synchronous DC/DC converter. The powerful rail-to-rail
driver capability reduces switching losses in MOSFETs
with high gate capacitance.
The LTC4449 features a separate supply for the input logic
to match the signal swing of the controller IC. If the input
signal is not being driven, the LTC4449 activates a shutdown
mode that turns off both external MOSFETs. The input logic
signal is internally level-shifted to the bootstrapped supply,
which functions at up to 42V above ground.
The LTC4449 contains undervoltage lockout circuits on
both the driver and logic supplies that turn off the external
MOSFETs when an undervoltage condition is present. An
adaptive shoot-through protection feature is also built-in
to prevent the power loss resulting from MOSFET cross-
conduction current.
The LTC4449 is available in the 2mm
×
3mm DFN
package.
4V to 6.5V V
CC
Operating Voltage
38V Maximum Input Supply Voltage
Adaptive Shoot-Through Protection
Rail-to-Rail Output Drivers
3.2A Peak Pull-Up Current
4.5A Peak Pull-Down Current
8ns TG Rise Time Driving 3000pF Load
7ns TG Fall Time Driving 3000pF Load
Separate Supply to Match PWM Controller
Drives Dual N-Channel MOSFETs
Undervoltage Lockout
Low Profile (0.75mm) 2mm
×
3mm DFN Package
APPLICATIONS
n
n
Distributed Power Architectures
High Density Power Modules
L,
LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
Synchronous Buck Converter Driver
V
CC
4V TO 6.5V
V
CC
V
LOGIC
BOOST
V
IN
TO 38V
INPUT (IN)
5V/DIV
LTC4449 Driving 3000pF Capacitive Loads
LTC4449
TG
TS
V
OUT
TOP GATE
(TG - TS)
5V/DIV
PWM
IN
GND
BG
BOTTOM GATE
(BG) 5V/DIV
4449 TA01a
10ns/DIV
4449 TA01b
4449fa
1
LTC4449
ABSOLUTE MAXIMUM RATINGS
(Note 1)
PIN CONFIGURATION
TOP VIEW
TG 1
TS 2
BG 3
GND 4
9
8 BOOST
7 V
CC
6 V
LOGIC
5 IN
Supply Voltage
V
LOGIC
...................................................... –0.3V to 7V
V
CC
........................................................... –0.3V to 7V
BOOST – TS ............................................. –0.3V to 7V
BOOST Voltage .......................................... –0.3V to 42V
TS ................................................................. –5V to 38V
IN Voltage .................................................... –0.3V to 7V
Driver Output TG (with Respect to TS)......... –0.3V to 7V
Driver Output BG.......................................... –0.3V to 7V
Operating Junction Temperature Range
(Notes 2, 3) ............................................–40°C to 125°C
Storage Temperature Range...................–65°C to 150°C
DCB PACKAGE
8-LEAD (2mm 3mm) PLASTIC DFN
θ
JA
= 64°C/W,
θ
JC
= 10.6°C/W
EXPOSED PAD (PIN 9) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
LTC4449EDCB#PBF
LTC4449IDCB#PBF
TAPE AND REEL
LTC4449EDCB#TRPBF
LTC4449IDCB#TRPBF
PART MARKING*
LFKC
LFKC
PACKAGE DESCRIPTION
8-Lead (2mm
×
3mm) Plastic DFN
8-Lead (2mm
×
3mm) Plastic DFN
TEMPERATURE RANGE
–40°C to 125°C
–40°C to 125°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *Temperature grades are identified by a label on the shipping container.
