LM74700-Q1 SNOSD17 – OCTOBER 2017 1 Features 3 Description • • The LM74700-Q1 is a smart diode controller operates in conjunction with an external N-channel MOSFET as an ideal diode rectifier for low loss reverse polarity protection. The wide supply input range of 3 to 65 V allows control of many popular DC bus voltages. The device can withstand and protect the loads from negative supply voltages down to –65 V. With a low RDS(ON) external N-channel MOSFET, a very low forward voltage drop can be achieved while minimizing the amount of power dissipated in the MOSFET. For low load currents, the forward voltage is regulated to 20-mV to enable graceful shutdown of the MOSFET. External MOSFETs with 5 V or lower threshold voltage are recommended. With the enable pin low, the controller is off and draws approximately 3-µA of current. 1 • • • • • • • • • • • • Qualified for Automotive Applications AEC-Q100 Qualified With the Following Results – Device Temperature Grade 1: –40°C to +125°C Ambient Operating Temperature Range – Device HBM ESD Classification Level 2 – Device CDM ESD Classification Level C4B 3 V to 65 V Input Range –65 V Reverse Voltage Rating Charge Pump for External N-Channel MOSFET 20 mV ANODE to CATHODE Forward Voltage Drop Regulation Enable Pin Feature 3 µA Shutdown Current (EN=Low) 30 µA Operating Quiescent Current (EN=High) 1.5-A Peak Gate Turnoff Current Fast Response to Reverse Current Blocking: < 2 µs Meets Automotive ISO7637 Transient Requirements with a Suitable TVS Diode –40°C to +150°C Operating Junction Temperature 6-Pin SOT 23-6 Package (3-mm x 3-mm) The LM74700-Q1 controller provides a charge pump gate drive for an external N-channel MOSFET. The high voltage rating of LM74700-Q1 helps to simplify the system designs for automotive ISO7637 protection. Fast response to Reverse Current Blocking makes the device suitable for systems with output voltage holdup requirements during ISO7637 pulse testing as well as power fail and brownout conditions. The LM74700-Q1 is also suitable for ORing applications or AC rectification. Device Information(1) 2 Applications • • • • • • PART NUMBER LM74700-Q1 Automotive Battery Regulation Industrial Power Supplies Telecom and Datacom Systems Battery Powered System Active ORing for Redundant Power Full-Bridge Rectifier PACKAGE SOT 23-6 BODY SIZE (NOM) 2.9 mm x 1.6 mm (1) For all available packages, see the orderable addendum at the end of the data sheet. Typical Application Schematic VBAT TVS EN ANODE VCAP GATE Voltage Regulator CATHODE LM74700 GND Copyright © 2017, Texas Instruments Incorporated 1 An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications, intellectual property matters and other important disclaimers. ADVANCE INFORMATION for pre-production products; subject to change without notice. ADVANCE INFORMATION LM74700-Q1 Low IQ Always ON Smart Diode Controller LM74700-Q1 SNOSD17 – OCTOBER 2017 www.ti.com Table of Contents 1 2 3 4 5 6 7 Features .................................................................. Applications ........................................................... Description ............................................................. Revision History..................................................... Pin Configuration and Functions ......................... Specifications......................................................... 1 1 1 2 3 4 6.1 6.2 6.3 6.4 6.5 6.6 4 4 4 4 4 5 Absolute Maximum Ratings ...................................... Recommended Operating Conditions....................... Thermal Information .................................................. ESD Ratings.............................................................. Electrical Characteristics........................................... Switching Characteristics .......................................... 7.4 Device Functional Modes.......................................... 8 8 Application and Implementation ........................ 10 8.1 Application Information............................................ 10 8.2 Application Limitations ........................................... 12 9 Power Supply Recommendations...................... 13 10 Layout................................................................... 