LT3840 Datasheet PDF - Linear Technology

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LT3840
Linear Technology

Part Number LT3840
Description Wide Input Range Synchronous Regulator Controller
Page 24 Pages


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Features
LT3840
Wide Input Range
Synchronous Regulator Controller
with Accurate Current Limit
Description
n Wide Input Range: 2.5V to 60V
n Integrated Buck-Boost Supply for 7.5V MOSFET
Gate Drive
n Programmable Constant-Current Operation with
Current Monitor Output
n Low IQ: 75µA, 12VIN to 3.3VOUT
n Selectable Low Output Ripple Burst Mode®
Operation
n VOUT Up to 60V
n Adjustable and Synchronizable: 50kHz to 1MHz
n Internal OVLO Protects for Input Transients Up to 80V
n Accurate Input Overvoltage and Undervoltage Threshold
n Programmable Soft-Start with Voltage Tracking
n Power Good and Output OVP
n 28-Lead TSSOP and 38-Lead 4mm × 6mm QFN Packages
Applications
n Automotive Supplies
n Industrial Systems
n Distributed DC Power Systems
The LT®3840 is a high voltage synchronous step-down
switching regulator controller capable of operating from
a 2.5V to 60V supply.
The LT3840’s low quiescent current, when configured for
user selectable Burst Mode operation, helps extend run
time in battery-powered systems by increasing efficiency
at light loads. The LT3840 uses a constant frequency,
current mode architecture. High current applications are
possible with large N-channel gate drivers capable of
driving multiple low RDS(ON) MOSFETs.
An integrated buck-boost switching regulator generates
a 7.5V bias supply voltage for MOSFET gate drive and IC
power allowing higher efficiency operation over the entire
input voltage range and eliminating the need for an external
bias voltage. An accurate current limit set point regulates
the maximum output current. A current monitor reports
the average output current.
L, LT, LTC, LTM, Linear Technology, Burst Mode, and the Linear logo are registered
trademarks of Linear Technology Corporation. All other trademarks are the property of their
respective owners.
Typical Application
VIN
4V TO 60V
High Efficiency Synchronous Step-Down Converter
68µF 1µF 33µH
×2
49.9k
AUXBST AUXSW1
EN
VIN
AUXVIN
UVLO
LT3840
AUXSW2
INTVCC
BOOST
OVLO
TG
PG SW
SYNC
BG
20k
1500pF
MODE
RT SENSE+
VC SENSE
TK/SS
FB
100pF
IMON
ICOMP
GND
ICTRL
2200pF
7.68k
470pF
4.7µF
1µF
1.5µH
16.9k
10k
2m
VOUT
3.3V
20A
330µF
×2
3840 TA01a
12VIN to 3.3VOUT Efficiency
100
95
90
85
80
75
70
65
60
55
50
0
5 10 15
LOAD CURRENT (A)
20
3840 TA01b
For more information www.linear.com/LT3840
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LT3840
Absolute Maximum Ratings
(Note 1)
AUXVIN, VIN, EN and UVLO........................ –0.3V to 80V
PG............................................................... –0.3V to 25V
MODE............................................................ –0.3V to 9V
SENSE+ and SENSE................................... –0.3V to 60V
SENSE+ to SENSE............................................–1V to 1V
OVLO, VC, FB, SYNC, TK/SS and ICTRL........ –0.3V to 6V
Junction Temperature Range
LT3840E (Note 2)............................... –40°C to 125°C
LT3840I.............................................. –40°C to 125°C
LT3840H............................................. –40°C to 150°C
LT3840MP.......................................... –55°C to 150°C
Lead Temperature (Soldering, 10 sec)
TSSOP Only........................................................... 300°C
Storage Temperature............................. –65°C to 150°C
Pin Configuration
TOP VIEW
AUXSW1 1
28 AUXBST
PGND 2
27 AUXSW2
AUXVIN 3
26 INTVCC
SYNC 4
25 BG
RT 5
24 BGRTN
TK/SS 6
23 BOOST
FB 7
VC 8
PG 9
29 22 TG
GND 21 SW
20 SENSE
MODE 10
19 SENSE+
OVLO 11
18 ICOMP
UVLO 12
17 ICTRL
EN 13
16 IMON
VIN 14
15 GND
FE PACKAGE
28-LEAD PLASTIC TSSOP
θJA = 30°C/W, θJC = 10°C/W
EXPOSED PAD (PIN 29) IS GND, MUST BE SOLDERED TO PCB
TOP VIEW
AUXVIN 1
NC 2
SYNC 3
RT 4
NC 5
TK/SS 6
FB 7
VC 8
PG 9
NC 10
MODE 11
OVLO 12
38 37 36 35 34 33 32
39
GND
13 14 15 16 17 18 19
31 NC
30 INTVCC
29 BG
28 BGRTN
27 NC
26 BOOST
25 TG
24 SW
23 NC
22 SENSE
21 SENSE+
20 ICOMP
UFE PACKAGE
38-LEAD (4mm × 6mm) PLASTIC QFN
θJA = 38°C/W, θJC = 4°C/W
EXPOSED PAD (PIN 39) IS GND, MUST BE SOLDERED TO PCB
Order Information
LEAD FREE FINISH
TAPE AND REEL
PART MARKING*
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LT3840EFE#PBF
LT3840EFE#TRPBF
LT3840FE
28-Lead Plastic TSSOP
