HC5513BIM 查看數據表（PDF） - Intersil

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HC5513BIM

TR909 DLC/FLC SLIC with Low Power Standby

Intersil 

HC5513

Figure 15 shows the relationship between the saturation

guard voltage, the loop current and the loop resistance. Notice

from Figure 15 that for a loop resistance <1.2kΩ (RSG =

21.4kΩ) the SLIC is operating in the constant current feed

region and for resistances >1.2kΩ the SLIC is operating in the

resistive feed region. Operation in the resistive feed region

allows long loop and off-hook transmission by keeping the tip

and ring voltages off the rails. Operation in this region is

transparent to the customer.

50

VBAT = -48V, RSG = 21.4kΩ

40

30

CONSTANT CURRENT

FEED REGION

SATURATION GUARD

VOLTAGE, VTR = 38V

20

VBAT = -24V, RSG = ∞

10 RESISTIVE FEED

REGION

0

0

10

20

30

LOOP CURRENT (mA)

SATURATION GUARD

VOLTAGE, VTR = 13V

RL 100kΩ

RL 100kΩ

4kΩ

1.5kΩ

2kΩ

700Ω

<1.2kΩ RRSG = 21.4kΩ

<400Ω RRSG = ∞ Ω

FIGURE 15. VTR vs IL AND RL

The Saturation Guard circuit (Figure 13) monitors the tip to

ring voltage via the transconductance amplifier A1. A1

generates a current that is proportional to the tip to ring

voltage difference. I1 is internally set to sink all of A1’s current

until the tip to ring voltage exceeds 12.5V. When the tip to ring

voltage exceeds 12.5V (with no RSG resistor) A1 supplies

more current than I1 can sink. When this happens A2

amplifies its input current by a factor of 12 and the current

through R1 becomes the difference between I2 and the output

current from A2. As the current from A2 increases, the voltage

across R1 decreases and the output voltage on RDC

decreases. This results in a corresponding decrease in the

loop current. The RSG pin provides the ability to increase the

saturation guard reference voltage beyond 12.5V. Equation 3

gives the relationship between the RSG resistor value and the

programmable saturation guard reference voltage:

VSGREF = 12.5 + 5----R-•---S--1--G-0----5-

(EQ. 3)

where:

VSGREF = Saturation Guard reference voltage.

RSG = Saturation Guard programming resistor.

When the Saturation guard reference voltage is exceeded,

the tip to ring voltage is calculated using Equation 4:

VTR = RL × -R----L---1--+-6---.(--6-R--6--D---+--C---5-1----•+----1-R--0---D-5---C-⁄---R2----)-S--⁄-G--6---0---0--

where:

VTR = Voltage differential between tip and ring.

RL = Loop resistance.

(EQ. 4)

For on-hook transmission RL = ∞, Equation 4 reduces to:

VTR = 16.66 + 5----R-•---S--1--G-0----5-

(EQ. 5)

The value of RSG should be calculated to allow maximum

loop length operation. This requires that the saturation guard

reference voltage be set as high as possible without clipping

the incoming or outgoing VF signal. A voltage margin of -4V

on tip and -4V on ring, for a total of -8V margin, is

recommended as a general guideline. The value of RSG is

calculated using Equation 6:

RSG=

-----------------------------------------------------------------5----•-----1---0----5----------------------------------------------------------------

( VBAT

–

VMARGIN)

×



1



+

(---R-----D----C-6---10----0+----R-R---L--D----C----2----)

– 16.66V

(EQ. 6)

where:

VBAT = Battery voltage.

VMARGIN = Recommended value of -8V to allow a maximum

overload level of 3.1VPEAK.

For on-hook transmission, RL = ∞, Equation 6 reduces to:

RSG = --V----B----A----T------–-----V----M-5----A•----R-1---G0----5I--N------–----1----6---.--6---6----V--

(EQ. 7)

SLIC in the Standby Mode

Overall system power is saved by configuring the SLIC in the

standby state when not in use. In the standby state the tip

and ring amplifiers are disabled and internal resistors are

connected between tip to ground and ring to VBAT. This

connection enables a loop current to flow when the phone

goes off-hook. The loop current detector then detects this

current and the SLIC is configured in the active mode for

voice transmission. The loop current in standby state is

calculated as follows:

IL ≈ R--V---L-B----+A----T1----8--–-0---0-3---Ω-V--

where:

IL = Loop current in the standby state.

RL = Loop resistance.

VBAT = Battery voltage.

(EQ. 8)

(AC) Transmission Path

SLIC in the Active Mode

Figure 16 shows a simplified AC transmission model. Circuit

analysis yields the following design equations:

VTR = VTX + IM • 2RF

(EQ. 9)

V---Z--T--T-X-- + -VZ----RR----XX-- = 1----0I--M-0----0-

VTR = EG – IM • ZL

(EQ. 10)

(EQ. 11)

62

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