Data Sheet
June 1998

L7590C Telephone Ringing Driver

Features

Applies a battery-backed, single-ended, sinusoidal
ringing signal to the telephone loop

Ringing capability:
-- 40 Vrms into 5 North American REN
-- 30 mApeak into 4 German REN

Built-in current limiting

Low power dissipation in idle and ringing modes

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

REF

NEG

GNDR

CB1

CB2

NEG

Lucent Technologies Inc.

Data Sheet

June 1998

L7590C Telephone Ringing Driver

Pin Information

Absolute Maximum Ratings

= 25

Stresses in excess of the absolute maximum ratings can cause permanent damage to the device. These are abso-
lute stress ratings only. Functional operation of the device is not implied at these or any other conditions in excess
of those given in the operational sections of this data sheet. Exposure to absolute maximum ratings for extended
periods may adversely affect device reliability.

Pin

Symbol

Type

Name/Function

+5 V Power Supply

GNDD

Digital Ground

GNDR

Ringing Ground

NEG

Negative Power Supply

. Determines the swing of the ringing generator. Connect

a 1

F capacitor from V

NEG

to V

REF

Internal Reference Voltage

. Connect a 1

F capacitor from V

REF

to V

NEG

CLK

Clock

. Modulated pulse stream. Low = 0 V. High = V

OUT

Ringing Generator Output

. Connect to ringing relay contact through a filter.

CB1

Bootstrap Capacitor

. Connect a 0.1

F capacitor between CB1 and CB2.

CB2

Bootstrap Capacitor

. Connect a 0.1

F capacitor between CB1 and CB2.

Filter Inductor

. Connect an inductor to pin L2.

Filter Inductor

. Connect an inductor to pin L1.

Not Enable

. A logic low activates the internal circuitry. A logic high puts the device

in a low-power powerdown mode.

Parameter

Min

Typ

Max

Unit

7.0

NEG

200

Timing Input Voltage

0.5

7.0

Storage Temperature Range

125

Maximum Junction Temperature

150

Relative Humidity Range

Lucent Technologies Inc.

Data Sheet
June 1998

L7590C Telephone Ringing Driver

Recommended Operating Conditions

Electrical Characteristics

Electrical characteristics apply for 25

C. Unless noted, V

= +5 V, V

NEG

= 170 V,

= low, L1 = 20 mH

(Rdc = 20

, Ceff = 20 pF), CLK = 100 kHz. Positive currents flow into the device. Typical is defined as 25

Parameter

Min

Typ

Max

Unit

Ambient Temperature

Supply Voltage

4.75

5.0

5.25

NEG

Supply Voltage

170

130

Parameter

Min

Typ

Max

Unit

Power Supply--Idle (CLK = H or L,

= high, dc):

NEG

Power Dissipation

--
--
--

13.5

Power Supply--Active, No Load:

NEG

Power Dissipation

--
--
--

3.2

1.38

mA
mA

Efficiency =

{[

OUT

)

LOAD

]/(V

NEG

)

}

Sinking Current, R

LOAD

= 1400

Load to GND

Sourcing Current, R

LOAD

= 1400

Load to V

NEG

40
40

80
80

--
--

%
%

ON-resistance:

CLK = H, I

OUT

= 20 mA

CLK = L, I

OUT

= +20 mA

0
0

10
10

20
20

Current Limit

mApeak

Lucent Technologies Inc.

Data Sheet

June 1998

L7590C Telephone Ringing Driver

Functional Description

Ringer Requirements

This discussion highlights some of the requirements in
the United States and Germany. Beginning with the
telephone set ringer to be powered, the United States
requires 40 Vrms to be delivered to the equivalent of
five parallel telephone sets, or 5 REN (Ringer Equiva-
lence Number), that translates to 1386

+ 40

F. In

Germany, 30 mApeak must be delivered to four parallel
telephone sets. In Germany, 4 REN have an imped-
ance of 450

+ 3.4

F. The difference results from the

impedance of the telephone-set ringers of the two
countries.

Ringing Requirements

In Germany, both single-ended ringing and balanced
ringing can be used. This is not so in the United States,
where some ringers on older equipment have a ground
connection at the telephone set, and the signal lead is
either the Tip or Ring wire of the twisted pair. This has
led to the recommended use of single-ended ringing.
Both administrations allow ringing with a negative dc
level, known as battery-backed ringing, but in the
United States, there is a constraint that this level can-
not be more negative than 75 V.

With the exception of the United States, most world-
wide administrations require an injection of a pure sine
wave. Depending on the country, the distortion require-
ment is in the range of 3% to 5%. In the United States,
the wave does not need to resemble a sine wave, but it
cannot be a square wave. The shape requirement of
the wave in the United States is expressed as a crest
factor (c.f.). This is the ratio of the peak to the rms volt-
age of the signal. The requirement is 1.2 < c.f. < 1.6.