14 10.1 Layout Guidelines ................................................. 14 10.2 Layout Example .................................................... 14 11 Device and Documentation Support ................. 15 11.1 11.2 11.3 11.4 11.5 Detailed Description .............................................. 6 7.1 Overview ................................................................... 6 7.2 Functional Block Diagram ......................................... 6 7.3 Feature Description................................................... 7 Receiving Notification of Documentation Updates Community Resources.......................................... Trademarks ........................................................... Electrostatic Discharge Caution ............................ Glossary ................................................................ 15 15 15 15 15 12 Mechanical, Packaging, and Orderable Information ........................................................... 15 ADVANCE INFORMATION 4 Revision History 2 DATE REVISION NOTES October 2017 * Initial release. Submit Documentation Feedback Copyright © 2017, Texas Instruments Incorporated Product Folder Links: LM74700-Q1 LM74700-Q1 www.ti.com SNOSD17 – OCTOBER 2017 5 Pin Configuration and Functions SOT 23-6 Package 6-Pin Top View ANODE LM74700 VCAP GND GATE CATHODE EN Pin Functions I/O (1) DESCRIPTION NO. NAME 1 VCAP O Charge pump output. Connect to external charge pump capacitor 2 GND G Ground pin 3 EN I Enable pin. Can be connected to ANODE. 4 CATHODE I Cathode of the diode. Connect to the drain of the external N-channel MOSFET 5 GATE O Gate drive output. Connect to gate of the external N-channel MOSFET 6 ANODE I Anode of the diode and input power. Connect to the source of the external N-channel MOSFET. (1) ADVANCE INFORMATION PIN I = Input, O = Output, G = GND Submit Documentation Feedback Copyright © 2017, Texas Instruments Incorporated Product Folder Links: LM74700-Q1 3 LM74700-Q1 SNOSD17 – OCTOBER 2017 www.ti.com 6 Specifications 6.1 Absolute Maximum Ratings over operating free-air temperature range (unless otherwise noted) (1) ANODE to GND Input Pins MAX UNIT –65 65 V 65 V 65 V 20 V 20 V 150 °C CATHODE to GND EN to GND –65 GATE to ANODE Output Pins VCAP to ANODE Input to Output Pins ANODE to CATHODE –75 Storage temperature, Tstg (1) MIN V –40 Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability. 6.2 Recommended Operating Conditions ADVANCE INFORMATION over operating free-air temperature range (unless otherwise noted) MIN ANODE to GND Input Pins NOM MAX –60 CATHODE to GND Input to Output pins UNIT 60 60 EN to GND –60 ANODE to CATHODE –70 Operating junction temperature range, TJ V 60 V –40 150 °C 6.3 Thermal Information LM74700-Q1 THERMAL METRIC (1) DBV (SOT-23) UNIT 6 PINS RθJA Junction-to-ambient thermal resistance 189.8 °C/W RθJC(top) Junction-to-case (top) thermal resistance 103.8 °C/W RθJB Junction-to-board thermal resistance 45.8 °C/W ΨJT Junction-to-top characterization parameter 19.4 °C/W ΨJB Junction-to-board characterization parameter 45.5 °C/W (1) For more information about traditional and new thermal metrics, see the Semiconductor and IC Package Thermal Metrics application report, SPRA953. 6.4 ESD Ratings VALUE Human body model (HBM), per AEC Q100-002 (1) V(ESD) (1) Electrostatic discharge Charged device model (CDM), per AEC Q100-011 UNIT ±2000 Corner pins (VCAP, EN, ANODE, CATHODE) ±750 Other pins ±500 V JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process. 6.5 Electrical Characteristics VANODE =12 V, VCAP-VANODE =10 V over operating free-air temperature range (unless otherwise noted) PARAMETER TEST CONDITIONS MIN TYP MAX 3 15 UNIT VANODE SUPPLY VOLTAGE ISHDN 4 Shutdown Supply Current VEN = 0 V Submit Documentation Feedback µA Copyright © 2017, Texas Instruments Incorporated Product Folder Links: LM74700-Q1 LM74700-Q1 www.ti.com SNOSD17 – OCTOBER 2017 Electrical Characteristics (continued) VANODE =12 V, VCAP-VANODE =10 V over operating free-air temperature range (unless otherwise noted) PARAMETER IQ VANODE POR TEST CONDITIONS Operating quiescent current TYP MAX VEN = 3.3 V, VANODE-VCATHODE = 10 mV, VCAP=15 V 30 40 VEN = 3.3 V, VANODE-VCATHODE = 10 mV, VCAP=10 V 1.5 3 3 3.2 V 4 V Minimum operating supply voltage VANODE-VCATHODE = 100 mV