ing regulator controller. It drives a P-channel power
MOSFET switch allowing 100% duty cycle operation. It
enables a low part count, simple, and robust solution for
high reliability, high voltage applications.
The LTC3894 operates over a wide input voltage range
from 4.5V to 150V and can regulate output voltages
from 0.8V to 60V. It offers excellent light load efficiency,
drawing only 9μA quiescent current while regulating the
output voltage with no load. Its peak current mode, con-
stant frequency architecture provides for good control of
switching frequency and output current limit. The switch-
ing frequency can be programmed from 50kHz to 850kHz
with an external resistor and can be synchronized to an
external clock from 75kHz to 800kHz.
The LTC3894 offers programmable output voltage soft-
start or tracking. Safety features include overvoltage,
overcurrent and overtemperature protection with a power
good output monitor with adjustable threshold.
The LTC3894 is available in a thermally enhanced 20-Pin
TSSOP package with leads removed to accommodate
high voltage creepage and clearance requirements.
All registered trademarks and trademarks are the property of their respective owners.
n
n
n
n
n
Wide Operating V
IN
Range: 4.5V to 150V
Wide V
OUT
Range: 0.8V to 60V
9μA I
Q
when Regulating 48V
IN
to 3.3V
OUT
16μA I
Q
when Regulating 12V
IN
to 3.3V
OUT
Very Low Dropout Operation: 100% Duty Cycle
Adjustable Input Overvoltage Lockout
Programmable PGOOD Undervoltage Monitor
R
SENSE
or Inductor DCR Current Sensing
Selectable High Efficiency Burst Mode
®
Operation or
Pulse-Skipping Mode at Light Loads
Programmable Fixed Frequency: 50kHz to 850kHz
Phase-Lockable Frequency: 75kHz to 800kHz
Internal Fixed Soft-Start and External Programmable
Soft-Start or Voltage Tracking
Strong MOSFET Gate Driver with Selectable
Undervoltage Lockout Thresholds
Optional External NMOS for Gate Driver Bias in High
Power Applications
APPLICATIONS
n
n
n
Automotive and Industrial Power Systems
Telecommunication Power Systems
Distributed Power Systems
TYPICAL APPLICATION
High Efficiency 150V to 5V Step-Down Regulator
V
IN
6V to 150V
12µF
×2
RUN
V
IN
GATE
22µH
20m
1nF
330µF
10µF
×2
EFFICIENCY (%)
V
OUT
5V, 3A
100
90
80
70
60
50
40
30
20
10
80.6k
0
0.0001
0.001
0.01
0.1
LOAD CURRENT (A)
POWER LOSS
V
IN
= 12V
V
IN
= 24V
1
3
1
10
EFFICIENCY
100
Burst Mode OPERATION
1k
POWER LOSS (mW)
Efficiency and Power Loss vs
Load Current
10k
SENSE
+
SENSE
–
PGOOD
LTC3894
PGUV
V
FB
TRACK/SS PLLIN/MODE
0.1µF
100k
422k
0.47µF
3.3nF
5.76k
CAP
OVLO
DRVUV/EXTG
EXTS
ITH
GND FREQ
47pF
36.5k
0.1
3894 TA01b
3894 TA01a
Document Feedback
For more information
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1
Rev 0
LTC3894
ABSOLUTE MAXIMUM RATINGS
(Note 1)
PIN CONFIGURATION
TOP VIEW
GATE
RUN
SENSE
+
SENSE
–
ITH
PGUV
V
FB
1
3
5
6
7
8
9
20 V
IN
18 CAP
16 DRVUV/EXTG
15 EXTS
14 OVLO
13 FREQ
12 PGOOD
11 PLLIN/MODE
Input Supply Voltage (V
IN
), RUN .............. –0.3V to 150V
SENSE
+
, SENSE
–
, PGOOD Voltage ............. –0.3V to 65V
V
IN
-V
CAP
Voltage ........................................ –0.3V to 10V
V
FB
, PLLIN/MODE, PGUV, OVLO,
EXTS Voltages ............................................. –0.3V to 6V
TRACK/SS Voltage (Note 11) .................... –0.3V to 2.8V
ITH, FREQ Voltage........................................ –0.3V to 5V
DRVUV/EXTG Voltage .................................. –0.3V to 9V
Operating Junction Temperature Range (Notes 2, 3)
LTC3894E, LTC3894I ......................... –40°C to 125°C
Storage Temperature Range .................. –65°C to 150°C
Lead Temperature (Soldering, 10 sec)................... 300°C
21
GND
TRACK/SS 10
FE PACKAGE
20(16)-LEAD PLASTIC TSSOP
T
JMAX
= 150°C,
θ
JA
= 38°C/W
EXPOSED PAD (PIN 21) IS GND, MUST BE SOLDERED TO PCB FOR RATED
ELECTRICAL AND THERMAL CHARACTERISTICS
ORDER INFORMATION
LEAD FREE FINISH
LTC3894EFE#PBF
LTC3894IFE#PBF
TAPE AND REEL
LTC3894EFE#TRPBF
LTC3894IFE#TRPBF
http://www.linear.com/product/LTC3894#orderinfo
PART MARKING*
LTC3894FE
LTC3894FE
PACKAGE DESCRIPTION
20(16)-Lead Plastic TSSOP
20(16)-Lead Plastic TSSOP
TEMPERATURE RANGE
–40°C to 125°C
–40°C to 125°C
Consult ADI Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
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/.
