Active solid-state devices (e.g. – transistors – solid-state diode – Lead frame – With structure for mounting semiconductor chip to lead frame
Reexamination Certificate
2000-12-01
2003-05-13
Lee, Eddie (Department: 2815)
Active solid-state devices (e.g., transistors, solid-state diode
Lead frame
With structure for mounting semiconductor chip to lead frame
C257S666000, C257S723000, C257S672000, C361S808000, C361S813000, C361S820000, C438S111000, C438S112000, C438S123000
Reexamination Certificate
active
06563203
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a motor driving device.
2. Description of the Prior Art
Motor driving devices are known that are provided with a drive circuit for driving a motor and a protection diode for preventing the drive circuit from being destroyed when a power source is connected thereto with reverse polarities.
FIG. 2
shows an example of a circuit configuration of an output stage of a pre-drive circuit
1
for a two-phase half-wave fan motor. A MOS-type field-effect transistor (or bipolar transistor)
100
an a resistor
200
are connected in series between a supplied-power terminal T
1
and a ground terminal T
2
. A node between the transistor
100
and the resistor
200
is connected to an output terminal T
3
.
In actual use, to the output terminal T
3
, the base of an NPN-type power transistor
3
is connected through resistor
6
. The transistor
3
has its emitter grounded, and has its collector connected to one end of a coil
4
of a fan motor. The other end of the coil
4
is connected to a cathode of a diode
5
. An anode of the diode
5
is connected to a supplied voltage V
cc
.
With a motor driving device provided with the pre-drive circuit
1
as described above, there is a risk of a power source being connected thereto with reverse polarities, for example, as a result of improper insertion of a connector. Therefore, to prevent destruction, resulting from reverse connection of a power source, of the circuit elements, such as the MOS transistor
100
, constituting the pre-drive circuit
1
, it has been customary to connect to the supplied-power terminal T
1
of the pre-drive circuit
1
the cathode of a protection diode
2
of which the anode is connected to a terminal (not shown) to which the supplied power is supplied.
Here, the current that flows into the base of the transistor
3
to drive the motor is supplied directly from the power source, and therefore the protection diode
2
needs to have a high current capacity. In general, however, it is difficult to obtain a satisfactorily high current capacity with a diode formed within an IC (integrated circuit). For this reason, usually, in
FIG. 2
, whereas the pre-drive circuit
1
is formed as a one-chip IC, the protection diode
2
is connected externally to the IC. As a result, conventional motor driving devices provided with a pre-drive circuit and a protection diode has the disadvantage of requiring an unduly large mounting area and also requiring an extra assembly step.
The same problem is addressed by Japanese Patent Application Laid-Open No. H7-130927, which proposes, as a solution, mounting a MOS transistor and a diode on a single island. However, this is possible only with a single MOS transistor; that is, with a common IC, which is not formed on a single substrate together with a diode, it is impossible to mount the IC and the diode on a single island.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a motor driving device that, despite being provided with a drive circuit for driving a motor and a protection diode, requires a reduced mounting area and a reduced number of assembly steps.
To achieve the above object, according to the present invention, a motor driving device is provided with: an IC chip incorporating a circuit for driving a motor; a diode chip provided in a power-supply path through which electric power is supplied to the IC chip; a leadframe having a first island on which the IC chip is mounted and a second island on which the diode chip is mounted; a wire connecting together a supplied-power island provided on the IC chip and the second island; and a package incorporating the leadframe, the IC chip, and the diode chip.
This structure eliminates the need to connect a protection diode externally. Moreover, this structure makes it possible to obtain not only a higher current capacity but also a higher peak inverse voltage in the protection diode than when it is formed within an IC.
REFERENCES:
patent: 4855257 (1989-08-01), Kouda
patent: 6184585 (2001-02-01), Martinez et al.
patent: 6313598 (2001-11-01), Tamba et al.
patent: 60081877 (1985-05-01), None
patent: 04167568 (1992-06-01), None
patent: 04354386 (1992-12-01), None
patent: 06342818 (1994-12-01), None
Arent Fox Kintner Plotkin & Kahn
Chu Chris C.
Lee Eddie
Rohm & Co., Ltd.
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