Consult LTC Marketing for information on 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/
ELECTRICAL CHARACTERISTICS
SYMBOL
V
LOGIC
I
VLOGIC
UVLO
PARAMETER
Operating Range
DC Supply Current
Undervoltage Lockout Threshold
Logic Supply (V
LOGIC
)
The
l
denotes the specifications which apply over the full operating junction
temperature range, otherwise specifications are at T
A
= 25°C. V
CC
= V
LOGIC
= V
BOOST
= 5V, V
TS
= GND = 0V, unless otherwise noted. (Note 2)
CONDITIONS
MIN
3
IN = Floating
V
LOGIC
Rising
V
LOGIC
Falling
Hysteresis
l
l
TYP
MAX
6.5
UNITS
V
μA
V
V
mV
V
μA
V
V
mV
μA
730
2.5
2.4
2.75
2.65
100
900
3
2.9
Gate Driver Supply (V
CC
)
V
CC
I
VCC
UVLO
Operating Range
DC Supply Current
Undervoltage Lockout Threshold
IN = Floating
V
CC
Rising
V
CC
Falling
Hysteresis
IN = Floating
l
l
4
300
2.75
2.60
3.20
3.04
160
300
6.5
400
3.65
3.50
400
I
BOOST
DC Supply Current
4449fa
2
LTC4449
ELECTRICAL CHARACTERISTICS
SYMBOL
Input Signal (IN)
V
IH(TG)
V
IL(TG)
V
IH(BG)
V
IL(BG)
I
IN(SD)
TG Turn-On Input Threshold
TG Turn-Off Input Threshold
BG Turn-On Input Threshold
BG Turn-Off Input Theshold
Maximum Current Into or Out of IN in
Shutdown Mode
TG High Output Voltage
TG Low Output Voltage
TG Peak Pull-Up Current
TG Peak Pull-Down Current
BG High Output Voltage
BG Low Output Voltage
BG Peak Pull-Up Current
BG Peak Pull-Down Current
BG Low to TG High Propagation Delay
IN Low to TG Low Propagation Delay
TG Low to BG High Propagation Delay
IN High to BG Low Propagation Delay
TG Output Rise Time
TG Output Fall Time
BG Output Rise Time
BG Output Fall Time
10% to 90%, C
L
= 3nF
90% to 10%, C
L
= 3nF
10% to 90%, C
L
= 3nF
90% to 10%, C
L
= 3nF
I
BG
= –100mA, V
OH(BG)
= V
CC
– V
BG
I
BG
= 100mA
l
l
The
l
denotes the specifications which apply over the full operating junction
temperature range, otherwise specifications are at T
A
= 25°C. V
CC
= V
LOGIC
= V
BOOST
= 5V, V
TS
= GND = 0V, unless otherwise noted. (Note 2)
PARAMETER
CONDITIONS
V
LOGIC
≥ 5V, IN Rising
V
LOGIC
= 3.3V, IN Rising
V
LOGIC
≥ 5V, IN Falling
V
LOGIC
= 3.3V, IN Falling
V
LOGIC
≥ 5V, IN Falling
V
LOGIC
= 3.3V, IN Falling
V
LOGIC
≥ 5V, IN Rising
V
LOGIC
= 3.3V, IN Rising
V
LOGIC
≥ 5V, IN Floating
V
LOGIC
= 3.3V, IN Floating
I
TG
= –100mA, V
OH(TG)
= V
BOOST
– V
TG
I
TG
= 100mA, V
OL(TG)
= V
TG
– V
TS
l
l
l
l
l
l
l
l
l
l
MIN
3
1.9
2.75
1.8
0.8
0.8
1.05
0.9
150
75
TYP
3.5
2.2
3.25
2.09
1.25
1.1
1.5
1.21
300
150
140
80
MAX
4
2.6
3.75
2.5
1.6
1.4
1.85
1.5
UNITS
V
V
V
V
V
V
V
V
μA
μA
mV
mV
A
A
mV
mV
A
A
ns
ns
ns
ns
ns
ns
ns
ns
High Side Gate Driver Output (TG)
V
OH(TG)
V
OL(TG)
I
PU(TG)
I
PD(TG)
V
OH(BG)
V
OL(BG)
I
PU(BG)
I
PD(BG)
Switching Time
t
PLH(TG)
t
PHL(TG)
t
PLH(BG)
t
PHL(BG)
t
r(TG)
t
f(TG)
t
r(BG)
t
f(BG)
14
13
13
11
8
7
7
4
2
1.5
3.2
2.4
100
100
Low Side Gate Driver Output (BG)
2
3
3.2
4.5
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 LTC4449 is tested under pulsed load conditions such that
T
J
≈ T
A
. The LTC4449E is guaranteed to meet specifications from
0°C to 85°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
LTC4449I 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. The junction temperature T
J
is calculated from the ambient temperature T
A
and power dissipation P
D
according to the following formula:
T
J
= T
A
+ (P
D
• 64°C/W)
Note 3:
This IC includes overtemperature protection that is intended
to protect the device during momentary overload conditions. Junction
temperature will exceed 125°C when overtemperature protection is active.
Continuous operation above the specified maximum operating junction
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