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LTC4444-5 High Voltage Synchronous N-Channel MOSFET Driver FEATURES

DESCRIPTION
The LTC(R)4444-5 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. The powerful driver capability reduces switching losses in MOSFETs with high gate capacitance. The LTC4444-5's pull-up for the top gate driver has a peak output current of 1.4A and its pull-down has an output impedance of 1.5. The pull-up for the bottom gate driver has a peak output current of 1.75A and the pull-down has an output impedance of 0.75. The LTC4444-5 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 LTC4444-5 contains undervoltage lockout circuits that disable the external MOSFETs when activated. The LTC4444-5 also contains adaptive shoot-through protection to prevent both MOSFETs from conducting simultaneously. The LTC4444-5 is available in the thermally enhanced 8-lead MSOP package. For a similar driver in this product family, please refer to the chart below.
PARAMETER LTC4444-5 LTC4446 LTC4444 Shoot-Through Protection Yes No Yes Absolute Max TS 100V 100V 100V MOSFET Gate Drive 4.5V to 13.5V 7.2V to 13.5V 7.2V to 13.5V 4V 6.6V 6.6V VCC UV+ 3.5V 6.15V 6.15V VCC UV-
Bootstrap Supply Voltage to 114V Wide VCC Voltage: 4.5V to 13.5V Adaptive Shoot-Through Protection 1.4A Peak Top Gate Pull-Up Current 1.75A Peak Bottom Gate Pull-Up Current 1.5 Top Gate Driver Pull-Down 0.75 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
APPLICATIONS

Distributed Power Architectures Automotive Power Supplies High Density Power Modules Telecommunication Systems
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.
TYPICAL APPLICATION
High Input Voltage Buck Converter
VCC 4.5V TO 13.5V BOOST PWM1 (FROM CONTROLLER IC) PWM2 (FROM CONTROLLER IC) TG LTC4444-5 TS TINP BINP GND
44445 TA01a
LTC4444-5 Driving a 1000pF Capacitive Load
BINP 5V/DIV BG 5V/DIV TINP 5V/DIV TG-TS 5V/DIV 20ns/DIV
44445 TA01b
VIN 100V VCC
VOUT
BG
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LTC4444-5 ABSOLUTE MAXIMUM RATINGS
(Note 1)
PIN CONFIGURATION
TOP VIEW TINP BINP VCC BG 1 2 3 4 8 7 6 5 TS TG BOOST NC 9
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 (Note 2) .............................................-55C to 125C Storage Temperature Range...................-65C to 150C Lead Temperature (Soldering, 10 sec) .................. 300C
MS8E PACKAGE 8-LEAD PLASTIC MSOP TJMAX = 125C, JA = 40C/W, JC = 10C/W (NOTE 4) EXPOSED PAD (PIN 9) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH LTC4444EMS8E-5#PBF LTC4444IMS8E-5#PBF LTC4444MPMS8E-5#PBF TAPE AND REEL LTC4444EMS8E-5#TRPBF LTC4444IMS8E-5#TRPBF LTC4444MPMS8E-5#TRPBF PART MARKING* LTDPY LTDPY LTFDF PACKAGE DESCRIPTION 8-Lead Plastic MSOP 8-Lead Plastic MSOP 8-Lead Plastic MSOP TEMPERATURE RANGE -40C to 85C -40C to 85C -55C to 125C
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/
The denotes the specifications which apply over the full operating junction temperature range, otherwise specifications are at TA = 25C. VCC = VBOOST = 6V, VTS = GND = 0V, unless otherwise noted.
