HC5515IP datasheet(13/17 Pages) INTERSIL

13 / 17 page

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

determines if the 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 20 (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 HC5515’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 HC5515 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 20

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.

The fuse resistors (RF) serve a dual purpose of being

nondestructive power dissipaters during surge and fuses

when the line in exposed to a power cross.

Power-Up Sequence

The HC5515 has no required power-up sequence. This is a

result of the Dielectrically Isolated (DI) process used in the

fabrication of the part. By using the DI process, care is no

longer required to insure that the substrate be kept at the

most negative potential as with junction isolated ICs.

Printed Circuit Board Layout

Care in the printed circuit board layout is essential for proper

operation. All connections to the RSN pin should be made as

close to the device pin as possible, to limit the interference

that might be injected into the RSN terminal. It is good

practice to surround the RSN pin with a ground plane.

The analog and digital grounds should be tied together at

the device.

SLIC Operating States

3dB

•

()

-----------------------------------------------------

(EQ. 28)

TABLE 1. LOGIC TRUTH TABLE

SLIC OPERATING STATE

ACTIVE DETECTOR

DET OUTPUT

Open Circuit

No Active Detector

Logic Level High

Active

Loop Current Detector

Loop Current Status

Ringing

Ring Trip Detector

Ring Trip Status

Standby

Loop Current Detector

Loop Current Status

Open Circuit

No Active Detector

Logic Level High

Active

Loop Current Detector

Ringing

Ring Trip Detector

Standby

Loop Current Detector

HC5515

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