LINER LTC4446IMS8E

LTC4446
High Voltage High Side/
Low Side N-Channel
MOSFET Driver
DESCRIPTION
FEATURES
n
n
n
n
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n
n
n
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Bootstrap Supply Voltage Up to 114V
Wide VCC Voltage: 7.2V to 13.5V
2.5A Peak Top Gate Pull-Up Current
3A Peak Bottom Gate Pull-Up Current
1.2Ω Top Gate Driver Pull-Down
0.55Ω Bottom Gate Driver Pull-Down
5ns Top Gate Fall Time Driving 1nF Load
8ns Top Gate Rise Time Driving 1nF Load
3ns Bottom Gate Fall Time Driving 1nF Load
6ns Bottom Gate Rise Time Driving 1nF Load
Drives Both High and Low Side N-Channel MOSFETs
Undervoltage Lockout
Thermally Enhanced 8-Pin MSOP Package
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The LTC4446 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 LTC4446 contains undervoltage lockout circuits that
disable the external MOSFETs when activated.
APPLICATIONS
n
The LTC®4446 is a high frequency high voltage gate driver
that drives two N-channel MOSFETs in a DC/DC converter
with supply voltages up to 100V. The powerful driver capability reduces switching losses in MOSFETs with high
gate capacitance. The LTC4446’s pull-up for the top gate
driver has a peak output current of 2.5A and its pull-down
has an output impedance of 1.2Ω. The pull-up for the bottom gate driver has a peak output current of 3A and the
pull-down has an output impedance of 0.55Ω.
Distributed Power Architectures
Automotive Power Supplies
High Density Power Modules
Telecommunication Systems
The LTC4446 is available in the thermally enhanced 8-lead
MSOP package.
L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
Protected by U.S. Patents including 6677210.
The LTC4446 does not have adaptive shoot-through protection. For similar drivers with adaptive shoot-through
protection, please refer to the chart below.
PARAMETER
LTC4446
LTC4444
LTC4444-5
Shoot-Through Protection
No
Yes
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
6.6V
6.6V
4V
VCC UV+
6.15V
6.15V
3.55V
VCC UV–
TYPICAL APPLICATION
Two Switch Forward Converter
LTC4446 Driving a 1000pF Capacitive Load
VIN
36V TO 72V
(100V ABS MAX)
VCC
7.2V TO 13.5V
BOOST
VCC
PWM1
(FROM CONTROLLER IC)
PWM2
(FROM CONTROLLER IC)
BINP
5V/DIV
BG
10V/DIV
TG
LTC4446
TINP
TS
BINP
BG
•
•
GND
TO
SECONDARY
CIRCUIT
TINP
5V/DIV
TG-TS
10V/DIV
20ns/DIV
4446 TA01b
4446 TA01a
4446f
1
LTC4446
ABSOLUTE MAXIMUM RATINGS
PIN CONFIGURATION
(Note 1)
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 Temperature Range (Note 2).... –40°C to 85°C
Junction Temperature (Note 3) ............................. 125°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
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
LTC4446EMS8E#PBF
LTC4446EMS8E#TRPBF
LTDPZ
8-Lead Plastic MSOP
–40°C to 85°C
LTC4446IMS8E#PBF
LTC4446IMS8E#TRPBF
LTDPZ
8-Lead Plastic MSOP
–40°C to 85°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/
ELECTRICAL CHARACTERISTICS
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VCC = VBOOST = 12V, VTS = GND = 0V, unless otherwise noted.
