Rohm Co., Ltd.

Tamotsu Suzuki

Yoshikazu Shimada

Hiroyuki Ashida

Masatoshi Tsuji

A frequency modulating (FM) transmitter includes a reference frequency generator, a reference frequency divider, a stereo modulation circuit, an oscillator circuit, a program counter, and a PLL frequency synthesizer. The reference frequency generator is for generating a reference frequency. The reference frequency divider is for frequency dividing the reference frequency. The stereo modulation circuit is for frequency modulating audio signals by using one output of the reference frequency divider to supply resultant stereo modulated signals as FM signals. The oscillator circuit is for generating carrier waves to transmit the FM signals. The program counter is for frequency dividing the carrier waves into variable frequency components. The PLL frequency synthesizer has a phase comparator circuit for comparing the variable frequency components output from the program counter with another output of the reference frequency divider.

FM transmitter

A data processor is provided with a data input mode and a data output mode. The data input mode is set by an external signal. A serial data supplied from an external apparatus to a data input register has a signal to specify the start of the operation at its specific bit. The data processor is provided with a circuit which starts to operate by the operation start signal. This circuit generates an operation completion signal. Based on the operation completion signal, the mode of the data processor is automatically changed to the data output mode.

Data transfer apparatus which outputs data based upon a control signal

A first amplifier circuit having a high frequency characteristic and a second amplifier circuit having a low frequency characteristic have first and second input terminals, respectively. The first and second amplifier circuits have first and second feedback resistors for self-bias and first and second switching elements capable of interrupting outputs of the amplifier circuits, respectively. Between the first and second input terminals, a third switching element is connected. A device for controlling on and off of the switching elements is provided in order that according to a signal input to the first and second input terminals, the signal is transmitted to either the first amplifier circuit or the second amplifier circuit. As a result, irrespective of whether the front end has one output terminal or two output terminals, the input circuit can be connected to the PLL synthesizer IC as it is by connecting the output to the first input terminal or to the two input terminals.

Input circuit of counter circuit, and integrated circuit for frequency

A functional circuit is formed in a chip. A selector circuit is provided, which connects monitor points to electrode pads for external connections for testing the monitor points of the functional circuit. A control circuit is provided for supplying to the selector circuit a control signal which determines whether or not the monitor point is to be connected to the electrode pad by the selector circuit. The control circuit includes a counter circuit having a plurality of cascade-connected flip-flops, a clock signal input terminal for supplying a clock signal to each of the flip-flops in sequence from the flip-flop at an end of the counter circuit, and a reset signal input terminal for supplying a reset signal.

Integrated circuit having a control circuit for controlling connection

A low-pass passive filter is inserted in the phase locked loop of a voltage-controlled oscillating circuit having a varactor diode. The filter has a first resistor, a capacitor and a second resistor connected in that order and the blocking characteristics of the filter are changed in accordance with a selected value of the second resistor. A push-pull output circuit in which the upstream transistor is connected directly to the supply voltage line receives the signal from a phase comparator circuit (which is indicative of the result of phase comparison) and outputs it to the low-pass passive filter. The low-pass passive filter controls the terminal voltage of the varactor diode in accordance with the terminal voltage of the capacitor and the value of the second resistor is selected depending on the desired blocking characteristics of the filter.

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Kyoto, Japan

Tamotsu Suzuki