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LT3845IFE#PBF

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P21P22-P24P25-P26
LT3845
1
3845fd
TYPICAL APPLICATION
FEATURES
APPLICATIONS
DESCRIPTION
High Voltage Synchronous
Current Mode Step-Down
Controller with Adjustable
Operating Frequency
The LT
®
3845 is a high voltage, synchronous, current
mode controller used for medium to high power, high
effi ciency supplies. It offers a wide 4V to 60V input range
(7.5V minimum start-up voltage). An onboard regulator
simplifi es the biasing requirements by providing IC power
directly from V
IN
.
Burst Mode
®
operation maintains high effi ciency at light
loads by reducing IC quiescent current to 120μA. Light
load effi ciency is also improved with the reverse inductor
current inhibit function which supports discontinuous
operation.
Additional features include adjustable fi xed operating
frequency that can be synchronized to an external clock
for noise sensitive applications, gate drivers capable of
driving large N-channel MOSFETs, a precision undervoltage
lockout, 10μA shutdown current, short-circuit protection
and a programmable soft-start.
The LT3845 is available in a 16-lead thermally enhanced
TSSOP package and 16-pin through hole N package.
■
High Voltage Operation: Up to 60V
■
Synchronizable Up to 600kHz
■
Adjustable Constant Frequency: 100kHz to 500kHz
■
Output Voltages Up to 36V
■
Adaptive Nonoverlap Circuitry Prevents Switch
Shoot-Through
■
Reverse Inductor Current Inhibit for Discontinuous
Operation Improves Effi ciency with Light Loads
■
Programmable Soft-Start
■
120μA No Load Quiescent Current
■
10μA Shutdown Supply Current
■
1% Regulation Accuracy
■
Standard Gate N-Channel Power MOSFETs
■
Current Limit Unaffected by Duty Cycle
■
Reverse Overcurrent Protection
■
16-Lead Thermally Enhanced TSSOP Package,
16-Pin PDIP
■
12V and 42V Automotive and Heavy Equipment
■
48V Telecom Power Supplies
■
Avionics and Industrial Control Systems
■
Distributed Power Converters
High Voltage Step-Down Regulator 48V to 12V at 75W
Effi ciency and Power Loss vs
Load Current
L, LT, LTC, LTM, Burst Mode, 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, 6611131, 6304066, 6498466, 6580258.
V
IN
SHDN
C
SS
BURST_EN
V
FB
V
C
SYNC
f
SET
BOOST
TG
SW
V
CC
BG
PGND
SENSE
+
SENSE
–
SGND
BAS521
1N4148
3845 TA01a
0.1μF
1500pF
Si7370DP
Si7370DP
B160
15μH
0.01Ω
LT3845
1μF
33μF
×3
V
OUT
12V
75W
1M
82.5k
16.2k
V
IN
20V TO 55V
2.2μF
100V
49.9k
20k
100pF
2200pF
143k
47μF
63V
LOAD CURENT (A)
65
80
75
70
100
95
90
85
0
3
2
1
7
6
5
4
3845 TA01b
EFFICIENCY(%)
POWER LOSS (W)
0.1
10
1
V
IN
= 48V
LOSS
LT3845
2
3845fd
ORDER INFORMATION
ABSOLUTE MAXIMUM RATINGS
(Note 1)
Input Supply Voltage (V
IN
) ........................................65V
Boosted Supply Voltage (BOOST) .............................80V
Switch Voltage (SW) (Note 8) ....................... 65V to –2V
Differential Boost Voltage
(BOOST to SW) .....................................................24V
Bias Supply Voltage (V
CC
) .........................................24V
SENSE
+
and SENSE
–
Voltages ..................................40V
Differential Sense Voltage
(SENSE
+
to SENSE
–
) ................................... 1V to –1V
LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE
LT3845EFE#PBF LT3845EFE#TRPBF 3845FE 16-Lead Plastic TSSOP –40°C to 125°C
LT3845IFE#PBF LT3845IFE#TRPBF 3845FE 16-Lead Plastic TSSOP –40°C to 125°C
LT3845MPFE#PBF LT3845MPFE#TRPBF 3845FE 16-Lead Plastic TSSOP –55°C to 125°C
LT3845EN#PBF LT3845EN#TRPBF 3845N 16-Lead PDIP –40°C to 125°C
Consult LTC Marketing for parts specifi ed with wider operating temperature ranges. *The temperature grade is identifi ed by a label on the shipping container.
Consult LTC Marketing for information on non-standard lead based fi nish parts.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/