Supply Voltage Charge pump enabled VCAP - VANODE = 0 V MIN UNIT µA mA ENABLE INPUT VIL Enable input low threshold 0.5 1 1.1 VIH Enable input high threshold 1.2 2 2.5 IIH Enable sink current 5 8 VEN = 12 V V µA VANODE to VCATHODE 45 50 IGATE regulation source current to IGATE regulation sink current 15 20 –10 –5 mV 5 7 mA IGATE regulation sink current to IGATE maximum sink current mV 25 mV ADVANCE INFORMATION VAK IGATE regulation source current to IGATE maximum source current GATE DRIVE Peak source current VANODE-VCATHODE = 100 mV, VGATEVANODE = 5 V Regulation max source current VANODE-VCATHODE = 35 mV, VGATEVANODE = 5 V TBD 25 TBD µA Regulation max sink current VANODE-VCATHODE = 0 mV, VGATEVANODE = 5 V TBD 1 TBD µA Peak sink current VANODE-VCATHODE = -20 mV, VGATEVANODE = 5 V IGATE RDSON discharge switch RDSON 1500 VANODE-VCATHODE = -20 mV, VGATE VANODE = 100 mV 0.8 Charge Pump source current (Charge pump on) VCAP - VANODE = 7 V 250 Charge Pump sink current (Charge pump off) VCAP - VANODE = 12 V mA 2.8 Ω CHARGE PUMP ICAP Charge pump turn on voltage VCAP 430 10 9 15 VANODE-VCATHODE = 100 mV VCAP UV hysterisis 5.6 300 µA V Charge pump turn off voltage VCAP UV release at rising edge µA 6 600 V V mV CATHODE VANODE =12 V, VANODE VCATHODE=100 mV ICATHODE CATHODE sink current VANODE =12 V, VANODE - VCATHODE= –100 mV VANODE = –12 V, VCATHODE =12 V 1.5 2 µA 1.5 2 µA 0 1 µA TYP MAX UNIT 100 µs 1 µs 6.6 Switching Characteristics over operating free-air temperature range (unless otherwise noted) PARAMETER TEST CONDITIONS ENTDLY EN (low to high) to IGATE delay Treverse Time from reverse voltage detection to VANODE-VCATHODE = 100 mV to –100 IGATE sink mV recovery MIN 0.6 Submit Documentation Feedback Copyright © 2017, Texas Instruments Incorporated Product Folder Links: LM74700-Q1 5 LM74700-Q1 SNOSD17 – OCTOBER 2017 www.ti.com 7 Detailed Description 7.1 Overview The LM74700-Q1 ideal diode control has all the features necessary to implement an efficient and fast reverse polarity protection circuit or be used in an ORing configuration while minimizing the number of external components. This easy to use ideal diode controller is paired with an external N-channel MOSFET to replace other reverse polarity schemes such as a P-channel MOSFET or a Schottky diode. An internal charge pump is used to drive the external N-Channel MOSFET to a maximum gate drive voltage of approximately 15 V. The charge pump allows the N-channel MOSFET to be enhance without refresh pulses that disable the N-channel MOSFET. The voltage drop across the MOSFET is continuously monitored between the ANODE and CATHODE pins, and the GATE to ANODE voltage is adjusted as needed to drive the N-channel MOSFET. During light load currents, the forward voltage drop of the N-channel MOSFET is regulated to 20 mV. At heavier load conditions, the MOSFET is fully enhanced and the voltage drop is proportional to the load current and RDS(ON) of the selected MOSFET. A reverse current condition is detected when there is –5 mV between the ANODE and CATHODE pin, resulting in the GATE pin being internally connected to the ANODE pin turning off the external Nchannel MOSFET, and utilizing the body diode to block any the reverse current. An enable pin (EN) is available to place the LM74700-Q1 in shutdown mode disabling the N-Channel MOSFET and minimizing the quiescent current. ADVANCE INFORMATION 7.2 Functional Block Diagram ANODE CATHODE GATE VANODE VCAP COMPARTOR + ± + ± Bias Rails 50 mV GM AMP + ± + ± GATE DRIVER ENABLE LOGIC 20 mV COMPARTOR + ± S Q R Q VANODE ENGATE VANODE VCAP_UV VCAP_UV + ± -5 mV VANODE VANODE Charge Pump Charge Pump Enable Logic VCAP ENABLE LOGIC REVERSE PROTECTION LOGIC VCAP_UV VCAP VCAP EN GND Copyright © 2017, Texas Instruments Incorporated 6 Submit Documentation Feedback Copyright © 2017, Texas Instruments Incorporated Product Folder Links: LM74700-Q1 LM74700-Q1 www.ti.com SNOSD17 – OCTOBER 2017 7.3 Feature Description 7.3.1 Input Voltage The ANODE pin is used to power the LM74700-Q1's internal circuitry, typically drawing 30 µA when enabled and 3 µA when disabled. If the ANODE pin voltage is greater then specified minimum operating voltage, the LM74700-Q1 operates in either shutdown mode or conduction mode in accordance with the EN pin