EPC2152: 80 V, 15 A ePower™ Stage

ePower is EPC’s trademark for a growing family of Integrated Power Stage products that combine the control functions with the power output devices. We call them ePower™ Stage.

The most common building block in power conversion is the half-bridge, which can be used in synchronous buck, synchronous boost, LLC converter, and even switched cap or multi-level converter.

Initially, the thrust in the ePower™ product family will be a series of Power Stage (ePower Stage) products, which will include driver functions integrated with half-bridge output FETs. The first product in the series, the EPC2152, can operate from 80 V max with a rated output current of 12.5 A, and operating PWM frequency exceeding 2MHz.

Within a year the family will be filled out with products capable of operating at high frequency up to a 3 to 5 MHz range as well as high current from 15 A to 30 A per Power Stage.

The ePower™ Stage is designed as a functional block from LOGIC IN to POWER OUT. It interfaces directly with PWM logic signal, either from a digital or analog controller, to turn the PWM commands into output power pulses capable of high voltage and high current.

Conventional designs using discrete FETs, either GaN FETs or Si MOSFETs, require external gate drivers with skillful layout techniques to achieve optimum gate drive. Half-bridge designs require additional attention paid to level shifting and bootstrap designs.

ePower™ Stages simplify the design, save space, switch faster and achieve higher efficiency when compared to discrete FETs.

To use a popular quote, since “eGaN^® FETs will crush Si MOSFETs”, the ePower™ Stage will eventually emerge as THE POWER STAGE of choice when the input voltage and output current requirements are met by the ePower™ Stage range of product offerings.

There are other Power Stage products on the market, mainly by integrating Si gate driver with Si MOSFET in either multi-chip module or in monolithic Si ICs.

In the industry, this product category is generally referred to as DrMOS. DrMOS Power Stages had dominated the 12 V POL market for years over discrete designs. However, DrMOS Power Stages are typically limited by V_in range and operating PWM frequency range.

EPC’s ePower™ Stage can operate at higher frequency with high efficiency because it integrates the GaN half bridge within the IC. The first series of products can operate up to 80 V max with PWM frequency exceeding 2 MHz.

These ePower™ Stage specifications meet the requirements for 48 V DC-DC and Motor Drive Inverter applications and exceed what is possible with DrMOS Power Stage.

EPC utilizes a proprietary GaN IC technology that can integrate small signal devices and high voltage level shifting devices together with output Power FETs on same chip.

The output current capabilities are only limited by die size and thermal consideration. For applications requiring even higher current, EPC will utilize multi-chip packaging capabilities to integrate the ePower™ Stage into a single quad flat module (QFM) in upcoming product offerings.

EPC GaN FETs are lateral devices built on a GaN Epitaxial layer with an isolation layer between the active device regions and the supporting Si substrate.

Small signal FET devices with different maximum voltage withstand capabilities from 5 V to 100 V FETs can be built on the same chip with passive devices such as resistor and capacitors. That forms the basic platform for constructing useful circuits integrated with GaN output devices.

The output devices can be configured as a half bridge or other topologies. And most importantly, the GaN output devices in IC platform vs. the discrete GaN FETs, are not compromised in performance figure of merit.

Traditional Si MOSFET structure is vertical conduction, called VDMOS, that are not easily integrated with small signal CMOS or bipolar devices.

The BCDMOS IC platform typically requires very high mask counts to integrate all the devices, and the output VDMOS devices are less efficient than the optimized discrete counterparts.

Lower voltage monolithic BCD platform (less than 40 V) uses LDMOS for easier integration with acceptable performance. However, both BCDMOS platforms suffer from substrate current conduction which could cause latch-up. Special layout techniques or use of expensive SOI structures are needed for isolating the output FETs, especially during diode conduction. Since there is no parasitic diode associated with GaN FETs, there is less concern about parasitic substrate current conduction.

The GaN IC platform is in the initial phase of development with a limited toolbox available for devices as well as circuit techniques. Si IC technologies are very mature with BCD platforms able to support digital logic, precision analog circuits and, most importantly, the ability to design circuit with very low current consumption. Whereas GaN ICs typically have much higher current consumption and less precision at this stage of development.