SYMBOL
PARAMETER
Gate Driver Supply, VCC
VCC
Operating Voltage
DC Supply Current
IVCC
UVLO
Undervoltage Lockout Threshold
Bootstrapped Supply (BOOST – TS)
DC Supply Current
IBOOST
Input Signal (TINP, BINP)
BG Turn-On Input Threshold
VIH(BG)
BG Turn-Off Input Threshold
VIL(BG)
TG Turn-On Input Threshold
VIH(TG)
TG Turn-Off Input Threshold
VIL(TG)
Input Pin Bias Current
ITINP(BINP)
High Side Gate Driver Output (TG)
TG High Output Voltage
VOH(TG)
TG Low Output Voltage
VOL(TG)
TG Peak Pull-Up Current
IPU(TG)
TG Pull-Down Resistance
RDS(TG)
CONDITIONS
MIN
TYP
MAX
UNITS
13.5
550
7.20
6.70
V
μA
V
V
mV
0.1
2
μA
2.75
2.3
2.75
2.3
±0.01
3.25
2.75
3.25
2.75
±2
V
V
V
V
μA
220
V
mV
A
2.2
Ω
7.2
TINP = BINP = 0V
VCC Rising
VCC Falling
Hysteresis
l
l
6.00
5.60
TINP = BINP = 0V
BINP Ramping High
BINP Ramping Low
TINP Ramping High
TINP Ramping Low
ITG = –10mA, VOH(TG) = VBOOST – VTG
ITG = 100mA, VOL(TG) = VTG –VTS
l
l
l
l
2.25
1.85
2.25
1.85
l
l
l
1.7
350
6.60
6.15
450
0.7
120
2.5
1.2
4446f
2
LTC4446
ELECTRICAL CHARACTERISTICS
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VCC = VBOOST = 12V, VTS = GND = 0V, unless otherwise noted.
SYMBOL
PARAMETER
Low Side Gate Driver Output (BG)
BG High Output Voltage
VOH(BG)
BG Low Output Voltage
VOL(BG)
BG Peak Pull-Up Current
IPU(BG)
BG Pull-Down Resistance
RDS(BG)
CONDITIONS
MIN
IBG = –10mA, VOH(BG) = VCC – VBG
IBG = 100mA
l
l
2
l
Switching Time (BINP (TINP) is Tied to Ground While TINP (BINP) is Switching. Refer to Timing Diagram)
l
TG Low-High (Turn-On) Propagation Delay
tPLH(TG)
l
TG High-Low (Turn-Off) Propagation Delay
tPHL(TG)
l
BG Low-High (Turn-On) Propagation Delay
tPLH(BG)
l
BG High-Low (Turn-Off) Propagation Delay
tPHL(BG)
l
Delay Matching BG Turn-Off and TG Turn-On
tDM(BGTG)
l
Delay Matching TG Turn-Off and BG Turn-On
tDM(TGBG)
TG Output Rise Time
10% – 90%, CL = 1nF
tr(TG)
10% – 90%, CL = 10nF
TG Output Fall Time
10% – 90%, CL = 1nF
tf(TG)
10% – 90%, CL = 10nF
BG Output Rise Time
10% – 90%, CL = 1nF
tr(BG)
10% – 90%, CL = 10nF
BG Output Fall Time
10% – 90%, CL = 1nF
tf(BG)
10% – 90%, CL = 10nF
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 LTC4446E is guaranteed to meet specifications from
0°C to 85°C. Specifications over the –40°C to 85°C operating
temperature range are assured by design, characterization and correlation
–15
–25
TYP
0.7
55
3
0.55
25
22
19
14
10
–3
8
80
5
50
6
60
3
30
MAX
UNITS
110
V
mV
A
1.1
Ω
45
40
35
30
35
25
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
with statistical process controls. The LTC4446I is guaranteed over the full
–40°C to 85°C operating temperature range.
Note 3: TJ is calculated from the ambient temperature TA and power
dissipation PD according to the following formula:
TJ = TA + (PD • θJA°C/W)
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.
