LTC7000JMSE#WTRPBF

LTC7000/LTC7000-1 Fast 150V Protected High Side NMOS Static Switch Driver FEATURES DESCRIPTION Wide Operating VIN: 3.5V to 135V (150V Abs Max) n 1Ω Pull-Down, 2.2Ω Pull-Up for Fast Turn-On and Turn-Off Times with 35ns Propagation Delays n Internal Charge Pump for 100% Duty Cycle n Short-Circuit Protected n Adjustable Current Trip Threshold (LTC7000) n Current Monitor Output (LTC7000) n Automatic Restart Timer n Open-Drain Fault Flag n Adjustable Turn-On Slew Rate n Gate Driver Supply from 3.5V to 15V n Adjustable V Undervoltage and Overvoltage IN Lockouts (LTC7000) n Adjustable Driver Supply V CC Undervoltage Lockout n Low Shutdown Current: 1µA n CMOS Compatible Input n Thermally Enhanced, High Voltage Capable 16-Lead MSOP Packages n AEC-Q100 Qualified for Automotive Applications The LTC®7000/LTC7000-1 is a fast high side N-channel MOSFET gate driver that operates from input voltages up to 135V. It contains an internal charge pump that fully enhances an external N-channel MOSFET switch, allowing it to remain on indefinitely. n APPLICATIONS Static Switch Driver n Load and Supply Switch Driver n Electronic Valve Driver n High Frequency High Side Gate Driver n Its powerful driver can easily drive large gate capacitances with very short transition times, making it well suited for both high frequency switching applications or static switch applications that require a fast turn-on and/or turn-off time. When an internal comparator senses that the switch current has exceeded a preset level, a fault flag is asserted and the switch is turned off after a period of time set by an external timing capacitor. After a cooldown period, the LTC7000/LTC7000-1 automatically retries. The LTC7000/LTC7000-1 is available in the thermallyenhanced 16-lead MSOP packages. LTC7000 LTC7000-1 16-Lead MSOP MSE16 16-Lead MSOP MSE16(12) High Voltage Pin Spacing 0.157mm 0.657mm RUN/OVLO/ISET/IMON Pins Yes No Package All registered trademarks and trademarks are the property of their respective owners. TYPICAL APPLICATION High Side Switch with 100% Duty Cycle and Overcurrent Protection Turn-On Transient Waveform VIN 3.5V TO 135V VCC 1µF 100k 1nF OFF ON VIN = 135V SNS+ VIN LTC7000-1 SNS– FAULT TGUP TIMER TGDN BST INP VCCUV GND TS 0.007Ω 100Ω 0.1µF LOAD 3.5V TO 135V 3A CONTINUOUS MAX 7000 TA01a VINP 2V/DIV VLOAD 50V/DIV 20ns/DIV 7000 TA01b Rev. E Document Feedback For more information www.analog.com 1 LTC7000/LTC7000-1 TABLE OF CONTENTS Features............................................................................................................................. 1 Applications........................................................................................................................ 1 Typical Application ................................................................................................................ 1 Description......................................................................................................................... 1 Absolute Maximum Ratings...................................................................................................... 3 Pin Configuration.................................................................................................................. 3 Order Information.................................................................................................................. 3 Electrical Characteristics......................................................................................................... 5 Typical Performance Characteristics........................................................................................... 