voltage. The voltage from ANODE to GND is designed to vary from 65 V to –65 V, allowing the LM74700-Q1 to withstand negative voltage transients or inputs from an AC source. The charge pump supplies the voltage necessary to drive the external N-channel MOSFET. An external capacitor is placed between VCAP and ANODE to provide energy allowing the external MOSFET to be turned on quickly. In order for the charge pump to supply current to the external capacitor, the ANODE to GND voltage must be greater than the specified minimum operating voltage, and the EN pin must be above the specified input high threshold. If both of these conditions are not achieved, the charge pump remains disabled. To ensure that the external MOSFET can be driven above its specified threshold voltage, the VCAP to ANODE voltage must be above the undervoltage lockout threshold, typically 6 V, before the internal gate driver is enabled. To remove any chatter on the gate drive approximately 600 mV of hysteresis is added to the VCAP undervoltage lockout. The charge pump remains enabled until the VCAP to ANODE voltage reaches 15 V, typically, at which point the charge pump is disabled decreasing the current draw on the ANODE pin. The charge pump remains disabled until the VCAP to ANODE voltage is below to 9 V typically at which point the charge pump is enabled. The voltage between VCAP and ANODE continue to charge and discharge between 9 V and 15 V as shown in Figure 1. By enabling and disabling the charge pump, the ANODE pin current of the LM74700-Q1 is greatly reduced. The ANODE pin typically sinks 1.5 mA when the charge pump is enabled . When the charge pump is disabled the ANODE pin typically sinks 30 µA. VCAPUVLO TON TOFF VIN VANODE 0V VEN 15 V 9V VCAP-VANODE 6V GATE DRIVER ENABLE Figure 1. Charge Pump Operation Submit Documentation Feedback Copyright © 2017, Texas Instruments Incorporated Product Folder Links: LM74700-Q1 7 ADVANCE INFORMATION 7.3.2 Charge Pump LM74700-Q1 SNOSD17 – OCTOBER 2017 www.ti.com Feature Description (continued) 7.3.3 Gate Driver The gate driver is used to control the external N-Channel MOSFET by setting the GATE to ANODE voltage to the corresponding mode of operation. There are three defined modes of operation that the gate driver operates under; forward regulation, full conduction mode and reverse current protection, according to the ANODE to CATHODE voltage. Forward regulation mode, full conduction mode and reverse current protection mode are described in more detail in Regulated Conduction Mode, Full Conduction Mode and Reverse Current Protection Mode respectively. Figure 2 depicts how the modes of operation vary according to the ANODE to CATHODE voltage of the LM74700-Q1. The threshold between forward regulation mode and conduction mode is typically when the ANODE to CATHODE voltage is 50 mV. The threshold between forward regulation mode and reverse current protection mode is typically when the ANODE to CATHODE voltage is –5 mV. Reverse Current Protection Mode ADVANCE INFORMATION GATE connected to ANODE -5 mV Full Conduction Mode Forward Regulation Mode GATE connected to VCAP GATE to ANODE Voltage Regulated 0 mV 20 mV VANODE ± VCATHODE 50 mV Figure 2. Gate Driver Mode Transitions Before the gate driver is enabled the three conditions must be achieved: • The EN pin voltage must be greater than the specified input high voltage. • The VCAP to ANODE voltage must be greater than the undervoltage lockout voltage. • The ANODE voltage must be greater than the specified minimum operating voltage. If all three conditions are not achieved, the GATE pin is internally connected to the ANODE pin, assuring that the external MOSFET is disabled. Once these conditions are achieved the gate driver operates in the correct mode depending on the ANODE to CATHODE voltage. 7.3.4 Enable The LM74700-Q1 has an available enable pin, EN. The enable pin allows for the gate driver to be either enabled or disabled by an external signal. If the EN pin voltage is greater than the rising threshold, the gate driver and charge pump operates as described in Gate Driver and Charge Pump respectively. If the enable pin voltage is less than the input low threshold, the charge pump and gate driver are disabled placing the LM74700-Q1 in shutdown mode. The EN pin can withstand a voltage as large as 65 V and as little at –65 V. This allows for the EN pin to be connected directly to the ANODE pin if enable functionality is not needed. It is not recommended to leave the EN pin floating. 