UnitedSiC has revealed four 750V silicon carbide power transistors, the first devices from its fourth generation process it unveiled earlier this year.

UnitedSiC-4L-package
The unusual 750V rating is to allow additional design margin for 400V or 500V battery and bus applications compared with 650V devices, and improvements compared with the company’s third generation means that “gen4 750V transistors are better than Gen3 630V transistors”, UnitedSiC v-p engineering Anup Bhalla told Electronics Weekly – see table below.
For example, an improved unit cell has reduced Rds(on)/area, leading to smaller die. Then to get heat out of the smaller die, heat transfer has been improved by a switch to advanced sintered die-attach. The increase in Ron with temperature has suffered slightly (see table). The integral diode drops <1.75V.
Technology Generation    Gen 4    Gen 3
Nominal part    6mΩ, 750V    7mΩ, 650V
Vdsmax    750V    650V
Typical Ron at RT    6mΩ    6.7mΩ
Ron(175°C)/Ron(25°C)    2.08    1.6
Qrr at 400V, 1400A/us    462nC    840nC
Etot at 400V, 55A, RT, HB    560mJ    840mJ
assed short-circuit time at RT    8ms    3ms
Passed 10us surge current of body diode at RT    1,570A    773A
RthJC (°C/W) typ/max    0.21/0.27    0.15/0.19
Relative die size    0.65    1
UnitedSiC-3L-pacakgeThere are four initial devices, with 18 and 60mΩ options, and a choice of three or four lead TO247 package. “The world just won’t let these packages go, especially the three lead version, said Bhalla. Mind you “you can extract a lot of heat from them. We are at least trying to get people over to the four lead version, it almost halves switching losses.” – The four lead version has a separate source connection for the gate drive circuit.

UnitedSiC-750V-hardSwitchFor gen 4 devices the company is claiming “unmatched figures-of-merit with reduced on-resistance per unit area and low intrinsic capacitance”.
The figures, for the three and four lead 18mΩ R devices (UJ4C075018K3S and 4S, table below) are:
For hard-switching (right above), Rds(on) x Eoss is 220mΩμJ at 25°C (370mΩμJ at 125°C) for low turn-on and turn-off loss
UnitedSiC-750V-softSwitchFor soft switching (right), Rds(on) x Coss(tr) is 5mΩnF at 25°C (9mΩnF at 125°C) for lower conduction loss and higher frequency
Cascode construction (below left) has been retained by the company, with an internal low-voltage silicon mosfet switching the source of the main power SiC JFET.
UnitedSiC-cascodeThe custom-designed physically-small 25V mosfet means that no special gate drive is required, and that any driver intended for silicon mosfets can be used that can deliver 0-12V switching. The gate is ±20V tolerant, and has a 5V threshold for noise immunity.
The first four devices (below) are aimed at dc-dc conversion in on-vehicle chargers, power factor correction and solar inverters.
“We will be announcing many new gen 4 devices over the next nine months, which will further improve on cost-effectiveness, heat efficiency and design headroom,” said Bhalla.