ML7396AB datasheet(38/140 Pages) LAPIS

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FEDL7396A/B/E-07

ML7396A/B/E

38/140

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Diversity Function

ML7396 family supports two antenna diversity function.

While setting 2DIV_EN ([2DIV_CNTRL: B0 0x71(0)])=0b1, as soon as RX_ON is set, diversity mode will start. When

diversity mode is started, and upon RX data detection, each ED value will be acquired by switching two antennas. And then

antenna with higher ED value will be selected automatically. As diversity uses preamble data for ED value acquisition, longer

preamble length is desirable. If preamble is too short, accurate ED values may not be obtained.

The timing example is as below.

RX packet

Preamble

Length

Data

SFD

ED values and antenna diversity result will be cleared when as below:

1. Diversity search completion interrupt (INT[09] group2) is cleard.

2. FIFO* RX competion interrupt (INT[18] or INT[19] group3) is cleared

3. Diversity resume by errounous detection

ED values and diversity result should be read before clearing Diversity search completion or FIFO* RX completion interrupt.

During receiving state, clearing Diversity search completion interrupt causes the data error since diversity operation wlll

resume by the interrupt clearance. Diverstiy search completion interrupt should be cleared at same timing of FIFO* RX

completion interrupt clearance.

ML7396 supports recovering function from incorrect diversity completion caused by errornous detection due to thermal noize,

After dicersity search completion, if preamble can not be detected until antenna search timer expiration, ML7396 judges the

previous diversity search completion is incorrect and resume diversity operation automatically.

When resume diversity operation for next packet receiving, please clear RX completion interrupt and Diversity search

completion interrupt.

(Note)

When an incorrect diversity completion caused by errornous detection due to thermal noize, ML7396 resume antenna

diversity automatically. But when receiving a desired signal during the process of errounous detection, ED value

obtained by [ANT1_ED:B0 0x73] or [ANT2_ED:B0 0x74] may indicate a low value different from the actual input

level.

If this event occures, the actual ED value of desired signal can be achibed by reading [ED_RSLT:B0 0x16] registers after

SFD detection interrupt (INT[11] group2) generation.

When RF state is changed to TX_ON state immediately after an incorrect diversity completion caused by errornous

detection, ML7396 judges Diversity search is done. Then, Diversity search is not operated at next receiving. In this case,

please clear Diversity search completion interrupt (INT[09] group2) by next receiving.

RF STATE

Antenna

ANT1 ED

search period

Antenna

selection

SEARCH_TIME[6:0]

([2DIV_SEARCH: B0 0x6F(6-0)])

TRX_OFF

RX_ON

Receive

ANT1/ANT2 search

is repeated

INT[09] (Diversity search completion)

[INT_SOURCE_GRP2: B0 0x25]

ANT1/2

ANT2

Antenna with higher ED

ANT1

ANT2 ED

stabilization

search period

period

RSSI_STABLE[3:0]

([RSSI_STABLE_TIME: B0 0x22(3-0)])

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