LTC4446EMS8E-PBF

FEATURES n n n n n n n n n n n n n LTC4446 High Voltage High Side/ Low Side N-Channel MOSFET Driver 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 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. 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. The LTC4446 is available in the thermally enhanced 8-lead MSOP package. 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– 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 APPLICATIONS n n n n 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 Two Switch Forward Converter VCC 7.2V TO 13.5V BOOST VCC PWM1 (FROM CONTROLLER IC) PWM2 (FROM CONTROLLER IC) TINP BINP GND TG LTC4446 TS BG VIN 36V TO 72V (100V ABS MAX) LTC4446 Driving a 1000pF Capacitive Load BINP 5V/DIV BG 10V/DIV TINP 5V/DIV TG-TS 10V/DIV 20ns/DIV 4446 TA01a 4446 TA01b • • TO SECONDARY CIRCUIT 4446f 1 LTC4446 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 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 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 LTC4446EMS8E#PBF LTC4446IMS8E#PBF TAPE AND REEL LTC4446EMS8E#TRPBF LTC4446IMS8E#TRPBF PART MARKING* LTDPZ LTDPZ PACKAGE DESCRIPTION 8-Lead Plastic MSOP 8-Lead Plastic MSOP TEMPERATURE RANGE –40°C to 85°C –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/ 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 CONDITIONS MIN 7.2 TINP = BINP = 0V VCC Rising VCC Falling Hysteresis TINP = BINP = 0V BINP Ramping High BINP Ramping Low TINP Ramping High TINP Ramping Low l l l l l l ELECTRICAL CHARACTERISTICS TYP MAX 13.5 550 7.20 6.70 UNITS V μA V V mV μA V V V V μA V mV A Ω 4446f 6.00 5.60 350 6.60 6.15 450 0.1 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) 2 3.25 2.75 3.25 2.75 ±2 2.25 1.85 2.25 1.85 2.75 2.3 2.75 2.3 ±0.01 0.7 120 2.5 1.2 ITG = –10mA, VOH(TG) = VBOOST – VTG ITG = 100mA, VOL(TG) = VTG –VTS l l l 220 2.2 1.7 2 LTC4446 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 IBG = –10mA, VOH(BG) = VCC – VBG IBG = 100mA MIN TYP 0.7 55 3 0.55 25 22 19 14 10 –3 8 80 5 50 6 60 3 30 MAX UNITS V mV A Ω ns ns ns ns ns ns ns ns ns ns ns ns ns ns ELECTRICAL CHARACTERISTICS l l l 110 1.1 45 40 35 30 35 25 2 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 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 VCC Supply Quiescent Current vs Voltage 450 400 QUIESCENT CURRENT (μA) 350 300 250 200 150 100 50 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 VCC SUPPLY VOLTAGE (V) 4446 G01 BOOST-TS Supply Quiescent Current vs Voltage 400 350 QUIESCENT CURRENT (μA) 300 250 200 150 100 50 TINP = BINP = 0V 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 BOOST SUPPLY VOLTAGE (V) 4446 G02 VCC Supply Current vs Temperature 380 370 VCC SUPPLY CURRENT (μA) 360 TINP = BINP = 0V 350 340 330 TINP(BINP) = 12V 320 310 300 –40 –25 –10 5 20 35 50 65 80 95 110 125 TEMPERATURE (°C) 4446 G03 TA = 25°C BOOST = 12V TS = GND TINP = BINP = 0V TA = 25°C VCC = 12V TS = GND TINP = 12V, BINP = 0V VCC = BOOST = 12V TS = GND TINP(BINP) = 12V TINP = 0V, BINP = 12V 4446f 3 LTC4446 TYPICAL PERFORMANCE CHARACTERISTICS Boost Supply Current vs Temperature 400 BOOST SUPPLY CURRENT (μA) 350 300 250 200 150 100 50 TINP = BINP = 0V 0 –40 –25 –10 5 20 35 50 65 80 95 110 125 TEMPERATURE (°C) 4446 G04 Output Low Voltage (VOL) vs Supply Voltage 160 VOL(TG) TG OR BG OUTPUT VOLTAGE (V) 140 OUTPUT VOLTAGE (mV) 120 100 80 VOL(BG) 60 40 20 0 7 8 9 12 11 10 SUPPLY VOLTAGE (V) 13 14 4446 G05 Output High Voltage (VOH) vs Supply Voltage 15 14 13 12 11 10 9 8 7 6 