LTC4444
High Voltage Synchronous
N-Channel MOSFET Driver
FEATURES
DESCRIPTION
AEC-Q100 Qualified for Automotive Applications
nn Bootstrap Supply Voltage to 114V
nn Wide V
CC Voltage: 7.2V to 13.5V
nn Adaptive Shoot-Through Protection
nn 2.5A Peak TG Pull-Up Current
nn 3A Peak BG Pull-Up Current
nn 1.2Ω TG Driver Pull-Down
nn 0.55Ω BG Driver Pull-Down
nn 5ns TG Fall Time Driving 1nF Load
nn 8ns TG Rise Time Driving 1nF Load
nn 3ns BG Fall Time Driving 1nF Load
nn 6ns BG Rise Time Driving 1nF Load
nn Drives Both High and Low Side N-Channel MOSFETs
nn Undervoltage Lockout
nn Thermally Enhanced 8-Lead MSOP Package
The LTC®4444 is a high frequency high voltage gate driver
that drives two N-channel MOSFETs in a synchronous
DC/DC converter with supply voltages up to 100V. This
powerful driver reduces switching losses in MOSFETs
with high gate capacitance.
nn
APPLICATIONS
Distributed Power Architectures
nn Automotive Power Supplies
nn High Density Power Modules
nn Telecommunications
nn
All registered trademarks and trademarks are the property of their respective owners. Protected
by U.S. patents, including 6677210.
The LTC4444 is configured for two supply-independent
inputs. The high side input logic signal is internally
level‑shifted to the bootstrapped supply, which may function at up to 114V above ground.
The LTC4444 contains undervoltage lockout circuits that
disable the external MOSFETs when activated. Adaptive
shoot-through protection prevents both MOSFETs from
conducting simultaneously.
For a similar driver in this product family, please refer to
the chart below.
PARAMETER
LTC4444
LTC4446
LTC4444-5
Shoot-Through Protection
Yes
No
Yes
Absolute Max TS
100V
100V
100V
MOSFET Gate Drive
7.2V to 13.5V 7.2V to 13.5V 4.5V to 13.5V
VCC UV+
6.6V
6.6V
4V
VCC UV–
6.15V
6.15V
3.55V
TYPICAL APPLICATION
High Input Voltage Buck Converter
LTC4444 Driving a 1000pF Capacitive Load
VIN
100V
(ABS MAX)
VCC
7.2V TO 13.5V
BINP
5V/DIV
BG
10V/DIV
BOOST
VCC
PWM1
(FROM CONTROLLER IC)
PWM2
(FROM CONTROLLER IC)
LTC4444
TINP
TG
TS
VOUT
BG
BINP
TINP
5V/DIV
TG-TS
10V/DIV
GND
4444 TA01a
20ns/DIV
4444 TA01b
Rev. C
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1
LTC4444
ABSOLUTE MAXIMUM RATINGS
(Note 1)
PIN CONFIGURATION
Supply Voltage
VCC......................................................... –0.3V to 14V
BOOST – TS............................................ –0.3V to 14V
TINP Voltage...................................................–2V to 14V
BINP Voltage...................................................–2V to 14V
BOOST Voltage..........................................–0.3V to 114V
TS Voltage................................................... –5V to 100V
Operating Junction Temperature Range
(Notes 2, 3)......................................... –55°C to 150°C
Storage Temperature Range...................–65°C to 150°C
Lead Temperature (Soldering, 10 sec).................... 300°C
TOP VIEW
TINP
BINP
VCC
BG
1
2
3
4
9
GND
8
7
6
5
TS
TG
BOOST
NC
MS8E PACKAGE
8-LEAD PLASTIC MSOP
TJMAX = 125°C, θJA = 40°C/W, θJC = 10°C/W (NOTE 4)
EXPOSED PAD (PIN 9) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
TAPE AND REEL
PART MARKING*
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LTC4444EMS8E#PBF
LTC4444EMS8E#TRPBF
LTDBF
8-Lead Plastic MSOP
–40°C to 125°C
LTC4444IMS8E#PBF
LTC4444IMS8E#TRPBF
LTDBF
8-Lead Plastic MSOP
–40°C to 125°C
LTC4444HMS8E#PBF
LTC4444HMS8E#TRPBF
LTDBF
8-Lead Plastic MSOP
–40°C to 150°C
LTC4444MPMS8E#PBF
LTC4444MPMS8E#TRPBF
LTDBF
8-Lead Plastic MSOP
–55°C to 150°C
LTC4444EMS8E#WPBF
LTC4444EMS8E#WTRPBF
LTDBF
8-Lead Plastic MSOP
–40°C to 125°C
LTC4444IMS8E#WPBF
LTC4444IMS8E#WTRPBF
LTDBF
8-Lead Plastic MSOP
–40°C to 125°C
LTC4444HMS8E#WPBF
LTC4444HMS8E#WTRPBF
LTDBF
8-Lead Plastic MSOP
–40°C to 150°C
AUTOMOTIVE PRODUCTS**
Contact the factory for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
Tape and reel specifications. Some packages are available in 500 unit reels through designated sales channels with #TRMPBF suffix.
