Patent ID: 9614531
Date: 2017-04-04
CPC Classifications: H03K,H04L

Claim:
1. A termination resistance adjustment circuit configured to adjust values of termination resistances of a transmission circuit including a plurality of drive circuits generating output signals with a plurality of voltage levels respectively corresponding to values of an input data with a plurality of bits, by adjusting the number of use of the drive circuits corresponding to each bit of the input data with the plurality of bits, the termination resistance adjustment circuit comprising: a replica circuit configured to include output resistances having the same characteristics as the termination resistances of the drive circuits; a current source configured to be able to adjust the amount of a load current which is supplied to an output terminal of the replica circuit; a voltage generation circuit configured to generate a plurality of reference voltages respectively corresponding to a plurality of values which are represented by the input data with the plurality of bits; a comparison circuit configured to compare a monitoring voltage which is output from the output terminal of the replica circuit with the plurality of reference voltages; and a control circuit configured to drive the replica circuit by setting an input signal of the replica circuit to any one of a first logic level and a second logic level, configured to change the amount of the load current by controlling the current source, configured to calculate values of the output resistances of the replica circuit for each of a plurality of levels of the monitoring voltage, based on the amount of the load current at when a comparison result by the comparison circuit changes, configured to adjust the number of use of the drive circuits for each bit of the input data with the plurality of bits, based on the values of the output resistances which are calculated for each of the plurality of levels, so that the values of the termination resistances of the transmission circuit are adjusted.