5 7 8 11 10 9 12 SUPPLY VOLTAGE (V) 13 14 –100mA –1mA –10mA TA = 25°C BOOST = VCC TS = GND VCC = BOOST = 12V TS = GND TINP = 12V BINP = 0V TINP = 0V BINP = 12V TA = 25°C ITG(BG) = 100mA BOOST = VCC TS = GND 4446 G06 Input Thresholds (TINP BINP) vs , Supply Voltage 3.1 3.0 TG OR BG INPUT THRESHOLD (V) 2.9 2.8 2.7 2.6 2.5 2.4 2.3 2.2 2.1 7 8 11 10 9 12 SUPPLY VOLTAGE (V) 13 14 VIL(TG,BG) TG OR BG INPUT THRESHOLD (V) TA = 25°C BOOST = VCC TS = GND VIH(TG,BG) 3.0 Input Thresholds (TINP BINP) vs , Temperature TG OR BG INPUT THRESHOLD HYSTERESIS (mV) VCC = BOOST = 12V 2.9 TS = GND 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) 4446 G08 Input Thresholds (TINP BINP) , Hysteresis vs Voltage 500 TA = 25°C VCC = BOOST TS = GND VIH(TG,BG) 475 450 VIL(TG,BG) 425 400 375 7 8 11 10 9 12 SUPPLY VOLTAGE (V) 13 14 4446 G07 4446 G09 Input Thresholds (TINP BINP) , Hysteresis vs Temperature TG OR BG INPUT THRESHOLD HYSTERESIS (mV) 500 VCC = BOOST = 12V TS = GND VCC SUPLLY VOLTAGE (V) 6.7 6.6 6.5 6.4 6.3 6.2 6.1 375 –40 –25 –10 5 20 35 50 65 80 95 110 125 TEMPERATURE (°C) 4446 G10 VCC Undervoltage Lockout Thresholds vs Temperature BOOST = VCC TS = GND RISING THRESHOLD 32 30 28 26 24 22 20 18 16 14 12 10 8 6 Rise and Fall Time vs VCC Supply Voltage TA = 25°C BOOST = VCC TS = GND CL = 3.3nF 475 tr(TG) 450 RISE/FALL TIME (ns) tr(BG) 425 FALLING THRESHOLD tf(TG) 400 tf(BG) 7 8 11 10 9 12 SUPPLY VOLTAGE (V) 13 14 6.0 –40 –25 –10 5 20 35 50 65 80 95 110 125 TEMPERATURE (°C) 4446 G11 4446 G12 4446f 4 LTC4446 TYPICAL PERFORMANCE CHARACTERISTICS Rise and Fall Time vs Load Capacitance 80 70 RISE/FALL TIME (ns) 60 50 tr(BG) 40 30 20 10 0 1 2 tf(BG) 5 6 3 4 7 8 LOAD CAPACITANCE (nF) 9 10 tf(TG) TA = 25°C VCC = BOOST = 12V TS = GND PULL-UP CURRENT (A) tr(TG) 3.4 3.2 3.0 2.8 2.6 IPU(TG) 2.4 2.2 2.0 –40 –25 –10 5 20 35 50 65 80 95 110 125 TEMPERATURE (°C) 4446 G14 Peak Driver (TG, BG) Pull-Up Current vs Temperature VCC = BOOST = 12V TS = GND IPU(BG) OUTPUT DRIVER PULL-DOWN RESISTACNE (Ω) 2.0 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 Output Driver Pull-Down Resistance vs Temperature BOOST-TS = 12V BOOST-TS = 7V RDS(TG) BOOST-TS = 14V VCC = 12V VCC = 7V VCC = 14V RDS(BG) 0 –40 –25 –10 5 20 35 50 65 80 95 110 125 TEMPERATURE (°C) 4446 G15 4445 G13 Propagation Delay vs VCC Supply Voltage 30 28 PROPAGATION DELAY (ns) 26 24 22 20 18 16 14 12 10 7 8 11 10 9 12 SUPPLY VOLTAGE (V) 13 14 tPHL(BG) tPHL(TG) tPLH(BG) tPLH(TG) TA = 25°C BOOST = VCC TS = GND PROPAGATION DELAY (ns) 37 32 27 22 Propagation Delay vs Temperature VCC = BOOST = 12V TS = GND tPLH(TG) tPHL(TG) tPLH(BG) 17 tPHL(BG) 12 7 2 –40 –25 –10 5 20 35 50 65 80 95 110 125 TEMPERATURE (°C) 4446 G17 4444 G16 Switching Supply Current vs Input Frequency 4.0 3.5 SUPPLY CURRENT (mA) 3.0 2.5 2.0 1.5 1.0 0.5 0 IBOOST (BG SWITCHING) 0 200 400 800 600 SWITCHING FREQUENCY (kHz) 1000 4446 G18 Switching Supply Current vs Load Capacitance IVCC (BG SWITCHING AT 1MHz) IBOOST (TG SWITCHING AT 500kHz) TA = 25°C VCC = BOOST = 12V TS = GND IVCC (BG SWITCHING) SUPPLY CURRENT (mA) IBOOST (TG SWITCHING) 100 10 IVCC (TG SWITCHING) 1 IVCC (BG SWITCHING AT 500kHz) IVCC IVCC (TG SWITCHING (TG SWITCHING AT 500kHz) AT 1MHz) IBOOST (BG SWITCHING AT 1MHz OR 5OOkHz) IBOOST (TG SWITCHING AT 1MHz) 0.1 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. 