LTC3895
150V Low I
Q
, Synchronous
Step-Down DC/DC Controller
FeaTures
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DescripTion
The
LTC
®
3895
is a high performance step-down switching
regulator DC/DC controller that drives an all N-channel
synchronous power MOSFET stage that can operate from
input voltages up to 140V. A constant frequency current
mode architecture allows a phase-lockable frequency of
up to 850kHz.
The gate drive voltage can be programmed from 5V to 10V
to allow the use of logic or standard-level FETs to maxi-
mize efficiency. An integrated switch in the top gate driver
eliminates the need for an external bootstrap diode. An
internal charge pump allows for 100% duty cycle operation.
The low 40μA no-load quiescent current extends operating
run time in battery-powered systems. OPTI-LOOP
®
com-
pensation allows the transient response to be optimized
over a wide range of output capacitance and ESR values.
The LTC3895 features a precision 0.8V reference and
power good output indicator. The output voltage can be
programmed between 0.8V to 60V using external resistors
or pin-programmed for a fixed 5V or 3.3V.
L,
LT, LTC, LTM, Burst Mode, OPTI-LOOP PolyPhase, Linear Technology and the Linear logo
,
are registered trademarks of Linear Technology Corporation. All other trademarks are the
property of their respective owners. Protected by U.S. Patents including 5481178, 5705919,
5929620, 6144194, 6177787, 6580258.
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Wide V
IN
Range: 4V to 140V (150V Abs Max)
Wide Output Voltage Range: 0.8V to 60V
Adjustable Gate Drive Level: 5V to 10V (OPTI-DRIVE)
Low Operating I
Q
: 40μA (Shutdown = 10μA)
100% Duty Cycle Operation
No External Bootstrap Diode Required
Selectable Gate Drive UVLO Thresholds
Onboard LDO or External NMOS LDO for DRV
CC
EXTV
CC
LDO Powers Drivers from V
OUT
Phase-Lockable Frequency (75kHz to 850kHz)
Programmable Fixed Frequency (50kHz to 900kHz)
Selectable Continuous, Pulse-Skipping or Low Ripple
Burst Mode
®
Operation at Light Loads
Adjustable Burst Clamp and Current Limit
Adjustable or Fixed (5V/3.3V) Output Voltage
Power Good Output Voltage Monitor
Programmable Input Overvoltage Lockout
38-Lead TSSOP High Voltage Package
applicaTions
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Automotive and Industrial Power Systems
High Voltage Battery Operated Systems
Telecommunications Power Systems
Typical applicaTion
High Efficiency High Voltage 12V Output Step-Down Regulator
V
IN
7V to 140V
100µF
NDRV
4.7µF
V
IN
RUN
TG
BOOST
LTC3895
INTV
CC
0.1µF
CPUMP_EN
ITH
10k
100pF
4.7nF
0.1µF
30.1k
GND
SS
FREQ
SW
BG
SENSE+
SENSE–
EXTV
CC
V
FB
36.5k
0.1µF
*V
OUT
FOLLOWS V
IN
WHEN V
IN
< 12V
33µH
6m
EFFICIENCY (%)
V
OUT
12V*
5A
150µF
x3
1nF
100
90
80
70
60
50
40
30
20
511k
10
0
0.0001
0.001
0.01
0.1
LOAD CURRENT (A)
1
10
3895 TA01b
Efficiency and Power Loss
vs Load Current
10k
EFFICIENCY
1k
POWER LOSS (mW)
DRV
CC
V
IN
= 24V
V
IN
= 48V
POWER LOSS
100
10
1
3895fa
For more information
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1
LTC3895
absoluTe MaxiMuM raTings
(Note 1)
pin conFiguraTion
TOP VIEW
OVLO
VPRG
SENSE
+
SENSE
–
SS
V
FB
ITH
MODE
GND
1
2
3
4
5
6
7
8
9
39
GND
30 V
IN
28 NDRV
26 DRV
CC
24 BG
22 BOOST
21 SW
20 TG
32 EXTV
CC
34 RUN
38 INTV
CC
37 ILIM
36 PHASMD
Input Supply Voltage (V
IN
) ....................... –0.3V to 150V
Top Side Driver Voltage BOOST ............... –0.3V to 150V
Switch Voltage (SW) ................................... –5V to 150V
DRV
CC
, (BOOST-SW) Voltages....................–0.3V to 11V
