SI3066 Просмотр технического описания (PDF) - Silicon Laboratories

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SI3066

V.32 FCC+ EMBEDDED DIRECT ACCESS ARRANGEMENT

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Si3066

4.4. Loop Current Sensing

The Si3066 measures loop current when off-hook. The

LCS[4:0] bits measure loop current with 3.3 mA/bit

resolution. The following functions can be performed

with the LCS bits:

„ While off-hook, detect if a parallel phone goes on- or

off-hook.

„ Determine if sufficient loop current is available for

proper operation.

„ Detect if there is an overload condition.

4.4.1. Loop Current Measurement

When the DAA is off-hook, the LCS[4:0] bits measure

loop current with 3.3 mA/bit resolution. These bits can

be used to detect another device going off-hook by

monitoring the dc loop current. The transfer function for

LCS is shown in Figure 6 and is detailed in Table 6. The

LCS bits report loop current down to the minimum

operating loop current for the DAA. Below this

threshold, the reported value of loop current is

unpredictable and may vary between zero and the

minimum operating current.

When the LCS bits have reached their maximum value,

the Loop Current Sense Overload Interrupt bit fires;

however, LCSOI firing does not necessarily guarantee

that an overload situation has occurred.

Overload

30

25

20

LCS BITS

15

10

5

0

0

13.2

Loop Current (mA)

102.3

160

Figure 6. Typical LCS Transfer Function

Table 6. Loop Current Sense Transfer Function

LCS[4:0]

Condition

00000b – 00011b Insufficient line current for normal operation. Use the DODI bit

(Register 4, bit 3) to determine if a line is still connected.

00100b – 11110b Normal operation.

11111b

Loop current is excessive (>160 mA).

Rev. 1.0

11

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