SYMBOL VCC IVCC UVLO PARAMETER Operating Voltage DC Supply Current Undervoltage Lockout Threshold TINP = BINP = 0V VCC Rising VCC Falling Hysteresis TINP = BINP = 0V BINP Ramping High BINP Ramping Low TINP Ramping High TINP Ramping Low

ELECTRICAL CHARACTERISTICS
CONDITIONS
MIN 4.5
TYP
MAX 13.5
UNITS V A V V mV A V V V V A
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Gate Driver Supply, VCC 320 3.60 3.20 4.00 3.55 450 0.1 2.25 1.85 2.25 1.85 2.75 2.3 2.75 2.3 0.01 520 4.40 3.90
Bootstrapped Supply (BOOST - TS) IBOOST VIH(BG) VIL(BG) VIH(TG) VIL(TG) ITINP(BINP) DC Supply Current BG Turn-On Input Threshold BG Turn-Off Input Threshold TG Turn-On Input Threshold TG Turn-Off Input Threshold Input Pin Bias Current 2 3.25 2.75 3.25 2.75 2 Input Signal (TINP, BINP)
2
LTC4444-5
The denotes the specifications which apply over the full operating junction temperature range, otherwise specifications are at TA = 25C. VCC = VBOOST = 6V, VTS = GND = 0V, unless otherwise noted.
SYMBOL VOH(TG) VOL(TG) IPU(TG) RDS(TG) VOH(BG) VOL(BG) IPU(BG) RDS(BG) tPLH(TG) tPHL(TG) tPLH(BG) tPHL(BG) tr(TG) tf(TG) tr(BG) tf(BG) PARAMETER TG High Output Voltage TG Low Output Voltage TG Peak Pull-Up Current TG Pull-Down Resistance BG High Output Voltage BG Low Output Voltage BG Peak Pull-Up Current BG Pull-Down Resistance TG Low-High Propagation Delay TG High-Low Propagation Delay BG Low-High Propagation Delay BG High-Low Propagation Delay TG Output Rise Time TG Output Fall Time BG Output Rise Time BG Output Fall Time 10% - 90%, CL = 1nF 10% - 90%, CL = 10nF 10% - 90%, CL = 1nF 10% - 90%, CL = 10nF 10% - 90%, CL = 1nF 10% - 90%, CL = 10nF 10% - 90%, CL = 1nF 10% - 90%, CL = 10nF IBG = -10mA, VOH(BG) = VCC - VBG IBG = 100mA

ELECTRICAL CHARACTERISTICS
High Side Gate Driver Output (TG)
CONDITIONS ITG = -10mA, VOH(TG) = VBOOST - VTG ITG = 100mA, VOL(TG) = VTG -VTS

MIN
TYP 0.7 150
MAX
UNITS V
250 2.5
mV A V
1
1.4 1.5 0.7 75 130 1.3 55 40 45 30
Low Side Gate Driver Output (BG) mV A ns ns ns ns ns ns ns ns ns ns ns ns
1.15
1.75 0.75 33 24 27 15 8 80 5 50 6 60 3 30
Switching Time (BINP (TINP) is Tied to Ground While TINP (BINP) is Switching. Refer to Timing Diagram)

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 LTC4444E-5 is guaranteed to meet specifications from 0C to 85C. Specifications over the -40C to 125C operating junction temperature range are assured by design, characterization and correlation with statistical process controls. The LTC4444I-5 is guaranteed over the
-40C to 85C operating junction temperature range. The LTC4444MP-5 is guaranteed over the full -55C to 125C operating junction temperature range. Note 3: TJ is calculated from the ambient temperature TA and power dissipation PD according to the following formula: TJ = TA + (PD * JAC/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 40C/W.