**Versions of this part are available with controlled manufacturing to support the quality and reliability requirements of automotive applications. These
models are designated with a #W suffix. Only the automotive grade products shown are available for use in automotive applications. Contact your
local Analog Devices account representative for specific product ordering information and to obtain the specific Automotive Reliability reports for
these models.
ELECTRICAL CHARACTERISTICS
The l denotes the specifications which apply over the full operating junction
temperature range, otherwise specifications are at TA = 25°C (Note 2). VCC = VBOOST = 12V, VTS = GND = 0V, unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
13.5
V
Gate Driver Supply, VCC
VCC
Operating Voltage
7.2
IVCC
DC Supply Current
TINP = BINP = 0V
UVLO
Undervoltage Lockout Threshold
VCC Rising
VCC Falling
Hysteresis
l
l
6.00
5.60
350
550
µA
6.60
6.15
450
7.20
6.70
V
V
mV
0.1
2
µA
Bootstrapped Supply (BOOST – TS)
IBOOST
2
DC Supply Current
TINP = BINP = 0V
Rev. C
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LTC4444
ELECTRICAL CHARACTERISTICS
The l denotes the specifications which apply over the full operating junction
temperature range, otherwise specifications are at TA = 25°C (Note 2). VCC = VBOOST = 12V, VTS = GND = 0V, unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Input Signal (TINP, BINP)
VIH(BG)
BG Turn-On Input Threshold
BINP Ramping High
l
2.25
2.75
3.25
V
VIL(BG)
BG Turn-Off Input Threshold
BINP Ramping Low
l
1.85
2.3
2.75
V
VIH(TG)
TG Turn-On Input Threshold
TINP Ramping High
l
2.25
2.75
3.25
V
VIL(TG)
TG Turn-Off Input Threshold
TINP Ramping Low
l
1.85
2.3
2.75
V
ITINP(BINP)
Input Pin Bias Current
±0.01
±2
µA
High Side Gate Driver Output (TG)
VOH(TG)
TG High Output Voltage
ITG = –10mA, VOH(TG) = VBOOST – VTG
0.7
VOL(TG)
TG Low Output Voltage
ITG = 100mA, VOL(TG) = VTG –VTS
IPU(TG)
TG Peak Pull-Up Current
l
RDS(TG)
TG Pull-Down Resistance
l
120
l
1.7
V
250
2.5
1.2
mV
A
2.5
Ω
Low Side Gate Driver Output (BG)
VOH(BG)
BG High Output Voltage
IBG = –10mA, VOH(BG) = VCC – VBG
0.7
VOL(BG)
BG Low Output Voltage
IBG = 100mA
IPU(BG)
BG Peak Pull-Up Current
l
RDS(BG)
BG Pull-Down Resistance
l
55
l
2
V
125
3
mV
A
0.55
1.25
Ω
Switching Time [BINP (TINP) is Tied to Ground While TINP (BINP) is Switching. Refer to Timing Diagrams]
tPLH(TG)
TG Low-High Propagation Delay
l
25
50
ns
tPHL(TG)
TG High-Low Propagation Delay
l
22
45
ns
tPLH(BG)
BG Low-High Propagation Delay
l
19
40
ns
tPHL(BG)
BG High-Low Propagation Delay
l
14
35
ns
tr(TG)
TG Output Rise Time
10% – 90%, CL = 1nF
10% – 90%, CL = 10nF
8
80
ns
ns
tf(TG)
TG Output Fall Time
10% – 90%, CL = 1nF
10% – 90%, CL = 10nF
5
50
ns
ns
tr(BG)
BG Output Rise Time
10% – 90%, CL = 1nF
10% – 90%, CL = 10nF
6
60
ns
ns
tf(BG)
BG Output Fall Time
10% – 90%, CL = 1nF
10% – 90%, CL = 10nF
3
30
ns
ns
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 LTC4444 is tested under pulsed load conditions such that
TJ ≈ TA. The LTC4444E 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 LTC4444I
is guaranteed over the –40°C to 125°C operating temperature range, the
LTC4444H is guaranteed over the –40°C to 150°C operating temperature
range and the LTC4444MP is tested and guaranteed over the full –55°C to
150°C operating junction temperature range. High junction temperatures
degrade operating lifetimes; operating lifetime is derated for junction
temperatures greater than 125°C. 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.
