JP4195976B2 - Light emitting / receiving semiconductor device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a light receiving and emitting semiconductor device that includes a light emitting element and a light receiving element as a pair, and is used particularly for infrared communication.
[0002]
[Prior art]
In mobile phones, PDAs (Personal Digital Assistance), and personal computers, functions that enable communication between them are becoming standard specifications. An example of a device having such a function is an IrDA standard light emitting / receiving device.
[0003]
IrDA (Infrared Data Association) is an industry organization established to develop technical specifications for near-field data communication using infrared rays. Current standards include a communication distance of 1 m and a communication speed of 115.2 kbps. Version 1.0 specification, 1.1 specification within 1 m, up to 4 Mbps, 1.2 specification within 0.2 m, and 115.2 kbps (low power consumption version). Although it is mainly used to connect a desktop computer and a portable computer such as a notebook computer wirelessly, it has also been adopted in mobile phones and PDAs called third generation. This IrDA standard is different from the specifications of remote controls for home appliances such as televisions and videos.
[0004]
FIG. 3 is a block diagram of a conventional IrDA standard light emitting / receiving semiconductor device.
[0005]
In FIG. 3, the substrate 1 housed in one package is mounted with a light emitting element LED 3 and a light receiving element photodiode 4, and amplifies the driver transistor 6 of the LED 3 and the light receiving current of the photodiode 4. A signal processing circuit 5 that converts the signal into a pulse signal by a comparator is incorporated. The driver transistor 6 and the signal processing circuit 5 are mounted on the substrate 1 as a signal processing IC (integrated circuit) 2.
[0006]
The base 1 is provided with a power supply terminal VLED for supplying a drive current to the LED for transmission and reception of signals from the outside, a signal input terminal TXD for determining whether the LED is turned on / off, a power supply terminal VCC for the light receiving element signal processing circuit, VCC power supply current flows by setting the power supply terminals VLED and VCC to ground level GND, the output terminal RXD after the signal processing circuit for the received light signal, and the active level when the light receiving function is not used to suppress the current consumption of the signal processing circuit. A power saving signal terminal VSD that provides the function of disappearing is provided.
[0007]
At this time, the light emitting function and the light receiving function are not used at the same time.
[0008]
A timing chart at the time of light emission is shown in FIG. (A) is a TXD signal. According to the TXD signal, an LED current flows as shown in (b).
[0009]
In recent years, for example, there is a concept of remotely controlling home appliances such as televisions and videos using a mobile phone as a remote controller (see, for example, Patent Document 1). In that case, a maximum communication distance of 1 m may be used for IrDA-specific equipment, but a communication distance of about 8 m is required as a remote control for home appliances. There is a case where the drive current of the LED 3 is switched from a low current (for example, 30 to 50 mA) to a large current (for example, 130 to 150 mA) in order to increase the communication distance by infrared rays in response to such a request. As an example of drive current switching in this case, there is a circuit as shown in FIG.
[0010]
In this circuit, a second LED driver transistor 7 is provided in parallel with the first LED driver transistor 6 in order to increase the current flowing through the LED 3, and the TXD terminal is connected to one input terminal of the AND circuit 8. The light emission output switching signal (S) is input to the other input terminal.
[0011]
The operation is as shown in FIG. When the TXD signal comes periodically as shown in (a) and the switching signal (S) shown in (b) is H (high level), the first LED drive transistor 6 and the second LED drive transistor 7 operate simultaneously. As shown in (c), the current flowing through the LED 3 is Ia + Ib. On the other hand, when the switching signal (S) is L (low level), the second LED drive transistor 7 is turned off, and only the first LED drive transistor 6 is operated, and the current flowing through the LED 3 is Ib.
[0012]
Thus, when the light emission output switching signal (S) becomes H or L, the light emission intensity of the LED 3 can be switched between large and small.
[0013]
[Patent Document 1]
JP 2001-244498 A (page 2-3)
[0014]
[Problems to be solved by the invention]
However, the conventional circuit shown in FIG. 5 requires two signals, a signal TXD for determining whether the LED 3 is turned on and off, and a signal (S) for switching the capability of the driver circuit. In comparison, the signal (S) for switching the current increases, and it is necessary to add another terminal to the substrate 1 as a package.
[0015]
In recent mobile phones, miniaturization, light weight, and thinning have progressed, and circuit components have become extremely dense. In such a situation, increasing the number of terminals increases the size of a package designed with marginal dimensions. In addition, the number of wires connected to the terminal is increased by one, which is a difficult problem for mobile phones that are required to be further downsized.
[0016]
An object of the present invention is to provide a light receiving and emitting semiconductor device capable of switching the magnitude of a drive current flowing through a light emitting element without increasing the number of terminals.
[0017]
[Means for Solving the Problems]
In the light receiving / emitting semiconductor device of the present invention, in the light receiving / emitting semiconductor device provided with the AND circuit and the second driver element for increasing the current flowing through the light emitting element, the light emission input to the other input terminal of the AND circuit. The output switching signal is provided from a power saving signal input terminal that provides a signal for suppressing power consumption of the signal processing circuit.
[0018]
According to the present invention, it is possible to obtain a light receiving and emitting semiconductor device capable of switching the magnitude of the drive current flowing through the light emitting element without increasing the number of terminals.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
According to a first aspect of the present invention, a light emitting element, a first driver element that causes a first driving current to flow through the light emitting element, a light receiving element, and an output of the light receiving element are provided on one substrate. A signal processing circuit for performing amplification and pulse conversion, a second driver element for increasing a current flowing through the light emitting element is connected to the light emitting element, and an ON / OFF signal input terminal is connected to one input terminal of the AND circuit A light emitting output switching signal is input to the other input terminal of the AND circuit, and the input terminal of the second driver element is connected to the output terminal of the AND circuit. A light emitting / receiving semiconductor device characterized in that a light emission output switching signal input to the other input terminal is provided from a power saving signal input terminal that provides a signal for suppressing power consumption of the signal processing circuit. Is obtained by a device, an effect that at the time of the drive of the light emitting device by using a power saving signal input terminal of the signal processing circuit at rest, the current flowing to the light emitting element is switched.
