Active solid-state devices (e.g. – transistors – solid-state diode – Responsive to non-electrical signal – Electromagnetic or particle radiation
Reexamination Certificate
1998-07-15
2001-03-06
Saadat, Mahshid (Department: 2815)
Active solid-state devices (e.g., transistors, solid-state diode
Responsive to non-electrical signal
Electromagnetic or particle radiation
C257S463000, C257S723000, C257S724000
Reexamination Certificate
active
06198146
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a photo detective unit and an electric apparatus using the same. More particularly, the present invention relates to a photo detective unit used for data transmission with light and an electric apparatus such as a remote controller using the photo detective unit.
2. Description of the Background Art
In the case of electric apparatuses including video apparatuses such as televisions and VTRs (Video Tape Recorders) and audio apparatuses such as stereos, which are provided with remote controllers, operation of each electric apparatus can be controlled even from a distance by operation of the remote controller. Data transmission of the remote controller is generally carried out with radiowaves or infrared rays. For domestic use, a remote controller with infrared rays having a shorter signal reachable distance but having less interference and also being cheaper is often used.
FIG. 5
is a block diagram showing a photo detective unit provided within a conventional remote controller. In
FIG. 5
, photo detective unit
4
includes a photodiode
41
and a signal processing IC (Integrated Circuit)
42
, both of which are accommodated in a metal case
45
. Photodiode
41
is an element through which current flows according to a light quantity of infrared rays L, and this current is applied through an interconnection
44
to signal processing IC
42
. Signal processing IC
42
converts current flowing in photodiode
41
into voltage, carries out waveform shaping for removing an infrared ray carrier signal contained in the voltage signal, and demodulates a digital data signal transmitted from the remote controller for transmission to a control circuit of each electric apparatus.
However, a photodiode for use in such a photo detective unit generally has such a property that photocurrent may change only by about several &mgr;A per 100 lux light, and therefore, the output impedance thereof will be increased. Accordingly, since the impedance of interconnection
44
for connecting photodiode
41
with signal processing IC
42
in photo detective unit
4
shown in
FIG. 5
is increased and interconnection
44
is long with a length of at least several mm, an error signal resulting from noise from the outside of photo detective unit
4
is likely to be generated in interconnection
44
, and a wrong data signal is transmitted to each electric apparatus, so that the electric apparatus might carry out operation different from that designated by the remote controller.
In order to prevent this, the whole photo detective unit is generally shielded with metal case
45
from noise, but in this case, the size of metal case
45
will be increased. If photo detective unit
4
is large in size, reduction in size of each electric apparatus provided with the photo detective unit is prevented, so that an external shape (design) of each electric apparatus may be restrained. Furthermore, purchase of the metal case and maintenance cost thereof are additionally required.
On the other hand, photo detective unit
4
could be formed with a one-chip semiconductor device, and in that case, only a short interconnection between photodiode
41
and signal processing IC
42
such as that having a length of several tens or several hundreds of &mgr;m is required, and therefore, the photo detective unit is less likely to be subjected to external noise, whereby shielding of the whole photo detective unit with metal case
45
will not be necessary. However, in order to provide a semiconductor device having as small chip size as possible at low cost, a signal processing circuit and a photodiode are simultaneously formed with manufacturing conditions (processes) for formation of the signal processing circuit, resulting in difficulty in sufficient increase in the infrared ray detecting capability (photosensitivity) of the photodiode.
SUMMARY OF THE INVENTION
It is a primary object of the present invention to provide a photo detective unit requiring no shielding with a metal case, achieving reduction in size and having superior sensitivity, and an electric apparatus using the same.
To put the present invention briefly, a photo detective unit accommodated in a single package and responsive to light for processing data includes a photo detective semiconductor chip formed under a first manufacturing condition and including a photo detective element formed under the first manufacturing condition and a buffer circuit for shaping output voltage waveform of the photo detective element; and a signal processing semiconductor chip formed under a second manufacturing condition and responsive to output voltage from the photo detective semiconductor chip for generating digital data.
Therefore, according to the present invention, the photo detective unit can receive an optical data signal with sufficient sensitivity at the photo detective element and is less likely to generate an error signal resulting from external noise, so that the reachable distance of a remote control signal can be increased. Furthermore, the size of the photo detective unit can be reduced and the chip size of the signal processing semiconductor chip will not be increased, and therefore, the number of chips per wafer is increased, so that the signal processing semiconductor chip and the photo detective unit using the same can be manufactured at low cost.
In a preferred embodiment, the photo detective semiconductor chip is formed with a semiconductor substrate having such impurity concentration that improvement in photo detective sensitivity of the photo detective element is given priority, and the signal processing semiconductor chip is formed with a semiconductor substrate having such impurity concentration that improvement in integration degree is given priority, which is higher than that of the first manufacturing condition.
In a further preferred embodiment, the photo detective element includes a photodiode and a resistance for converting current flowing in the photodiode into voltage, and the buffer circuit includes an amplification circuit for amplifying voltage resulting from conversion by the resistance, and a transistor connected to an output of the amplification circuit.
In a still further preferred embodiment, the photo detective unit is used as a photo detective unit for a remote controller using infrared rays.
According to another aspect of the present invention, an electric apparatus using a photo detective unit is provided, wherein the photo detective unit is accommodated in a single package and is constituted by a photo detective semiconductor chip including a photo detective element formed on a first manufacturing condition and a buffer circuit for shaping output voltage waveform of the photo detective element, and a signal processing semiconductor chip formed on a second manufacturing condition and responsive to output voltage from the photo detective semiconductor chip for generating digital data.
Therefore, according to the above mentioned another aspect of the present invention, reduction in size of the photo detective unit can be achieved, and restriction on an external shape of the electric apparatus is reduced, so that the electric apparatus can be designed arbitrarily.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.
REFERENCES:
patent: 4847210 (1989-07-01), Hwang et al.
patent: 5291054 (1994-03-01), Tanaka et al.
patent: 5598022 (1997-01-01), Kyomasu
patent: 5986317 (1999-11-01), Wiese
Yamamoto et al. IEEE Transactions on Electron. Devices, vol. 42, No. 1, Jan. 1995.
Ogawa Tadayoshi
Yamamoto Yosuke
Yano Shinji
Arent Fox Kintner & Plotkin & Kahn, PLLC
Rohm & Co., Ltd.
Saadat Mahshid
Wilson Allan R.
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