HC5526IP datasheet(7/18 Pages) INTERSIL

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Circuit Operation and Design Information

The HC5526 is a current feed voltage sense Subscriber Line

Interface Circuit (SLIC). This means that for short loop

applications the SLIC provides a programmed constant

current to the tip and ring terminals while sensing the tip to

ring voltage.

The following discussion separates the SLIC’s operation into

its DC and AC paths, then follows up with additional circuit

and design information.

Constant Loop Current (DC) Path

SLIC in the Active Mode

The DC path establishes a constant loop current that ﬂows

out of tip and into the ring terminal. The loop current is

programmed by resistors RDC1, RDC2 and the voltage on

the RDC pin (Figure 13). The RDC voltage is determined by

the voltage across R1 in the saturation guard circuit. Under

constant current feed conditions, the voltage drop across R1

sets the RDC voltage to -2.5V. This occurs when current

ﬂows through R1 into the current source I2. The RDC voltage

establishes a current (IRSN) that is equal to VRDC/(RDC1

+RDC2). This current is then multiplied by 1000, in the loop

current circuit, to become the tip and ring loop currents.

For the purpose of the following discussion, the saturation

guard voltage is deﬁned as the maximum tip to ring voltage

at which the SLIC can provide a constant current for a given

battery and overhead voltage.

SUPPLY CURRENTS (VBAT = -28V)

ICC, On-Hook

Open Circuit State (C1, 2 = 0, 0)

1.5

Standby State (C1, 2 = 1, 1)

1.7

Active State (C1, 2 = 0,1)

5.5

IEE, On-Hook

Open Circuit State (C1, 2 = 0, 0)

0.8

Standby State (C1, 2 = 1, 1)

0.8

Active State (C1, 2 = 0, 1)

2.2

IBAT, On-Hook

Open Circuit State (C1, 2 = 0, 0)

0.4

Standby State (C1, 2 = 1, 1)

0.6

Active State (C1, 2 = 0, 1)

3.9

PSRR

VCC to 2 or 4-Wire Port

(Note 30, Figure 12)

VEE to 2 or 4-Wire Port

(Note 30, Figure 12)

VBAT to 2 or 4-Wire Port

(Note 30, Figure 12)

FIGURE 12. POWER SUPPLY REJECTION RATIO

Electrical Speciﬁcations

TA =0

oCto70oC, V

CC =5V ±5%, VEE = -5V ±5%, VBAT = -28V, AGND = BGND = 0V, RDC1 =RDC2 = 41.2kΩ,

RD = 39kΩ,RSG = ∞,RF1 =RF2 =0Ω,CHP = 10nF, CDC = 1.5µF, ZL = 600Ω, Unless Otherwise Speciﬁed. All

pin number references in the ﬁgures refer to the 28 lead PLCC package. (Continued)

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

RRX

600k

Ω

300k

Ω

VTX

600

Ω

100mVRMS, 50Hz TO 4kHz

-48V SUPPLY

5V SUPPLY

-5V SUPPLY

PSRR = 20 log (VTX/VIN)

TIP

VTX

RING

RSN

HC5526

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