HC5513 datasheet(14/20 Pages) RENESAS

14 / 20 page

HC5513

FN3963 Rev.12.00

Page 14 of 20

August 2003

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 = 330k.

Thermal Shutdown Protection

The HC5513’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 HC5513 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.

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 HC5513 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.

FIGURE 20A.

FIGURE 20B.

FIGURE 20. LONGITUDINAL IMPEDANCE NETWORK

TIP

RING

VBAT/2

I1

I2

RLARGE

VT

ILONG

HC5513

ILONG

VR

VBAT/2

RLARGE

TIP

RING



2I0

I1

TIP CURRENT SOURCE

WITH DIFFERENTIAL INPUTS

TIP DIFFERENTIAL

TRANSCONDUCTANCE

AMPLIFIER

f3dB





RHP



CHP





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

(EQ. 28)

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