LTC4444-5 High Voltage Synchronous N-Channel MOSFET Driver FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ DESCRIPTION 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 1.5Ω Top Gate Driver Pull-Down 0.75Ω 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 ■ ■ ■ 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. APPLICATIONS ■ The LTC®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 1.5Ω. 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 0.75Ω. Distributed Power Architectures Automotive Power Supplies High Density Power Modules Telecommunication Systems The LTC4444-5 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. 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– TYPICAL APPLICATION LTC4444-5 Driving a 1000pF Capacitive Load High Input Voltage Buck Converter VCC 4.5V TO 13.5V BINP 5V/DIV BG 5V/DIV VIN 100V BOOST VCC PWM1 (FROM CONTROLLER IC) PWM2 (FROM CONTROLLER IC) TG LTC4444-5 TS TINP BINP VOUT TINP 5V/DIV TG-TS 5V/DIV BG GND 44445 TA01a 20ns/DIV 44445 TA01b 44445fa 1 LTC4444-5 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 Junction Temperature Range (Note 2) .............................................–55°C to 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 8 7 6 5 9 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-5#PBF LTC4444EMS8E-5#TRPBF LTDPY 8-Lead Plastic MSOP –40°C to 85°C LTC4444IMS8E-5#PBF LTC4444IMS8E-5#TRPBF LTDPY 8-Lead Plastic MSOP –40°C to 85°C LTC4444MPMS8E-5#PBF LTC4444MPMS8E-5#TRPBF LTFDF 8-Lead Plastic MSOP –55°C to 125°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 ● denotes the specifications which apply over the full operating junction temperature range, otherwise specifications are at TA = 25°C. VCC = VBOOST = 6V, VTS = GND = 0V, unless otherwise noted. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS 13.5 V 320 520 μA 4.00 3.55 450 4.40 3.90 V V mV 0.1 2 μA Gate Driver Supply, VCC VCC Operating Voltage 4.5 IVCC DC Supply Current TINP = BINP = 0V UVLO Undervoltage Lockout Threshold VCC Rising VCC Falling Hysteresis ● ● 3.60 3.20 Bootstrapped Supply (BOOST – TS) IBOOST DC Supply Current TINP = BINP = 0V Input Signal (TINP, BINP) VIH(BG) BG Turn-On Input Threshold BINP Ramping High ● 2.25 2.75 3.25 V VIL(BG) BG Turn-Off Input Threshold BINP Ramping Low ● 1.85 2.3 2.75 V VIH(TG) TG Turn-On Input Threshold TINP Ramping High ● 2.25 2.75 3.25 V VIL(TG) TG Turn-Off Input Threshold TINP Ramping Low ● 1.85 2.3 2.75 V ITINP(BINP) Input Pin Bias Current ±0.01 ±2 μA 44445fa 2 LTC4444-5 ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating junction temperature range, otherwise specifications are at TA = 25°C. VCC = VBOOST = 6V, VTS = GND = 0V, unless otherwise noted. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS 250 mV High Side Gate Driver Output (TG) VOH(TG) TG High Output Voltage ITG = –10mA, VOH(TG) = VBOOST – VTG VOL(TG) TG Low Output Voltage ITG = 100mA, VOL(TG) = VTG –VTS 0.7 IPU(TG) TG Peak Pull-Up Current ● RDS(TG) TG Pull-Down Resistance ● ● 150 1 V 1.4 1.5 A 2.5 Ω 130 mV Low Side Gate Driver Output (BG) VOH(BG) BG High Output Voltage IBG = –10mA, VOH(BG) = VCC – VBG VOL(BG) BG Low Output Voltage IBG = 100mA 0.7 IPU(BG) BG Peak Pull-Up Current ● RDS(BG) BG Pull-Down Resistance ● 0.75 1.3 Ω ● 75 1.15 V 1.75 A Switching Time (BINP (TINP) is Tied to Ground While TINP (BINP) is Switching. Refer to Timing Diagram) tPLH(TG) TG Low-High Propagation Delay ● 33 55 ns tPHL(TG) TG High-Low Propagation Delay ● 24 40 ns tPLH(BG) BG Low-High Propagation Delay ● 27 45 ns tPHL(BG) BG High-Low Propagation Delay ● 15 30 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 LTC4444E-5 is guaranteed to meet specifications from 0°C to 85°C. 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-5 is guaranteed over the –40°C to 85°C operating junction temperature range. The LTC4444MP-5 is guaranteed over the full –55°C to 125°C 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 • 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. 44445fa 3 LTC4444-5 TYPICAL PERFORMANCE CHARACTERISTICS VCC Supply Quiescent Current vs Voltage TA = 25°C BOOST = 6V TS = GND 400 325 TINP = 6V, BINP = 0V 320 350 TINP = BINP = 0V 350 QUIESCENT CURRENT (μA) QUIESCENT CURRENT (μA) 400 VCC Supply Current vs Temperature 300 TINP (BINP) = 6V 250 200 150 100 TINP = 0V, BINP = 6V 300 250 200 150 100 50 50 0 0 TINP = BINP = 0V TA = 25°C VCC = 6V TS = GND VCC SUPPLY CURRENT (μA) 450 BOOST-TS Supply Quiescent Current vs Voltage 44445 G03 160 14 140 13 TINP = 0V, BINP = 6V 200 150 100 VCC = BOOST = 6V TS = GND VOL(TG) 120 100 80 VOL(BG) 60 40 TA = 25°C ITG(BG) = 100mA BOOST = VCC TS = GND 20 TINP = BINP = 0V 0 –40 –25 –10 5 20 35 50 65 80 95 110 125 TEMPERATURE (°C) TG OR BG OUTPUT VOLTAGE (V) 300 OUTPUT VOLTAGE (mV) 0 12 11 10 9 8 6 5 44445 G05 44445 G06 3.0 2.2 TA = 25°C BOOST = VCC TS = GND 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 TG OR BG INPUT THRESHOLD (V) 2.9 VIL(TG,BG) –100mA 7 Input Thresholds (TINP, BINP) vs Temperature 2.6 –1mA 3 4.5 5.5 6.5 7.5 8.5 9.5 10.5 11.5 12.5 13.5 SUPPLY VOLTAGE (V) Input Thresholds (TINP, BINP) vs Supply Voltage VIH(TG,BG) –10mA 4.5 5.5 6.5 7.5 8.5 9.5 10.5 11.5 12.5 13.5 SUPPLY VOLTAGE (V) 44445 G04 3.0 TA = 25°C BOOST = VCC TS = GND 4 Input Thresholds (TINP, BINP) Hysteresis vs Voltage VCC = BOOST = 6V TS = GND 2.8 2.7 VIH(TG,BG) 2.6 2.5 2.4 VIL(TG,BG) 2.3 2.2 2.1 2.0 –40 –25 –10 5 20 35 50 65 80 95 110 125 TEMPERATURE (°C) 44445 G08 TG OR BG INPUT THRESHOLD HYSTERESIS (mV) BOOST SUPPLY CURRENT (μA) TINP (BINP) = 6V Output High Voltage (VOH) vs Supply Voltage 350 50 TG OR BG INPUT THRESHOLD (V) 290 15 TINP = 6V, BINP = 0V 2.0 295 VCC = BOOST = 6V TS = GND 280 –40 –25 –10 5 20 35 50 65 80 95 110 125 TEMPERATURE (°C) 400 2.4 300 Output Low Voltage (VOL) vs Supply Voltage Boost Supply Current vs Temperature 2.8 305 44445 G02 44445 G01 250 TINP = BINP = 0V 310 285 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 BOOST SUPPLY VOLTAGE (V) 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 VCC SUPPLY VOLTAGE (V) 315 500 475 TA = 25°C BOOST = VCC TS = GND 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 44445fa 4 LTC4444-5 TYPICAL PERFORMANCE CHARACTERISTICS VCC Undervoltage Lockout Thresholds vs Temperature 4.2 VCC = BOOST = 6V TS = GND 4.1 475 450 425 400 Rise and Fall Time vs VCC Supply Voltage 4.0 RISING THRESHOLD 3.9 3.8 3.7 FALLING THRESHOLD 3.6 3.5 3.4 –40 –25 –10 5 20 35 