LTC4446IMS8E-TRPBF [Linear]
High Voltage High Side/Low Side N-Channel MOSFET Driver; 高电压高侧/低侧N沟道MOSFET驱动器
| 型号： | LTC4446IMS8E-TRPBF |
| 厂家： | 
Linear |
| 描述： | High Voltage High Side/Low Side N-Channel MOSFET Driver |
| 文件： | 总12页 (文件大小：180K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LTC4446
High Voltage High Side/
Low Side N-Channel
MOSFET Driver
FEATURES
DESCRIPTION
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 ca-
pability 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 bot-
tom gate driver has a peak output current of 3A and the
pull-down has an output impedance of 0.55Ω.
n
Bootstrap Supply Voltage Up to 114V
n
Wide V Voltage: 7.2V to 13.5V
CC
n
2.5A Peak Top Gate Pull-Up Current
n
3A Peak Bottom Gate Pull-Up Current
n
1.2Ω Top Gate Driver Pull-Down
n
0.55Ω Bottom Gate Driver Pull-Down
n
5ns Top Gate Fall Time Driving 1nF Load
n
8ns Top Gate Rise Time Driving 1nF Load
n
3ns Bottom Gate Fall Time Driving 1nF Load
n
6ns Bottom Gate Rise Time Driving 1nF Load
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.
n
Drives Both High and Low Side N-Channel MOSFETs
n
Undervoltage Lockout
n
Thermally Enhanced 8-Pin MSOP Package
The LTC4446 contains undervoltage lockout circuits that
disable the external MOSFETs when activated.
APPLICATIONS
n
Distributed Power Architectures
The LTC4446 is available in the thermally enhanced 8-lead
MSOP package.
n
Automotive Power Supplies
n
High Density Power Modules
Telecommunication Systems
The LTC4446 does not have adaptive shoot-through pro-
tection. For similar drivers with adaptive shoot-through
protection, please refer to the chart below.
n
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.
PARAMETER
Shoot-Through Protection
Absolute Max TS
LTC4446
No
100V
LTC4444
Yes
100V
LTC4444-5
Yes
100V
MOSFET Gate Drive
7.2V to 13.5V 7.2V to 13.5V 4.5V to 13.5V
+
V
CC
V
CC
UV
UV
6.6V
6.6V
4V
–
6.15V
6.15V
3.55V
TYPICAL APPLICATION
Two Switch Forward Converter
LTC4446 Driving a 1000pF Capacitive Load
V
IN
BINP
V
CC
36V TO 72V
5V/DIV
BG
7.2V TO 13.5V
(100V ABS MAX)
BOOST
10V/DIV
V
TG
TS
BG
CC
LTC4446
TINP
PWM1
(FROM CONTROLLER IC)
PWM2
(FROM CONTROLLER IC)
5V/DIV
TINP
BINP
•
•
TO
SECONDARY
CIRCUIT
TG-TS
10V/DIV
GND
4446 TA01b
20ns/DIV
4446 TA01a
4446f
1
LTC4446
ABSOLUTE MAXIMUM RATINGS
PIN CONFIGURATION
(Note 1)
TOP VIEW
Supply Voltage
TINP
BINP
1
2
3
4
8 TS
7 TG
6 BOOST
5 NC
V ......................................................... –0.3V to 14V
CC
9
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
V
CC
BG
MS8E PACKAGE
8-LEAD PLASTIC MSOP
T
= 125°C, θ = 40°C/W, θ = 10°C/W (NOTE 4)
JA JC
EXPOSED PAD (PIN 9) IS GND, MUST BE SOLDERED TO PCB
JMAX
ORDER INFORMATION
LEAD FREE FINISH
LTC4446EMS8E#PBF
LTC4446IMS8E#PBF
TAPE AND REEL
PART MARKING*
LTDPZ