BG, TG ............................................................... (Note 8)
RUN Voltage............................................. –0.3V to 150V
SENSE
+
, SENSE
–
Voltages ......................... –0.3V to 65V
PLLIN, PGOOD Voltages .............................. –0.3V to 6V
MODE, DRVUV Voltages .............................. –0.3V to 6V
ILIM, VPRG, FREQ, PHASMD Voltages ........ –0.3V to 6V
DRVSET, CPUMP_EN Voltages..................... –0.3V to 6V
NDRV ................................................................. (Note 9)
EXTV
CC
Voltage ......................................... –0.3V to 14V
ITH, V
FB
Voltages ......................................... –0.3V to 6V
SS, OVLO Voltages ...................................... –0.3V to 6V
Operating Junction Temperature Range (Notes 2, 3)
LTC3895E, LTC3895I ......................... –40°C to 125°C
LTC3895H .......................................... –40°C to 150°C
Storage Temperature Range .................. –65°C to 150°C
CPUMP_EN 10
CLKOUT 11
GND 12
PLLIN 13
PGOOD 14
GND 15
NC 16
FREQ 17
DRVSET 18
DRVUV 19
FE PACKAGE
VARIATION: FE38(31)
38-LEAD PLASTIC TSSOP
T
JMAX
= 150°C,
θ
JA
= 28°C/W
EXPOSED PAD (PIN 39) IS GND, MUST BE
SOLDERED TO PCB FOR RATED ELECTRICAL AND
THERMAL CHARACTERISTICS
orDer inForMaTion
LEAD FREE FINISH
LTC3895EFE#PBF
LTC3895IFE#PBF
LTC3895HFE#PBF
TAPE AND REEL
LTC3895EFE#TRPBF
LTC3895IFE#TRPBF
LTC3895HFE#TRPBF
http://www.linear.com/product/LTC3895#orderinfo
PART MARKING
LTC3895FE
LTC3895FE
LTC3895FE
PACKAGE DESCRIPTION
38-Lead Plastic TSSOP
38-Lead Plastic TSSOP
38-Lead Plastic TSSOP
TEMPERATURE RANGE
–40°C to 125°C
–40°C to 125°C
–40°C to 150°C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
Consult LTC Marketing for information on nonstandard 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/.
Some packages are available in 500 unit reels through
designated sales channels with #TRMPBF suffix.
2
3895fa
For more information
www.linear.com/LTC3895
LTC3895
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
= 12V, V
RUN
= 5V, V
EXTVCC
= 0V, V
DRVSET
= 0V,
VPRG = FLOAT unless otherwise noted.
SYMBOL
V
IN
V
OUT
V
FB
PARAMETER
Regulated Output Voltage Set Point
Regulated Feedback Voltage
(Note 4); ITH Voltage = 1.2V
0°C to 85°C, VPRG = FLOAT
VPRG = FLOAT
VPRG = 0V
VPRG = INTV
CC
(Note 4)
VPRG = FLOAT
VPRG = 0V or INTV
CC
(Note 4) V
IN
= 4.5V to 150V
(Note 4) Measured in Servo Loop,
∆ITH Voltage = 1.2V to 0.7V
(Note 4) Measured in Servo Loop,
∆ITH Voltage = 1.2V to 1.6V
g
m
I
Q
Transconductance Amplifier gm
Input DC Supply Current
(Note 4) ITH = 1.2V, Sink/Source 5µA
(Note 5) V
DRVSET
= 0V
2.5
40
10
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elecTrical characTerisTics
CONDITIONS
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MIN
4
0.8
0.792
0.788
3.220
4.875
TYP
MAX
140
60
UNITS
V
V
V
V
V
V
µA
µA
%/V
%
%
mmho
mA
Input Supply Operating Voltage Range (Note 10) DRVUV = 0V
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0.800
0.800
3.300
5.000
–0.006
4
0.002
0.01
–0.01
2.2
0.808
0.812
3.380
5.125
±0.050
6
0.02
0.1
–0.1
I
FB
Feedback Current
Reference Voltage Line Regulation
Output Voltage Load Regulation
Pulse Skip or Forced Continuous Mode V
FB
= 0.83V (No Load)
Sleep Mode
V
FB
= 0.83V (No Load)
Shutdown
UVLO
Undervoltage Lockout
RUN = 0V
DRV
CC
Ramping Up
DRVUV = 0V
DRVUV = INTV
CC
, DRVSET = INTV
CC
DRV
CC
Ramping Down
DRVUV = 0V
DRVUV = INTV
CC
, DRVSET = INTV
CC
V
RUN
ON
V
RUN
Hyst
OVLO
OVLO Hyst
RUN Pin ON Threshold
RUN Pin Hysteresis