50 65 80 95 110 125 TEMPERATURE (°C) 375 –40 –25 –10 5 20 35 50 65 80 95 110 125 TEMPERATURE (°C) 3.0 PULL-UP CURRENT (A) 60 tr(TG) 50 tr(BG) 40 tf(TG) 30 tf(BG) 20 IPU(TG) BOOST–TS = 12V IPU(BG) VCC = 12V 2.5 2.0 IPU(BG) VCC = 6V 1.5 IPU(TG) BOOST–TS = 6V 10 2 5 6 3 4 7 8 LOAD CAPACITANCE (nF) 9 10 1.0 –40 –25 –10 5 20 35 50 65 80 95 110 125 TEMPERATURE (°C) Propagation Delay vs VCC Supply Voltage 52 TA = 25°C BOOST = VCC TS = GND 35 30 tPLH(TG) 25 20 tPLH(BG) tPHL(TG) 15 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) 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 V = 6V CC 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 Propagation Delay vs Temperature 45 40 tf(TG) 44445 G14 44445 G13 tPHL(BG) 47 PROPAGATION DELAY (ns) 1 PROPAGATION DELAY (ns) 0 tr(BG) Output Driver Pull-Down Resistance vs Temperature Peak Driver (TG, BG) Pull-Up Current vs Temperature TA = 25°C VCC = BOOST = 6V TS = GND 70 tr(TG) 44445 G12 OUTPUT DRIVER PULL-DOWN RESISTANCE (Ω) Rise and Fall Time vs Load Capacitance 80 TA = 25°C BOOST = VCC TS = GND CL = 3.3nF 44445 G11 44445 G10 RISE/FALL TIME (ns) 34 32 30 28 26 24 22 20 18 16 14 12 10 8 6 BOOST = VCC TS = GND RISE/FALL TIME (ns) 500 VCC SUPPLY VOLTAGE (V) TG OR BG INPUT THRESHOLD HYSTERESIS (mV) Input Thresholds (TINP, BINP) Hysteresis vs Temperature VCC = BOOST = 6V TS = GND 42 37 tPLH(TG) tPHL(TG) 32 27 22 17 tPLH(BG) tPHL(BG) 12 7 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 44445fa 5 LTC4444-5 TYPICAL PERFORMANCE CHARACTERISTICS Switching Supply Current vs Input Frequency 1.6 SUPPLY CURRENT (mA) 1000 TA = 25°C VCC = BOOST = 6V TS = GND 1.4 1.2 IBOOST (TG SWITCHING) 1.0 IVCC (BG SWITCHING) 0.8 0.6 IVCC (TG SWITCHING) 0.4 SUPPLY CURRENT (mA) 1.8 Switching Supply Current vs Load Capacitance IVCC (BG SWITCHING AT 1MHz) 100 IBOOST (TG SWITCHING IBOOST AT 1MHz) (TG SWITCHING AT 1MHz) IVCC IVCC 1 (TG SWITCHING AT 500kHz) (TG SWITCHING AT 1MHz) 10 IBOOST (BG SWITCHING) 0.2 IVCC (BG SWITCHING AT 500kHz) IBOOST (BG SWITCHING AT 500kHz) 0 0 0 1000 800 200 600 400 SWITCHING FREQUENCY (kHz) 44445 G18 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. 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. 44445fa 6 LTC4444-5 BLOCK DIAGRAM 6 4.5V TO 13.5V 3 9 VCC BOOST 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 44445 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 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. 44445fa 7 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). LTC4444-5 BOOST VIN UP TO 100V 6 Q1 TG CGD 7 M1 TS CGS 8 HIGH SIDE POWER MOSFET LOAD INDUCTOR VCC 3 Q2 BG CGD 4 M2 GND CGS LOW SIDE POWER MOSFET 9 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 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. 44445fa 8 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 (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 LTC4444-5 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 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 160°C. Normal operation will resume when the junction temperature cools to less than 135°C. 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. 44445fa 9 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. 