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LTC4446EMS8E#TRPBF
LTC4446IMS8E#TRPBF
8-Lead Plastic MSOP
8-Lead Plastic MSOP
–40°C to 85°C
–40°C to 85°C
LTDPZ
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
CONDITIONS
MIN
TYP
MAX
UNITS
Gate Driver Supply, V
CC
V
Operating Voltage
7.2
13.5
550
V
CC
I
DC Supply Current
TINP = BINP = 0V
350
μA
VCC
l
l
UVLO
Undervoltage Lockout Threshold
V
V
Rising
Falling
6.00
5.60
6.60
6.15
450
7.20
6.70
V
V
mV
CC
CC
Hysteresis
Bootstrapped Supply (BOOST – TS)
DC Supply Current
Input Signal (TINP, BINP)
I
TINP = BINP = 0V
0.1
2
μA
BOOST
l
l
l
l
V
V
V
V
BG Turn-On Input Threshold
BG Turn-Off Input Threshold
TG Turn-On Input Threshold
TG Turn-Off Input Threshold
Input Pin Bias Current
BINP Ramping High
BINP Ramping Low
TINP Ramping High
TINP Ramping Low
2.25
1.85
2.25
1.85
2.75
2.3
3.25
2.75
3.25
2.75
2
V
V
IH(BG)
IL(BG)
2.75
2.3
V
IH(TG)
V
IL(TG)
I
0.01
μA
TINP(BINP)
High Side Gate Driver Output (TG)
V
V
TG High Output Voltage
TG Low Output Voltage
TG Peak Pull-Up Current
TG Pull-Down Resistance
I
I
= –10mA, V
= 100mA, V
= V
– V
TG
0.7
120
2.5
1.2
V
mV
A
OH(TG)
OL(TG)
PU(TG)
TG
OH(TG)
OL(TG)
BOOST
l
l
l
= V –V
220
2.2
TG
TG
TS
I
1.7
R
Ω
DS(TG)
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
CONDITIONS
MIN
TYP
MAX
UNITS
Low Side Gate Driver Output (BG)
V
V
BG High Output Voltage
BG Low Output Voltage
BG Peak Pull-Up Current
BG Pull-Down Resistance
I
I
= –10mA, V
= 100mA
= V – V
BG
0.7
55
V
mV
A
OH(BG)
OL(BG)
PU(BG)
BG
OH(BG)
CC
l
l
l
110
1.1
BG
I
2
3
R
0.55
Ω
DS(BG)
Switching Time (BINP (TINP) is Tied to Ground While TINP (BINP) is Switching. Refer to Timing Diagram)
l
l
l
l
l
l
t
t
t
t
t
t
t
TG Low-High (Turn-On) Propagation Delay
TG High-Low (Turn-Off) Propagation Delay
BG Low-High (Turn-On) Propagation Delay
BG High-Low (Turn-Off) Propagation Delay
Delay Matching BG Turn-Off and TG Turn-On
Delay Matching TG Turn-Off and BG Turn-On
TG Output Rise Time
25
22
19
14
10
–3
45
40
35
30
35
25
ns
ns
ns
ns
ns
ns
PLH(TG)
PHL(TG)
PLH(BG)
PHL(BG)
DM(BGTG)
DM(TGBG)
r(TG)
–15
–25
10% – 90%, C = 1nF
8
80
ns
ns
L
10% – 90%, C = 10nF
L
t
t
t
TG Output Fall Time
BG Output Rise Time
BG Output Fall Time
10% – 90%, C = 1nF
5
ns
ns
f(TG)
r(BG)
f(BG)
L
10% – 90%, C = 10nF
50
L
10% – 90%, C = 1nF
6
60
ns
ns
L
10% – 90%, C = 10nF
L
10% – 90%, C = 1nF
3
30
ns
ns
L
10% – 90%, C = 10nF
L
with statistical process controls. The LTC4446I is guaranteed over the full
–40°C to 85°C operating temperature range.
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 3: T is calculated from the ambient temperature T and power
J
A
dissipation P according to the following formula:
D
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
T = T + (P • θ °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.
