ns
ns
0.6
1.10
40
35
1
1.22
120
53
2.2
1.2
2.1
1.1
25
25
25
25
30
30
90
5
0.5
INTV
CC
Linear Regulator
5.2
V
%
3851a1fa
3
LTC3851A-1
elecTrical characTerisTics
SYMBOL
f
NOM
f
LOW
f
HIGH
R
MODE/PLLIN
f
MODE
I
FREQ
PGOOD Output
V
PGL
I
PGOOD
V
PG
PGOOD Voltage Low
PGOOD Leakage Current
PGOOD Trip Level
I
PGOOD
= 2mA
V
PGOOD
= 5V
V
FB
with Respect to Set Regulated Voltage
V
FB
Ramping Negative (UV)
V
FB
Ramping Positive (OV)
–12.5
7.5
–10
10
0.1
0.3
±1
–7.5
12.5
V
µA
%
%
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
460
205
690
500
235
750
100
250
750
–90
75
540
265
810
kHz
kHz
kHz
kΩ
kHz
kHz
µA
µA
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.
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 LTC3851A-1 is tested under pulsed load conditions such that
T
A
≈ T
J
. The LTC3851AE-1 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-1 is guaranteed to meet specifications over the –40°C
to 125°C operating junction temperature range, the LTC3851AH-1 is
guaranteed over the –40°C to 150°C operating junction temperature range
and the LTC3851AMP-1 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:
LTC3851AMSE-1: T
J
= T
A
+ (P
D
• 40°C/W)
LTC3851AUD-1: T
J
= T
A
+ (P
D
• 68°C/W)
Note 4:
The LTC3851A-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. 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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