7 Pin Functions....................................................................................................................... 9 Block Diagram.....................................................................................................................10 Timing Diagram...................................................................................................................11 Operation..........................................................................................................................11 Applications Information........................................................................................................13 Package Description.............................................................................................................27 Revision History..................................................................................................................29 Typical Application...............................................................................................................30 Related Parts......................................................................................................................30 Rev. E 2 For more information www.analog.com LTC7000/LTC7000-1 ABSOLUTE MAXIMUM RATINGS (Note 1) Supply Voltages VIN........................................................ –0.3V to 150V BST-TS.................................................... –0.3V to 15V VCC......................................................... –0.3V to 15V TS Voltage................................................... –6V to 150V BST, SNS+ and SNS– Voltages ................. –0.3V to 150V SNS+ – SNS– Continuous.......................................... –0.3V to +0.3V The VCC pin provides the power for the MOSFET gate drivers and internal circuitry. The LTC7000/LTC7000-1 features an internal P-channel low dropout regulator (LDO) that can supply power at VCC from the VIN supply pin or VCC can be driven from an external power supply. If the internal P-channel LDO is used to power VCC, it must have a minimum 1.0µF low ESR ceramic capacitor to ensure stability and should not be connected to any other circuitry other than optionally biasing some pins on the LTC7000/LTC7000-1 (FAULT, INP or TIMER). Maximum switching frequency with internal LDO < BST TS VCC Generation 30µA 2 • MOSFET Q G ≅ 500Hz A Schottky diode should not be used between VCC and BST, as the reverse leakage of the Schottky diode at hot will be more current than the charge pump can overcome. Some example silicon diodes with low leakage include: • MMBD1501A - Fairchild Semiconductor • CMPD3003 - Central Semiconductor 1mA 2 • MOSFET Q G ≅ 20kHz For higher gate charge applications, an external silicon diode between VCC and BST should be used and VCC can be driven from a high efficiency external supply. VCC should never be driven higher than VIN or permanent damage to the LTC7000/LTC7000-1 could occur. VCC Undervoltage Comparator The LTC7000/LTC7000-1 contains an adjustable undervoltage lockout (UVLO) on the VCC voltage that pulls TGDN to TS and can be easily programmed using a resistor (RVCCUV) between the VCCUV pin and ground. The voltage generated on VCCUV by RVCCUV and the internal 10µA current source set the VCC UVLO. The rising VCC UVLO is internally limited within the range of 3.5V and 10.5V. If VCCUV is open the rising VCC UVLO is set internally to 7.0V. The typical value of resistor for a particular rising VCC UVLO can be selected using Figure 11 or the following equation: R VCCUV = Rising VCC UVLO 70µA Rev. E 18 For more information www.analog.com LTC7000/LTC7000-1 APPLICATIONS INFORMATION Limiting Inrush Current During Turn-On Where 3.5V < Rising VCC UVLO < 10.5V. 11 10 9 VCC UVLO (V) 8 7 6 5 4 3 2 RISING