SAMSUNG Proprietary-Contents may change without notice
10-4
STH-A225
Circuit Description & Circuit Diagrams
1-3. IF INTERFACE CHIP (IFC :U101)
The IFC provides the radio IF and audio interfaces (Figure2). Differential Rx I/Q and Tx I/Q signal pairs
interface directly with the RF interface chip (RFIC : U304) device. MOD, AFC, AGC, RSSI, and PA_CNT signals
also directly control the radio circuitry. Three audio paths are implemented. The primary path utilizes the
microphone and speaker, located on the keypad and display board respectively. Both microphone and speaker
utilize the main differential circuits in the IFC to minimize noise pickup. The speaker output is amplified
internally to enable direct connection to the speaker. The second audio path connects to the headset jack. The
headset microphone and speaker are passed to the IFC’s auxiliary input and output, respectively. The headset
jack terminals indicate via the HEADSET_SENSE line when the headset is present as well as when the headset
button is pushed via the SEND_END line. The third audio path to the HFK shares the auxiliary output with the
headset for its speaker and uses the second auxiliary input for its microphone. Since the auxiliary output is not
internally amplified, an external audio amplifier is applied before connection to the two headset and HFK.
Figure 2. IFC interface and block diagram