Some packages are available in 500 unit reels through
designated sales channels with #TRMPBF suffix.
The
l
denotes the specifications which apply over the specified operating
junction temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 12V, unless otherwise noted. (Note 2)
SYMBOL
Input Supply
V
IN
V
OUT
I
Q
Input Voltage Operating Range
Regulated Output Voltage Set Point
No Load DC Supply Current (Note 5)
Shutdown V
IN
Pin Current
Sleep Mode V
IN
Pin Current
Sleep Mode SENSE
–
Pin Current (Note 6)
Pulse-Skipping Mode V
IN
Pin Current
RUN = 0V
V
SENSE–
= 2.5V, V
FB
= 0.83V
V
SENSE–
≥ 3.2V, V
FB
= 0.83V
V
SENSE–
≥ 3.2V, V
FB
= 0.83V
V
FB
= 0.83V
V
SENSE
– = 0V
V
SENSE
– = 3.3V
V
SENSE
– = 5V
7
27
7
21
1.8
1.5
0.8
11
40
10
30
µA
µA
µA
µA
mA
mA
mA
Rev 0
ELECTRICAL CHARACTERISTICS
PARAMETER
CONDITIONS
(Note 4) DRVUV = 0V
MIN
4.5
0.8
TYP
MAX
150
60
UNITS
V
V
2
For more information
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LTC3894
ELECTRICAL CHARACTERISTICS
SYMBOL
I
Q(VINR)
PARAMETER
The
l
denotes the specifications which apply over the specified operating
junction temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 12V, unless otherwise noted. (Note 2)
CONDITIONS
MIN
TYP
16
22
9
11
l
MAX
UNITS
µA
µA
µA
µA
Total Input Supply Current in Regulation at V
IN
= 12V
No Load in Burst Mode (Note 7)
Figure 13 Circuit, V
OUT
= 3.3V
Figure 11 Circuit, V
OUT
= 5V
V
IN
= 48V
Figure 13 Circuit, V
OUT
= 3.3V
Figure 11 Circuit, V
OUT
= 5V
Output Sensing
V
FB
Regulated Feedback Voltage
Feedback Voltage Line Regulation
Feedback Voltage Load Regulation
g
m(EA)
I
FB
Error Amplifier Transconductance
Feedback Input Bias Current
V
FB
= 0.7V, V
SENSE–
= 3.3V
V
SENSE+
= 3.3V
V
SENSE–
= 3.3V
V
SENSE–
= 5V
V
RUN
Rising
V
SS
= 0V or 0V to 0.8V
V
OVLO
Rising Up
Hysteresis
DRVUV = 0
(V
IN
-V
CAP
) Ramping Up Threshold
(V
IN
-V
CAP
) Ramping Down Threshold
Hysteresis
DRVUV = Floating
(V
IN
-V
CAP
) Ramping Up Threshold
(V
IN
-V
CAP
) Ramping Down Threshold
Hysteresis
V
CAP
V
CAPDROP
R
UP
R
DN
t
ON(MIN)
f
Gate Bias LDO Output Voltage (V
IN
-V
CAP
)
I
CAP
= 0mA, 9V ≤ V
IN
≤ 150V (Note 9)
I
CAP
= 0mA to 20mA
Gate High
Gate Low
(Note 10)
R
FREQ
= 25kΩ
R
FREQ
= 64.9kΩ
R
FREQ
= 105kΩ
Gate Bias LDO Dropout Voltage (V
IN
-V
CAP
) V
IN
= 5V, I
CAP
= 15mA (Note 9)
Gate Pull-Up Resistance
Gate Pull-Down Resistance
Gate Minimum On-Time
Programmable Switching Frequency
l
l
l
V
ITH
= 1.2V (Note 8)
V
IN
= 4.5V to 150V (Note 8)
V
ITH
= 0.6V to 1.8V (Note 8)
V
ITH
= 1.2V, ∆I
ITH
= ±5µA (Note 8)
0.788
0.800
±0.002
0.03
2
–10
0.812
0.015
0.15
±50
112
1
300
1260
1.34
14
0.82
V
%/V
%
mS
nA
mV
µA
µA
µA
V
mV
µA
V
mV
Current Sensing
V
SENSE(MAX)
Maximum Current Sense Threshold
(V
SENSE+
– V
SENSE–
)
I
SENSE+
I
SENSE–
SENSE
+
Pin Input Current
SENSE
–
Pin Input Current in Non-Sleep
Mode (Note 6)
RUN Pin Enable Threshold
RUN Pin Hysteresis
Soft-Start Pin Charging Current
Overvoltage Lockout Threshold
8
0.77
88
100
0.1
200
880
1.14
1.24
125
11
0.8
30
Start-Up and Shutdown
V
RUN
V
RUNHYS
I
SS
V
OVLO
Gate Driver and V
IN
-Cap LDO
V
UVLO
Undervoltage Lockout
l
l
3.4
3.25
3.75
3.50
0.25
6.0
5.55
0.45
8.0
4.4
–1.3
2
0.9
125
100
440
810
4.3
3.75
V
V
V
V
V
V
V
V
%
Ω
Ω
ns
kHz
kHz
kHz
l
l
l
5.65
5.2
7.5
4.1
–2.8
6.45
5.85
8.5
∆V
CAP(LOAD)
Gate Bias LDO Load Regulation
Switching Frequency and Clock Synchronization
375
505
For more information
www.analog.com
3
Rev 0
LTC3894
ELECTRICAL CHARACTERISTICS
SYMBOL
f
LO
f
HI
f
SYNC
V
CLK(HI)
V
CLK(LO)
V
PGL
I
PG
V
PGOV
V
PGUV
t