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LTC4444-5 TYPICAL PERFORMANCE CHARACTERISTICS
VCC Supply Quiescent Current vs Voltage
450 400 QUIESCENT CURRENT (A) 350 300 TINP (BINP) = 6V 250 200 150 100 50 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 VCC SUPPLY VOLTAGE (V)
44445 G01
BOOST-TS Supply Quiescent Current vs Voltage
400 TINP = 6V, BINP = 0V 325 320 VCC SUPPLY CURRENT (A) 315 350 QUIESCENT CURRENT (A) 300 250 200 150 100 50 0 TINP = BINP = 0V TA = 25C VCC = 6V TS = GND TINP = 0V, BINP = 6V
VCC Supply Current vs Temperature
TA = 25C BOOST = 6V TS = GND
TINP = BINP = 0V
TINP = BINP = 0V 310 305 300 295 290 285 TINP (BINP) = 6V
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 BOOST SUPPLY VOLTAGE (V)
44445 G02
VCC = BOOST = 6V TS = GND 280 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
44445 G03
Boost Supply Current vs Temperature
400 TINP = 6V, BINP = 0V BOOST SUPPLY CURRENT (A) 350 140 OUTPUT VOLTAGE (mV) 300 250 200 150 100 50 VCC = BOOST = 6V TS = GND TINP = 0V, BINP = 6V 120 100 80 60 40 20 0 160
Output Low Voltage (VOL) vs Supply Voltage
15 14 VOL(TG) TG OR BG OUTPUT VOLTAGE (V) 13 12 11 10 9 8 7 6 5 4
Output High Voltage (VOH) vs Supply Voltage
TA = 25C BOOST = VCC TS = GND
-10mA -1mA -100mA
VOL(BG)
TINP = BINP = 0V 0 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
44445 G04
TA = 25C ITG(BG) = 100mA BOOST = VCC TS = GND 4.5 5.5 6.5 7.5 8.5 9.5 10.5 11.5 12.5 13.5 SUPPLY VOLTAGE (V)
44445 G05
3 4.5 5.5 6.5 7.5 8.5 9.5 10.5 11.5 12.5 13.5 SUPPLY VOLTAGE (V)
44445 G06
Input Thresholds (TINP BINP) , vs Supply Voltage
3.0 TG OR BG INPUT THRESHOLD (V) 2.8 2.6 2.4 2.2 2.0 1.8 4.5 5.5 6.5 7.5 8.5 9.5 10.5 11.5 12.5 13.5 SUPPLY VOLTAGE (V)
44445 G07
Input Thresholds (TINP BINP) , vs Temperature
3.0 TG OR BG INPUT THRESHOLD (V) TG OR BG INPUT THRESHOLD HYSTERESIS (mV) 2.9 2.8 2.7 2.6 2.5 2.4 2.3 2.2 2.1 2.0 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
44445 G08
Input Thresholds (TINP BINP) , Hysteresis vs Voltage
500 475 450 425 400 375 350 325 300 4.5 5.5 6.5 7.5 8.5 9.5 10.5 11.5 12.5 13.5 SUPPLY VOLTAGE (V)
44445 G09
VIH(TG,BG)
VCC = BOOST = 6V TS = GND
TA = 25C BOOST = VCC TS = GND
VIH(TG,BG)
VIL(TG,BG)
VIL(TG,BG)
TA = 25C BOOST = VCC TS = GND
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LTC4444-5 TYPICAL PERFORMANCE CHARACTERISTICS
Input Thresholds (TINP BINP) , Hysteresis vs Temperature
TG OR BG INPUT THRESHOLD HYSTERESIS (mV) 500 VCC = BOOST = 6V TS = GND VCC SUPPLY VOLTAGE (V) 475 4.2 4.1 4.0 RISING THRESHOLD 3.9 3.8 3.7 3.6 3.5 375 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
44445 G10
VCC Undervoltage Lockout Thresholds vs Temperature
BOOST = VCC TS = GND RISE/FALL TIME (ns) 34 32 30 28 26 24 22 20 18 16 14 12 10 8 6
Rise and Fall Time vs VCC Supply Voltage
TA = 25C BOOST = VCC TS = GND CL = 3.3nF
tr(TG)
450
tr(BG) tf(TG)
425
400
FALLING THRESHOLD
tf(BG) 4.5 5.5 6.5 7.5 8.5 9.5 10.5 11.5 12.5 13.5 SUPPLY VOLTAGE (V)
44445 G12