Overvoltage Lockout Threshold
OVLO Hysteresis
OVLO Delay
Feedback Overvoltage Protection
I
SENSE
+
I
SENSE
–
SENSE
+
Pin Current
SENSE
–
Pin Current
Maximum Duty Factor
SENSE
–
< V
INTVCC
– 0.5V
SENSE
–
> V
INTVCC
+ 0.5V
In Dropout
CPUMP_EN = 0V, FREQ = 0V
CPUMP_EN = INTV
CC
V
SS
= 0V
V
FB
= 0.7V, V
SENSE
– = 3.3V
ILIM = FLOAT
ILIM = 0V
ILIM = INTV
CC
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55
20
4.2
7.8
4.0
7.0
1.3
1.3
µA
µA
V
V
V
V
V
mV
V
mV
µs
4.0
7.5
3.6
6.4
1.1
1.1
3.8
6.7
1.2
80
1.2
100
1
V
RUN
Rising
V
OVLO
Rising
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Measured at V
FB
, Relative to Regulated V
FB
7
10
13
±1
±1
%
µA
µA
µA
%
850
98
100
8
66
43
90
99
10
75
50
100
I
SS
Soft-Start Charge Current
12
84
57
109
µA
mV
mV
mV
V
SENSE(MAX)
Maximum Current Sense Threshold
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For more information
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3
LTC3895
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
= 12V, V
RUN
= 5V, V
EXTVCC
= 0V, V
DRVSET
= 0V,
VPRG = FLOAT unless otherwise noted.
SYMBOL
Gate Driver
TG Pull-up On-Resistance
TG Pull-down On-Resistance
BG Pull-up On-Resistance
BG 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
Synchronous Switch-On Delay Time
Bottom Gate Off to Top Gate On Delay
Top Switch-On Delay Time
t
ON(MIN)
I
CPUMP
TG Minimum On-Time
Charge Pump Output Current
Charge Pump for High Side Driver Supply
V
BOOST
=16V, V
SW
= 12V, V
FREQ
= 0V
V
BOOST
=19V, V
SW
= 12V, V
FREQ
= 0V
NDRV Driving External NFET, V
EXTVCC
= 0V
7V < V
IN
< 150V, DRVSET = 0V
11V < V
IN
< 150V, DRVSET = INTV
CC
NDRV Driving External NFET
I
CC
= 0mA to 50mA, V
EXTVCC
= 0V
NDRV = DRV
CC
, V
EXTVCC
= 0V
7V < V
IN
< 150V, DRVSET = 0V
11V < V
IN
< 150V, DRVSET = INTV
CC
I
CC
= 0mA to 50mA, V
EXTVCC
= 0V
DRVSET = 0V
DRVSET = INTV
CC
7V < V
EXTVCC
< 13V, DRVSET = 0V
11V < V
EXTVCC
< 13V, DRVSET = INTV
CC
I
CC
= 0mA to 50mA
DRVSET = 0V, V
EXTVCC
= 8.5V
DRVSET = INTV
CC
, V
EXTVCC
= 13V
EXTV
CC
Ramping Positive
DRVUV = 0V
DRVUV = INTV
CC
, DRVSET = INTV
CC
R
DRVSET
= 50k
NDRV Driving External NFET, V
EXTVCC
= 0V
R
DRVSET
= 70k
NDRV Driving External NFET, V
EXTVCC
= 0V
R
DRVSET
= 90k
NDRV Driving External NFET, V
EXTVCC
= 0V
6.4
4.5
7.4
5.8
9.6
5.6
9.5
65
55
µA
µA
V
DRVSET
= INTV
CC
V
DRVSET
= INTV
CC
2.2
1.0
2.0
1.0
11
25
15
25
15
55
50
80
Ω
Ω
Ω
Ω
Ω
ns
ns
ns
ns
ns
ns
ns
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
elecTrical characTerisTics
BOOST to DRV
CC
Switch On-Resistance V
SW
= 0V, V
DRVSET
= INTV
CC
(Note 6) V
DRVSET
= INTV
CC
C
LOAD
= 3300pF
C
LOAD
= 3300pF
(Note 6) V
DRVSET
= INTV
CC
C
LOAD
= 3300pF
C
LOAD
= 3300pF
C
LOAD
= 3300pF each driver, V
DRVSET
= INTV
CC
C
LOAD
= 3300pF each driver, V
DRVSET
= INTV
CC
(Note 7) V
DRVSET
= INTV
CC
DRV
CC
LDO Regulator
DRV
CC
Voltage from NDRV LDO
Regulator
DRV
CC
Load Regulation from NDRV
LDO Regulator
DRV
CC
Voltage from Internal V
IN
LDO
DRV
CC
Load Regulation from V
IN
LDO
DRV
CC
Voltage from Internal EXTV
CC
LDO
DRV
CC
Load Regulation from Internal
EXTV
CC
LDO
EXTV
CC
LDO Switchover Voltage
EXTV
CC
Hysteresis
Programmable DRV
CC
Programmable DRV
CC
Programmable DRV
CC
5.8
9.6
6.0
10.0
0
5.85
9.85
1.4
0.9
6.0
10.0
0.7
0.5
4.7
7.7
250
5.0
7.0
9.0
7.6
6.2
10.4
1.0
6.1
10.3
2.5
2.0
6.2
10.4
2.0
2.0
4.9
8.0
V
V
%
V
V
%
%
V
V
%
%
V
V
mV
V
V
V
4
3895fa
For more information
www.linear.com/LTC3895
LTC3895
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
= 12V, V
RUN
= 5V, V
EXTVCC
= 0V, V
DRVSET
= 0V,
VPRG = FLOAT unless otherwise noted.