Future enhancement of the GaN IC technology platform will allow the design of fault detection and protection circuits on chip with the output FETs. Eventually sensing functions can be added to enable controller integration into the ePower™ Stage product range.

The first product in our ePower™ Stage family is the EPC2152. It has an 80 V max V_in rating and rated output current of 12.5 A, switching at 1 MHz PWM frequency. Depending on operating conditions, the device can operate with a PWM frequency range up to 3 MHz.

The output devices are configured as a half bridge with R_DSon less than 10mΩ for both high side and low side FETs. The internal gate drive circuit is designed to match with the output FETs and switching time is less than 1ns from 0 V to 60 V at rated current.

High frequency operation is possible with delay times less time 20ns and matched high-side vs. low-side delay times ease the use of low deadtimes less than 10ns.

Inputs are compatible with 3.3V logic allowing users to interface directly with an MCU or with analog controllers.

The EPC2152 is packaged using a wafer-level chip-scale package (WLCSP) in an LGA outline. The layout of the solder bumps is designed with current flow direction in mind to minimize the power loop inductance in practical PCB application. EPC’s development board (EPC90120) has a power loop inductance less than 0.2nH.

The integration of the half-bridge configuration practically eliminates common source inductance (CSI) between high-side and low-side FETs. And the integrated gate drivers eliminate gate drive loop inductance. Both of which contribute to the fast switching time (<1ns).

The gate drive level is internally regulated using feedback to individually match the gate drive requirements of the driven FETs, driving them to low R_DSon , when needed, while always staying in safe operating level.

The internal level shifter is designed to be robust in all eight types of switch node transition events (above rail transient, below ground transient and high dv/dt).

Another unique design is the internal synchronous bootstrap charging circuit that always maintains low dropout in the charging path and has no Qrr to allow for high frequency operation.

Design is easier since the EPC2152 is configured as a functional block with LOGIC IN and POWER OUT. Customers need only to focus on system control issues since the ePower™ Stage takes care of translating the PWM commands into power pulses with minimum distortion and high efficiency.

Manufacturing is easier since the CSP EPC2152 replaces at least three (3) discrete chips (gate driver + 2 FETs), not counting the synchronous bootstrap circuit.

The EPC2152 saves at least 33% in space as compared to a comparable discrete design using a discrete gate driver and GaN FETs, both in CSP form factors. Compared to Si MOSFET design, using SMD packages, even more space is saved.

The peak efficiency of the EPC2152 is above 96% when operating in a buck converter V_in = 48 V, V_out = 12 V, fsw = 1 Mhz and I_out = 12.5 A.

The EPC2152 is mainly targeted to be used for DC-DC converters requiring high efficiency and small size. These are critical benefits for telecom, server and client computing, industrial, automotive and military markets. Also targeted are space and other high radiation environments due to the unique properties of GaN IC construction.

Different converter topologies can be built using the EPC2152 half-bridge configurations. Customers are designing in these devices for buck and boost converters as well as in LLC converters. Some customers are even trying the device in switched cap topologies.

Another promising application is motor drive inverters for robotics, drones and e-scooters. These motor drive applications require lighter weight, higher bandwidth and lower torque ripple, which are the advantages for inverters built using the ePower™ Stage.

The starting point for design support is the EPC2152 datasheet which gives the details of the electrical specifications and packaging information.

The EPC90120 Development Board is a good demonstration of what the EPC2152 can do in actual application circuit. In addition to learning about the switching performance of the device, the PCB design also provide a reference layout to achieve the maximum performance of the device. Refer to the Quick Start Guide and the Gerber File.

The first complete reference design using the EPC2152 will be a 10 ARMS, 15 A peak motor drive inverter designed to drive a 3-phase BLDC motor at PWM frequency greater than 100kHz.

Additional reference designs, such as a 1/8th brick 2-phase buck DC/DC converter and an LLC converter are planned for the EPC2152 as well as for additional products in the ePower™ family.

The EPC2152 ePower Stage is priced at $5.03 each in 1Ku volumes.

The EPC90120 development board is priced at $123.75 each

The EPC2152 and EPC90120 are available for immediate delivery from DigiKey