7.4 Device Functional Modes 7.4.1 Shutdown Mode The LM74700-Q1 enters shutdown mode when the EN pin voltage is below the specified input low threshold or the ANODE to GND voltage is below the minimum operating voltage. Both the gate driver and the charge pump are disabled in shutdown mode. During shutdown mode the LM74700-Q1 enters low IQ operation with the ANODE pin only sinking typically 3 µA and the CATHODE pin sinking typically less than 1 µA. When the LM74700-Q1 is in shutdown mode, forward current flow through the external MOSFET is not interrupted but is conducted through the MOSFET's body diode. 8 Submit Documentation Feedback Copyright © 2017, Texas Instruments Incorporated Product Folder Links: LM74700-Q1 LM74700-Q1 www.ti.com SNOSD17 – OCTOBER 2017 Device Functional Modes (continued) 7.4.2 Conduction Mode Conduction mode occurs when the gate driver is enabled. There are three regions of operating during conduction mode based on the ANODE to CATHODE voltage of the LM74700-Q1. Each of the three modes is described in Regulated Conduction Mode, Full Conduction Mode and Reverse Current Protection Mode. 7.4.2.1 Regulated Conduction Mode For the LM74700-Q1 to operate in regulated conduction mode, the gate driver must be enabled as described in Gate Driver and the current from source to drain of the external MOSFET must be within the range to result in an ANODE to CATHODE voltage drop of –5 mV to 50 mV. During forward regulation mode the ANODE to CATHODE voltage is regulated to 20 mV by adjusting the GATE to ANODE voltage. By regulation this voltage the power loss of the external MOSFET can be minimized while resulting in fast turnoff in result of any reverse current. For the LM74700-Q1 to operate in full conduction mode the gate driver must be enabled as described in Gate Driver and the current from source to drain of the external MOSFET must be large enough to result in an ANODE to CATHODE voltage drop of greater than 50 mV typically. If these conditions are achieved the GATE pin is internally connected to the VCAP pin resulting in the GATE to ANODE voltage being approximately the same as the VCAP to ANODE voltage. By connecting VCAP to GATE the external MOSFET's RDS(ON) is minimized reducing the power loss of the external MOSFET when forward currents are large. 7.4.2.3 Reverse Current Protection Mode For the LM74700-Q1 to operate in reverse current protection mode, the gate driver must be enabled as described in Gate Driver and the current of the external MOSFET must be flowing from the drain to the source. When the ANODE to CATHODE voltage is typically less than –5 mV reverse current protection mode is entered and the GATE pin is internally connected to the ANODE pin. The connection of the GATE to ANODE pin disables the external MOSFET. The body diode of the MOSFET blocks any reverse current from flowing from the drain to source. Submit Documentation Feedback Copyright © 2017, Texas Instruments Incorporated Product Folder Links: LM74700-Q1 9 ADVANCE INFORMATION 7.4.2.2 Full Conduction Mode LM74700-Q1 SNOSD17 – OCTOBER 2017 www.ti.com 8 Application and Implementation NOTE Information in the following applications sections is not part of the TI component specification, and TI does not warrant its accuracy or completeness. TI’s customers are responsible for determining suitability of components for their purposes. Customers should validate and test their design implementation to confirm system functionality. 8.1 Application Information The LM74700-Q1 is used with N-Channel MOSFET controller in a typical reverse polarity protection application. The schematic for the typical application is shown in Figure 3 where the LM74700-Q1 is used in series with a battery to drive the MOSFET Q1. The TVS is not required for the LM74700-Q1. However, they are typically used to clamp the positive and negative voltage surges respectively. The output capacitor Cout is recommended to protect the immediate output voltage collapse as a result of line disturbance. 