| US 7,515,008 B2 | ||
| Semiconductor integrated circuit having oscillator frequency compensation function | ||
| Shuichi Ide, Kanagawa (Japan) | ||
| Assigned to NEC Electronics Corporation, Kanagawa (Japan) | ||
| Filed on May 18, 2007, as Appl. No. 11/798,986. | ||
| Claims priority of application No. 2006-140252 (JP), filed on May 19, 2006. | ||
| Prior Publication US 2007/0268167 A1, Nov. 22, 2007 | ||
| Int. Cl. H03L 1/02 (2006.01) | ||
| U.S. Cl. 331—176 [331/57] | 9 Claims |
| 1. A semiconductor integrated circuit comprising:
a signal voltage output unit configured to output a first signal voltage having temperature dependency and a second signal
voltage being constant independently on a temperature;
an A/D converter configured to convert an input signal voltage into a digital signal based on a reference signal; and
a compensation code generation unit configured to compensate a frequency of an oscillator in response to the digital signal
outputted from the A/D converter,
wherein the A/D converter generates a first conversion signal by digitalizing a first difference voltage being a ratio between
the first signal voltage and the reference voltage and a second conversion signal by digitalizing a second difference voltage
being a ratio between the second signal voltage and the reference voltage, and
the compensation code generation unit generates the compensation code in response to the first conversion signal and the second
conversion signal.
|