Innovations Embedded Gate Drivers Selection Guide Gate Driver Selection Guide Overview Selecting a Gate Driver requires consideration of a number of factors. This guide will attempt to present the various options somewhat in order of importance, since for example if the driver does not meet the isolation voltage requirements it will not matter what temperature range it covers, or if it doesn't meet the temperature range needed it won't matter what level of output current can be delivered and so forth. MOSFET. For a single MOSFET as shown below anything over 1.5 W is sufficient. However, when driving a Power Module (such as the BSM120D12P2C005) at 100 kHz approximately 3W is needed. If you decide to use an 'offthe-shelf' supply choose one with low-capacitance between primary and secondary. Some manufacturers offer DC / DC converters made specifically for Gate Drive applications. The 'Isolated DC / DC Power Supply' is responsible for providing the secondary voltage(s) used to drive the gate of the MOSFET. The isolation voltage rating of this supply needs to be appropriate for the application. In addition, it should have very low capacitance from primary to secondary. The power needed for this supply is dependent on the operating frequency of the Gate Driver and the input capacitance of the For those waiting to build their own isolated supply, ROHM offers Gate Drivers with built-in controllers (BM60051FV, 52FV, 54FV) and a Power Supply IC with integrated MOSFET (BD7F100HFN) which may be helpful. The isolation transformer needs to have low capacitance between primary and secondary (5 pF or so). Also keep in mind that agency approvals of a custom isolation transformer may take months. Figure 1. Typical Gate Driver (BM60015FV) and Support Circuitry 2 Gate Driver Selection Guide Key Gate Driver Characteristics: Isolation Voltage: At the present time ROHM Gate Drivers are available in 2500 Vrms or 3750 Vrms ratings. What this means is that the devices have been tested in accordance with UL 1577 at either 2500 Vrms or 3750 Vrms for 60 seconds without failure. The insulation system is classified as BASIC INSULATION, recognized under UL File Number E181974. 100% of production parts rated at 2500 Vrms are tested at 3000 Vrms for 1 second. 100% of production parts rated for 3750 Vrms are tested at 4500 Vrms for 1 second. Creepage and Clearance: Creepage is defined as the shortest distance along the surface of the insulating material between two conductive surfaces. For ROHM parts rated at 2500 Vrms the creepage distance is 6.2 mm. For parts rated at 3750 Vrms the creepage distance is 8.2 mm. Clearance distance will normally be the same as creepage unless something in the PCB layout is compromised. Dirty environments require more creepage. The 'Working Voltage' between the primary side (left) and secondary side (right) is significantly less than the rated voltage. The allowable working voltage is highly dependent on the “Pollution Degree” of the environment, or in other words how dirty of an environment the product is expected to see. Figure 2 shows definitions in accordance with IEC 60664-1: Pollution Degree Categories • Pollution Degree 1 No pollution or only dry, non-conductive pollution occurs. The pollution has no effect. • Pollution Degree 2 Normally only non-conductive pollution occurs, except that occasionally temporary conductivity caused by condensation can be expected. • Pollution Degree 3 Conductive pollution or dry non-conductive pollution that becomes conductive due to condensation occurs. • Pollution Degree 4 Persistent conductivity occurs due to conductive dust, rain, or snow. * Source: IEC 60664-1, Ed. 1.2, Clause 2.5.1 Figure 2 As a general guideline (for clean environments categorized as Pollution Degrees 1 or 2) from DIN EN 60747-5-2, if the DC Link (DC Bus) voltage is expected to be 566 VDC or less 2500 Vrms rated parts can be used. And for DC Link voltages greater than 566 V but less than 891 V 3750 Vrms rated parts are recommended. Currently we cannot support applications with a DC Link voltage greater than 891 VDC. 3 Gate Driver Selection Guide Temperature Range: Miller Clamp: Most ROHM Gate Drivers are rated for operation at ambient temperatures from -40° C to 125° C. A few (such as the BM6105FW and BM60015FV) are rated from -40° C to 105° C. The maximum junction temperature for all our Gate Drivers is +150° C. Most power applications involve half-bridge, full-bridge, or three half-bridge topologies. When the upper transistor is switched ON the drain of the lower transistor experiences a very rapid dV/ dT transition. Capacitance between the lower transistor’s gate and drain tends to turn ON the lower device when it is supposed to be OFF. Likewise, when the upper transistor is switched OFF and the lower transistor is switched ON if the upper turns on the result can be catastrophic. Output Current: ROHM Gate Drivers provide peak output currents