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LT3845AEFE#PBF

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P21P22-P24P25-P26
LT3845A
1
3845afa
TYPICAL APPLICATION
FEATURES
APPLICATIONS
DESCRIPTION
High Voltage Synchronous
Current Mode Step-Down
Controller with Adjustable
Operating Frequency
The LT
®
3845A is a high voltage, synchronous, current
mode controller used for medium to high power, high
efficiency supplies. It offers a wide 4V to 60V input range
(7.5V minimum start-up voltage). An onboard regulator
simplifies the biasing requirements by providing IC power
directly from V
IN
.
Burst Mode
®
operation maintains high efficiency at light
loads by reducing IC quiescent current to 120µA. Light load
efficiency is also improved with the reverse inductor current
inhibit function which supports discontinuous operation.
Additional features include adjustable fixed 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 LT3845A is available in a 16-lead thermally enhanced
TSSOP package.
n
High Voltage Operation: Up to 60V
n
Synchronizable Up to 600kHz
n
Adjustable Constant Frequency: 100kHz to 500kHz
n
Output Voltages Up to 36V
n
Stable Operation in Current Limit
n
Adaptive Nonoverlap Circuitry Prevents Switch
Shoot-Through
n
Reverse Inductor Current Inhibit for Discontinuous
Operation Improves Efficiency with Light Loads
n
Programmable Soft-Start
n
120µA No Load Quiescent Current
n
10µA Shutdown Supply Current
n
1% Regulation Accuracy
n
Standard Gate N-Channel Power MOSFETs
n
Reverse Overcurrent Protection
n
16-Lead Thermally Enhanced TSSOP Package
n
12V and 42V Automotive and Heavy Equipment
n
48V Telecom Power Supplies
n
Avionics and Industrial Control Systems
n
Distributed Power Converters
High Voltage Step-Down Regulator 48V to 12V at 75W
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.
SGND
BAS521
1N4148
3845A TA01a
0.1µF
1500pF
Si7370DP
Si7370DP
B160
15µH
0.008Ω
LT3845A
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
BOOST
TG
SW
V
CC
BG
PGND
SENSE
+
SENSE
–
V
IN
SHDN
C
SS
BURST_EN
V
FB
V
C
SYNC
f
SET
Efficiency and Power Loss
vs Load Current
LOAD CURENT (A)
65
80
75
70
100
95
90
85
0
3
2
1
7
6
5
4
3845A TA01b
EFFICIENCY(%)
POWER LOSS (W)
0.1
10
1
V
IN
= 48V
LOSS
LT3845A
2
3845afa
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
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)
LT3845AE (Note 3) ............................ –40°C to 125°C
LT3845AI .......................................... –40°C to 125°C
LT3845AMP ....................................... –55°C to 125°C
Storage Temperature.............................. –65°C to 150°C
Lead Temperature (Soldering, 10 sec)
...................300°C
LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE
LT3845AEFE#PBF LT3845AEFE#TRPBF 3845AFE 16-Lead Plastic TSSOP –40°C to 125°C
LT3845AIFE#PBF LT3845AIFE#TRPBF 3845AFE 16-Lead Plastic TSSOP –40°C to 125°C
LT3845AMPFE#PBF LT3845AMPFE#TRPBF 3845AFE 16-Lead Plastic TSSOP –55°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/
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, q
JA
= 40°C/W, q
JC
= 10°C/W
EXPOSED PAD (PIN 17) IS SGND, MUST BE SOLDERED TO PCB
PIN CONFIGURATION
LT3845A
3
3845afa
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
l
l
l
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
l
20
20
9
15
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
l
l
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
l
l
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
l
l
–40
3
100
20
–150
3.7 mA
µA
µA
mA
Error Amp Reference Voltage Measured at V
FB
Pin
l
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
l
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
l
l
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
l
270 300 330 kHz
Minimum Programmable Frequency
Maximum Programmable Frequency
l
l
500
100 kHz
kHz
External Sync Frequency Range
l
100 600 kHz
SYNC Input Resistance 40 kΩ
SYNC Voltage Threshold
l
1.4 2 V
Soft-Start Capacitor Control Current 2 µA
Error Amp Transconductance
l
270 340 410 µS
Error Amp DC Voltage Gain 62 dB
Error Amp Sink/Source Current ±30 µA
ELECTRICAL CHARACTERISTICS
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications 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

LT3845AEFE#PBF

Mfr. #:
Buy LT3845AEFE#PBF
Manufacturer:
Analog Devices / Linear Technology
Description:
Switching Voltage Regulators High Voltage Synchronous Current Mode Step-Down Controller with Adjustable Operating Frequency
Lifecycle:
New from this manufacturer.
Delivery:
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