J
A
D
JA
TYPICAL PERFORMANCE CHARACTERISTICS
VCC Supply Quiescent Current
vs Voltage
BOOST-TS Supply Quiescent
Current vs Voltage
VCC Supply Current vs
Temperature
450
400
350
300
250
200
150
100
50
400
350
300
250
200
150
100
50
380
370
360
350
340
330
320
310
300
T
= 25°C
= 12V
V
= BOOST = 12V
CC
T
= 25°C
A
CC
A
TINP = 12V, BINP = 0V
TINP = 0V, BINP = 12V
V
TS = GND
BOOST = 12V
TS = GND
TINP = BINP = 0V
TINP(BINP) = 12V
TS = GND
TINP = BINP = 0V
TINP(BINP) = 12V
TINP = BINP = 0V
0
0
–40 –25 –10
5
20 35 50 65 80 95 110
TEMPERATURE (°C)
125
0
1
2
3
4
5
14
0
1
2
3
4
5
14
6
7
8
9 10 11 12 13
6
7
8
9 10 11 12 13
V
SUPPLY VOLTAGE (V)
BOOST SUPPLY VOLTAGE (V)
CC
4446 G03
4446 G01
4446 G02
4446f
3
LTC4446
TYPICAL PERFORMANCE CHARACTERISTICS
Boost Supply Current
vs Temperature
Output Low Voltage (VOL
)
Output High Voltage (VOH) vs
Supply Voltage
vs Supply Voltage
15
14
13
12
11
10
9
160
400
350
300
250
200
150
100
50
V
= BOOST = 12V
TINP = 12V
BINP = 0V
T = 25°C
A
CC
TS = GND
BOOST = V
TS = GND
CC
140
120
V
OL(TG)
OL(BG)
TINP = 0V
–1mA
100
80
60
40
20
BINP = 12V
–10mA
–100mA
V
8
T
= 25°C
A
7
I
= 100mA
CC
TG(BG)
BOOST = V
TS = GND
6
TINP = BINP = 0V
0
5
0
7
9
10
11
12
13
14
8
9
11
12
13
14
–40 –25 –10
5
20 35 50 65 80 95 110
TEMPERATURE (°C)
7
10
8
125
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
4446 G06
4446 G05
4446 G04
Input Thresholds (TINP, BINP) vs
Supply Voltage
Input Thresholds (TINP, BINP) vs
Temperature
Input Thresholds (TINP, BINP)
Hysteresis vs Voltage
3.1
3.0
2.9
2.8
2.7
2.6
2.5
2.4
2.3
2.2
2.1
500
475
450
425
400
375
3.0
2.9
2.8
2.7
2.6
2.5
2.4
2.3
2.2
2.1
2.0
V
= BOOST = 12V
T
= 25°C
CC
T
= 25°C
CC
A
A
TS = GND
V
= BOOST
BOOST = V
TS = GND
CC
TS = GND
V
IH(TG,BG)
V
IH(TG,BG)
V
IL(TG,BG)
V
IL(TG,BG)
–40 –25 –10
5
20 35 50 65 80 95 110 125
TEMPERATURE (°C)
4446 G08
7
9
10
11
12
13
14
7
8
9
10
11
12
13
14
8
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
4446 G07
4446 G09
Input Thresholds (TINP, BINP)
Hysteresis vs Temperature
VCC Undervoltage Lockout
Thresholds vs Temperature
Rise and Fall Time vs
VCC Supply Voltage
32
30
28
26
24
22
20
18
16
14
12
10
8
500
475
450
425
400
375
6.7
6.6
BOOST = V
CC
TS = GND
T
= 25°C
V
= BOOST = 12V
A
CC
BOOST = V
TS = GND
TS = GND
CC
t
C
= 3.3nF
r(TG)
r(BG)
L
RISING THRESHOLD
6.5
6.4
6.3
6.2
6.1
t
t
f(TG)
FALLING THRESHOLD
t
f(BG)
6
6.0
7