Note 3: The junction temperature (TJ, in °C) is calculated from the ambient
temperature (TA , in °C) and power dissipation (PD, in watts) according to
the formula:
TJ = TA + (PD • θJA)
where θJA (in °C/W) is the package thermal impedance.
Note 4: Failure to solder the exposed back side of the MS8E package to the
PC board will result in a thermal resistance much higher than 40°C/W.
Rev. C
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3
LTC4444
TYPICAL PERFORMANCE CHARACTERISTICS
400
350
300
TINP(BINP) = 12V
250
200
150
100
200
150
100
0
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
VCC SUPPLY VOLTAGE (V)
Boost Supply Current
vs Temperature
350
TINP = 0V
BINP = 12V
200
150
100
0
–55
TINP = BINP = 0V
100
80
40
–25
5
35
65
95
TEMPERATURE (°C)
125 150
TA = 25°C
ITG(BG) = 100mA
BOOST = VCC
TS = GND
3.1
VIH(TG,BG)
2.8
2.7
2.6
2.5
2.4
VIL(TG,BG )
2.3
12
11
10
SUPPLY VOLTAGE (V)
9
13
2.2
2.7
2.6
2.5
VIL(TG,BG)
2.3
8
11
10
9
12
SUPPLY VOLTAGE (V)
13
14
2.2
4444 G07
2.0
–55
–25
–10mA
10
–100mA
9
8
7
5
35
65
95
TEMPERATURE (°C)
7
8
11
10
9
12
SUPPLY VOLTAGE (V)
13
14
4444 G06
Input Thresholds (TINP, BINP)
Hysteresis vs Voltage
VIH(TG,BG)
2.4
–1mA
11
4444 G05
2.1
7
12
5
14
VCC = BOOST = 12V
2.9 TS = GND
2.8
4444 G03
6
3.0
TG OR BG INPUT THRESHOLD (V)
2.9
8
125 150
TA = 25°C
BOOST = VCC
TS = GND
13
Input Thresholds (TINP, BINP)
vs Temperature
TA = 25°C
BOOST = VCC
TS = GND
3.0
7
4444 G04
Input Thresholds (TINP, BINP)
vs Supply Voltage
TG OR BG INPUT THRESHOLD (V)
VOL(BG)
60
5
35
65
95
TEMPERATURE (°C)
Output High Voltage (VOH)
vs Supply Voltage
VOL(TG)
120
0
TINP(BINP) = 12V
320
14
20
50
330
15
140
300
250
340
300
–55 –25
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
BOOST SUPPLY VOLTAGE (V)
4444 G02
160
TINP = 12V
BINP = 0V
TINP = BINP = 0V
350
310
TINP = BINP = 0V
TG OR BG OUTPUT VOLTAGE (V)
VCC = BOOST = 12V
TS = GND
360
Output Low Voltage (VOL)
vs Supply Voltage
OUTPUT VOLTAGE (mV)
BOOST SUPPLY CURRENT (µA)
400
4
TINP = 0V, BINP = 12V
250
VCC = BOOST = 12V
TS = GND
370
300
4444 G01
2.1
TINP = 12V, BINP = 0V
50
50
0
380
TA = 25°C
VCC = 12V
TS = GND
350
TINP = BINP = 0V
VCC Supply Current
vs Temperature
TG OR BG INPUT THRESHOLD HYSTERESIS (mV)
QUIESCENT CURRENT (µA)
400
TA = 25°C
BOOST = 12V
TS = GND
QUIESCENT CURRENT (µA)
450
BOOST-TS Supply Quiescent
Current vs Voltage
VCC SUPPLY CURRENT (µA)
VCC Supply Quiescent Current
vs Voltage
125 150
500
TA = 25°C
VCC = BOOST = 12V
TS = GND
475
450
425
400
375
7
8
11
9
12
10
SUPPLY VOLTAGE (V)
13
14
4444 G09
4444 G08
Rev. C
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LTC4444
TYPICAL PERFORMANCE CHARACTERISTICS
6.7
VCC = BOOST = 12V
TS = GND
6.6
475
450
425
400
RISING THRESHOLD
6.5
6.4
6.3
6.2
FALLING THRESHOLD
5
35
65
95
TEMPERATURE (°C)
6.0
–55
125 150
3.4
PULL-UP CURRENT (A)
tr(TG)
50
tr(BG)
40
30
tf(TG)
20
2
5
6
3
4
7
8