3.4 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
44445 G11
Rise and Fall Time vs Load Capacitance
80 70 RISE/FALL TIME (ns) 60 tr(TG) 50 tr(BG) 40 30 20 10 0 1 2 5 6 3 4 7 8 LOAD CAPACITANCE (nF) 9 10 tf(BG) tf(TG) TA = 25C VCC = BOOST = 6V TS = GND PULL-UP CURRENT (A) 3.0
Peak Driver (TG, BG) Pull-Up Current vs Temperature
OUTPUT DRIVER PULL-DOWN RESISTANCE () IPU(BG) VCC = 12V
Output Driver Pull-Down Resistance vs Temperature
2.6 BOOST-TS = 4.5V 2.4 2.2 BOOST-TS = 6V 2.0 BOOST-TS = 12V 1.8 R DS(TG) 1.6 1.4 VCC = 4.5V 1.2 VCC = 6V 1.0 0.8 0.6 VCC = 12V 0.4 RDS(BG) 0.2 0 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
44445 G15
IPU(TG) BOOST-TS = 12V 2.5
2.0 IPU(BG) VCC = 6V 1.5 IPU(TG) BOOST-TS = 6V 1.0 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
44445 G14
44445 G13
Propagation Delay vs VCC Supply Voltage
45 40 PROPAGATION DELAY (ns) 35 30 25 20 15 tPLH(BG) tPHL(TG) tPHL(BG) tPLH(TG) TA = 25C BOOST = VCC TS = GND 52 47 PROPAGATION DELAY (ns) 42 37 32 27 22 17 12 7
Propagation Delay vs Temperature
VCC = BOOST = 6V TS = GND tPLH(TG) tPHL(TG)
tPLH(BG) tPHL(BG)
10 4.5 5.5 6.5 7.5 8.5 9.5 10.5 11.5 12.5 13.5 SUPPLY VOLTAGE (V)
44445 G16
2 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
44445 G17
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LTC4444-5 TYPICAL PERFORMANCE CHARACTERISTICS
Switching Supply Current vs Input Frequency
1.8 1.6 SUPPLY CURRENT (mA) 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 0 800 200 600 400 SWITCHING FREQUENCY (kHz) 1000
44445 G18
Switching Supply Current vs Load Capacitance
1000 IVCC (BG SWITCHING AT 1MHz) IVCC (BG SWITCHING AT 500kHz)
TA = 25C VCC = BOOST = 6V TS = GND
IBOOST (TG SWITCHING) IVCC (BG SWITCHING) IVCC (TG SWITCHING) IBOOST (BG SWITCHING)
SUPPLY CURRENT (mA)
100
10
IBOOST (TG SWITCHING IBOOST AT 1MHz) (TG SWITCHING AT 1MHz) IVCC IVCC 1 (TG SWITCHING AT 500kHz) (TG SWITCHING AT 1MHz) IBOOST (BG SWITCHING AT 500kHz)
0 1 2 3 4 5 6 7 8 LOAD CAPACITANCE (nF) 9 10
44445 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. NC (Pin 5): No Connect. No connection required. 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.
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LTC4444-5 BLOCK DIAGRAM
6 3 9 VCC GND HIGH SIDE LEVEL SHIFTER LDO VINT ANTISHOOT-THROUGH PROTECTION VCC BINP NC 5
44445 BD
BOOST VCC UVLO TG TS
VIN UP TO 100V
4.5V TO 13.5V
7 8
1
TINP
VCC BG 4
2
LOW SIDE LEVEL SHIFTER
TIMING DIAGRAM
INPUT RISE/FALL TIME < 10ns TINP (BINP) BINP (TINP) BG (TG) 90% 10%
90% TG (BG) 10% tr tPHL
90% 10% tf tPLH
44445 TD
OPERATION
Overview The LTC4444-5 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). Input Stage The LTC4444-5 employs CMOS compatible input thresholds that allow a low voltage digital signal to drive standard power MOSFETs. The LTC4444-5 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 LTC4444-5 input buffers have high input impedance and draw negligible input current, simplifying the drive circuitry required for the inputs.