9
10
11
12
13
14
–40 –25 –10
5
20 35 50 65 80 95 110 125
110 125
35 50 65 80 95
8
–40
5
–25 –10
20
SUPPLY VOLTAGE (V)
TEMPERATURE (°C)
TEMPERATURE (°C)
4446 G12
4446 G10
4446 G11
4446f
4
LTC4446
TYPICAL PERFORMANCE CHARACTERISTICS
Output Driver Pull-Down
Resistance vs Temperature
Rise and Fall Time vs
Load Capacitance
Peak Driver (TG, BG) Pull-Up
Current vs Temperature
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
80
70
60
50
40
30
20
10
0
3.4
3.2
V
= BOOST = 12V
T
= 25°C
CC
CC
A
TS = GND
V
= BOOST = 12V
BOOST-TS = 12V
BOOST-TS = 7V
TS = GND
I
3.0
t
PU(BG)
r(TG)
R
DS(TG)
BOOST-TS = 14V
= 12V
2.8
2.6
2.4
2.2
t
r(BG)
V
CC
V
= 7V
CC
I
PU(TG)
t
t
f(TG)
V
= 14V
CC
R
DS(BG)
f(BG)
2.0
–40 –25 –10
5
20 35 50 65 80 95 110 125
TEMPERATURE (°C)
5
6
1
2
3
4
7
8
9
10
–40
5
35 50 65 80 95 110 125
–25 –10
20
TEMPERATURE (°C)
LOAD CAPACITANCE (nF)
4446 G15
4445 G13
4446 G14
Propagation Delay vs
VCC Supply Voltage
Propagation Delay vs Temperature
30
28
26
24
22
20
18
16
14
12
10
37
32
T
= 25°C
V
= BOOST = 12V
A
CC
BOOST = V
TS = GND
TS = GND
CC
t
PLH(TG)
t
PLH(TG)
27
t
PHL(TG)
t
PHL(TG)
22
17
12
7
t
t
PLH(BG)
PLH(BG)
t
PHL(BG)
t
PHL(BG)
13
2
7
9
10
11
12
14
8
–40
5
35 50 65 80 95 110 125
–25 –10
20
SUPPLY VOLTAGE (V)
TEMPERATURE (°C)
4444 G16
4446 G17
Switching Supply Current vs
Input Frequency
Switching Supply Current vs
Load Capacitance
4.0
3.5
3.0
2.5
T
= 25°C
CC
A
I
BOOST
V
= BOOST = 12V
(TG SWITCHING
AT 500kHz)
I
VCC
TS = GND
I
(BG SWITCHING
AT 1MHz)
BOOST
100
10
1
(TG SWITCHING)
I
VCC
I
(BG SWITCHING)
BOOST
(TG SWITCHING
AT 1MHz)
2.0
1.5
I
VCC
(BG SWITCHING
AT 500kHz)
I
VCC
I
(TG SWITCHING
AT 1MHz)
VCC
1.0
0.5
0
I
(TG SWITCHING AT 500kHz)
VCC
(TG SWITCHING)
I
(BG SWITCHING AT 1MHz OR 5OOkHz)
BOOST
I
(BG SWITCHING)
BOOST
0.1
200
400
800
0
1000
600
1
2
3
4
5
6
7
8
9
10
LOAD CAPACITANCE (nF)
SWITCHING FREQUENCY (kHz)
4446 G19
4446 G18
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).
BOOST (Pin 6): High Side Bootstrapped Supply. An ex-
ternal capacitor should be tied between this pin and TS
(Pin 8). Normally, a bootstrap diode is connected between
V
V
(Pin 3) and this pin. Voltage swing at this pin is from
CC
CC
BINP (Pin 2): Low Side Input Signal. This input controls
the low side driver output (BG).
– V to V + V – V , where V is the forward volt-
D
IN
CC
D
D
age drop of the bootstrap diode.