Operation

On the L7590C, the prefiltered output is a high-
voltage replica of the PWM digital signal that is applied
to the CLK input. The signal at OUT is produced by
level shifting and control of the high-voltage transistors.
The level is determined by the magnitude of the nega-
tive dc voltage applied to the output stage transistors.
The output, ideally, should be an exact time replica of
the CLK input to faithfully reproduce the modulating
waveform. This high-voltage replica of the CLK input is
filtered to leave only the low-frequency, high-voltage
sine wave ringing signal. Figure 3, parts A and B, illus-
trates the PWM signal with relation to the modulating
signal frequency. The PWM signal is at a 100 kHz rate
and modulated at the desired ringing signal frequency,
typically 20 Hz to 30 Hz. Laboratory equipment genera-
tion of the required signal is shown in Figure 5. Propa-
gation delays and switching parameters associated
with the control circuitry and output stage transistors
can cause skewing which will produce a distorted out-
put of the modulating waveform. Skewing is illustrated
in Figure 4, parts A, B, and C. The skewing can be
seen as an increase in the duty cycle of the L7590C
output compared to the input signal duty cycle.

Using the test arrangement as shown in Figure 5, the
harmonic distortion of the filtered output of the L7590C
was measured with two different loading circuits. With
the North American 5 REN (1386

+ 40

F) load, the

THD was typically 2.0% to 2.5%. With the Germany
4 REN (450

+ 3.4

F) load, the THD was typically

1.5% to 2.0%. The 25 Hz output of the

* 3311A

generator showed a typical THD of 1.5% when supply-
ing a signal to the

8116A.

A 20

resistor (R

ILIM

) must be added between L1 and

OUT for 5 REN loads.

is a registered trademark of Hewlett-Packard Company.

Lucent Technologies Inc.

Data Sheet
June 1998

L7590C Telephone Ringing Driver

Application

* C

NEG

connects to V

NEG

pin at chip.

12-3058.E (F)

Figure 2. Basic Battery-Backed Ringing Application

Table 1. Parts List for Application, Ringing Driver IC

Name

Value

Function

20 mH

Part of LC output filter

F, 250 V, 20%

Part of LC output filter

F, 20 V, 20%

REF

filter

0.1

F, 10 V, 20%

Voltage doubling capacitor

, 1 W

Hot insertion limiter

ILIM

to 100

Current-limiter adjustment

GNDD

REF

NEG

CLK

OUT

TIP

RING

L7581

RELAY

PWM

SIGNAL

C1
1.0

L7590C

RINGING

GENERATOR

TS1

400

250 V PROT

RING TRIP
DETECT

SLIC

XMT

RCV

CODEC

NEG

20 mH

GNDR

0.1

CB1

CB2

ILIM

NEG

1.0

Lucent Technologies Inc.

Data Sheet

June 1998

L7590C Telephone Ringing Driver

Application

(continued)

12-3375.B(F)

Notes:

THD % =

x 100.

RX = 15

Figure 5. L7590C Test Connections

HP 3311A

SIGNAL

GENERATOR

25 Hz

+5 V

0.1

100 kHz (PWM)

SIGNAL LEVEL = 0 V TO 5 V

PULSE/FUNCTION

GENERATOR

100 kHz RATE

HP 8116A

CB1 CB2

GNDD

OUT

GNDR

ILIM

20 mH

C1
1.0

450

3.4

1386

HP 3585A

SPECTRUM

ANALYZER

NEG

= 170 V

C2
1

CLK

NEG

REF

L7590C

NEG

1.0

. . .

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

Data Sheet

June 1998

L7590C Telephone Ringing Driver

Lucent Technologies Inc. reserves the right to make changes to the product(s) or information contained herein without notice. No liability is assumed as a result of their use or application. No
rights under any patent accompany the sale of any such product(s) or information.

June 1998
DS98-340ALC (Replaces DS97-512ALC)

For additional information, contact your Microelectronics Group Account Manager or the following:

INTERNET: http://www.lucent.com/micro
E-MAIL: docmaster@micro.lucent.com
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Tel. (65) 778 8833, FAX (65) 777 7495

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Shanghai 200233 P. R. China

Tel. (86) 21 6440 0468, ext. 316, FAX (86) 21 6440 0652

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Tel. (81) 3 5421 1600, FAX (81) 3 5421 1700

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ITALY: (39) 2 6608131 (Milan), SPAIN: (34) 1 807 1441 (Madrid)

Ordering Information

Device Part No. Description Package Comcode

LUCL7590CAE-D Telephone Ringing Driver 16-Pin SOG 108191107

LUCL7590CAE-DT Telephone Ringing Driver 16-Pin SOG (Tape and Reel) 108191115

Part Number L7590C

Document Outline