Data Sheet

June 1998

L7590C Telephone Ringing Driver

Features

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Applies a battery-backed, single-ended, sinusoidal

ringing signal to the telephone loop

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Ringing capability:

— 40 Vrms into 5 North American REN

— 30 mApeak into 4 German REN

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Built-in current limiting

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Low power dissipation in idle and ringing modes

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Requires 5 V, a high-value negative dc supply, and

a digital input sequence

Description

The L7590C Telephone Ringing Driver produces a

low-frequency sinusoidal ringing signal for analog

telephone loops. This is accomplished by producing

an output pulse stream that is an amplified replica of

the digital input. The output is then filtered to produce

a sine wave. The peak-to-peak output level is deter-

mined by the magnitude of the negative high-voltage

dc applied to the device (up to –170 V).

The required input is a 100 kHz CMOS-compatible

pulse stream, pulse-width modulated (PWM) at the

desired ringing frequency. The output stage consists

of one upper and one lower drive transistor with an

internal control circuit.

The L7590C IC is optimized for low power dissipation

and is available in a 16-pin, surface-mount package.

12-3057a (f)

Figure 1. Block Diagram

CLOCK

CONTROL

LEVEL

SHIFT

AND

OUTPUT

TIMING

CURRENT

LIMIT

BIAS

CIRCUIT

OUT

GNDD

CLK

GNDR

CB1

CB2

EN

30

Ω

L1

L2