Filtering a single wire protocol (SWP) current signal to be provided to a near field communications (NFC) device

摘要

A communications device is disclosed that includes a united integrated circuit card (UICC) that provides a single wire protocol (SWP) current signal to a near field communications (NFC) device. The SWP current signal is filtered by a filter to remove noise from the SWP current signal. The filter is precharged by a reference voltage when the SWP current signal is in a low state and then filters the SWP current signal when the SWP current signal is in a high state. A switching network provides the filter with the reference voltage to precharge when the SWP is current signal is in the low state and then provides the filter with the SWP current signal to filter when the SWP current signal is in the high state.

主权项

1. An integrated circuit for use in a communications device, the integrated circuit comprising:
a single wire protocol (SWP) interface circuit configured to receive a SWP signal; a filter configured to filter the SWP signal in a first mode of operation and to be precharged in a second mode of operation; a first switch configured to provide the SWP signal to the filter in the first mode of operation; a second switch configured to precharge the filter in the second mode of operation; a controller configured to transition the communications device from the second mode of operation to the first mode of operation based upon a characteristic of the SWP signal; and a near field communications (NFC) device configured to receive the filtered SWP signal in the first mode of operation.