Cambridge GaN Devices CGD65A055SH2 | Demoboard AN2206 - Current Sensing with ICeGaN

Description

This application note relates to Cambridge GaN Devices (CGD) H2 series devices1. It explains why current sensing is required in most power conversion circuits. The document considers the strengths and weaknesses of existing methods and goes on to describe a unique property of CGD ICeGaN devices: that they provide a current sense function without breaking into, and thereby compromising, the high current loop (from supply decoupling capacitor, through the magnetic and device and back to the decoupling capacitor).Some years ago, International Rectifier produced a (silicon) MOSFET with current sensing [1],[2]. It suffered from an expensive package and a vertical construction. Although the desirability of a power switch which incorporated current sense was clear, it was not commercially successful. However, lateral GaN power devices, like ICeGaN, have an inherent advantage over vertical devices as low-side switches because lateral devices dissipate heat through the grounded sourcepad. Vertical devices dissipate heat through the switching drain node. The implications of this for current sensing are significant and explained below.The current sense mechanism in ICeGaN devices (see Figure 1) is described in detail, along with its limitations, performance characteristics and accuracy. There are three ways to use the current sense pin of ICeGaN devices:1. On-state voltage sensing.2. Accurate current sense with zero temperature coefficient.3. Indicative current sense with positive temperature coefficient.The applications of each function are considered and a range of circuits to process the ICeGaN current sense signal isdiscussed. The design engineer can then select the appropriate price-to-performance ratio for their needs. Examples of waveforms and components from practical circuits are also presented.

Features

Introducing the CGD65A055SH2, an enhancement mode GaN-on-silicon power transistor that capitalizes on the unique material properties of GaN to deliver high current, high breakdown voltage, and high switching frequency for a wide range of electronics applications.

Featuring CGD's ICeGaN gate technology, the CGD65A055SH2 offers compatibility with almost all gate drivers and controller chips. The integrated current sense function eliminates the need for a separate current sense resistor in series with the source, reducing efficiency losses. As a result, the device can be directly soldered to the large copper area of the ground plane, enhancing thermal performance and simplifying thermal design.

The H2 series ICeGaN also incorporates an advanced NL³ Circuit, leading to record low power losses at No Load and Light Load operations.

Packaged in a DFN 8x8 SMD, the CGD65A055SH2 supports high-frequency operation while ensuring exceptional thermal performance.

Typical applications

• PV inverters
• PSUs, Industrial SMPS and inverters
• LED drivers
• AC/DC and DC/DC converters, AC inverters, General purpose SMPS
• Gaming PSUs, PC power, High power ClassD Audio Amplifiers
• Server power and data centers, Telecom rectifiers

More information

• Datasheet
• IC product information