VCC UVLO FALLING VCC UVLO 1 0 0 30 60 90 120 150 180 210 240 VCCUV RESISTOR TO GROUND (kΩ) 7000 F11 Figure 11. VCCUV Resistor Selection MOSFET Selection The most important parameters in high voltage applications for MOSFET selection are the breakdown voltage BVDSS, on-resistance RDS(ON) and the safe operating area, SOA. The MOSFET, when off, will see the full input range of the input power supply plus any additional ringing than can occur when driving inductive loads. Driving large capacitive loads such as complex electrical systems with large bypass capacitors should be powered using the circuit shown in Figure 12. The pull-up gate drive to the power MOSFET from TGUP is passed through an RC delay network, RG and CG, which greatly reduces the turn-on ramp rate of the MOSFET. Since the MOSFET source voltage follows the gate voltage, the load is powered smoothly from ground. This dramatically reduces the inrush current from the source supply and reduces the transient ramp rate of the load allowing for slower activation of sensitive electrical loads. The turn-off of the MOSFET is not affected by the RC delay network as the pull-down for the MOSFET gate is directly from the TGDN pin. Note that the voltage rating on capacitor CG needs to be the same or higher than the external MOSFET and CLOAD. Adding CG to the gate of the external MOSFET can cause high frequency oscillation. A low power, low ohmic value resistor (10Ω) should be placed in series with CG to dampen the oscillations as shown in Figure 12 whenever CG is used in an application. Alternatively, the low ohmic value resistor can be placed in series with the gate of the external MOSFET. External conduction losses are minimized when using low RDS(ON) MOSFETs. Since many high voltage MOSFETs have higher threshold voltages (typical VTH ≥ 5V) and RDS(ON) is directly related to the (VGS–VTH) of the MOSFET, the LTC7000/LTC7000-1 maximum gate drive of greater than 10V makes it an ideal solution to minimize external conduction losses associated with external high voltage MOSFETs. SOA is specified in Typical Characteristic curves in power N-channel MOSFET data sheets. The SOA curves show the relationship between the voltages and current allowed in a timed operation of a power MOSFET without causing damage to the MOSFET. The overcurrent trip point (RSNS and RISET) of the LTC7000/LTC7000-1 and TIMER capacitor should be chosen to stay within the SOA region of the MOSFET selected for the application. LTC7000/ LTC7000-1 VIN SNS+ SNS– TGUP TGDN RFLT RSNS RG 100k BST TS CB 1µF 7000 F12 10Ω CG 0.047µF CLOAD 100µF LOAD Figure 12. Powering Large Capacitive Loads The values for RG and CG to limit the inrush current can be calculated from the below equation: IIN _ RUSH ≅ 0.7 • 12V • CLOAD R G • CG Rev. E For more information www.analog.com 19 LTC7000/LTC7000-1 APPLICATIONS INFORMATION For the values shown in Figure 12 the inrush current will be: IIN _ RUSH ≅ 0.7 • 12V • 100µF 100kΩ • 0.047µF ≅ 180mA Correspondingly, the ramp rate at the load for the circuit in Figure 12 is approximately: Δ VLOAD ΔT ≅ 0.7 • 12V R G • CG ≅ 2V / ms Reverse Current Protection To protect the load from discharging back into VIN when the external MOSFET is off and the VIN voltage drops below the load voltage, two external N-channel MOSFETs should be used and must be configured in a back-to-back arrangement as shown in Figure  14. Dual N-channel packages such as the Vishay/Siliconix Si7956DP are a good choice for space saving designs. VIN When CG is added to the circuit in Figure 12, the value of the bootstrap capacitor, CB, must be increased to be able to supply the charge to both to MOSFET gate and capacitor CG. The relationship for CB that needs