SYMBOL
V
INTVCC
PARAMETER
INTV
CC
Voltage
Programmable Frequency
Programmable Frequency
Programmable Frequency
Low Fixed Frequency
High Fixed Frequency
f
SYNC
Synchronizable Frequency
PLLIN Input High Level
PLLIN Input Low Level
PGOOD Output
V
PGL
I
PGOOD
PGOOD Voltage Low
PGOOD Leakage Current
PGOOD Trip Level
I
PGOOD
= 2mA
V
PGOOD
= 3.3V
V
FB
with Respect to Set Regulated Voltage
V
FB
Ramping Negative
Hysteresis
V
FB
with Respect to Set Regulated Voltage
V
FB
Ramping Positive
Hysteresis
Delay for Reporting a Fault
Note 1:
Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Ratings for extended periods may affect device reliability and
lifetime.
Note 2:
The LTC3895 is tested under pulsed load conditions such that T
J
≈
T
A
. The LTC3895E 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 LTC3895I is guaranteed over the
–40°C to 125°C operating junction temperature range and the LTC3895H
is guaranteed over the –40°C to 150°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
= 28°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.
–13
–10
2.5
10
2.5
40
0.02
0.04
10
–7
V
µA
%
%
%
%
µs
CONDITIONS
I
CC
= 0mA to 2mA
R
FREQ
= 25k, PLLIN = DC Voltage
R
FREQ
= 65k, PLLIN = DC Voltage
R
FREQ
=105k, PLLIN = DC Voltage
V
FREQ
= 0V, PLLIN = DC Voltage
V
FREQ
= INTV
CC
, PLLIN = DC Voltage
PLLIN = External Clock
PLLIN = External Clock
PLLIN = External Clock
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elecTrical characTerisTics
INTV
CC
LDO Regulator
MIN
4.7
TYP
5.0
105
MAX
5.2
UNITS
V
kHz
Oscillator and Phase-Locked Loop
375
320
485
75
2.8
440
835
350
535
380
585
850
0.5
505
kHz
kHz
kHz
kHz
kHz
V
V
7
13
Note 4:
The LTC3895 is tested in a feedback loop that servos V
ITH
to a
specified voltage and measures the resultant V
FB
. The specification at 85°C
is not tested in production and is assured by design, characterization and
correlation to production testing at other temperatures (125°C for the
LTC3895E and LTC3895I, 150°C for the LTC3895H). For the LTC3895I
and LTC3895H, the specification at 0°C is not tested in production and is
assured by design, characterization and correlation to production testing
at –40°C.
Note 5:
Dynamic supply current is higher due to the gate charge being
delivered at the switching frequency. See the Applications information
section.
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).
Note 8:
Do not apply a voltage or current source to these pins. They must
be connected to capacitive loads only, otherwise permanent damage may
occur.
Note 9:
Do not apply a voltage or current source to the NDRV pin, other
than tying NDRV to DRV
CC
when not used. If used it must be connected
to capacitive loads only (see DRV
CC
Regulators in the Applications
Information section), otherwise permanent damage may occur.
Note 10:
The minimum input supply operating range is dependent on the
DRV
CC
UVLO thresholds as determined by the DRVUV pin setting.
3895fa
For more information
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5
