HC5523IP datasheet(13/18 Pages) INTERSIL

13 / 18 page

Active State (C1 = 0, C2 = 1)

The tip output is capable of sourcing loop current and for open

circuit conditions is about -4V from ground. The ring output is

capable of sinking loop current and for open circuit conditions is

about VBAT +4V. VF signal transmission is normal. The loop

current and ground key detectors are both active, E0 and E1

determine which detector is gated to the DET output.

Ringing State (C1 = 1, C2 = 0)

The ring relay driver and the ring trip detector are activated.

Both the tip and ring line drive ampliﬁers are powered down.

Both tip and ring are disconnected from the line via the

external ring relay.

Standby State (C1 = 1, C2 = 1)

Both the tip and ring line drive ampliﬁers are powered down.

Internal resistors are connected between tip to ground and

ring to VBAT to allow loop current detect in an off-hook

condition. The loop current and ground key detectors are

both active, E0 and E1 determine which detector is gated to

the DET output.

AC Transmission Circuit Stability

To ensure stability of the AC transmission feedback loop two

compensation capacitors CTC and CRC are required.

Figure 21 (Application Circuit) illustrates their use.

Recommended value is 2200pF.

AC-DC Separation Capacitor, CHP

The high pass ﬁlter capacitor connected between pins HPT

and HPR provides the separation between circuits sensing

tip to ring DC conditions and circuits processing AC signals.

A 10nf CHP will position the low end frequency response

3dB break point at 48Hz. Where:

where RHP = 330kΩ

Thermal Shutdown Protection

The HC5523’s thermal shutdown protection is invoked if a

fault condition on the tip or ring causes the temperature of

the die to exceed 160oC. If this happens, the SLIC goes into

a high impedance state and will remain there until the

temperature of the die cools down by about 20oC. The SLIC

will return back to its normal operating mode, providing the

fault condition has been removed.

Surge Voltage Protection

The HC5523 must be protected against surge voltages and

power crosses. Refer to “Maximum Ratings” TIPX and

RINGX terminals for maximum allowable transient tip and

ring voltages. The protection circuit shown in Figure 21

utilizes diodes together with a clamping device to protect tip

and ring against high voltage transients.

Positive transients on tip or ring are clamped to within a

couple of volts above ground via diodes D1 and D2. Under

normal operating conditions D1 and D2 are reverse biased

and out of the circuit.

Negative transients on tip and ring are clamped to within a

couple of volts below ground via diodes D3 and D4 with the

help of a Surgector. The Surgector is required to block

conduction through diodes D3 and D4 under normal

operating conditions and allows negative surges to be

returned to system ground.

TIP

RING

VBAT/2

∆I1

∆I2

RLARGE

∆VT

ILONG

HC5523

ILONG

∆VR

VBAT/2

RLARGE

TIP

RING

Ω

2I0

∆I1

TIP CURRENT SOURCE

WITH DIFFERENTIAL INPUTS

TIP DIFFERENTIAL

TRANSCONDUCTANCE

AMPLIFIER

FIGURE 20A.

FIGURE 20B.

FIGURE 20. LONGITUDINAL IMPEDANCE NETWORK

3dB

•

()

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(EQ. 28)

HC5523

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