PGDL
V
FBOV
PARAMETER
Low Switching Frequency
High Switching Frequency
Synchronization Frequency
Clock Input High Level into PLLIN/MODE
Clock Input Low Level into PLLIN/MODE
PGOOD Voltage Low
PGOOD Leakage Current
PGOOD Overvoltage Trip Threshold
I
PGOOD
= 2mA
V
PGOOD
= 65V
V
FB
Ramping Positive with Respect to Set
Regulated Voltage
Hysteresis
V
PGUV
Ramping Negative
Hysteresis
PGOOD High to Low
PGOOD Low to High
V
FB
Ramping Positive with Respect to Set
Regulated Voltage
Hysteresis
7
10
2.5
700
720
2.5
100
100
10
2.5
740
The
l
denotes the specifications which apply over the specified operating
junction temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 12V, unless otherwise noted. (Note 2)
CONDITIONS
FREQ = 0V
FREQ = Open
l
l
l
MIN
320
470
75
2
TYP
350
530
MAX
380
590
800
0.5
UNITS
kHz
kHz
kHz
V
V
V
µA
%
%
mV
%
µs
µs
%
%
PGOOD Output
0.2
0.35
1
13
PGOOD Undervoltage Trip Threshold
PGOOD Delay
V
FB
Overvoltage Lockout Threshold
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 LTC3894 is tested under pulsed load conditions such that
T
J
≈ T
A
. The LTC3894E is guaranteed to meet performance specifications
from 0°C to 85°C. Specifications over the –40°C to 125°C operating
junction temperature range are assured by design, characterization and
correlation with statistical process controls. The LTC3894I is guaranteed
over the –40°C to 125°C operating junction temperature range. 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. High temperatures degrade operating lifetimes; operating lifetime
is derated for junction temperatures greater than 125ºC. The junction
temperature (T
J
, in °C) is calculated from the ambient temperature (T
A
, in
°C) and power dissipation (P
D
, in Watts) according to the formula:
T
J
= T
A
+ (P
D
•
θ
JA
)
where
θ
JA
= 38°C/W for the TSSOP package.
Note 3:
This IC includes overtemperature protection that is intended to
protect the device during momentary overload conditions. The maximum
rated junction temperature will be exceeded when this protection is active.
Continuous operation above the specified absolute maximum operating
junction temperature may impair device reliability or permanently damage
the device.
Note 4:
The minimum input supply operating range is dependent on the
UVLO thresholds as determined by the DRVUV/EXTG pin setting.
Note 5:
The DC supply current is measured when the LTC3894 is not
switching. Dynamic supply current is higher due to the gate charge being
delivered at the switching frequency.
Note 6:
SENSE1
–
bias current is reflected to the input supply by the
formula
I
VIN
= I
SENSE1–
• V
OUT
/(V
IN
•
η),
where
η
is the efficiency.
Note 7:
The total input supply current in Burst Mode is the total current
drawn from input supply as measured in the Typical Application circuit on
page 1 and Figure 13 on page 30 with no load current. The specification
is not tested in production.
Note 8:
The LTC3894 is tested in a feedback loop that servos the error
amplifier output voltage (on ITH pin) to a specified voltage and measures
the resultant V
FB
voltage.
Note 9:
Positive I
CAP
current flows into the CAP pin and discharges the
capacitor between the V
IN
and CAP pins.
Note 10:
The minimum on-time condition is specified for an inductor
peak-to-peak ripple current > 40% of I
MAX
.
Note 11:
The absolute maximum rating for TRACK/SS pin is 2.8V when
the pin is driven externally. When the pin is not driven, it may be pulled
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