to be maintained when CG is used is given by: LTC7000/ LTC7000-1 SNS– TGUP INP M1A M1B LOAD Figure 14. Protecting Load from Voltage Drops on VIN When turning off a power MOSFET that is connected to an inductive load (inductor, long wire or complex load), the TS pin can be pulled below ground until the current in the inductive load has completely discharged. The TS pin is tolerant of voltages down to –6V, however, an optional Schottky diode with a voltage rating at least as high as the load voltage should be connected between TS and ground to prevent discharging the load through the TS pin of the LTC7000/LTC7000-1. See Figure 13. VIN SNS+ RSNS RFLT TGUP M1A TGDN L1 TS 7000 F13 RSNS TS 7000 F14 Optional Schottky Diode Usage on TS SNS– RFLT TGDN MOSFET Q G CB > + 10 • C G 1V LTC7000/ LTC7000-1 SNS+ LOAD D2 Figure 13. Optional Schottky Diode Usage Design Example As a design example, consider a fast power supply switch with the following specifications: VIN = VLOAD = 8V to 135V, ILOAD = 3A, Insertion Loss < 0.5W at room temp with maximum load, output rise time with a 1µF load is 1V/µs (1A inrush current) and a shorted load should immediately turn off the MOSFET. The first item to select is the N-channel MOSFET. The IRF7815PBF is selected because it has sufficient breakdown voltage (BVDSS_MIN = 150V), sufficient continuous current rating for a 3A load (ID_MAX = 4.1A) and the on-resistance is low enough (RDS(ON)_MAX = 43mΩ) to be able to meet the power loss specification. Examining the MOSFET data sheet, the VGS vs RDS(ON) typical performance curve shows a sharp increase in RDS(ON) as the MOSFET VGS gets below 8.0V. Since the default VCC UVLO is 7.0V, a resistor (RVCCUV ) should be placed between VCCUV and ground to increase the VCC Rev. E 20 For more information www.analog.com LTC7000/LTC7000-1 APPLICATIONS INFORMATION UVLO to 8.0V. The value of RVCCUV is calculated and rounded to the nearest standard value as follows: R VCCUV = 8.0V 70µA = 113kΩ The value of the current sense resistor, RSNS is calculated next. The LTC7000-1 has a fixed current sense threshold, ΔVTH, of 30mV typical and 22mV minimum. To provide a minimum 3A load current, the minimum specified ΔVTH = 22mV should be used for the RSNS calculation below: R SNS = 22mV = 7.3mΩ 3A The closest standard value is 7mΩ. The power dissipation of RSNS is 63mW so choose a power rating of greater than 0.25W to provide adequate margin. The next item to check is to make sure the insertion loss specification is satisfied. The insertion loss is given by: 2 ( PLOSS = ILOAD • RDS(ON)(MAX) + R SNS ) 2 = 3A • ( 0.043Ω + 0.007Ω ) = 0.45W Which meets the design specification of less than 0.5W. The fast output slew rate specification of 1V/µs into a 1µF load can be met by placing a resistor, RG, in series with the TGUP pin to the MOSFET gate, as well as connecting TGDN and a capacitor, CG, to ground on the MOSFET gate. The values of RG and TG can be calculated from the following expression: R G • CG ≅ 0.7 • 12V 1V / µs = 8.4µs CG needs to have a voltage rating as high as the BVDSS of the MOSFET. A good choice for CG is the AVX 06032C471KAT2A which has a value of 470pF and a voltage rating of 200V. RG is then calculated to be 17.8kΩ. The bootstrap capacitor CB can be calculated from the gate charge as specified in the MOSFET data sheet and CG as follows: Q 30nC CB > G + 10 • C G = + 10 • 470pF 1V 1V ≅ 0.33nF. 100nF will be used. To meet the short-circuit specification, the TIMER pin should be connected to VCC to enable immediate turn-off (approximately 70ns) of the MOSFET in the case of an overcurrent condition. If an overcurrent condition turns off the MOSFET, it will not turn back on until the INP pin has cycled low then