STLC30R81

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Figure 6. PWM signal Input vs Sinusoidal Output

GROUND START

This mode is selected when the SLIC is adopted in a system using the Ground Start feature.

In this mode, the TIP termination is set in High Impedance ( 100K

Ω ) while the RING one is active and fixed at

-33V @ Vbat1 (= -38V). In case RING termination is connected to GND the sinked current is limited to 35mA.

When RING is connected to GND both Off-Hook and Ground-Key detectors are set low.

TEST MODES

This device can provide three kind of tests:

1. Phone Detection

2. Short circuit

3. Loop back

Phone Detection

This test feature checks whether a phone is connected to the line.

Starting from Active Reverse Polarity status, just changing the D0 input bit, it is possible to perform the Phone

Detection function.

The MCU measures the time span of DET. Time longer then 4ms indicates that a phone is hooked up with the

line, if no phone is connected, the time span is less than 2ms.

Table 4. Phone detection - D0 variation

Control Word

Operating Mode

D0

D1

D2

D3

0

1

1

0

Active - Reverse Polarity

1

1

1

0

High Impedance Feeding - Normal Polarity

Rxin-

Rg+

Rg-

Rxin+

OpAmp 1

OpAmp 2

LPF

PWM Ring

IN

CODEC