from 1A to 5A. The amount of current required is directly related to the required Gate Charge (Qg) and operating speed. Power Modules (with multiple devices inside) will almost certainly require adding a high current buffer stage following the Gate Driver. This is generally accomplished with a pair of bipolar transistors and a few resistors. A good article regarding gate charge information can be found here. One way to prevent this from happening is by clamping the device’s gate to source with a low impedance clamp (called a Miller Clamp). This can be achieved using a small external MOSFET. Some of ROHM’s drivers such as the BM6105FW and BM60051FV series include a built-in MOSFET Miller Clamps pass current if a positive voltage tries to appear at the gate of the power device - when it is supposed to be off. The Miller Clamp can also be used with a negative gate supply, where it will shut off once the gate voltage is low enough. Input-Output Delay Time: All drivers regardless of isolation technology introduce some delay time from the logic input to the output. Ideally this delay is the same whether the device is turned ON or OFF. It is also good to have the delay remain constant over temperature. ROHM offers drivers with delays ranging from 90 nanoseconds to 350 nanoseconds. In general the highest operating frequencies are achieved in drivers with the smallest delay. The datasheet for each device specifies the delay and the minimum input pulse width that may be applied. Negative Power Supply: Another way to guarantee that the Power MOSFET stays OFF in the presence of large noise is by using a negative voltage at the gate. Currently, ROHM’s SiC MOSFETs can be used with -5V applied to the gate to guarantee they stay OFF when they are supposed to be OFF. Most of our drivers can accommodate a negative supply for this purpose. Other drivers include an application circuit showing how to effectively use a negative voltage with just a few external components. Temperature Monitor: Several ROHM gate drivers integrate temperature monitoring. For example, the BM6101FV has a simple comparator circuit which is able to stop operation and send a “Fault” signal to the primary side, while the BM60051FV Driver includes circuitry which can be used with either 10k NTC Thermistors or diode temperature sensors, and a signal is fed back across the isolation barrier to the primary side as a pulsewidth modulated signal. The pulse width is proportional to the measured temperature. Many IGBT Power modules also incorporate an internal temperature sensor fastened to the baseplate. Under certain IGBT failure modes the internal temperature sensors pins may come into contact with DC link voltages, making it necessary to isolate the sensor signal from the primary circuitry. Separated Output: Sometimes customers may want to asymmetrically drive their power devices, mostly to achieve faster turn-off than turn-on in order to guarantee no “shoot-through”. (Shoot-through is a condition where BOTH the upper and associated lower power device are turned on simultaneously). Some ROHM drivers bring out the positive-going and negative-going edges on separate pins. This makes it easy to use different value resistors to achieve different value turn-on and turn-off times. Simple drivers typically have a single output pin and require additional components to achieve this function. 4 Gate Driver Selection Guide Safety Features: Desat: All ROHM Gate Drivers include Under Voltage Lockout (UVLO) detection for both the Primary and Secondary sides. This prevents activation of the Driver when either of the supply voltages are too low for proper operation. Our more advanced drivers feature a 'Fault Output' pin on the Primary side which can be detected by a microcontroller to give information about problems such as under voltage or over temperature conditions. Some abnormal situations (such as a shorted motor winding) can cause so much current to flow that the power device will come out of saturation and be in danger of burning up. In order to prevent this, some drivers have a feature called Desat(uration) detection basically involves monitoring the voltage drop across the power device and turning the power OFF if the voltage drop exceeds a certain value when the device is ON, preventing excessive current flow. Some drivers include a 'Fault Output' pin on the Primary side. This is an open-drain output pin which is driven LOW to indicate a problem. Depending on the features of the Driver you select, the pin may indicate an under-voltage lock out, an over temperature condition, or that the 'Short-Circuit Protection' function (SCP) has been activated. All error conditions share the same pin. If the device is turned OFF at normal speed a larger than normal current may produce a dangerous voltage spike, which is likely to destroy the power device. Therefore, a gentler turn-off is required. Soft turn off is achieved