V
CC
(Pin 3): Supply. This pin powers input buffers, logic
TG (Pin 7): High Side Gate Driver Output (Top Gate). This
pin swings between TS and BOOST.
and the low side gate driver output directly and the high
side gate driver output through an external diode con-
nected between this pin and BOOST (Pin 6). A low ESR
ceramic bypass capacitor should be tied between this pin
and GND (Pin 9).
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.
BG (Pin 4): Low Side Gate Driver Output (Bottom Gate).
This pin swings between V and GND.
CC
NC (Pin 5): No Connect. No connection required.
BLOCK DIAGRAM
6
BOOST
V
IN
V
CC
UP TO 100V
3
9
V
UVLO
CC
7.2V TO
13.5V
GND
TG
TS
HIGH SIDE
LEVEL SHIFTER
7
8
LDO
V
INT
TINP
BINP
V
V
CC
CC
1
2
BG
LOW SIDE
LEVEL SHIFTER
4
NC
5
4446 BD
TIMING DIAGRAM
INPUT RISE/FALL TIME < 10ns
90%
TINP (BINP)
10%
BINP (TINP)
BG (TG)
90%
10%
90%
10%
TG (BG)
4444 TD
t
t
r
f
t
t
PLH
PHL
4446f
6
LTC4446
OPERATION
Overview
LTC4446
V
BOOST
6
IN
UP TO 100V
TheLTC4446receivesground-referenced,lowvoltagedigi-
talinputsignalstodrivetwoN-channelpowerMOSFETsin
asynchronousbuckpowersupplyconfiguration. Thegate
Q1
C
C
GD
TG
7
HIGH SIDE
POWER
MOSFET
of the low side MOSFET is driven either to V or GND,
CC
M1
GS
TS
8
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).
LOAD
INDUCTOR
V
CC
3
Q2
C
C
Input Stage
GD
BG
4
LOW SIDE
POWER
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
MOSFET
M2
GS
GND
9
4446 F01
Figure 1. Capacitance Seen by BG and TG During Switching
(V = 2.75V, V = 2.3V) to be independent of variations in
IH
IL
V .The450mVhysteresisbetweenV andV eliminates
CC
IH
IL
Rise/Fall Time
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.
The LTC4446’s rise and fall times are determined by the
peak current capabilities of Q1 and M1. The predriver that
drivesQ1andM1usesanonoverlappingtransitionscheme
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 ma-
jority 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-downonthedriveroutputsisthepreventionofcross-
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 V very rapidly. This high frequency positive
voltage transient will couple through the C 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
Output Stage
AsimplifiedversionoftheLTC4446’soutputstageisshown
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 V (~0.7V)
of their positive rails (V 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 nega-
tive rails, GND and TS. The large voltage swing of the BG
and TG output pins is important in driving external power
MOSFETs, whose R
gate overdrive voltage (V − V ).
BE
CC
IN
GD
is inversely proportional to the
DS(ON)
GS
TH
4446f
7
LTC4446
OPERATION
load with 6ns rise and 3ns fall times using a supply volt-
both the high side and low side MOSFETs conducting,
age V of 12V.
significant cross-conduction current will flow through the
CC
MOSFETs from V to ground and will cause substantial
IN
Undervoltage Lockout (UVLO)
power loss. A similar effect occurs on TG due to the C
GS
and C capacitances of the high side MOSFET.
GD
The LTC4446 contains an undervoltage lockout detector
that monitors V supply. When V falls below 6.15V,
CC
CC
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 V
12V while its low side driver is capable of driving a 1nF
the output pins BG and TG are pulled down to GND and
TS, respectively. This turns off both external MOSFETs.
When V has adequate supply voltage, normal operation
CC
will resume.
of
BOOST-TS
APPLICATIONS INFORMATION
Power Dissipation
The LTC4446 consumes very little quiescent current. The
DC power loss at V = 12V and V
= 12V is only
CC
BOOST-TS
To ensure proper operation and long-term reliability, the
LTC4446 must not operate beyond its maximum tem-
perature rating. Package junction temperature can be
calculated by:
(350μA)(12V) = 4.2mW.
