IRF7807VPBF datasheet(4/8 Pages) IRF

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IRF7807VPbF

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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.

Figure 3

Figure 4

Figure 2: Q

oss Characteristic

For the synchronous MOSFET Q2, R

ds(on) is an im-

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

rr both generate losses that

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

in. As Q1 turns on and off there is

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

gd/Qgs1 must be minimized to reduce the

potential for Cdv/dt turn on.

Spice model for IRF7807V can be downloaded in

machine readable format at www.irf.com.

3.3V Supply : Q1=Q2= IRF7807V

5.0V Supply : Q1=Q2= IRF7807V

123

Load current (A)

Vin=24V

Vin=14V

Vin=10V

345

Load current (A)

Vin=24V

Vin=14V

Vin=10V

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