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HEMT (GaN) Forum Discussions

Bougnoul_Oh
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Hello: Looking for a robust GaN with 150V or higher breakdown voltage.

Came across this peculiar device IGO60R070D1.

Its Vgs is NEGATIVE WITH CURRENT CONTROEL of the gate?

We cannot use it but is there an equivalent GaN with + Vgs?

 

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Abhilash_P
Moderator
Moderator 25 likes received 250 replies posted 250 sign-ins
Moderator

Hi,

 

    Thank you for posting on the Infineon Community. 

 

CoolGaN™ GIT HEMT is a normally-off device, and its improved figure of merit (FOM) makes it an ideal replacement for a silicon MOSFET in SMPS applications. CoolGaN™ GIT HEMTs have diode-like input characteristics. This provides voltage clamp and helps avoid any overvoltage damage to the transistor gate.    

The GaN HEMT has no intrinsic body diode from source to drain like a SJ MOSFET and  the gate does have a diode structure that clamps the gate-source (or gate-drain) voltage to approximately 3.5 V. The exact voltage will vary with the temperature-dependent diode forward voltage, and the gate current running through the internal RG(int) plus the diode impedance Rdio. As a result of these impedances and shared current paths, VG’’S’’, which controls the 2DEG enhancement, is a function of both gate current and drain current. Due to these factors, it is not feasible to specify a single externally measured gate-source voltage that will properly enhance the gate under all variations of temperature and drain current. For example, at high temperature and maximum drain current, a VGS of 4V may be just enough to keep the device on and result in a gate current of 10 mA. But at a lower temperature and zero drain current, the same applied VGS could result in hundreds of mA of unnecessary gate current. Moreover, specifying an absolute maximum gate voltage is not feasible due to the ID and temperature dependency.
For these reasons, the nominal and maximum gate voltages in the forward direction are not specified, only the
gate current is specified, as the p-gate diode will clamp the voltage to a safe level even at the maximum
specified gate current.

Abhilash_P_2-1658236270886.png

As explained in the above section, the gate voltage in the forward direction is a function of both gate current and drain current. Therefore, the datasheet does not specify a forward gate voltage limit, only a forward gate current limit is specified. In the negative direction, the gate voltage is clamped by a protection diode circuit  which begins clamping at about -12 V 

Abhilash_P_1-1658235807456.png

I hope the above pictorial representation of the GaN turn ON and turn OFF waveform will help you understand the need for the negative voltage. 

"We cannot use it but is there an equivalent GaN with + Vgs?"
            Yes, with a plus and minus gate driver supply, a standard gate driver can be used with 600 V CoolGaN™. BUT, using the GaN EiceDRIVER™ will provide additional performance benefits over a standard FET gate driver.

For more details on how to drive the GaN FETs please refer to attached application note. 

Regards,
Abhilash P

 

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1 Reply
Abhilash_P
Moderator
Moderator 25 likes received 250 replies posted 250 sign-ins
Moderator

Hi,

 

    Thank you for posting on the Infineon Community. 

 

CoolGaN™ GIT HEMT is a normally-off device, and its improved figure of merit (FOM) makes it an ideal replacement for a silicon MOSFET in SMPS applications. CoolGaN™ GIT HEMTs have diode-like input characteristics. This provides voltage clamp and helps avoid any overvoltage damage to the transistor gate.    

The GaN HEMT has no intrinsic body diode from source to drain like a SJ MOSFET and  the gate does have a diode structure that clamps the gate-source (or gate-drain) voltage to approximately 3.5 V. The exact voltage will vary with the temperature-dependent diode forward voltage, and the gate current running through the internal RG(int) plus the diode impedance Rdio. As a result of these impedances and shared current paths, VG’’S’’, which controls the 2DEG enhancement, is a function of both gate current and drain current. Due to these factors, it is not feasible to specify a single externally measured gate-source voltage that will properly enhance the gate under all variations of temperature and drain current. For example, at high temperature and maximum drain current, a VGS of 4V may be just enough to keep the device on and result in a gate current of 10 mA. But at a lower temperature and zero drain current, the same applied VGS could result in hundreds of mA of unnecessary gate current. Moreover, specifying an absolute maximum gate voltage is not feasible due to the ID and temperature dependency.
For these reasons, the nominal and maximum gate voltages in the forward direction are not specified, only the
gate current is specified, as the p-gate diode will clamp the voltage to a safe level even at the maximum
specified gate current.

Abhilash_P_2-1658236270886.png

As explained in the above section, the gate voltage in the forward direction is a function of both gate current and drain current. Therefore, the datasheet does not specify a forward gate voltage limit, only a forward gate current limit is specified. In the negative direction, the gate voltage is clamped by a protection diode circuit  which begins clamping at about -12 V 

Abhilash_P_1-1658235807456.png

I hope the above pictorial representation of the GaN turn ON and turn OFF waveform will help you understand the need for the negative voltage. 

"We cannot use it but is there an equivalent GaN with + Vgs?"
            Yes, with a plus and minus gate driver supply, a standard gate driver can be used with 600 V CoolGaN™. BUT, using the GaN EiceDRIVER™ will provide additional performance benefits over a standard FET gate driver.

For more details on how to drive the GaN FETs please refer to attached application note. 

Regards,
Abhilash P