–40°C to 125°C
LT3840IFE#PBF
LT3840IFE#TRPBF
LT3840FE
28-Lead Plastic TSSOP
–40°C to 125°C
LT3840HFE#PBF
LT3840HFE#TRPBF
LT3840FE
28-Lead Plastic TSSOP
–40°C to 150°C
LT3840MPFE#PBF
LT3840MPFE#TRPBF
LT3840FE
28-Lead Plastic TSSOP
–55°C to 150°C
LT3840EUFE#PBF
LT3840EUFE#TRPBF
3840
38-Lead (4mm × 6mm) Plastic QFN
–40°C to 125°C
LT3840IUFE#PBF
LT3840IUFE#TRPBF
3840
38-Lead (4mm × 6mm) Plastic QFN
–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 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/
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LT3840
E lectrical Characteristics The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C.
PARAMETER
CONDITIONS
MIN TYP MAX
Input Supply
VVIINN
Minimum Operating
Supply Current
Voltage
VIN Burst Mode Current
VIN Shutdown Current
AUXVIN Minimum Operating Voltage
AUXVIN Overvoltage Lockout
AAUUXXVVIINN
Supply Current
Burst Mode Current
AUXVIN Shutdown Current
EN Enable Threshold (Rising)
EN Hysteresis
EN Pin Bias Current
UVLO Enable Threshold (Rising)
UVLO Hysteresis
UVLO Pin Bias Current
OVLO Threshold (Rising)
OVLO Hysteresis
OVLO Pin Bias Current
Voltage Regulation
VMODE = 0V
VEN = 0.3V
(Note 3)
VMODE = 0V
VEN = 0.3V
VEN = 1.25V
VUVLO = 1.25V
VOVLO = 1.25V
l 2.5
20
20 30
l 0.1 1
l 2.5
l 60
300
0.1
0.1 1
l 1.20 1.25 1.30
30
2
l 1.20 1.25 1.30
45
1
l 1.20 1.25 1.30
125
1
Regulated FB Voltage
E- and I-Grade
l 1.237 1.250 1.263
Regulated FB Voltage
MP- and H-Grade
l 1.232 1.250 1.263
FB Overvoltage Protection
% Above FB Voltage
l8
12 16
FB Overvoltage Protection Hysteresis
2.5
FB Input Bias Current
5 20
FB Voltage Line Regulation
FB Error Amp Transconductance
2.5V ≤ VIN ≤ 60V
0.002
300
0.02
FB Error Amp Sink/Source Current
±25
Peak Current Limit Sense Voltage
0% Duty Cycle
80 95 110
Peak Current Limit Sense Voltage
100% Duty Cycle
60
TK/SS Charge Current
9
Current Regulation
Sense Common Mode Range
l0
60
Average Current Limit Sense Voltage
IMON Voltage
ICTRL Current
Reverse Protect Sense Voltage
Reverse Current Sense Voltage Offset
Sense Input Current
VICTRL = Open
VICTRL = 800mV
VSENSE = 50mV
VSENSE = 20mV
VICTRL = 1V
VMODE = 7.5V
VMODE = VFB or VMODE = 0V
SENSE+ = SENSE= 12V
l 47.5 50 52.5
40
l 0.95 1.00 1.05
0.4
7
–50
5
300
Oscillator
Switching Frequency
SYNC Threshold
RRTT
=
=
49.9k
348k
RT = 13.7k
l 280 300 320
50
1000
1.2
UNITS
V
µA
µA
µA
V
V
µA
µA
µA
V
mV
nA
V
mV
nA
V
mV
nA
V
V
%
%
nA
%/V
µS
µA
mV
mV
µA
V
mV
mV
V
V
µA
mV
mV
µA
kHz
kHz
kHz
V
For more information www.linear.com/LT3840
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LT3840
E lectrical Characteristics The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C.
PARAMETER
Power Good
PG Threshold as a Percentage of VFB
PG Hysteresis as a Percentage of VFB
PG Leakage
PG Sink Current
MOSFET Gate Drivers
Non-Overlap Time TG to BG
Non-Overlap Time BG to TG
TG Minimum On Time
TG Minimum Off Time
TG Maximum Duty Cycle
TG, BG Drive On Voltage
TG, BG Drive Off Voltage
TG, BG Drive Rise Time
TG, BG Drive Fall Time
BOOST UVLO (Rising)
BOOST UVLO Hysteresis
Internal Auxiliary Supply
INTVCC Regulation Voltage
INTVCC UVLO Threshold (Rising)
INTVCC UVLO Hysteresis
INTVCC Current in Shutdown
INTVCC Output Current
INTVCC Burst Mode Current
CONDITIONS
VFB Rising
VPG = 5V
VPG = 0.3V
RT = 49.9k
CTG = CBG = 3300pF
CTG = CBG = 3300pF
VBOOST - VSW
VEN = 0.3V
2.5V ≤ VIN ≤ 60V (Note 4)
VMODE = 0V
MIN TYP MAX UNITS
l 87 90 93
2.5
0.1 1
l 35
65
%
%
µA
µA
75
75
150
240
99
7.5
5
20
20
4.5 5.3
350
ns
ns
ns
ns
%
V
mV
ns
ns
V
mV
l 7.25 7.5 7.75
6.25 6.5 6.75
300
6
l 100
60
V
V
mV
µA
mA
µA
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 LT3840E is guaranteed to meet performance specifications
from 0°C to 125°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
LT3840I is guaranteed over the –40°C to 125°C operating junction
temperature range. The LT3840H is guaranteed over the full –40°C to
150°C operating junction temperature range. The LT3840MP is 100%
tested and guaranteed over the –55°C to 150°C temperature range. High
junction temperatures degrade operating lifetimes; Operating lifetime is
derated for junction temperatures greater than 125°C.
Note 3: Supply current specification does not include switch drive
currents. Actual supply currents will be higher.
Note 4: Specification is not tested but is guaranteed by design,
characterization and correlation with statistical process controls.
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