Ataparticularswitchingfrequency,theinternalpowerloss
increases due to both AC currents required to charge and
discharge internal node capacitances and cross-conduc-
tion currents in the internal logic gates. The sum of the
quiescent current and internal switching current with no
loadareshownintheTypicalPerformanceCharacteristics
plot of Switching Supply Current vs Input Frequency.
T = T + P (θ )
J
A
D
JA
where:
T = Junction temperature
J
T = Ambient temperature
A
The gate charge losses are primarily due to the large AC
currentsrequiredtochargeanddischargethecapacitance
of the external MOSFETs during switching. For identical
P = Power dissipation
D
θ
= Junction-to-ambient thermal resistance
JA
pure capacitive loads C
on TG and BG at switching
LOAD
Power dissipation consists of standby and switching
power losses:
frequency f , the load losses would be:
IN
2
2
P
= (C
)(f)[(V
) + (V ) ]
CLOAD
LOAD
BOOST-TS
CC
P = P + P + P
D
DC
AC
QG
In a typical synchronous buck configuration, V
BOOST-TS
where:
is equal to V – V , where V is the forward voltage
CC
D
D
drop across the diode between V and BOOST. If this
P
= Quiescent power loss
CC
DC
drop is small relative to V , the load losses can be
CC
P
AC
= Internal switching loss at input frequency, f
IN
approximated as:
P
= Loss due turning on and off the external MOSFET
QG
2
P
= 2(C
)(f )(V )
LOAD IN CC
CLOAD
with gate charge QG at frequency f
IN
4446f
8
LTC4446
APPLICATIONS INFORMATION
Unlike a pure capacitive load, a power MOSFET’s gate
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.
capacitance seen by the driver output varies with its V
GS
voltagelevelduringswitching.AMOSFET’scapacitiveload
power dissipation can be calculated using its gate charge,
Q . The Q value corresponding to the MOSFET’s V
GS
G
G
value (V in this case) can be readily obtained from the
CC
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.
manufacturer’s Q vs V curves. For identical MOSFETs
G
GS
on TG and BG:
P
= 2(V )(Q )(f )
QG
CC
G
IN
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
operationwillresumewhenthejunctiontemperaturecools
to less than 135°C.
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
2
to a 2500mm 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.
Bypassing and Grounding
The LTC4446 requires proper bypassing on the V
CC
and V
supplies due to its high speed switching
BOOST-TS
(nanoseconds)andlargeACcurrents(Amperes).Careless
component placement and PCB trace routing may cause
excessive ringing.
To obtain the optimum performance from the LTC4446:
A. Mount the bypass capacitors as close as possible
between the V and GND pins and the BOOST and
CC
TS pins. The leads should be shortened as much as
possible to reduce lead inductance.
4446f
9
LTC4446
TYPICAL APPLICATION
•
•
•
•
•
•
•
•
•
•
•
4446f
10
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
1.83 0.102
(.072 .004)
0.889 0.127
(.035 .005)
2.794 0.102
(.110 .004)
5.23
(.206)
MIN
3.20 – 3.45
(.126 – .136)
2.083 0.102
(.082 .004)
8
3.00 0.102
(.118 .004)
(NOTE 3)
0.52
(.0205)
REF
0.65
(.0256)
BSC
0.42 0.038
(.0165 .0015)
TYP
8
7 6 5
RECOMMENDED SOLDER PAD LAYOUT
3.00 0.102
(.118 .004)
(NOTE 4)
4.90 0.152
(.193 .006)
DETAIL “A”