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 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. D. Keep the copper trace between the driver output pin and the load short and wide. TYPICAL APPLICATION LTC3780 High Efficiency 36V-72V VIN to 48V/6A Buck-Boost DC/DC Converter VBIAS 6V VBIAS 10k 0.022μF SENSE+ 1000pF 100pF 0.1μF 100V 1 68pF SENSE– VOS+ 487k 1% D2 D1 VBIAS 2.2μF 100V s4 3 100Ω 220k 1μF 16V 100Ω 2 47pF 15k SENSE+ SW1 SENSE– VIN 6 7 9 10 220k VIN LTC3780EG TG1 4 8 D5 SS BOOST1 3 5 8.25k 1% PGOOD 11 12 ITH EXTVCC VOSENSE INTVCC SGND RUN BG1 PGND FCB BG2 PLLFLTR SW2 PLLIN TG2 STBYMD BOOST2 24 2 22 21 0.1μF 16V 20 19 18 10μF 10V 17 4 6 TINP BOOST LTC4444-5 7 TG BINP BG TS 8 VIN 36V TO 72V C1 100μF 100V 0.22μF 16V VOS+ GND 1μF 16V 10W 9 L1 10μH D3 16 D4 2.2μF 100V s8 + VOUT 48V C2,C3 6A 220μF 63V s2 15 14 13 VBIAS D6 0.1μF 16V 0.1μF 16V 2.2μF, 100V, TDK C4532X7R2A225MT C1: SANYO 100ME100HC +T C2, C3: SANYO 63ME220HC + T D1: ON SEMI MMDL770T1G D2: DIODES INC. 1N5819HW-7-F 1 23 VCC + 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 44445 TA02a Efficiency 98 VIN = 36V EFFICIENCY (%) VIN = 48V 97 VIN = 72V 96 95 1 2 3 4 LOAD CURRENT (A) 5 6 44445 TA02b 44445fa 10 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 2.06 p 0.102 (.081 p .004) 1 0.889 p 0.127 (.035 p .005) 2.794 p 0.102 (.110 p .004) 0.29 REF 1.83 p 0.102 (.072 p .004) 0.05 REF 5.23 (.206) MIN DETAIL “B” CORNER TAIL IS PART OF DETAIL “B” THE LEADFRAME FEATURE. FOR REFERENCE ONLY NO MEASUREMENT PURPOSE 2.083 p 0.102 3.20 – 3.45 (.082 p .004) (.126 – .136) 8 0.42 p 0.038 (.0165 p .0015) TYP 3.00 p 0.102 (.118 p .004) (NOTE 3) 0.65 (.0256) BSC 8 7 6 5 0.52 (.0205) REF RECOMMENDED SOLDER PAD LAYOUT 0.254 (.010) 3.00 p 0.102 (.118 p .004) (NOTE 4) 4.90 p 0.152 (.193 p .006) DETAIL “A” 0o – 6o TYP GAUGE PLANE 1 0.53 p 0.152 (.021 p .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 p 0.0508 (.004 p .002) MSOP (MS8E) 0908 REV E 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 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 0.1μF 0.01μF SENSE+ 100pF VOS+ 113k 1% 0.1μF 1 68pF SENSE– 100Ω 2 8.06k 1% VIN 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 LTC3780EG TG1 SENSE+ SW1 SENSE– VIN 6 7 9 D4 SS 4 8 220k BOOST1 PGOOD 3 5 47pF 80.6k D1 VBIAS 3 100Ω 20k 1μF 16V 0.22μF 16V D2 10 11 12 ITH EXTVCC VOSENSE INTVCC SGND BG1 RUN PGND FCB BG2 PLLFLTR SW2 PLLIN TG2 STBYMD BOOST2 24 23 VCC 6 TINP BOOST LTC4444-5 2 7 TG BINP 2.2μF 100V s5 1 TG1 22 SW1 21 0.1μF 16V 20 19 18 10μF 10V 17 1μF 16V 4 BG TS 8 10Ω TG1 L1 8μH 100μF 100V s2 VIN 8V TO 80V VOS+ 0.22μF 16V GND 9 + D3 22μF 16V s3 + C1 330μF s2 VOUT 12V 5A SW1 16 15 14 13 0.1μF D5 VBIAS 0.1μF 16V SENSE+ SENSE– 10Ω 10Ω 0.005Ω 1W 4444 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 LTC4443/LTC4443-1 High Speed Synchronous N-Channel MOSFET Drivers LTC4444 High Voltage Synchronous N-Channel MOSFET Driver LTC4446 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 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 No RSENSE is a trademark of Linear Technology Corporation. 44445fa 12 Linear Technology Corporation LT 1108 REV A • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com © LINEAR TECHNOLOGY CORPORATION 2008