TYPICAL PERFORMANCE CHARACTERISTICS
QUIESCENT CURRENT (μA)
400
TA = 25°C
BOOST = 12V
TS = GND
400
350
300
250
350
TINP = BINP = 0V
TINP(BINP) = 12V
200
150
100
QUIESCENT CURRENT (μA)
450
BOOST-TS Supply Quiescent
Current vs Voltage
TA = 25°C
VCC = 12V
TS = GND
VCC Supply Current vs
Temperature
380
TINP = 12V, BINP = 0V
300
250
TINP = 0V, BINP = 12V
200
150
100
50
50
370
VCC SUPPLY CURRENT (μA)
VCC Supply Quiescent Current
vs Voltage
VCC = BOOST = 12V
TS = GND
360
TINP = BINP = 0V
350
340
330
TINP(BINP) = 12V
320
310
TINP = BINP = 0V
0
0
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
VCC SUPPLY VOLTAGE (V)
4446 G01
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
BOOST SUPPLY VOLTAGE (V)
4446 G02
300
–40 –25 –10 5 20 35 50 65 80 95 110 125
TEMPERATURE (°C)
4446 G03
4446f
3
LTC4446
TYPICAL PERFORMANCE CHARACTERISTICS
Boost Supply Current
vs Temperature
TINP = 0V
BINP = 12V
200
150
100
VOL(TG)
120
100
80
VOL(BG)
60
40
TA = 25°C
ITG(BG) = 100mA
BOOST = VCC
TS = GND
20
50
TINP = BINP = 0V
3.1
8
12
11
10
SUPPLY VOLTAGE (V)
9
TG OR BG INPUT THRESHOLD (V)
2.7
2.6
2.5
2.4
VIL(TG,BG)
2.3
2.2
VCC = BOOST = 12V
2.9 TS = GND
VIH(TG,BG)
2.8
2.7
2.6
2.5
2.4
VIL(TG,BG)
2.3
2.2
2.1
2.1
7
8
11
10
9
12
SUPPLY VOLTAGE (V)
13
2.0
–40 –25 –10 5 20 35 50 65 80 95 110 125
TEMPERATURE (°C)
14
7
7
6.7
VCC = BOOST = 12V
TS = GND
6.6
VCC SUPLLY VOLTAGE (V)
450
425
6.5
RISING THRESHOLD
6.4
6.3
6.2
14
13
Input Thresholds (TINP, BINP)
Hysteresis vs Voltage
500
TA = 25°C
VCC = BOOST
TS = GND
475
450
425
400
375
7
8
11
10
9
12
SUPPLY VOLTAGE (V)
14
13
4446 G09
BOOST = VCC
TS = GND
FALLING THRESHOLD
6.1
4446 G10
11
10
9
12
SUPPLY VOLTAGE (V)
Rise and Fall Time vs
VCC Supply Voltage
400
375
–40 –25 –10 5 20 35 50 65 80 95 110 125
TEMPERATURE (°C)
8
4446 G06
VCC Undervoltage Lockout
Thresholds vs Temperature
Input Thresholds (TINP, BINP)
Hysteresis vs Temperature
TG OR BG INPUT THRESHOLD HYSTERESIS (mV)
8
4446 G08
4446 G07
475
–100mA
9
14
RISE/FALL TIME (ns)
TG OR BG INPUT THRESHOLD (V)
2.8
500
13
3.0
VIH(TG,BG)
–10mA
10
Input Thresholds (TINP, BINP) vs
Temperature
TA = 25°C
BOOST = VCC
TS = GND
–1mA
11
4446 G05
Input Thresholds (TINP, BINP) vs
Supply Voltage
2.9
12
5
7
4446 G04
3.0
13
6
0
0
–40 –25 –10 5 20 35 50 65 80 95 110 125
TEMPERATURE (°C)
TA = 25°C
BOOST = VCC
TS = GND
14
140
300
250
15
160
TINP = 12V
BINP = 0V
TG OR BG OUTPUT VOLTAGE (V)
350
Output High Voltage (VOH) vs
Supply Voltage