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. BLOCK DIAGRAM 6 3 9 VCC GND HIGH SIDE LEVEL SHIFTER LDO VINT BOOST VCC UVLO TG TS VIN UP TO 100V 7.2V TO 13.5V 7 8 1 TINP VCC LOW SIDE LEVEL SHIFTER NC 5 VCC BG 4 2 BINP 4446 BD 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 4444 TD 4446f 6 LTC4446 OPERATION Overview 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). 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. 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). LTC4446 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 4446 F01 LOW SIDE POWER MOSFET 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. 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. 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. 4446f 9 LTC4446 • A C 51Ω 2W 2 • • • VH • • 2 • • 1 • 10 LTC3722/LTC4446 420W 36V-72VIN to 12V/35A Isolated Full-Bridge Supply 51Ω 2W D2 3 10 D6 0.82μF 100V –VOUT VOUT VOUT 1 Si7852DP 2 7 L3 0.85μH 11 10 4 8 VH VCC 6 TINP BOOST LTC4446 7 Si7852DP 2 BINP TG D 2 BG GND TS 4 L2 150nH 9 8 0.22μF 0.47μF 0.47μF 100V 100V D4 D5 4 11 470pF 200V 47Ω 1W VOUT 12V D3 T1 5(105μH):1:1 2k 1/2W L1 1.3μH VIN VIN 36V TO 72V 1μF 100V –VIN 1μF 100V 4 12V 3 VCC 6 TINP BOOST LTC4446 7 2 BINP B TG BG GND TS 1 TYPICAL APPLICATION 4 9 8 0.22μF + 1μF 12V/35A 8 Si7852DP 2 Si7852DP 4 T2 5:5(105μH):1:1 VOUT Q1 6 D8 D9 3.3V 2.21k 6 B 9 100Ω 220pF B C 20 16 200k 3 750Ω MOC207 6 CT SPRG RLEB FB GND PGND 24 13 6.19k 33k 1M 8.25k 68nF 5 6 23 22 MMBT3904 7 SS COMP 4 D11 330pF 2.2nF 5 8 2 1 0.047μF 3 + Si7852DP ×2 7 C1, C2 180μF 16V 2 Si7852DP 4 1k ISNS 0.02Ω 1.5W Q3 1.5k 5 CSE– 2 3 0.02Ω 1.5W C3 68μF 20V 12V 100Ω 4.87k 1/4W L4 1mH D7 Q2 4.87k 1/4W 2.21k 11 Q4 1.5k 12 14 15 –VOUT VOUT –VOUT + VOUT 16 ME ME2 CSF+ LTC3901EGN CSF– MF MF2 VCC 1 PVCC GND PGND GND2 PGND2 8 4 10 13 TIMER 7 330pF VOUT –VOUT 39.2k 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 C T3 1(1.5μH):0.5 1 4 CSE+ SYNC 100Ω MMBT3904 1k • • 80.6k 0.1μF 22Ω 8 5 22pF A 11 21 OUTA OUTB OUTC OUTD OUTF OUTE 1 LTC3722EGN-1 CS ADLY PDLY 9 19 17 15 ISNS 5VREF 330Ω D 4.99k 68.1k 18.2k 80.6k 1μF 1μF D10 10V VIN 12V 4.99k 22pF 20k 1/4W 470Ω 1/4W 10k 2.7k 9.53k 22nF 150Ω 10 SBUS 18 182k VIN 12 UVLO VREF 8 5.1k 220pF 180pF 1 DPRG NC SYNC 220pF 5VREF 14 20k 2 V LT1431CS8 COLL REF C4 2.2nF 250V D12 5.1V GND-F GND-S 6 5 8 2.49k –VOUT 4446 TA02a 1μF 30.1k 0.47μF 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 1 2.06 ± 0.102 (.081 ± .004) 1.83 ± 0.102 (.072 ± .004) 2.794 ± 0.102 (.110 ± .004) 0.889 ± 0.127 (.035 ± .005) 5.23 (.206) MIN 2.083 ± 0.102 3.20 – 3.45 (.082 ± .004) (.126 – .136) 8 3.00 ± 0.102 (.118 ± .004) (NOTE 3) 0.42 ± 0.038 (.0165 ± .0015) TYP 0.65 (.0256) BSC 8 7 65 0.52 (.0205) REF RECOMMENDED SOLDER PAD LAYOUT DETAIL “A” 0° – 6° TYP 1 0.53 ± 0.152 (.021 ± .006) DETAIL “A” 0.18 (.007) SEATING PLANE 0.22 – 0.38 (.009 – .015) TYP 0.1016 ± 0.0508 (.004 ± .002) MSOP (MS8E) 0307 REV D 0.254 (.010) GAUGE PLANE 4.90 ± 0.152 (.193 ± .006) 3.00 ± 0.102 (.118 ± .004) (NOTE 4) 23 4 0.86 (.034) REF 1.10 (.043) MAX 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 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 VIN 0V TO 100V 6 0.33μF BZX84C12L 12V 0.01μF BAS21 100V BAS21 3 15k 200Ω 4.7k 100k MMBT2369 4.7nF 1 VCC BOOST 7 TG TINP LTC4446 2 8 TS BINP 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 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 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 No RSENSE is a trademark of Linear Technology Corporation. 4446f 12 Linear Technology Corporation (408) 432-1900 ● FAX: (408) 434-0507 ● LT 0508 • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 www.linear.com © LINEAR TECHNOLOGY CORPORATION 2008