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LTC4444-5 OPERATION
Output Stage A simplified version of the LTC4444-5'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). Rise/Fall Time The LTC4444-5'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 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 LTC4444-5 reduces the switching losses of the power MOSFET, which increase with transition time. The LTC4444-5's high side driver is
Figure 1. Capacitance Seen by BG and TG During Switching
LTC4444-5 BOOST 6 Q1 VIN UP TO 100V
TG 7
CGD
M1
TS 8
CGS
HIGH SIDE POWER MOSFET LOAD INDUCTOR
VCC 3 Q2 CGD
BG 4
M2
GND 9
CGS
LOW SIDE POWER MOSFET
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 LTC4444-5 contains an undervoltage lockout detector that monitors VCC supply. When VCC falls below 3.55V, 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. The adaptive shootthrough protection circuitry also monitors the level of the TS pin. If the TS pin stays high, BG will be turned on 150ns after TG is turned off.
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LTC4444-5 APPLICATIONS INFORMATION
Power Dissipation To ensure proper operation and long-term reliability, the LTC4444-5 must not operate beyond its maximum temperature rating. Package junction temperature can be calculated by: TJ = TA + PD (JA) where: TJ = Junction temperature TA = Ambient temperature PD = Power dissipation JA = 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 LTC4444-5 consumes very little quiescent current. The DC power loss at VCC = 12V and VBOOST-TS = 12V is only (350A)(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 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 LTC4444-5 includes a temperature monitor that will pull BG and TG low if the junction temperature rises above 160C. Normal operation will resume when the junction temperature cools to less than 135C. Bypassing and Grounding The LTC4444-5 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 LTC4444-5: 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 LTC4444-5 switches greater than 3A peak currents and any significant ground drop will degrade signal integrity.
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LTC4444-5 APPLICATIONS INFORMATION
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 LTC4444-5 package to the board. Correctly soldered to a 2500mm2 doublesided 1oz copper board, the LTC4444-5 has a thermal resistance of approximately 40C/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 40C/W.
TYPICAL APPLICATION
LTC3780 High Efficiency 36V-72V VIN to 48V/6A Buck-Boost DC/DC Converter
VBIAS 6V VBIAS D2 24 23 22 21 20 19 18 17 16 15 14 13 VBIAS 0.1F 16V SENSE+ 10 R1 0.025 1W R2 0.025 1W
44445 TA02a
1F 16V VBIAS 3 VCC
D1 2.2F 100V 4
10k 0.022F 1000pF 220k 100pF 0.1F 100V SENSE- 100 SENSE+ 100 68pF 1 2 3 4 VOS+ 487k 1% 5 8.25k 1% 6 7 8 D5 15k 220k VIN 9 10 11 12
+
PGOOD SS SENSE+ SENSE- ITH VOSENSE SGND RUN FCB PLLFLTR PLLIN STBYMD 0.1F 16V
BOOST1
VIN 36V TO 72V C1 100F 100V
1 2 4
LTC3780EG TG1 SW1 VIN EXTVCC INTVCC BG1 PGND BG2 SW2 TG2 BOOST2
6 TINP BOOST LTC4444-5 7 TG BINP BG GND 9 TS 8
0.1F 16V 1F 16V
0.22F 16V
VOS+ 10W
47pF
10F 10V
L1 10H
D3
D4
2.2F 100V 8
+
VOUT 48V C2,C3 6A 220F 63V 2
D6