TG OR BG INPUT THRESHOLD HYSTERESIS (mV)
VCC = BOOST = 12V
TS = GND
OUTPUT VOLTAGE (mV)
BOOST SUPPLY CURRENT (μA)
400
Output Low Voltage (VOL)
vs Supply Voltage
6.0
–40 –25 –10 5 20 35 50 65 80 95 110 125
TEMPERATURE (°C)
4446 G11
32
30
28
26
24
22
20
18
16
14
12
10
8
6
TA = 25°C
BOOST = VCC
TS = GND
CL = 3.3nF
tr(TG)
tr(BG)
tf(TG)
tf(BG)
7
8
11
10
9
12
SUPPLY VOLTAGE (V)
13
14
4446 G12
4446f
4
LTC4446
TYPICAL PERFORMANCE CHARACTERISTICS
60
tr(TG)
50
tr(BG)
40
30
tf(TG)
20
5
6
3
4
7
8
LOAD CAPACITANCE (nF)
2.8
2.6
IPU(TG)
2.4
2.2
9
2.0
–40 –25 –10 5 20 35 50 65 80 95 110 125
TEMPERATURE (°C)
10
4445 G13
30
26
24
tPHL(TG)
22
37
TA = 25°C
BOOST = VCC
TS = GND
tPLH(TG)
1.8
BOOST-TS = 12V
1.6
1.4
1.2
BOOST-TS = 7V
RDS(TG)
BOOST-TS = 14V
1.0
VCC = 12V
0.8
VCC = 7V
0.6
0.4
0.2
VCC = 14V
RDS(BG)
0
–40 –25 –10 5 20 35 50 65 80 95 110 125
TEMPERATURE (°C)
4446 G15
Propagation Delay vs Temperature
20
tPLH(BG)
18
16
tPHL(BG)
14
VCC = BOOST = 12V
TS = GND
32
PROPAGATION DELAY (ns)
28
2.0
4446 G14
Propagation Delay vs
VCC Supply Voltage
PROPAGATION DELAY (ns)
2
tPLH(TG)
27
tPHL(TG)
22
tPLH(BG)
17
tPHL(BG)
12
7
12
10
7
11
10
9
12
SUPPLY VOLTAGE (V)
8
13
2
–40 –25 –10 5 20 35 50 65 80 95 110 125
TEMPERATURE (°C)
14
4444 G16
4446 G17
Switching Supply Current vs
Input Frequency
4.0
Switching Supply Current vs
Load Capacitance
TA = 25°C
VCC = BOOST = 12V
TS = GND
3.5
SUPPLY CURRENT (mA)
1
IPU(BG)
3.0
tf(BG)
10
0
VCC = BOOST = 12V
TS = GND
3.2
PULL-UP CURRENT (A)
70
RISE/FALL TIME (ns)
3.4
TA = 25°C
VCC = BOOST = 12V
TS = GND
IBOOST
(TG SWITCHING)
3.0
SUPPLY CURRENT (mA)
80
Output Driver Pull-Down
Resistance vs Temperature
Peak Driver (TG, BG) Pull-Up
Current vs Temperature
OUTPUT DRIVER PULL-DOWN RESISTACNE (Ω)
Rise and Fall Time vs
Load Capacitance
IVCC
(BG SWITCHING)
2.5
2.0
1.5
1.0
IVCC
(TG SWITCHING)
100
200
400
800
600
SWITCHING FREQUENCY (kHz)
IVCC
(BG SWITCHING
AT 500kHz)
IVCC
IVCC
(TG SWITCHING
(TG SWITCHING AT 500kHz)
AT 1MHz)
1
IBOOST (BG SWITCHING AT 1MHz OR 5OOkHz)
IBOOST (BG SWITCHING)
0
IBOOST
(TG SWITCHING
AT 500kHz)
IBOOST
(TG SWITCHING
AT 1MHz)
10
0.5
0
IVCC
(BG SWITCHING
AT 1MHz)
0.1
1000
4446 G18
1
2
3
4
5
6
7
8
LOAD CAPACITANCE (nF)
9
10
4446 G19
4446f
5
LTC4446
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).
Exposed Pad (Pin 9): Ground. Must be soldered to PCB
ground for optimal thermal performance.
NC (Pin 5): No Connect. No connection required.
