High Voltage Design: A New Three-Phase Half Bridge Gate Driver from Diodes Inc.

Diodes Incorporated has announced a new three-phase half bridge gate driver with multiple protection features and the ability to drive N-Channel MOSFETs and IGBTs.

Diodes Inc. recently announced their new DGD2136, which is a three-phase half bridge gate driver intended to simplify drive circuitry for BLDC (brushless DC) motors and PMSMs (permanent magnet synchronous motors).

The DGD2136 is designed for applications including:

• washing machines, fridges, and other white goods
• A/C units
• power tools, robotics, and other industrial motor inverters
• general purpose three-phase inverters

 

Figure 1. The DGD2136, from Diodes Inc., is a 3-phase motor driver for household appliances, power tools, and industrial motor applications. Image taken from the DGD2136 New Product Announcement (PDF).

High-Voltage and High-Speed Applications using Standard TTL and CMOS Input Levels

Interfacing this SO-28 driver to a microcontroller is made a little easier by its ability to switch—on the high side—up to 600V in bootstrap operation while having its logic inputs compatible with standard TTL and CMOS logic signal voltage levels.

Although the rise time, fall time, and turn-off and turn-on propagation delays all vary slightly as a function of temperature and supply voltage, all of these timings are in the range of tens to hundreds of ns, which seems impressive. However, these timing characteristics are not exceptional when compared to those of other high-speed three-phase gate drivers.

 

Figure 2. The turn on and turn off propagation delays vs. supply voltage and temperature. Image taken from the datasheet (PDF).

 

Figure 3. High side and low side rise time and fall time vs. supply voltage and temperature. Image taken from the datasheet (PDF).

Protection Features

This device offers multiple protection features, including shoot-through protection, UVLO (undervoltage lockout), and overcurrent protection; the general description section and the "Pin Descriptions" table (page 3 of the datasheet) offer brief descriptions of these features.

The UVLO and the overcurrent protection features are tied to an automatic fault clear timer, which is adjustable with an external capacitor—which is really nice. What's less nice is not knowing the relationship between the capacitor value and the duration of the fault clear timer... because this information is currently missing from the datasheet.

Packaging and Layout Information

According to its datasheet, this IC is available only in an SO-28 package. Hand-placing and hand-soldering the device to a PCB wouldn't be too challenging given its larger size.

 

Figure 4. The IC is available only in an SO-28 package. Image taken from the datasheet (PDF).

 

The datasheet also includes a suggested pad layout for the IC. To simplify the task of verifying that this pad layout is consistent with the latest version, a hyperlink to the package outlines page on the Diodes Inc. website is embedded in the datasheet (see image below). This is super convenient!

The datasheet warns us to be mindful of high-voltage design practices:

 

Figure 5. Pad layout information including a link to Diodes Inc.'s latest package/outline versions and a high voltage note. Image taken from the datasheet (PDF).

 

It would be helpful, however, to have some generic guidelines provided in the datasheet.

In any event, this is a good reminder for those of us who rarely design circuits involving anything above, say, 12V. If you’d like to get a general idea of the extra considerations involved in high-voltage design, this article from Mouser might be a good place to start.

Wide Operating Temperature Range

The wide ambient operating temperature range (-40°C to +125°C) of this IC is not surprising given the fact that the device was designed to be used in industrial applications. As a reminder, this ambient extended temperature range is wider than all other temperature grades except for the military grade, which is -55°C to +125°C.

Be aware, however, that when operating at ambient temperatures greater than 90°C, the offset supply leakage current begins to increase noticeably (see image below). Although the maximum leakage current of approximately 5mA (occurring at +125°C) is still quite low, it's far greater than ~100nA at 25°C.

 

Figure 6. Offset supply leakage current vs. temperature; note the drastic current increase at higher temperatures. Image taken from the datasheet (PDF).

 

Have you had a chance to use this new three-phase half bridge gate driver? If so, leave a comment and tell us about your experiences.