For more information on tape and reel specifi cations, go to: http://www.linear.com/tapeandreel/
FE PACKAGE
16-LEAD PLASTIC TSSOP
1
2
3
4
5
6
7
8
TOP VIEW
16
15
14
13
12
11
10
9
V
IN
SHDN
C
SS
BURST_EN
V
FB
V
C
SYNC
f
SET
BOOST
TG
SW
V
CC
BG
PGND
SENSE
+
SENSE
–
17
T
JMAX
= 125°C, θ
JA
= 40°C/W, θ
JC
= 10°C/W
EXPOSED PAD (PIN 17) IS SGND, MUST BE SOLDERED TO PCB
N PACKAGE
16-LEAD PDIP
1
2
3
4
5
6
7
8
TOP VIEW
16
15
14
13
12
11
10
9
V
FB
V
C
f
SET
SGND
SENSE
–
SENSE
+
PGND
BG
BURST_EN
C
SS
SHDN
V
IN
BOOST
TG
SW
V
CC
T
JMAX
= 125°C, θ
JA
= 70°C/W, θ
JC
= 34°C/W
PIN CONFIGURATION
BURST_EN Voltage ...................................................24V
SYNC, V
C
, V
FB
, C
SS
, and SHDN Voltages ....................5V
SHDN Pin Currents ..................................................1mA
Operating Junction Temperature Range (Note 2)
LT3845E (Note 3) ............................... –40°C to 125°C
LT3845I .............................................. –40°C to 125°C
LT3845MP.......................................... –55°C to 125°C
Storage Temperature .............................. –65°C to 150°C
Lead Temperature (Soldering, 10 sec) .................. 300°C
LT3845
3
3845fd
PARAMETER CONDITIONS MIN TYP MAX UNITS
V
IN
Operating Voltage Range (Note 4)
V
IN
Minimum Start Voltage
V
IN
UVLO Threshold (Falling)
V
IN
UVLO Threshold Hysteresis
●
●
●
4
3.6 3.8
670
60
7.5
4
V
V
V
mV
V
IN
Supply Current
V
IN
Burst Mode Current
V
IN
Shutdown Current
V
CC
> 9V
V
BURST_EN
= 0V, V
FB
= 1.35V
V
SHDN
= 0V
●
20
20
915
μA
μA
μA
BOOST Operating Voltage Range
BOOST Operating Voltage Range (Note 5)
BOOST UVLO Threshold (Rising)
BOOST UVLO Threshold Hysteresis
V
BOOST
– V
SW
V
BOOST
– V
SW
V
BOOST
– V
SW
●
●
5
400
75
20
V
V
V
mV
BOOST Supply Current (Note 6)
BOOST Burst Mode Current
BOOST Shutdown Current
V
BURST_EN
= 0V
V
SHDN
= 0V
1.4
0.1
0.1
mA
μA
μA
V
CC
Operating Voltage Range (Note 5)
V
CC
Output Voltage
V
CC
UVLO Threshold (Rising)
V
CC
UVLO Threshold Hysteresis
Over Full Line and Load Range
●
●
8
6.25
500
20
8.3
V
V
V
mV
V
CC
Supply Current (Note 6)
V
CC
Burst Mode Current
V
CC
Shutdown Current
V
CC
Current Limit
V
BURST_EN
= 0V
V
SHDN
= 0V
●
●
–40
3
100
20
–150
3.7 mA
μA
μA
mA
Error Amp Reference Voltage Measured at V
FB
Pin
●
1.224
1.215
1.231 1.238
1.245
V
V
V
FB
Pin Input Current V
FB
= 1.231V 25 nA
SHDN Enable Threshold (Rising)
SHDN Threshold Hysteresis
●
1.3 1.35
120
1.4 V
mV
Sense Pins Common Mode Range
Current Limit Sense Voltage
Reverse Protect Sense Voltage
Reverse Current Inhibit Offset
V
SENSE
+
– V
SENSE
–
V
SENSE
+
– V
SENSE
–
, V
BURST_EN
= V
CC
V
BURST_EN
= 0V or V
BURST_EN
= V
FB
●
●
0
90 100
–100
10
36
115
V
mV
mV
mV
Input Current (I
SENSE
+
+ I
SENSE
–
)V
SENSE(CM)
= 0V
V
SENSE(CM)
= 2V
V
SENSE(CM)
> 4V
800
–20
–300
μA
μA
μA
Operating Frequency
●
270 300 330 kHz
Minimum Programmable Frequency
Maximum Programmable Frequency
●
●
500
100 kHz
kHz
External Sync Frequency Range
●
100 600 kHz
SYNC Input Resistance 40 kΩ
SYNC Voltage Threshold
●
1.4 2 V
Soft-Start Capacitor Control Current 2μA
Error Amp Transconductance
●
270 340 410 μS
Error Amp DC Voltage Gain 62 dB
Error Amp Sink/Source Current ±30 μA
ELECTRICAL CHARACTERISTICS
The l denotes the specifi cations which apply over the full operating
temperature range, otherwise specifi cations are at T
A
= 25°C. V
IN
= 20V, V
CC
= BOOST = BURST_EN = 10V, SHDN = 2V, R
SET
= 49.9kΩ,
SENSE
–
= SENSE
+
= 10V, SGND = PGND = SW = SYNC = 0V, unless otherwise noted.
P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P21P22-P24P25-P26

LT3845IFE#PBF

Mfr. #:
Buy LT3845IFE#PBF
Manufacturer:
Analog Devices / Linear Technology
Description:
Switching Voltage Regulators High Voltage Synch Current Mode Step-Down Controller
Lifecycle:
New from this manufacturer.
Delivery:
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