BLOCK DIAGRAM
6
7.2V TO
13.5V
3
9
VCC
BOOST
GND
2
TG
HIGH SIDE
LEVEL SHIFTER
LDO
1
VIN
UP TO 100V
VCC UVLO
VINT
TS
TINP
VCC
8
VCC
BG
LOW SIDE
LEVEL SHIFTER
BINP
7
4
NC
5
4446 BD
TIMING DIAGRAM
INPUT RISE/FALL TIME < 10ns
TINP (BINP)
90%
10%
BINP (TINP)
BG (TG)
90%
TG (BG)
90%
10%
tr
tPHL
10%
tf
tPLH
4444 TD
4446f
6
LTC4446
OPERATION
Overview
LTC4446 BOOST
The LTC4446 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).
Q1
Output Stage
A simplified version of the LTC4446’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 pull-down 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).
TG
CGD
HIGH SIDE
POWER
MOSFET
7
M1
TS
CGS
8
LOAD
INDUCTOR
VCC
3
Q2
Input Stage
The LTC4446 employs CMOS compatible input thresholds
that allow a low voltage digital signal to drive standard
power MOSFETs. The LTC4446 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 LTC4446 input
buffers have high input impedance and draw negligible
input current, simplifying the drive circuitry required for
the inputs.
VIN
UP TO 100V
6
BG
CGD
LOW SIDE
POWER
MOSFET
4
M2
GND
9
CGS
4446 F01
Figure 1. Capacitance Seen by BG and TG During Switching
Rise/Fall Time
The LTC4446’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 of crossconduction 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
4446f
7
LTC4446
OPERATION
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 LTC4446 reduces the
switching losses of the power MOSFET, which increase
with transition time. The LTC4446’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 LTC4446 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.
APPLICATIONS INFORMATION
Power Dissipation
To ensure proper operation and long-term reliability, the
LTC4446 must not operate beyond its maximum temperature rating. Package junction temperature can be
calculated by:
TJ = TA + PD (θJA)
where:
TJ = Junction temperature
TA = Ambient temperature
PD = Power dissipation
θJA = Junction-to-ambient thermal resistance
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
PQG = Loss due turning on and off the external MOSFET
with gate charge QG at frequency fIN
The LTC4446 consumes very little quiescent current. The
DC power loss at VCC = 12V and VBOOST-TS = 12V is only
(350μA)(12V) = 4.2mW.
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
4446f
8
LTC4446
APPLICATIONS INFORMATION
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 LTC4446
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.
Bypassing and Grounding
The LTC4446 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.
B. Use a low inductance, low impedance ground plane
to reduce any ground drop and stray capacitance.
Remember that the LTC4446 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 LTC4446 package to the board. Correctly soldered
to a 2500mm2 doublesided 1oz copper board, the
LTC4446 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.
To obtain the optimum performance from the LTC4446:
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.