8.1.1 Typical Application ADVANCE INFORMATION VBAT EN TVS ANODE VCAP GATE Voltage Regulator CATHODE LM74700 GND Copyright © 2017, Texas Instruments Incorporated Figure 3. Typical Application Circuit 8.1.1.1 Design Requirements For this design example, use the parameters listed in Table 1 as the input parameters Table 1. Design Parameters DESIGN PARAMETER EXAMPLE VALUE Input voltage range Max VDS of the MOSFET Output voltage Max VDS of the MOSFET Output current range Maximum drain current Output capacitance 47 µF 8.1.1.2 Detailed Design Procedure To begin the design process, determine the following: 8.1.1.2.1 Design Considerations • • • 10 Input voltage range Output current range MOSFET Gate threshold voltage Submit Documentation Feedback Copyright © 2017, Texas Instruments Incorporated Product Folder Links: LM74700-Q1 LM74700-Q1 www.ti.com SNOSD17 – OCTOBER 2017 8.1.1.2.2 MOSFET Selection The LM74700-Q1 can provide up to 15 V of gate to source voltage (VGS). The important MOSFET electrical parameters are the maximum continuous Drain current ID, the maximum drain-to-source voltage VDS(MAX), and the drain-to-source On resistance RDSON. The maximum continuous drain current, ID, rating must exceed the maximum continuous load current. The rating for the maximum current through the body diode, IS, is typically rated the same as, or slightly higher than the drain current, but body diode current only flows for a small period when the charge pump capacitor is being charged. The maximum drain-to-source voltage, VDS(MAX), must be high enough to withstand the highest differential voltage seen in the application. This would include any anticipated fault conditions. It is recommended to use MOSFETs with voltage rating up to 60 V with the LM74700-Q1. Time (2 ms/DIV) Figure 4. ISO Pulse 1 Test Setup Figure 5. Response to ISO 1 8.1.2 Selection of TVS Diodes in Automotive Reverse Polarity Applications TVS diodes can be used in automotive systems for protection against transients. In the application circuit show in Figure 6, a bi-directional TVS diode is used to clamp for positive pulses as seen in load dump and clamp for negative pulses such as seen in the ISO specs. There are two important specs: breakdown voltage and clamping voltage. Breakdown voltage is the voltage at which the TVS diode goes into avalanche similar to a zener diode and is specified at a low current value typ 1 mA. Clamping voltage is the voltage the TVS diode clamps to in high current pulse situations. In the case of an ISO 7637-2 pulse 1, the voltages go to –150 V with a generator impedance of 10 Ω. This translates to 15 A flowing through the TVS - and the voltage across the TVS would be close to its clamping voltage. A rule of thumb with TVS diode voltage selection is that the breakdown voltage should be higher than worst case steady state voltages seen in the system. TVS diodes are meant to clamp pulses and not meant for steady state voltages. The value of breakdown voltage of the TVS should be higher than 24 V which is a commonly used battery for jump start and the clamping voltage of the TVS should be upto ± 60 V. Submit Documentation Feedback Copyright © 2017, Texas Instruments Incorporated Product Folder Links: LM74700-Q1 11 ADVANCE INFORMATION 8.1.1.3 Application Curve LM74700-Q1 SNOSD17 – OCTOBER 2017 www.ti.com Q1 VBAT CIN 0.1 µF VCAP TVS 1 µF SMBJ33CA EN ANODE GATE CATHODE COUT 47 µF Voltage Regulator LM74700 VCAP GND Copyright © 2017, Texas Instruments Incorporated Figure 6. Typical Application with input Voltage Clamping The second criterion is that the abs max rating for reverse voltage of the LM74700 is not exceeded (–75 V). ADVANCE INFORMATION In case of reverse voltage pulses such as in ISO specs, the LM74700 turns the MOSFET off. When the MOSFET turns off the voltage seen by the LM74700, Anode to Cathode is - (clamping voltage of TVS (plus) the output capacitor voltage). If the max voltage on output capacitors is 16 V, then the clamping voltage of the TVS- should not exceed, 75 V – 16 V = 59 V. SMBJ33CA TVS diode can be used for TVS. The breakdown voltage and clamping voltage of TVS 36.7 V and 53.3 V respectively meets criteria one and two. As far as power levels for TVS diodes the ‘B’ in the SMBJ stands for 600 W peak power levels. This is sufficient for ISO 7637-2 pulses and suppressed load dump case (ISO-16750-2 pulse B). For unsuppressed load dumps (ISO-16750-2 pulse A) higher power TVS diodes such as SMCJ or SMDJ may be required. 