Panasonic Corporation

Michiko Tokumaru

Heiji Ikoma

Kouji Okamoto

A filter circuit includes two parallel digital filters, a DAC, and an LPF. The DAC includes two parallel decoders, a parallel-to-serial converter, a switch driver, and a switch. A PLL circuit supplies a reference clock to the DAC. A frequency divider provided in the DAC divides the frequency of the reference clock by two, and supplies the half frequency clock to a parallel processing section (the two decoders and the parallel-to-serial converter) of the DAC and the two digital filters. This makes it easy to secure a timing margin, permitting use in high-speed communication on the order of several GHz.

Filter circuit, semiconductor integrated circuit, communication apparatus, semiconductor device, and system

Filter circuit, transmission filter circuit, semiconductor integrated circuit, communication apparatus, and timing adjustment method for filter circuit

In a multi-channel current steering DA converter, e.g., a two-channel current steering DA converter, reference current sources Irefa and Irefb that can serve as current mirror sources for current sources Ia and Ib are provided in current source matricesandof the channels, respectively. During an operation, the reference current source Irefa or Irefb that is provided in the current source matrix of a channel that is not powered down is selected and used in accordance with control signalsand. Therefore, even when one channel is powered down, the full-scale current of the other channel can be maintained at a constant value, i.e., unchanged.

Current steering DAC

When a semiconductor circuit, in which a stabilizing capacitorfor stabilizing a reference voltage Vbias is connected to a reference voltage terminal RT, recovers from a power down state to an operational state, a current mirror circuitprovides current mirroring of a current Ia of a first current path Ph, which generates an OFF threshold voltage refof a hysteresis comparator, to generate a current Ib of a second current path Ph, which generates the reference voltage Vbias. The reference voltage Vbias is input to the comparatoras an input voltage vin. When the reference voltage Vbias becomes equal to the OFF threshold voltage ref, the comparatorimmediately stops the charging of the stabilizing capacitorby a current source I

Rapid recovery circuit

A multi-channel current steering DAC (Digital-to-Analog Converter), for example, a 2-channel current steering DAC, includes a plurality of current sources I, I, . . . corresponding to the number of bits of a digital input signal DS in each of channels A, B. Each of the plurality of current sources I, I, . . . is formed by two small-current sources (I, I), (I, I), . . . . In the case where a full-scale current is limited to a small value in any of the channels, one of the two divided current sources is turned off by switches Sa, Sa. Accordingly, a full-scale current of each channel can be adjusted with a common bias circuit without degrading the resolution.

Growing community of inventors

Osaka, Japan

Michiko Tokumaru