LOAD CAPACITANCE (nF)
2.4
2.0
–55
10
9
–25
4444 G13
5
35
65
95
TEMPERATURE (°C)
125 150
30
28
tPLH(TG)
26
37
TA = 25°C
BOOST = VCC
TS = GND
tPHL(TG)
20
tPLH(BG)
18
16
tPHL(BG)
14
tf(BG)
7
11
9
12
10
SUPPLY VOLTAGE (V)
8
13
14
4444 G12
2.2
2.0
BOOST-TS = 12V
1.8
1.6
BOOST-TS = 7V
1.4
1.2
RDS(TG)
BOOST-TS = 14V
1.0
VCC = 12V
0.8
VCC = 7V
0.6
0.4
0.2
–55
VCC = 14V
RDS(BG)
–25
5
35
65
95
TEMPERATURE (°C)
125 150
4444 G15
32
VCC = BOOST = 12V
TS = GND
tPLH(TG)
tPHL(TG)
27
tPLH(BG)
22
17
tPHL(BG)
12
7
12
10
tf(TG)
Propagation Delay vs Temperature
24
22
tr(BG)
4444 G14
Propagation Delay
vs VCC Supply Voltage
PROPAGATION DELAY (ns)
1
IPU(TG)
2.2
tf(BG)
10
2.8
2.6
tr(TG)
Output Driver Pull-Down
Resistance vs Temperature
IPU(BG)
3.0
TA = 25°C
BOOST = VCC
TS = GND
CL = 3.3nF
4444 G11
VCC = BOOST = 12V
TS = GND
3.2
60
125 150
32
30
28
26
24
22
20
18
16
14
12
10
8
6
Peak Driver (TG, BG) Pull-Up
Current vs Temperature
TA = 25°C
VCC = BOOST = 12V
TS = GND
70
5
35
65
95
TEMPERATURE (°C)
OUTPUT DRIVER PULL-DOWN RESISTACNE (Ω)
80
–25
4444 G10
PROPAGATION DELAY (ns)
–25
Rise and Fall Time
vs Load Capacitance
RISE/FALL TIME (ns)
BOOST = VCC
TS = GND
6.1
375
–55
0
Rise and Fall Time
vs VCC Supply Voltage
RISE/FALL TIME (ns)
500
VCC Undervoltage Lockout
Thresholds vs Temperature
VCC SUPLLY VOLTAGE (V)
TG OR BG INPUT THRESHOLD HYSTERESIS (mV)
Input Thresholds (TINP, BINP)
Hysteresis vs Temperature
7
8
11
10
9
12
SUPPLY VOLTAGE (V)
13
14
2
–55
4444 G16
–25
5
35
65
95
TEMPERATURE (°C)
125 150
4444 G17
Rev. C
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5
LTC4444
TYPICAL PERFORMANCE CHARACTERISTICS
Switching Supply Current
vs Input Frequency
Switching Supply Current
vs Load Capacitance
4.0
IBOOST
(TG SWITCHING)
3.0
SUPPLY CURRENT (mA)
SUPPLY CURRENT (mA)
TA = 25°C
3.5 VCC = BOOST = 12V
TS = GND
IVCC
(BG SWITCHING)
2.5
2.0
1.5
1.0
IVCC
(TG SWITCHING)
0.5
0
IBOOST (BG SWITCHING)
0
200
400
800
600
SWITCHING FREQUENCY (kHz)
1000
IVCC
(BG SWITCHING
AT 1MHz)
100
IBOOST
(TG SWITCHING
AT 1MHz)
10
IVCC
(BG SWITCHING
AT 500kHz)
IVCC
IVCC
(TG SWITCHING
(TG SWITCHING AT 500kHz)
AT 1MHz)
1
0.1
IBOOST
(TG SWITCHING
AT 500kHz)
IBOOST (BG SWITCHING AT 1MHz OR 5OOkHz)
1
4444 G18
2
3
4
5
6
7
8
LOAD CAPACITANCE (nF)
9
10
4444 G19
PIN FUNCTIONS
TINP (Pin 1): High Side Input Signal. Input referenced to
GND. This input controls the high side driver output (TG).
BINP (Pin 2): Low Side Input Signal. This input controls
the low side driver output (BG).
VCC (Pin 3): Supply. This pin powers input buffers, logic
and the low side gate driver output directly and the high
side gate driver output through an external diode connected between this pin and BOOST (Pin 6). A low ESR
ceramic bypass capacitor should be tied between this pin
and GND (Pin 9).
BG (Pin 4): Low Side Gate Driver Output (Bottom Gate).
This pin swings between VCC and GND.