4446f
9
12V
1μF
220pF
150Ω
20k
1/4W
D2
A
1
4
9
0.47μF
11
2
C
9
220pF
8
180pF
5.1k
1
L2
150nH
21
B
20
9
C
ISNS
4
33k
6.19k
5
6
1M
23
D
17
68nF
8.25k
22
MMBT3904
CT SPRG RLEB FB GND PGND
24 13
19
8 0.22μF
15
C3
68μF
20V
16
+
7
D11
3
330pF
4
SS COMP
CS
5VREF
750Ω
200k
ISNS
22Ω
D4
2.2nF
6
8
2
4
2
4
D8
D7
330Ω
5
C4
2.2nF
250V
8
MOC207
5
9
2
1
6
CSE+
VH
1.5k
5
D12
5.1V
3
11
8
3
2.7k
6
5
Q4
12
14 15
Q2
16
VOUT
VOUT
–VOUT
2.49k
22nF
10k
330pF
7
TIMER
PVCC
MF MF2 VCC
9.53k
13
4446 TA02a
8
10
470Ω
1/4W
GND-F GND-S
+
4
+
D6
470pF
200V
47Ω
1W
Si7852DP
s4
GND PGND GND2 PGND2
LTC3901EGN
VH
C1, C2
180μF
16V
s2
1.5k
CSF–
2.21k
4.87k
1/4W
CSF+
VOUT
ME ME2
2
Q1
V
LT1431CS8
COLL
REF
0.047μF
1
L3
0.85μH
Si7852DP
s4
Q3
CSE–
2.21k
4.87k
1/4W
SYNC
220pF
100Ω
1
6
7
8
10
11
7
8
10
11
T1
5(105μH):1:1
T2
5:5(105μH):1:1
D5
T3
1(1.5μH):0.5
1
4
L4
1mH
0.1μF
D9 3.3V
100Ω
Si7852DP
×2
Si7852DP
s2
51Ω
2W
0.47μF
0.47μF 100V
100V
12V
OUTA OUTB OUTC OUTD OUTF OUTE
A
4.99k
LTC3722EGN-1
22pF
1k
0.02Ω
1.5W
Si7852DP
s2
0.02Ω
1.5W
18.2k
ADLY PDLY
68.1k
DPRG NC SYNC
22pF
14
20k
UVLO
VREF
VIN
SBUS
5VREF
12
18
10
4.99k
80.6k
80.6k
B
8 0.22μF
1
D3
VCC
6
TINP
BOOST
LTC4446
7
Si7852DP 2
BINP
TG
D
s2
BG GND TS
C
3
12V
•
30.1k
VIN
3
12V
VCC
6
TINP
BOOST
LTC4446
7
2
BINP
B
TG
BG GND TS
1μF
100V
s4
0.47μF, 100V TDK C3216X7R2A474M
1μF, 100V TDK C4532X7R2A105M
C1,C2: SANYO 16SP180M
C3: AVX TPSE686M020R0150
C4: MURATA DE2E3KH222MB3B
D4-D6: MURS120T3
D2, D3, D7, D8: BAS21
D9: MMBZ5226B
D10: MMBZ5240B
D11: BAT54
D12: MMBZ231B
L1: SUMIDA CDEP105-1R3MC-50
L2: PULSE PA0651
L3: PA1294.910
L4: COILCRAFT DO1608C-105
Q1, Q2: ZETEX FMMT619
Q3, Q4: ZETEX FMMT718
T1, T2: PULSE PA0526
T3: PULSE PA0297
1μF
100V
51Ω
2W
•
182k
–VIN
36V TO 72V
VIN
•
L1
1.3μH
•
•
•
•
•
•
•
10
•
VIN
LTC3722/LTC4446 420W 36V-72VIN to 12V/35A Isolated Full-Bridge Supply
1
–VOUT
1μF
39.2k
–VOUT
1μF
VOUT
0.82μF
100V
2k
1/2W
VOUT
1μF
D10
10V
MMBT3904
100Ω
–VOUT
12V/35A
VOUT
–VOUT
VOUT
1k
LTC4446
TYPICAL APPLICATION
4446f
LTC4446
PACKAGE DESCRIPTION
MS8E Package
8-Lead Plastic MSOP, Exposed Die Pad
(Reference LTC DWG # 05-08-1662 Rev D)
BOTTOM VIEW OF
EXPOSED PAD OPTION
2.06 ± 0.102
(.081 ± .004)
1
5.23
(.206)
MIN
1.83 ± 0.102
(.072 ± .004)
0.889 ± 0.127
(.035 ± .005)
2.794 ± 0.102
(.110 ± .004)
2.083 ± 0.102 3.20 – 3.45
(.082 ± .004) (.126 – .136)
8
0.42 ± 0.038
(.0165 ± .0015)
TYP
3.00 ± 0.102
(.118 ± .004)
(NOTE 3)
0.65
(.0256)
BSC
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
1
0.53 ± 0.152
(.021 ± .006)
DETAIL “A”
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)
BSC
0.1016 ± 0.0508
(.004 ± .002)
MSOP (MS8E) 0307 REV D
NOTE:
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
4446f
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
11
LTC4446
TYPICAL APPLICATION
LTC4446 Fast Turn-On/Turn-Off DC Switch
