Power mosfet with integrated drivers in a common package

Details Power mosfet with integrated drivers in a common package Power mosfet with integrated drivers in a common package

2002-05-02

2003-07-15

Ho, Hoai (Department: 2818)

Active solid-state devices (e.g., transistors, solid-state diode

Field effect device

Having insulated electrode

C257S723000, C257S724000, C257S773000

Reexamination Certificate

active

06593622

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to semiconductor devices and more specifically relates to a power MOSFET device with driver FETs integrated into or copacked with the same package to provide drive current to the gate circuit of the power MOSFET.
BACKGROUND OF THE INVENTION
Power MOSFETs frequently require a high gate current pulse for their operation. For example, circuits containing control or synchronous power MOSFETs frequently require a high gate pulse current for their operation. As a specific example, high frequency dc to dc converters such as synchronous buck converters are operated in the region of 3 MHz and above, at breakdown voltages of about 30 volts and below. The gate driver current i
g
for the control and synchronous MOSFETs of those circuits is determined, approximately by:
i
g
=Q
g
/t
ON
For a typical SO-
8
packaged device such as the IRF
7811
W made by the International Rectifier Corporation, the gate charge Q
g
required to turn on the MOSFET is in the region of 14nC. If the MOSFET turn on time t
ON
is limited to 10 ns, the switching current can therefore be of the order
1
.
4
A. This poses a problem for control ICs where capability to deliver this current level is not economically viable, given manufacturing complexity versus chip area required.
Solving this problem has typically been addressed by the addition of separate driver ICs placed in circuit between the control IC and the MOSFETs. As switching frequencies increase, the layout related circuit efficiency of this approach reduces, and the parasitic inductances caused by the distance between the separate components cause higher losses during switching.
BRIEF DESCRIPTION OF THE INVENTION
A driver stage is placed inside the MOSFET package, and the driver current requirement can therefore be reduced to that of two small driver FETs. The total active area of these devices is approximately ¼ that of the main FET/switch. The input drive current will therefore be reduced by similar proportions thereby enabling the driver devices to be driven directly by the control IC, removing the need for discrete driver ICs. In one embodiment of the invention, the internal driver stage uses two separate MOSFET chips in a totem pole configuration. This minimizes the wafer level manufacturing complexity for providing the desired function. The small driver chips can also be integrated with one another, or into the main chip.
The three devices, the main MOSFET and the two smaller driver MOSFETs, when discrete chips, may be copacked in standard small footprint plastic encapsulated packages, such as the well known TSSOP, SOIC, or MLP packages.


REFERENCES:
patent: 5084753 (1992-01-01), Goida et al.
patent: 5313095 (1994-05-01), Tagawa et al.
patent: 5792676 (1998-08-01), Masumoto et al.
patent: 5814884 (1998-09-01), Davis et al.
patent: 6066890 (2000-05-01), Tsui et al.
patent: 6133632 (2000-10-01), Davis et al.
patent: 6388319 (2002-05-01), Cheah et al.
patent: 6448643 (2002-09-01), Cheah et al.

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