BOOST (Pin 6): High Side Bootstrapped Supply. An external capacitor should be tied between this pin and TS (Pin
8). Normally, a bootstrap diode is connected between VCC
(Pin 3) and this pin. Voltage swing at this pin is from
VCC – VD to VIN + VCC – VD, where VD is the forward voltage drop of the bootstrap diode.
TG (Pin 7): High Side Gate Driver Output (Top Gate). This
pin swings between TS and BOOST.
TS (Pin 8): High Side MOSFET Source Connection (Top
Source).
GND (Exposed Pad Pin 9): Ground. Must be soldered to
PCB ground for optimal thermal performance.
NC (Pin 5): No Connect. No connection required.
6
Rev. C
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LTC4444
BLOCK DIAGRAM
6
7.2V TO
13.5V
3
9
BOOST
VCC
GND
TG
HIGH SIDE
LEVEL SHIFTER
LDO
1
VIN
UP TO 100V
VCC UVLO
VINT
TS
8
ANTISHOOT-THROUGH
PROTECTION
TINP
VCC
2
7
VCC
BG
LOW SIDE
LEVEL SHIFTER
BINP
4
NC
5
4444 BD
TIMING DIAGRAMS
Adaptive Shoot-Through Protection
BINP
BINP
BG
BG
TINP
TINP
TG-TS
TG-TS
4444 TD01
Switching Time
INPUT RISE/FALL TIME < 10ns
TINP (BINP)
90%
10%
BINP (TINP)
BG (TG)
TG (BG)
90%
90%
10%
tr
tPHL
10%
tf
tPLH
4444 TD02
Rev. C
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7
LTC4444
OPERATION
Overview
Output Stage
The LTC4444 receives ground-referenced, low voltage digital input signals to drive two N-channel power
MOSFETs in a synchronous buck power supply configuration. The gate of the low side MOSFET is driven
either to VCC or GND, depending on the state of the input.
Similarly, the gate of the high side MOSFET is driven to
either BOOST or TS by a supply bootstrapped off of the
switching node (TS).
A simplified version of the LTC4444’s output stage is
shown in Figure 1. The pull-up devices on the BG and TG
outputs are NPN bipolar junction transistors (Q1 and Q2).
The BG and TG outputs are pulled up to within an NPN
VBE (~0.7V) of their positive rails (VCC and BOOST, respectively). Both BG and TG have N-channel MOSFET pulldown devices (M1 and M2) which pull BG and TG down
to their negative rails, GND and TS. The large voltage
swing of the BG and TG output pins is important in driving external power MOSFETs, whose RDS(ON) is inversely
proportional to the gate overdrive voltage (VGS − VTH).
Input Stage
The LTC4444 employs CMOS compatible input thresholds that allow a low voltage digital signal to drive standard power MOSFETs. The LTC4444 contains an internal
voltage regulator that biases both input buffers for high
side and low side inputs, allowing the input thresholds
(VIH = 2.75V, VIL = 2.3V) to be independent of variations
in VCC. The 450mV hysteresis between VIH and VIL eliminates false triggering due to noise during switching transitions. However, care should be taken to keep both input
pins (TINP and BINP) from any noise pickup, especially
in high frequency, high voltage applications. The LTC4444
input buffers have high input impedance and draw negligible input current, simplifying the drive circuitry required
for the inputs.
LTC4444
BOOST
The LTC4444’s rise and fall times are determined by the
peak current capabilities of Q1 and M1. The predriver
that drives Q1 and M1 uses a nonoverlapping transition
scheme to minimize cross-conduction currents. M1 is
fully turned off before Q1 is turned on and vice versa.
Since the power MOSFET generally accounts for the
majority of the power loss in a converter, it is important
to quickly turn it on or off, thereby minimizing the transition time in its linear region. An additional benefit of a
strong pull-down on the driver outputs is the prevention
VIN
UP TO 100V
6
Q1
Rise/Fall Time
TG
CGD
7
M1
TS
VCC
CGS
8
HIGH SIDE
POWER
MOSFET
LOAD
INDUCTOR
3
Q2
BG
CGD
4
M2
GND
CGS
LOW SIDE
POWER
MOSFET
9
4444 FO1
Figure 1. Capacitance Seen by BG and TG During Switching
8
Rev. C
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LTC4444
OPERATION
of cross- conduction current. For example, when BG turns
the low side (synchronous) power MOSFET off and TG
turns the high side power MOSFET on, the voltage on the
TS pin will rise to VIN very rapidly. This high frequency
positive voltage transient will couple through the CGD
capacitance of the low side power MOSFET to the BG
pin. If there is an insufficient pull-down on the BG pin, the
voltage on the BG pin can rise above the threshold voltage
of the low side power MOSFET, momentarily turning it
back on. With both the high side and low side MOSFETs
conducting, significant cross-conduction current will flow
through the MOSFETs from VIN to ground and will cause
substantial power loss. A similar effect occurs on TG due
to the CGS and CGD capacitances of the high side MOSFET.