12V
BZX84C12L
12V
0.01μF
BAS21 100V
3
15k
200Ω
4.7k
100k
BAS21
MMBT2369
4.7nF
VIN
0V TO 100V
6
0.33μF
VCC
BOOST
7
TG
TINP
LTC4446
2
8
TS
BINP
1
BG
GND
9
BAS21
3.3nF
LOAD
4446 TA03
RELATED PARTS
PART NUMBER
LTC1693 Family
LT®1952/LTC3900
LT3010/LT3010-5
LTC3703
LTC3722-1/
LTC3722-2
LTC3723-1/
LTC3723-2
LTC3780
LTC3785
LTC3810
LTC3813
LT3845
LTC3901
DESCRIPTION
High Speed Dual MOSFET Drivers
36V to 72V Input Isolated DC/DC Converter Chip Sets
COMMENTS
1.5A Peak Output Current, 4.5V ≤ VIN ≤ 13.2V
Synchronous Rectification; Overcurrent, Overvoltage, UVLO Protection;
Power Good Output Signal; Compact Solution
50mA, 3V to 80V Low Dropout Micropower Regulators Low Quiescent Current (30μA), Stable with Small (1μF) Ceramic Capacitor
100V Synchronous Switching Regulator Controller
No RSENSE™, Synchronizable Voltage Mode Control
Synchronous Dual Mode Phase Modulated Full-Bridge Adaptive Zero Voltage Switching, High Output Power Levels (Up to
Controllers
Kilowatts)
Synchronous Push-Pull PWM Controllers
Current Mode or Voltage Mode Push-Pull Controllers
High Power Buck-Boost Controller
Buck-Boost Controller
100V Current Mode Synchronous Step-Down Switching
Regulator Controller
100V Current Mode Synchronous Step-Up Controller
High Power Synchronous DC/DC Controller
Secondary Side Synchronous Driver for Push-Pull and
Full-Bridge Converters
High Speed, High Voltage, High Side Gate Drivers
LTC4440/
LTC4440-5
LTC4441
6A MOSFET Driver
LTC4442/LTC4442-1 High Speed Synchronous N-Channel MOSFET Drivers
LTC4443/LTC4443-1 High Speed Synchronous N-Channel MOSFET Driver
with Integrated Schottky Diode
LTC4444
High Voltage Synchronous N-Channel MOSFET Driver
LTC4444-5
High Voltage Synchronous N-Channel MOSFET Driver
Four Switch, 4V ≤ VIN ≤ 36V, 0.8V ≤ VOUT ≤ 30V, High Efficiency
High Efficiency, Four Switch, 2.7V ≤ VIN ≤ 10V, 2.7V ≤ VOUT ≤ 10V
No RSENSE, Synchronizable Tracking, Power Good Signal
No RSENSE, On-Board 1Ω Gate Drivers, Synchronizable
Current Mode Control, VIN Up to 60V, Low IQ
Programmable Time Out, Reverse Inductor Current Sense
Wide Operating VIN Range: Up to 80V DC, 100V Transient
Adjustable Gate Drive from 5V to 8V, 5V ≤ VIN ≤ 28V
5A Peak Output Current, 6V to 9.5V Gate Drive Supply, 38V Max Input
Supply
5A Peak Output Current, 6V to 9.5V Gate Drive Supply, 38V Max Input
Supply
3A/2.5A Peak Output Current, 7.2V to 13.5V Gate Drive Supply, 100V Max
Input Supply, Adaptive Shoot-Through Protection
1.75A/1.5A Peak Output Current, 4.5V to 13.5V Gate Drive Supply,
100V Max Input Supply, Adaptive Shoot-Through Protection
No RSENSE is a trademark of Linear Technology Corporation.
4446f
12 Linear Technology Corporation
LT 0508 • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507
●
www.linear.com
© LINEAR TECHNOLOGY CORPORATION 2008