IRF7807V Datasheet, PDF (4/8 Pages) International Rectifier – N Channel Application Specific MOSFET

IRF7807V
For the synchronous MOSFET Q2, R is an im-
ds(on)
portant characteristic; however, once again the im-
portance of gate charge must not be overlooked since
it impacts three critical areas. Under light load the
MOSFET must still be turned on and off by the con-
trol IC so the gate drive losses become much more
significant. Secondly, the output charge Q_oss and re-
verse recovery charge Q both generate losses that
rr
are transfered to Q1 and increase the dissipation in
that device. Thirdly, gate charge will impact the
MOSFETs’ susceptibility to Cdv/dt turn on.
The drain of Q2 is connected to the switching node
of the converter and therefore sees transitions be-
tween ground and V . As Q1 turns on and off there is
in
a rate of change of drain voltage dV/dt which is ca-
pacitively coupled to the gate of Q2 and can induce
a voltage spike on the gate that is sufficient to turn
the MOSFET on, resulting in shoot-through current .
The ratio of Q /Q must be minimized to reduce the
gd gs1
potential for Cdv/dt turn on.
Spice model for IRF7807V can be downloaded in
machine readable format at www.irf.com.
Figure 2: Q_oss Characteristic
Typical Mobile PC Application
The performance of these new devices has been tested
in circuit and correlates well with performance predic-
tions generated by the system models. An advantage of
this new technology platform is that the MOSFETs it
produces are suitable for both control FET and synchro-
nous FET applications. This has been demonstrated with
the 3.3V and 5V converters. (Fig 3 and Fig 4). In these
applications the same MOSFET IRF7807V was used for
both the control FET (Q1) and the synchronous FET
(Q2). This provides a highly effective cost/performance
solution.
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1
4
3.3V Supply : Q1=Q2= IRF7807V
Vin=24V
Vin=14V
Vin=10V
2
3
4
5
Load current (A)
Figure 3
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92
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90
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86
1
5.0V Supply : Q1=Q2= IRF7807V
Vin =24V
Vin =14V
Vin =10V
2
3
4
5
Load current (A)
Figure 4
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