SI3016 Просмотр технического описания (PDF) - Silicon Laboratories

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SI3016

3.3 V ENHANCED GLOBAL DIRECT ACCESS ARRANGEMENT

Silicon Laboratories 

Si3016

30

Overload

25

20

LVCS

BITS

15

CTR21

10

5

0

0 3 6 9 12 15 18 21 24 27 30 33 36 39 42 45 48 51 54 57 60 63 66 69 72 75 78 81 84 87 90 93

140

Loop Current (mA)

Figure 9. Typical Loop Current LVCS Transfer Function

Table 10. Loop Current Transfer Function

LVCS[4:0]

Condition

00000

Insufficient line current for normal

operation. Use the DOD bit to determine if

a line is still connected.

00001 Minimum line current for normal operation.

11111

Loop current is excessive (overload).

Overload > 140 mA in all modes except

CTR21.

Overload > 54 mA in CTR21 mode.

4.7. Off-Hook

The communication system generates an off-hook

command by setting the OH bit. With the OH bit set, the

system is in an off-hook state.

The off-hook state is used to seize the line for incoming/

outgoing calls and can also be used for pulse dialing.

When the DAA is on-hook, negligible dc current flows

through the hookswitch. When the DAA is placed in the

off-hook state, the hookswitch transistor pair, Q1 and

Q2, turn on. This applies a termination impedance

across TIP and RING and causes dc loop current to

flow. The termination impedance has both an ac and dc

component.

When executing an off-hook sequence, the Si3016

requires 1548/Fs seconds to complete the off-hook and

provide phone-line data on the serial link. This includes

the 12/Fs filter group delay. If necessary, for the shortest

delay, a higher Fs may be established prior to executing

the off-hook, such as an Fs of 10.286 kHz. The delay

allows for line transients to settle prior to normal use.

4.8. DC Termination

The Si3016 has four programmable dc termination

modes that are selected with the DCT[1:0] bits in

Register 16.

FCC mode (DCT[1:0] = 10 b), shown in Figure 10, is the

default dc termination mode and supports a transmit full

scale level of –1 dBm at TIP and RING. This mode

meets FCC requirements in addition to the requirements

of many other countries.

FCC DCT Mode

12

11

10

9

8

7

6

.01 .02 .03 .04 .05 .06 .07 .08 .09 .1 .11

Loop Current (A)

Figure 10. FCC Mode I/V Characteristics

CTR21 mode (DCT[1:0] = 11 b), shown in Figure 11,

16

Rev. 1.0

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