8.2 Application Limitations This section highlights some limitations in the application which were identified during bench evaluation of the existing LM74700-Q1 silicon on the evaluation module (EVM). 8.2.1 ANODE to CATHODE Forward Regulation Voltage: The voltage regulation from the ANODE to CATHODE pin when in forward regulation does not match the specified value of 20 mV. Testing has shown that the actual regulation voltage is approximately 30 mV. This rise in regulation voltage still allows for the LM74700-Q1 to operate as designed, but with slightly larger power dissipation in the external MOSFET. A design fix should be included in the next version of the IC. 8.2.2 ANODE to CATHODE Reverse Current Threshold: The voltage threshold between the ANODE and CATHODE pin triggering a reverse current condition does not match the specified voltage of –5 mV. Testing has shown that the actual threshold voltage is approximately –3 mV. This rise in the reverse current threshold voltage still allows for the LM74700-Q1 to operate as designed, but the external MOSFET will turn off at a slightly lower negative current than it would at the specified voltage. The engineering samples will test ok for reverse current threshold at room temperature and at cold temperatures. However at hot temperatures, the reverse current threshold can shift positive and cause oscillations on the GATE at light load currents. These oscillations can cause stress on the MOSFET, power supply and load. We do not recommend using the engineering samples for testing at hot temperatures. 12 Submit Documentation Feedback Copyright © 2017, Texas Instruments Incorporated Product Folder Links: LM74700-Q1 LM74700-Q1 www.ti.com SNOSD17 – OCTOBER 2017 Application Limitations (continued) A design fix should be included in the next version of the IC. 8.2.3 CATHODE Pin Current: The CATHODE pin leakage current when the LM74700-Q1 is enabled is large than the specified value of 2 uA. Testing has shown that the leakage current on the CATHODE pin, when the LM74700-Q1 is enabled, is approximately 2.2 uA as compared to the specified value of 2 uA. This is due to a design change in the IC to help overall performance of the LM74700-Q1. The specified value will be changed to reflect the design change. 8.2.4 Charge Pump Turn Disable Voltage Threshold: The charge pump disable threshold is higher than the specified value of 15 V. A design fix should be included in the next version of the IC. 9 Power Supply Recommendations The LM74700-Q1 Smart Diode Controller designed for the supply voltage range of 3 V ≤ VANODE ≤ 65 V. If the input supply is located more than a few inches from the device, an input ceramic bypass capacitor higher than 0.1 μF is recommended. To prevent LM74700-Q1 and surrounding components from damage under the conditions of a direct output short circuit, it is necessary to use a power supply having over load and short circuit protection. Submit Documentation Feedback Copyright © 2017, Texas Instruments Incorporated Product Folder Links: LM74700-Q1 13 ADVANCE INFORMATION Testing has shown that the charge pump is never disabled when the LM74700-Q1 is enabled. This rise in the threshold voltage will increase operating current on the ANODE pin pins substantially. The current drawn on the ANODE pin when the LM74700-Q1 is enabled will be approximately 1 mA. LM74700-Q1 SNOSD17 – OCTOBER 2017 www.ti.com 10 Layout 10.1 Layout Guidelines • • • • • • Connect ANODE, GATE and CATHODE pins of LM74700-Q1 close to the MOSFET's SOURCE, GATE and DRAIN pins respectively. The high current path of for this solution is through the MOSFET, therefore it is important to use thick traces for source and drain of the MOSFET to minimize resistive losses. The charge pump capacitor Vcap must be kept away from the MOSFET to lower the thermal effects on the capacitance value. The Gate Drive and Gate pull down pins of the LM74700-Q1 must be connected to the MOSFET gate without using vias. Avoid excessively thin traces to the Gate Drive. Obtaining acceptable performance with alternate layout schemes is possible, however the layout shown in has been shown to produce good results and is intended as a guideline. Keep the GATE Drive pin close to the MOSFET to avoid further reduce MOSFET turn-off delay. 