Frequently Asked Questions |ROHM Semiconductor

The system waits while changing channels until the receiver receives the radio wave from the transmitter. Is there anything to be aware of about this system?
- The receiver changes channels until it receives radio waves from the sender. For this reason, the transmission side must keep sending the preamble until the receiver detects the transmitted channel. Therefore, taking into account the number of channels to search for radio waves, a long preamble is required. Also, if there is only a radio wave, the receiving side may make an erroneous channel determination based on radio waves from other systems. For this reason, it is necessary to consider the "criterion for presence of radio waves (bit synchronization information, etc.)" that uses signals other than radio waves.
  Related Products: ML7344/ML7406 family, ML7345 family, ML7396 family, ML7404, ML7414

If there is interference (when radio waves simultaneously transmitted from different transmitters collide), it may be impossible to receive data (SyncWord or addresses) in the first place. Is there a way to avoid missing data to be received due to collision?
- If data is transmitted simultaneously on the same channel, it may become unable to receive the data due to the RF interference characteristics. However, ARIB STD T-108 requires CCA to be performed before transmission. For this reason, there is a mechanism to avoid interference due to simultaneous transmission from nearby transmitters.
  Related Products: ML7344/ML7406 family, ML7345 family, ML7396 family, ML7404, ML7414

After setting the register value of [PA_ADJ1 to 3] register (B1 0x04-0x06), [PA_REG_ADJ1 to 3] register (B1 0x33-0x35), [PA_REG_FINE_ADJ] register (B1 0x13) through adjusting PA of ML7396, how long does it take for them to be reflected in the wireless output?
- After completion of register settings, the control signal is sent to the PA without time lags. Therefore, the time taken for them to be reflected is almost equivalent to the response time of PA. Since PA provides quick response, they are reflected within 100 us.
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How can the matching between transmitting and receiving pins be adjusted?
- Reference values of the impedance of each pin measured with the LAPIS evaluation board are described in respective design guides. There is no problem to adjust one element at a time. In addition, it can be adjusted by fine-tuning the constants based on the topology in the reference circuit diagrams described in the design guides.
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When a detuning wave of several hundred kHz is input at a high level, sometimes the carrier sense (CCA) may not operate properly, causing the signal to be transmitted.
- It is an unavoidable event in terms of the circuit mechanism.
  If there is an interference wave at a distance from the BPF band, RSSI is not detected since it hardly passes through the channel filter band. However, the interference wave signal is input to the circuits (LNA, MIX, etc.) at the stage preceding BPF. Therefore, if the signal is strong the pre-stage circuit becomes saturated, causing gain compression. Such events may occur if the correct RSSI value is not obtained.
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What types of antenna switch parts are available for use with diversity?
- The following product is used so far:
  - HEXAWAVE HWS503
  Note: Use the RF input/output pins of the antenna switch with AC coupling. * For details, follow the antenna switch specifications.
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Is there any precaution in developing software?
- When contact us about problem on operation or behavior, lapis may ask you to show whole register setting data in that defective state. Therefore, installing register read function may reduce the time for analyzing the problem.
  Related Products: ML7344/ML7406 family, ML7345 family, ML7396 family, ML7404, ML7414