The powerful output driver of the LTC4444 reduces the
switching losses of the power MOSFET, which increase
with transition time. The LTC4444’s high side driver is
capable of driving a 1nF load with 8ns rise and 5ns fall
times using a bootstrapped supply voltage VBOOST-TS of
12V while its low side driver is capable of driving a 1nF
load with 6ns rise and 3ns fall times using a supply voltage VCC of 12V.
Undervoltage Lockout (UVLO)
The LTC4444 contains an undervoltage lockout detector
that monitors VCC supply. When VCC falls below 6.15V,
the output pins BG and TG are pulled down to GND and
TS, respectively. This turns off both external MOSFETs.
When VCC has adequate supply voltage, normal operation
will resume.
Adaptive Shoot-Through Protection
Internal adaptive shoot-through protection circuitry monitors the voltages on the external MOSFETs to ensure that
they do not conduct simultaneously. This feature improves
efficiency by eliminating cross-conduction current from
flowing from the VIN supply through both of the MOSFETs
to ground during a switch transition. If both TINP and
BINP are high at the same time, BG will be kept off and
TG will be turned on (refer to the Timing Diagrams). If BG
is still high when TINP turns on, TG will not be turned on
until BG goes low.
When TINP turns off, the adaptive shoot-through protection circuitry monitors the level of the TS pin. BG can be
turned on if the TS pin goes low. If the TS pin stays high,
BG will be turned on 150ns after TINP turns off.
APPLICATIONS INFORMATION
Power Dissipation
To ensure proper operation and long-term reliability, the
LTC4444 must not operate beyond its maximum temperature rating. Package junction temperature can be
calculated by:
TJ = TA + PD (θJA)
Power dissipation consists of standby and switching
power losses:
PD = PDC + PAC + PQG
where:
PDC = Quiescent power loss
PAC = Internal switching loss at input frequency, fIN
where:
PQG = Loss due turning on and off the external MOSFET
with gate charge QG at frequency fIN
TJ = Junction temperature
TA = Ambient temperature
PD = Power dissipation
θJA = Junction-to-ambient thermal resistance
The LTC4444 consumes very little quiescent current. The
DC power loss at VCC = 12V and VBOOST-TS = 12V is only
(350µA)(12V) = 4.2mW.
Rev. C
For more information www.analog.com
9
LTC4444
APPLICATIONS INFORMATION
At a particular switching frequency, the internal power
loss increases due to both AC currents required to charge
and discharge internal node capacitances and cross-conduction currents in the internal logic gates. The sum of the
quiescent current and internal switching current with no
load are shown in the Typical Performance Characteristics
plot of Switching Supply Current vs Input Frequency.
The gate charge losses are primarily due to the large AC
currents required to charge and discharge the capacitance
of the external MOSFETs during switching. For identical
pure capacitive loads CLOAD on TG and BG at switching
frequency fIN, the load losses would be:
PCLOAD = (CLOAD)(f)[(VBOOST-TS)2 + (VCC)2]
In a typical synchronous buck configuration, VBOOST-TS
is equal to VCC – VD, where VD is the forward voltage
drop across the diode between VCC and BOOST. If this
drop is small relative to VCC, the load losses can be
approximated as:
PCLOAD = 2(CLOAD)(fIN)(VCC)2
Unlike a pure capacitive load, a power MOSFET’s gate
capacitance seen by the driver output varies with its VGS
voltage level during switching. A MOSFET’s capacitive
load power dissipation can be calculated using its gate
charge, QG. The QG value corresponding to the MOSFET’s
VGS value (VCC in this case) can be readily obtained from
the manufacturer’s QG vs VGS curves. For identical
MOSFETs on TG and BG:
PQG = 2(VCC)(QG)(fIN)
To avoid damage due to power dissipation, the LTC4444
includes a temperature monitor that will pull BG and TG
low if the junction temperature rises above 160°C. Normal
operation will resume when the junction temperature
cools to less than 135°C.
10
Bypassing and Grounding
The LTC4444 requires proper bypassing on the VCC and
VBOOST-TS supplies due to its high speed switching (nanoseconds) and large AC currents (Amperes). Careless
component placement and PCB trace routing may cause
excessive ringing.
To obtain the optimum performance from the LTC4444:
A. Mount the bypass capacitors as close as possible
between the VCC and GND pins and the BOOST and
TS pins. The leads should be shortened as much as
possible to reduce lead inductance.
