Isolated Driver Chip Switches High-Voltage FETs

January 6, 2020 | 08:54
What's inside. Image: Maxim
What's inside. Image: Maxim
Maxim has announced a new family of gate drivers ICs for SiC and GaN FETs that not only have a high isolation voltage of 1.2 kV (5 kV peak), but also offer a 35 ns propagation delay (typical) and a minimal pulse width of 20 ns. The MAX2270X family offer high (300 kV/µs) Common-Mode Transient Immunity (CMTI) performance to make sure that the driver is not triggered by spurious input signal glitches or interference.

The ICs are available in an 8-pin SOIC package (3.9 x 4.9 mm) providing 4 mm creepage and clearance spacing. Maxim quote a part-to-part Propagation Delay time (PDT) matching within 2 ns (max) at +25°C ambient and 5 ns (max) over the full -40°C to +125°C operating temperature range. This allows for a shorter dead time of the switching power transistor and helps improve overall circuit efficiency.

Variants of the devices are available which offer an output for a gate driver common pin GNDB (MAX22700), a Miller Clamp (MAX22701) or the MAX22702 which features an adjustable under-voltage-lockout (UVLO) mechanism. The MAX22700 and the MAX22702 have a maximum RdsON of 1.25 Ω for the low-side driver, and the MAX22701 has an RdsON of 2.5 Ω for the low-side driver. All devices have a maximum RdsON of 4.5 Ω for the high-side driver.
Using a MAX22701E to drive an external high voltage FET. Image: Maxim.

The MAX22701 variant features a Miller Clamp; when both OUT and CLAMP pins are connected to the gate of the external power transistor an additional NMOS is connected in parallel to the pulldown NMOS transistor to prevent false turn-on of the external power transistor by providing an additional low-impedance path to VSSB for the signal.

A total of six versions are currently available; the 'E' variants have single ended inputs while the 'D' variants use differential inputs. Maxim also has have evaluation kit: The MAX22701EVKIT is available for less than 50 € from its distributors AVnet or Mouser
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