back high. The complete circuit is shown in Figure 15. Turn–On Transient VIN 8V TO 135V SNS+ VIN VCC 1µF SNS– TIMER FAULT LTC7000-1 TGUP TGDN 100Ω 17.8k INP BST VCCUV 113k 0.1µF GND 0.007Ω IRF7815TRPBF 10Ω CG 470pF 200V TS LOAD 8V TO 135V 1µF 3A CONTINUOUS MODE VINP 5V/DIV VIN = 135V VLOAD 50V/DIV IDMOSFET 1A/DIV 50µs/DIV 7000 F15b 7000 F15 Figure 15. Design Example Rev. E For more information www.analog.com 21 LTC7000/LTC7000-1 APPLICATIONS INFORMATION PC Board Layout Considerations 1. Solder the exposed pad on the backside of the LTC7000/ LTC7000-1 packages directly to the ground plane of the board. 2. Kelvin connect the resistor. SNS+ pin to the current sense 3. Limit the resistance of the TS trace, by making it short and wide. 4. CB needs to be close to chip. 5. Always include an option in the PC board layout to place a resistor in series with the gate of any external MOSFET. High frequency oscillations are design dependent and having the option to add a series dampening resistor can save a design iteration of the PC board. Pin Creepage and Clearance In some higher voltage applications, the MSE16 package may not provide sufficient PC board trace clearance between high and low voltage pins. In applications where clearance is required, the LTC7000-1 in the MSE16(12) package can be used. The MSE16(12) package has removed pins between all the adjacent high voltage and low voltage pins, providing 0.657mm clearance, which will be sufficient for most applications. For more information, refer to the printed circuit board design standards described in IPC-2221. Rev. E 22 For more information www.analog.com LTC7000/LTC7000-1 TYPICAL APPLICATIONS Protected Redundant Supply Switchover with Shoot Through Protection 0.003Ω MAIN POWER 7V TO 135V 2× BSC320N20NS3G 2× BSC320N20NS3G LOAD 0.0015Ω 10µF 10µF 100Ω 100Ω 10Ω 10Ω 100Ω 1nF 0.1µF SNS+ VIN RUN SNS– TGDN TGUP TS 200k BST INP FAULT LTC7000 6.98k 100k 1µF GND TIMER OVLO SNS+ VIN RUN NOTE: THE BACKUP PATH WILL LATCH-OFF WITH AN OVERCURRENT FAULT. LTC7000 1µF VCC FAULT VCCUV IMON ISET 0.1µF TGDN SNS– 0.1µF BST VCC INP TIMER OVLO 1nF VBACKUP 7V TO 135V 100Ω 0.1µF 4.99k TGUP TS 0.1µF 10µF GND VCCUV IMON ISET 7000 TA02 VLOAD vs Main Power Voltage 80 VMAIN Falling Through 33V VBACKUP = 60V VTG–TS MAIN 10V/DIV VLOAD (V) 70 60 50 40 30 RLOAD = 50Ω 10 20 30 40 50 60 MAIN POWER (V) 70 VTG–TS MAIN 10V/DIV VTG–TS BACKUP 10V/DIV VTG–TS BACKUP 10V/DIV VLOAD 20V/DIV VLOAD 20V/DIV 40µs/DIV 0 VMAIN Rising Through 36V 7000 TA02c RLOAD = 50Ω 10µs/DIV 7000 TA02d 80 7000 TA02b Rev. E For more information www.analog.com 23 LTC7000/LTC7000-1 TYPICAL APPLICATIONS High Side Switch with Input Overvoltage and Overcurrent Protection VIN 3.5V TO 60V (150V TOLERANT) 10µF SNS+ VIN RUN OVLO 953k 19.6k FAULT 1µF LTC7000 100k 1nF VCC OFF ON 0.1µF ISET IMON VCCUV GND INP BSC12DN20NS3G TS TIMER 0.005Ω 100Ω SNS– TGUP TGDN BST LOAD 3.5V TO 60V 10A CONTINUOUS MAX 150k 7000 TA03a High Side Switch with Overcurrent Protection and Fault Latchoff VIN 3.5V TO 135V 10µF 100k 1µF RTIMER 10nF SNS+ VIN VCC SNS– FAULT TIMER LTC7000-1 100Ω TGUP TGDN BSC12DN20NS3G BST 0.1µF TS OFF ON 0.04Ω INP GND VCCUV LOAD 3.5V TO 135V 0.5A CONTINUOUS 7000 TA04a RTIMER = OPEN 12Ω/100ms LOAD PULSE RTIMER = 100k 12Ω/100mS LOAD PULSE RLOAD 10kΩ/DIV RLOAD 10kΩ/DIV VLOAD 10V/DIV VLOAD 10V/DIV ILOAD 1A/DIV ILOAD 1A/DIV VTIMER 1A/DIV VTIMER 1V/DIV 100ms/DIV VIN = 12V VINP = 4V 7000 TA04b 100ms/DIV 7000 TA04c VIN = 12V VINP = 4V Rev. E 24 For more information www.analog.com LTC7000/LTC7000-1 TYPICAL APPLICATIONS Average Current Trip VIN 3.5V TO 135V VINP D Q SNS+ INP SNS– TGUP TGDN RB LTC7000 FAULT 249Ω 0.06Ω SI7738DP BST 100k 0.1µF VCC VCCUV TIMER OVLO 1µF TS IMON ISET GND LOAD 3.5V TO 135V