According to a second aspect of the present invention, when the light emission output switching signal is at an active level, the signal processing circuit can suppress power consumption, and the AND circuit outputs a signal from a lighting / light-out signal input terminal. The light-receiving / emitting semiconductor device according to claim 1, which is output to a terminal, has an effect that current flowing through the light-emitting element can be increased while suppressing power consumption of the signal processing circuit.
[0020]
In the present invention, the “base” refers to a component mounting member such as a printed board or a lead frame for mounting an electronic component.
[0021]
Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 and 2.
[0022]
(Embodiment)
FIG. 1 shows a block diagram of a light receiving and emitting semiconductor device according to the present embodiment, and FIG. 2 shows an operation waveform diagram. In FIG. 1, an LED 3 that is a light emitting element and a photodiode 4 that is a light receiving element are mounted on a substrate 1 that is housed in one package, and the light receiving current of the photodiode 4 is amplified and converted into a pulse signal by a comparator. The signal processing circuit 5, the first driver transistor 6 of the LED 3, the second driver transistor 7, and the AND circuit 8 are incorporated. The signal processing circuit 5, the first driver transistor 6, the second driver transistor 7, and the AND circuit 8 are mounted on the substrate 1 as a signal processing IC (integrated circuit) 2.
[0023]
The base 1 is provided with a power supply terminal VLED for supplying a drive current to the LED 3 for signal exchange with the outside, a signal input terminal TXD for determining whether the LED is turned on / off, a power supply terminal VCC for the light receiving element signal processing circuit, The ground terminal GND of VLED and VCC, the output terminal RXD after the signal processing circuit of the received light signal, and the function that prevents the VCC power supply current from flowing by setting the active level when the light receiving function is not used to suppress the current consumption of the signal processing circuit Is provided with a power saving signal terminal VSD. The number of terminals is the same as that formed on the conventional substrate shown in FIG.
[0024]
The signal input terminal TXD is connected to one input terminal of the AND circuit 8, the power saving signal terminal VSD is connected to the other terminal, and the output terminal of the AND circuit 8 is connected to the base of the second driver transistor 7. ing.
[0025]
The operation in this circuit will be described with reference to FIG.
[0026]
When the TXD signal is input as shown in FIG. 2A, and the signal from the power saving signal terminal VSD is H (high level) as shown in FIG. 2B, the output terminal of the AND circuit 8 is TXD. Since the signal is output, both the first driver transistor 6 and the second driver transistor 7 operate, and the current flowing through the LED 3 becomes Ia + Ib as shown in FIG. On the other hand, when the VSD signal is L (low level), the output of the AND circuit 8 is low level, so the second driver transistor 7 does not operate and only the first driver transistor 6 operates and flows to the LED 3. The current is Ib.
[0027]
In this way, the signal for switching the current flowing through the LED is combined with the power saving terminal VSD having the function of preventing the power supply current from flowing at the active level in order to suppress the power consumption of the reception signal processing circuit. Without addition, the LED drive current can be switched between large and small as required.
[0028]
【The invention's effect】
As described above, according to the present invention, in the light receiving and emitting semiconductor device provided with the AND circuit and the second driver element for increasing the current flowing through the light emitting element, the light emission input to the other input terminal of the AND circuit. By changing the output switching signal from the power-saving signal input terminal that provides a signal to reduce the power consumption of the signal processing circuit, the magnitude of the drive current flowing through the light emitting element can be switched without increasing the number of terminals. Can do. Accordingly, it is possible to add a function of switching the reach of light emitted from the light emitting element without increasing the size of the circuit package.
[Brief description of the drawings]
FIG. 1 is a block diagram of a light receiving / emitting semiconductor device according to the present embodiment. FIG. 2 is an operation waveform diagram of the light receiving / emitting semiconductor device according to the present embodiment. FIG. 4 is a timing chart at the time of light emission in a conventional device. FIG. 5 is a circuit diagram showing an example of drive current switching. FIG. 6 is a timing chart showing an operation in the circuit of FIG.
1 Substrate 2 Signal processing IC
3 Light emitting diode (LED)
4 Photodiode (PD)
5 Signal Processing Circuit 6 First Driver Transistor 7 Second Driver Transistor 8 AND Circuit

Claims (2)

A light-emitting element, a first driver element that causes a first drive current to flow through the light-emitting element, a light-receiving element, and a signal processing circuit that amplifies and pulse-converts the output of the light-receiving element are mounted on the substrate, A second driver element for increasing the current flowing through the light emitting element is connected to the light emitting element, a lighting / light-out signal input terminal is connected to one input terminal of the AND circuit, and light is emitted to the other input terminal of the AND circuit. In the light receiving and emitting semiconductor device that receives the output switching signal and connects the input terminal of the second driver element to the output terminal of the AND circuit,
A light emitting / receiving semiconductor device characterized in that a light emission output switching signal input to the other input terminal of the AND circuit is provided from a power saving signal input terminal that provides a signal for suppressing power consumption of the signal processing circuit . 2. The light receiving / emitting device according to claim 1, wherein when the light emission output switching signal is at an active level, the signal processing circuit suppresses power consumption, and the AND circuit outputs a signal from a light on / off signal input terminal to an output terminal. Semiconductor device.

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