2.2F 100V, TDK C4532X7R2A225MT , C1: SANYO 100ME100HC +T C2, C3: SANYO 63ME220HC + T D1: ON SEMI MMDL770T1G D2: DIODES INC. 1N5819HW-7-F
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-
10
Efficiency
98 VIN = 36V VIN = 48V EFFICIENCY (%) 97 VIN = 72V
96
95 1 2 3 4 LOAD CURRENT (A) 5 6
44445 TA02b
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LTC4444-5 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 1 2.06 0.102 (.081 .004) 1.83 0.102 (.072 .004) 0.29 REF
2.794 (.110
0.102 .004)
0.889 (.035
0.127 .005)
0.05 REF 5.23 (.206) MIN 2.083 (.082
0.102 3.20 - 3.45 .004) (.126 - .136)
8
0.42 0.038 (.0165 .0015) TYP
0.65 (.0256) BSC
3.00 0.102 (.118 .004) (NOTE 3)
DETAIL "B" CORNER TAIL IS PART OF DETAIL "B" THE LEADFRAME FEATURE. FOR REFERENCE ONLY NO MEASUREMENT PURPOSE 0.52 (.0205) REF
8
7 65
RECOMMENDED SOLDER PAD LAYOUT
DETAIL "A" 0 - 6 TYP 4.90 0.152 (.193 .006) 3.00 0.102 (.118 .004) (NOTE 4)
0.254 (.010) GAUGE PLANE
1 0.53 0.152 (.021 .006) DETAIL "A" 0.18 (.007) SEATING PLANE 0.22 - 0.38 (.009 - .015) TYP 1.10 (.043) MAX
23
4 0.86 (.034) REF
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
0.65 (.0256) BSC
0.1016 (.004
0.0508 .002)
MSOP (MS8E) 0908 REV E
44445fa
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
LTC4444-5 TYPICAL APPLICATION
LTC3780 High Efficiency 8V-80V VIN to 12V/5A Buck-Boost DC/DC Converter
VBIAS 6V VBIAS 10k 0.1F 0.01F 20k SENSE- 100 SENSE+ 100 68pF 1 2 3 4 0.1F VOS+ 113k 1% 5 8.06k 1% 6 7 8 9 80.6k D4 220k VIN 10 11 12 D2 24 23 22 21 20 19 18 17 16 15 14 13 VBIAS 0.1F 16V SENSE+ SENSE- D5 10 0.005 1W
4444 TA03
0.22F 16V VBIAS
1F 16V 3
D1 2.2F 100V 5
+
PGOOD SS SENSE+ SENSE- ITH VOSENSE SGND RUN FCB PLLFLTR PLLIN STBYMD 0.1F
BOOST1
LTC3780EG TG1 SW1 VIN EXTVCC INTVCC BG1 PGND BG2 SW2 TG2 BOOST2
TG1 SW1 0.1F 16V 1F 16V
100pF
VCC 6 TINP BOOST LTC4444-5 2 7 TG BINP 1 4 BG GND 9 TS 8
100F 100V 2
VIN 8V TO 80V
0.22F 16V 22F 16V 3 SW1
VOS+ 10 VOUT 12V 5A
+
47pF
10F 10V
TG1 L1 8H D3
C1 330F 2
2.2F 100V, TDK C4532X7R2A225MT , 100F 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
10
RELATED PARTS
PART NUMBER LTC1693 Family LT(R)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 (30A), Stable with Small (1F) Ceramic Capacitor 100V Synchronous Switching Regulator Controller No RSENSETM, 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 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 1 Gate Drivers, Synchronizable Current Mode Control, VIN Up to 60V, Low IQ Programmable Timeout, 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 3A/2.5A Peak Output Current, 7.2V to 13.5V Gate Drive Supply, 100V Max Input Supply, Adaptive Shoot-Through Protection 3A/2.5A Peak Output Current, 7.2V to 13.5V Gate Drive Supply, 100V Max Input Supply
44445fa
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 LTC4443/LTC4443-1 High Speed Synchronous N-Channel MOSFET Drivers LTC4444 LTC4446
High Voltage Synchronous N-Channel MOSFET Driver High Voltage Synchronous N-Channel MOSFET Driver
No RSENSE is a trademark of Linear Technology Corporation.
12 Linear Technology Corporation
(408) 432-1900 FAX: (408) 434-0507
LT 1108 REV A * PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
www.linear.com
(c) LINEAR TECHNOLOGY CORPORATION 2008

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