0.254
(.010)
0° – 6° TYP
GAUGE PLANE
1
2
3
4
0.53 0.152
(.021 .006)
1.10
(.043)
MAX
0.86
(.034)
REF
DETAIL “A”
0.18
(.007)
SEATING
PLANE
0.22 – 0.38
(.009 – .015)
TYP
0.1016 0.0508
(.004 .002)
0.65
(.0256)
BSC
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 representa-
tion 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
V
IN
0V TO 100V
0.33μF
3
6
0.01μF
100V
BZX84C12L
12V
15k
4.7k
4.7nF
V
TINP
BOOST
TG
CC
BAS21
BAS21
7
8
1
2
200Ω
LTC4446
TS
BINP
100k
BG
GND
BAS21
3.3nF
MMBT2369
9
LOAD
4446 TA03
RELATED PARTS
PART NUMBER
LTC1693 Family
LT®1952/LTC3900
DESCRIPTION
COMMENTS
High Speed Dual MOSFET Drivers
36V to 72V Input Isolated DC/DC Converter Chip Sets
1.5A Peak Output Current, 4.5V ≤ V ≤ 13.2V
IN
Synchronous Rectification; Overcurrent, Overvoltage, UVLO Protection;
Power Good Output Signal; Compact Solution
LT3010/LT3010-5
LTC3703
50mA, 3V to 80V Low Dropout Micropower Regulators Low Quiescent Current (30μA), Stable with Small (1μF) Ceramic Capacitor
™
, Synchronizable Voltage Mode Control
SENSE
100V Synchronous Switching Regulator Controller
No R
LTC3722-1/
LTC3722-2
Synchronous Dual Mode Phase Modulated Full-Bridge Adaptive Zero Voltage Switching, High Output Power Levels (Up to
Controllers
Kilowatts)
LTC3723-1/
LTC3723-2
Synchronous Push-Pull PWM Controllers
Current Mode or Voltage Mode Push-Pull Controllers
LTC3780
LTC3785
LTC3810
High Power Buck-Boost Controller
Buck-Boost Controller
Four Switch, 4V ≤ V ≤ 36V, 0.8V ≤ V
≤ 30V, High Efficiency
IN
OUT
High Efficiency, Four Switch, 2.7V ≤ V ≤ 10V, 2.7V ≤ V
≤ 10V
IN
OUT
100V Current Mode Synchronous Step-Down Switching No R
Regulator Controller
, Synchronizable Tracking, Power Good Signal
SENSE
LTC3813
LT3845
100V Current Mode Synchronous Step-Up Controller
High Power Synchronous DC/DC Controller
No R
, On-Board 1Ω Gate Drivers, Synchronizable
SENSE
Current Mode Control, V Up to 60V, Low I
IN
Q
LTC3901
Secondary Side Synchronous Driver for Push-Pull and Programmable Time Out, Reverse Inductor Current Sense
Full-Bridge Converters
LTC4440/
LTC4440-5
High Speed, High Voltage, High Side Gate Drivers
Wide Operating V Range: Up to 80V DC, 100V Transient
IN
LTC4441
6A MOSFET Driver
Adjustable Gate Drive from 5V to 8V, 5V ≤ V ≤ 28V
IN
LTC4442/LTC4442-1 High Speed Synchronous N-Channel MOSFET Drivers
5A Peak Output Current, 6V to 9.5V Gate Drive Supply, 38V Max Input
Supply
LTC4443/LTC4443-1 High Speed Synchronous N-Channel MOSFET Driver
with Integrated Schottky Diode
5A Peak Output Current, 6V to 9.5V Gate Drive Supply, 38V Max Input
Supply
LTC4444
High Voltage Synchronous N-Channel MOSFET Driver
High Voltage Synchronous N-Channel MOSFET Driver
is a trademark of Linear Technology Corporation.
3A/2.5A Peak Output Current, 7.2V to 13.5V Gate Drive Supply, 100V Max
Input Supply, Adaptive Shoot-Through Protection
LTC4444-5
1.75A/1.5A Peak Output Current, 4.5V to 13.5V Gate Drive Supply,
100V Max Input Supply, Adaptive Shoot-Through Protection
No R
SENSE
4446f
LT 0508 • PRINTED IN USA
LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
12
●
●
© LINEAR TECHNOLOGY CORPORATION 2008
(408) 432-1900 FAX: (408) 434-0507 www.linear.com
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