B. Use a low inductance, low impedance ground plane
to reduce any ground drop and stray capacitance.
Remember that the LTC4444 switches greater than
3A peak currents and any significant ground drop will
degrade signal integrity.
C. Plan the power/ground routing carefully. Know where
the large load switching current is coming from and
going to. Maintain separate ground return paths for
the input pin and the output power stage.
D. Keep the copper trace between the driver output pin
and the load short and wide.
E. Be sure to solder the Exposed Pad on the back side
of the LTC4444 package to the board. Correctly soldered to a 2500mm2 double sided 1oz copper board,
the LTC4444 has a thermal resistance of approximately
40°C/W for the MS8E package. Failure to make good
thermal contact between the exposed back side and
the copper board will result in thermal resistances far
greater than 40°C/W.
Rev. C
For more information www.analog.com
LTC4444
TYPICAL APPLICATION
LTC3780 High Efficiency 36V to 72V VIN to 48V/6A Buck-Boost DC/DC Converter
6V
10k
0.022µF
1000pF
SENSE+
100Ω
220k
100pF
0.1µF
100V
1
68pF
SENSE–
VOS+ 487k
1%
100Ω
2
3
4
5
8.25k
1%
47pF
6
7
8
D5
15k
VIN
9
10
220k
11
12
PGOOD
SS
LTC3780EG TG1
SENSE+
SW1
SENSE–
VIN
ITH
EXTVCC
VOSENSE
INTVCC
SGND
BG1
RUN
PGND
FCB
BG2
PLLFLTR
SW2
PLLIN
TG2
STBYMD
VBIAS
10V TO 12V
D2
BOOST1
BOOST2
D1
1
VCC
6
BOOST
LTC4444
2
7
BINP
TG
23
22
21
4
0.1µF
16V
20
19
6V
18
10µF
10V
17
2.2µF
100V
×4
3
24
TINP
BG
TS
8
+
VIN
C1
100µF
100V
0.22µF
16V
VOS+
GND
1µF
16V
10Ω
9
L1
10µH
16
D3
15
D4
2.2µF
100V
×8
+
VOUT
C2,C3
220µF
63V
×2
14
13
6V
D6
0.1µF
16V
0.1µF
16V
SENSE+
D3, D4: DIODES INC. PDS560-13
D5: DIODES INC. MMBZ5230B-7-F
D6: DIODES INC. B1100-13-F
L1: SUMIDA CDEP147NP-100MC-125
R1, R2: VISHAY DALE WSL2512R0250FEA
SENSE–
10Ω
10Ω
R1
0.025Ω
1W
R2
0.025Ω
1W
4444 TA02a
Efficiency
98
VIN = 36V
EFFICIENCY (%)
2.2µF, 100V, TDK C4532X7R2A225MT
C1: SANYO 100ME100HC +T
C2, C3: SANYO 63ME220HC + T
D1: ON SEMI MMDL770T1G
D2: DIODES INC. 1N5819HW-7-F
VBIAS
10V TO 12V
1µF
16V
VIN = 48V
97
VIN = 72V
96
95
1
2
3
4
LOAD CURRENT (A)
5
6
4444 TA02b
Rev. C
For more information www.analog.com
11
LTC4444
PACKAGE DESCRIPTION
MS8E Package
8-Lead Plastic MSOP, Exposed Die Pad
(Reference LTC DWG # 05-08-1662 Rev K)
BOTTOM VIEW OF
EXPOSED PAD OPTION
1.88
(.074)
1
1.88 ±0.102
(.074 ±.004)
0.29
REF
1.68
(.066)
0.889 ±0.127
(.035 ±.005)
0.05 REF
5.10
(.201)
MIN
DETAIL “B”
CORNER TAIL IS PART OF
DETAIL “B” THE LEADFRAME FEATURE.
FOR REFERENCE ONLY
NO MEASUREMENT PURPOSE
1.68 ±0.102 3.20 – 3.45
(.066 ±.004) (.126 – .136)
8
3.00 ±0.102
(.118 ±.004)
(NOTE 3)
0.65
(.0256)
BSC
0.42 ±0.038
(.0165 ±.0015)
TYP
8
7 6 5
0.52
(.0205)
REF
RECOMMENDED SOLDER PAD LAYOUT
0.254
(.010)
3.00 ±0.102
(.118 ±.004)
(NOTE 4)
4.90 ±0.152
(.193 ±.006)
DETAIL “A”
0° – 6° TYP
GAUGE PLANE
0.53 ±0.152
(.021 ±.006)
DETAIL “A”
1
2 3
4
1.10
(.043)
MAX
0.86
(.034)
REF
0.18
(.007)
SEATING
PLANE
0.22 – 0.38
(.009 – .015)
TYP
0.65
(.0256)
NOTE:
BSC
1. DIMENSIONS IN MILLIMETER/(INCH)
2. DRAWING NOT TO SCALE
3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS.
MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS.
INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX
6. EXPOSED PAD DIMENSION DOES INCLUDE MOLD FLASH. MOLD FLASH ON E-PAD
SHALL NOT EXCEED 0.254mm (.010") PER SIDE.
12
0.1016 ±0.0508
(.004 ±.002)
MSOP (MS8E) 0213 REV K
Rev. C
For more information www.analog.com
LTC4444
REVISION HISTORY
REV
DATE
DESCRIPTION
A
06/10
MP-grade part added. Reflected throughout the data sheet.
PAGE NUMBER
1 to 14
B
01/11
H-grade part added. Reflected throughout the data sheet.
1 to 14
C
12/18
Added AEC-Q100 approval and product information.
1 and 2
Rev. C
Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog
Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Specifications
subject to change without notice. No license For
is granted
implication or
otherwise under any patent or patent rights of Analog Devices.
more by
information
www.analog.com
13
LTC4444
TYPICAL APPLICATION
LTC3780 High Efficiency 8V to 80V VIN to 12V/5A Buck-Boost DC/DC Converter
6V
10k
0.1µF
0.01µF
SENSE+
SENSE–
VOS+ 113k
1%
0.1µF
1
68pF
20k
100pF
100Ω
100Ω
2
3
4
5
8.06k
1%
47pF
6
7
8
9
D4
VIN
150k
10
11
2.2µF, 100V, TDK C4532X7R2A225MT
100µF, 100V SANYO 100ME 100AX
C1: SANYO 16ME330WF
D1: DIODES INC. BAV19WS
D2: DIODES INC. 1N5819HW-7-F
D3: DIODES INC. B320A-13-F
D4: DIODES INC. MMBZ5230B-7-F
D5: DIODES INC. B1100-13-F
L1: SUMIDA CDEP147-8R0
12
PGOOD
SS
0.22µF
16V
D2
BOOST1
LTC3780EG TG1
SENSE+
SW1
SENSE–
VIN
ITH
EXTVCC
VOSENSE
INTVCC
SGND
BG1
RUN
PGND
FCB
BG2
PLLFLTR
SW2
PLLIN
TG2
STBYMD
BOOST2
1µF
16V
VBIAS
12V
22
21
1
TG1
18
17
4
0.1µF
16V
20
19
2
SW1
6V
10µF
10V
D1
3
24
23
VBIAS
12V
6
BOOST
LTC4444
7
BINP
TG
TINP
BG
TS
8
+
2.2µF
100V
×5
VCC
0.22µF
16V
VOS+
10Ω
GND
1µF
16V
VIN
8V TO 80V
100µF
100V
×2
9
TG1
L1 8µH
16
D3
22µF
16V
×3
+
VOUT
12V, 5A
C1
330µF
×2
SW1
15
14
13
6V
D5
0.1µF
16V
0.1µF
SENSE+
SENSE–
10Ω
10Ω
0.005Ω
1W
4444 TA03
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
LTC4446
High Voltage Synchronous N-Channel MOSFET
Driver without Shoot-Through Protection
Up to 100V Supply Voltage, 7.2V ≤ VCC ≤ 13.5V, 3A Peak Pull-Up/
0.55Ω Peak Pull-Down
LTC4440/LTC4440-5
High Speed, High Voltage, High Side Gate Driver
Up to 80V Supply Voltage, 8V ≤ VCC ≤ 15V, 2.4A Peak Pull-Up/
1.5Ω Peak Pull-Down
LTC4442
High Speed Synchronous N-Channel MOSFET Driver
Up to 38V Supply Voltage, 6V ≤ VCC ≤ 9.5V, 3.2A Peak Pull-Up/
4.5A Peak Pull-Down
LTC4449
High Speed Synchronous N-Channel MOSFET Driver
Up to 38V Supply Voltage, 4.5V ≤ VCC ≤ 6.5V, 3.2A Peak Pull-Up/
4.5A Peak Pull-Down
LTC4441/LTC4441-1
N-Channel MOSFET Gate Driver
Up to 25V Supply Voltage, 5V ≤ VCC ≤ 25V, 6A Peak Output Current
LTC1154
High Side Micropower MOSFET Driver
Up to 18V Supply Voltage, 85µA Quiescent Current, H-Grade Available
14
Rev. C
12/18
www.analog.com
For more information www.analog.com
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