10.2 Layout Example ADVANCE INFORMATION 14 Submit Documentation Feedback Copyright © 2017, Texas Instruments Incorporated Product Folder Links: LM74700-Q1 LM74700-Q1 www.ti.com SNOSD17 – OCTOBER 2017 11 Device and Documentation Support 11.1 Receiving Notification of Documentation Updates To receive notification of documentation updates, navigate to the device product folder on ti.com. In the upper right corner, click on Alert me to register and receive a weekly digest of any product information that has changed. For change details, review the revision history included in any revised document. 11.2 Community Resources The following links connect to TI community resources. Linked contents are provided "AS IS" by the respective contributors. They do not constitute TI specifications and do not necessarily reflect TI's views; see TI's Terms of Use. TI E2E™ Online Community TI's Engineer-to-Engineer (E2E) Community. Created to foster collaboration among engineers. At e2e.ti.com, you can ask questions, share knowledge, explore ideas and help solve problems with fellow engineers. 11.3 Trademarks E2E is a trademark of Texas Instruments. 11.4 Electrostatic Discharge Caution These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam during storage or handling to prevent electrostatic damage to the MOS gates. 11.5 Glossary SLYZ022 — TI Glossary. This glossary lists and explains terms, acronyms, and definitions. 12 Mechanical, Packaging, and Orderable Information The following pages include mechanical, packaging, and orderable information. This information is the most current data available for the designated devices. This data is subject to change without notice and revision of this document. For browser-based versions of this data sheet, refer to the left-hand navigation. Submit Documentation Feedback Copyright © 2017, Texas Instruments Incorporated Product Folder Links: LM74700-Q1 15 ADVANCE INFORMATION Design Support TI's Design Support Quickly find helpful E2E forums along with design support tools and contact information for technical support. PACKAGE OPTION ADDENDUM www.ti.com 18-Nov-2017 PACKAGING INFORMATION Orderable Device Status (1) Package Type Package Pins Package Drawing Qty Eco Plan Lead/Ball Finish MSL Peak Temp (2) (6) (3) Op Temp (°C) Device Marking (4/5) LM74700QDBVRQ1 PREVIEW SOT-23 DBV 6 2500 TBD Call TI Call TI -40 to 125 LM74700QDBVTQ1 PREVIEW SOT-23 DBV 6 250 TBD Call TI Call TI -40 to 125 PLM74700QDBVTQ1 ACTIVE SOT-23 DBV 6 250 TBD Call TI Call TI -40 to 125 (1) The marketing status values are defined as follows: ACTIVE: Product device recommended for new designs. LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect. NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design. PREVIEW: Device has been announced but is not in production. Samples may or may not be available. OBSOLETE: TI has discontinued the production of the device. (2) RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may reference these types of products as "Pb-Free". RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption. Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of <=1000ppm threshold. Antimony trioxide based flame retardants must also meet the <=1000ppm threshold requirement. (3) MSL, Peak Temp. - The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature. (4) There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device. (5) Multiple Device Markings will be inside parentheses. Only one Device Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a continuation of the previous line and the two combined represent the entire Device Marking for that device. (6) Lead/Ball Finish - Orderable Devices may have multiple material finish options. Finish options are separated by a vertical ruled line. Lead/Ball Finish values may wrap to two lines if the finish value exceeds the maximum column width. Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals. TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release. 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