by using the PROOUT pin as an output to drive the gate, through a resistor with significantly higher resistance than a normal gate drive resistor. This will result in an exponentially decaying gate drive voltage, which will gently turn off the power device preventing damage from an overshoot spike on the drain. Output State Feed Back (OSFB): Flyback Controller: This is also an open-drain output pin on the Primary side. During normal operation if input logic is set up to drive the gate of the Power MOSFET HIGH, but the gate is observed to be LOW, the OSFB pin will go LOW to indicate that there is a problem. Likewise, if logic inputs are set up to drive the gate LOW and the gate is observed to be HIGH the OSFB pin will go LOW to indicate a problem (the PROOUT bi-directional pin is used as an input to monitor the gate voltage). The BM6005xFV family includes a built-in flyback controller that makes it easier to configure an isolated power supply. All that's required is an external power device (typically a MOSFET) an isolation transformer, and a handful of resistors and capacitors. Fault Output: Exclusive OR Inputs: Some of our Gate Drivers include a feature to protect against a logic or microcontroller fault which would try to simultaneously turn on both the upper and lower power devices. This type of logic, called Exclusive-OR, is connected to the INA and INB input pins, which are normally at opposite logic levels. The gate will not be driven HIGH unless BOTH inputs are at the proper logic levels. However, this does require that both upper and lower device drive signals be wired to the upper and lower drivers. 5 Gate Driver Selection Guide Product Lineups These product tables can be used to quickly evaluate and search for the required characteristics. 'Simple Drivers' are those that provide only a 'one way' transfer of information from primary side to secondary side. They do not offer a 'Fault' output for monitoring secondary side failures. Simple Drivers Standard Part No. AEQ-100 Features No. of UL1577 UL1577 VDE0884-10 (Basic ISO) (Double ISO) (Reinforced ISO) Channels Package Isolation [kVrms] Delay Time Miller [ns] (max) Clamp Negative Power Supply BM60014FV-C ⎷ ⎷ � � 1ch SSOP-B20W 2.5 120 I � BM60015FV-LB � � P P 1ch SSOP-B10W 3.75 75 I � BM60016FV-C ⎷ TBD TBD � 1ch SSOP-B10W 2.5 75 I � BM60210FV-C ⎷ � � � Half Bridge SSOP-B20W High: 1.2kVDC Low: Not Isolated 75 I � P: Pending | I: Integrated Complex Drivers Part No. UL1577 (Basic ISO) Package Isolation [kVrms] Delay Time [ns] (max) Negative Power Supply Miller Clamp DESAT Short Current Temp S/M Output State Feedback RDY Output Flyback Controller Soft Turn OFF Features AEQ-100 Standards BM6101FV-C ⎷ ⎷ SSOP-B20W 2.5 350 ⎷ E ⎷ ⎷ S � � � ⎷ BM6102FV-C ⎷ ⎷ SSOP-B20W 2.5 200 � E ⎷ ⎷ S � � � ⎷ BM6104FV-C ⎷ ⎷ SSOP-B20W 2.5 150 ⎷ E ⎷ ⎷ � ⎷ � � ⎷ BM6108FV-LB � � SSOP-B20W 2.5 150 ⎷ E ⎷ ⎷ � ⎷ � � ⎷ BM6105FW-LB � P SOP16WM 2.5 95 ⎷ I ⎷ � � � ⎷ � � BM60051FV-C ⎷ ⎷ SSOP-B28W 2.5 260 � I � ⎷ M ⎷ � ⎷ ⎷ BM60052FV-C ⎷ ⎷ SSOP-B28W 2.5 110 ⎷ I ⎷ � S ⎷ ⎷ ⎷ ⎷ BM60054FV-C ⎷ ⎷ SSOP-B28W 2.5 110 ⎷ I ⎷ ⎷ S ⎷ ⎷ ⎷ ⎷ P: Pending | E: External Nch MOSFET | S: Shut down | M: Monitor output | I: Integrated Selection Guide tables adapted from “Gate drivers for high power applications” by Daiki Yanagishima. 6 ROHM Semiconductor 2323 Owen Street Santa Clara, CA 95054 www.rohm.com | 1.888.775.ROHM NOTE: For the most current product information, contact a ROHM sales representative in your area. ROHM assumes no responsibility for the use of any circuits described herein, conveys no license under any patent or other right, and makes no representations that the circuits are free from patent infringement. Specifications subject to change without notice for the purpose of improvement. The products listed in this catalog are designed to be used with ordinary electronic equipment or devices (such as audio visual equipment, office-automation equipment, communications devices, electrical appliances and electronic toys). Should you intend to use these products with equipment or devices which require an extremely high level of reliability and the malfunction of which would directly endanger human life (such as medical instruments, transportation equipment, aerospace machinery, nuclear-reactor controllers, fuel controllers and other safety devices), please be sure to consult with our sales representative in advance. © 2015 ROHM Semiconductor USA, LLC. Although every effort has been made to ensure accuracy, ROHM accepts no responsibility for errors or omissions. Specifications and product availability may be revised without notice. No part of this document represents an offer or contract. Industry part numbers, where specified, are given as an approximate comparative guide to circuit function only. Consult ROHM prior to use of components in safety, health or life-critical systems. All trademarks acknowledged. 1.800.775.ROHM www.rohm.com CUS15002_sg