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ETALDOC 551/8

Page 1 of 5

January 2001

PRODUCT DATA SHEET

TELEPHONE HANDSET DRIVER

P3143

Features

Applications

∗

Subminiature case size

∗

Powering telephone handsets

∗

Current drive - easy to interface

∗

Voice modems

∗

Easily programmable

∗

PABX least cost routers

∗

½ watt output power

∗

ISDN analogue handset driver

∗

ON/OFF control

∗

IEC 950, EN 60950 and EN 41003 certified

DESCRIPTION

P3143 is a safety-isolating programmable current
source intended to power telephone handsets
across a supplementary insulation barrier.

The current source provides a high output
impedance, greatly simplifying its use since current
can be injected at a chosen level without loading an
associated circuit.

The current source of P3143 is programmed by a
single external low-power resistor and will drive up
to 30mA into loads at up to 15Vdc, and up to 40mA
into loads at up to 12Vdc.

P3143 also provides a control pin which switches
the current source on/off across the safety barrier.

P3143 is powered from a standard +12V supply,
commonly found in telephone and computer
equipment.

P3143 is certified to IEC 950, EN 60950 and
EN 41003 Equipment incorporating P3143 is
capable of approval worldwide.

to Electronic Techniques

(Anglia) Limited

P3143

ETALDOC 551/8

Page 2 of 5

January 2001

SPECIFICATIONS

Electrical

At ambient temperature = 25ºC and test circuit as Fig 1 unless otherwise stated.

TABLE 1

Parameter

Conditions

Min

Typ

Max

Units

Output current I

OUT

(as Fig 1)
Load = 300

Ω

Output impedance

200 – 4000Hz

Ω

Vcc supply voltage range

To specification
Operational

11.3

-
-

12.7

V
V

Supply current

OUT

= 30mA

OUT

= 40mA

-
-

70
80

-
-

mA
mA

Quiescent current
Standby
No load

Control (pin 4) OFF.
Control (pin 4) ON.
Load disconnected.

-
-

mA
mA

Sensitivity of I

OUT

to Vcc

+1.1

mA/V

Sensitivity of I

OUT

to ambient

temperature

(operating range)

-0.07

mA/ºC

ON/OFF control

(1)

OFF
ON
Control input sink current

Pin 4

Pin 4 = 0.7V

4.0

-
-

0.7

V
V

Open circuit voltage (pins 6-7)

Load disconnected

Temperature range:
Operating
Storage

-25

-
-

+70
+85

ºC
ºC

Voltage isolation

(2)

50Hz
dc

2.12

3.0

-
-

kVrms

Notes:

1. Control voltages apply where voltage forcing is

used. If pin 4 is left unconnected the control
defaults to the ON condition. To guarantee turn
OFF, driver sourcing current into control pin 4
should be capable of 1mA at 4.5V.

2. Components are 100% tested at 3.25kV dc.

Vcc (+12V)

CONTROL

+5V OFF

0V ON

current return

3
4

Fig. 1 Application Circuit

R (22 )

Ω

current output (I 30mA)

O U T

SAFETY BARRIER

P3143

ETALDOC 551/8

Page 3 of 5

January 2001

APPLICATION

A simplified treatment for 600

Ω

match and with an

idealized signal transformer etc. is presented here.

For a fuller description of P3143's application, refer
to application notes (e.g. ETALDOC 561).

P3143 overcomes the traditional difficulties
associated with voltage output dc-dc converters,
(which unbalance matching circuits), by employing
a safety-isolated constant current source. Current
is set by a single programming resistor, R

, which

can be a miniature type of rating less than 50mW,
in accordance with fig. 2.

P3143's output impedance is around 20k

Ω

across

the voiceband, and therefore presents negligible
loading to matching circuits.

Fig. 3, which assumes an ideal transformer and
high value blocking capacitor, demonstrates the
simplicity of a 600

Ω

match with 30mA current feed.

An approved handset driven at 25mA develops a
voltage in accordance with regulatory
requirements. Therefore, with current forcing, an
acceptable operating point can always be
established. The current source must be capable
of driving a "worst case" handset, i.e. a handset
which develops the highest voltage at the sourced
current. In many countries a maximum permissible
terminal voltage is imposed for terminal equipment
driven at 25mA. P3143 will deliver 25mA at
voltages in excess of 14V (see fig. 4), satisfying
nearly all national requirements.

Fig 3

T X

+ 1 2 V

P3143

600

O N / O F F

4
3

3 0 m A

SAFETY BARRIER

R (22 )

Ω

OUT

Fig 4 Recommended operating region for

output VI characteristic

OUT

Fig 2 I

(typical) as a function of programme

resistor R

OUT

P3143

ETALDOC 551/8

Page 4 of 5

January 2001

INSTALLATION

Whilst P3143 suppresses supply voltage ripple by
around 20dB with a typical handset, excessive
audio frequency ripple (e.g. 120Hz ripple from a
poorly regulated rectified ac supply) will inevitably
cause some breakthrough to the handset. In such
cases, adding supply smoothing capacitors of
reasonable size may be ineffective. However,
P3143 permits an economical method of additional
suppression with capacitance (e.g. 47

F 35V)

added between pins 6 and 9 (positive terminal of
capacitor to pin 9).

Note

: do not connect capacitance across current

output terminals (pins 6-7) as this will severely
impair the high output impedance of P3143.

In common with all power switching devices,
P3143 switches relatively high voltages and
currents. The associated fields are unlikely to
be troublesome, but normal precautions should
be taken with sensitive magnetic components to
avoid coupling local fields. Such components
should not be sited within 3mm of the P3143
outline.

Observe prudent layout practices with power
switching devices. Do not run power tracks close
to sensitive signal tracks. Avoid siting sensitive
analogue components (eg. signal transformers)
close to power switching devices. If additional
decoupling/suppression is necessary, position
capacitors close to the component to be
decoupled.

CONSTRUCTION

Dimensions shown are in millimetres (inches)

FUNCTION

1
2
3
4
5
6
7
8
9

DO NOT CONNECT
+12V, Vcc
0V
Control: +5V OFF, 0V ON
DO NOT CONNECT
Current return
Current output
Current set resistor pin
Current set resistor pin

M A D E I N U K

View from underside

P3143

ETALDOC 551/8

Page 5 of 5

January 2001

SAFETY

CERTIFICATION

Manufactured from materials conforming to
flammability requirements of UL94V-0 and
EN 60950:1992 (BS7002:1992) sub-clause
1.2.13.2 (V0).
Distance through solid insulation 0.4mm minimum.
Constructed and fully encapsulated in accordance
with EN 60950:1992 (BS7002:1992) (Supplementary
insulation), 250Vrms working voltage, flammability
class V-0.

Certified by BSI (Certificate 8175) to
EN 60950:1992 (BS7002:1992) up to and
including amendment 5, and IEC950:1991, sub-
clauses 2.2.2, 2.9.1, 4.4.3 (V-0), and 5.3 for
supplementary insulation for a mains supply
voltage not exceeding 250Vrms (working voltage
250Vrms) and a maximum operating temperature
of 85ºC in a Pollution Degree 2 environment, and
BS EN 41003:1997 sub-clause 4.5.3.

Additionally, Profec Technologies certifies all
devices as providing voltage isolation of
2.12kVrms, 3.0kV dc minimum. All shipments are
supported by a certificate of conformity to current
applicable safety standards.

ABSOLUTE MAXIMUM RATINGS

COPYRIGHT

(Ratings of components independent of circuit).

Vcc (pin 2)

+ 15V

Control (pin 4)

+ 6V

Minimum current set resistance

Ω

Short term isolation voltage (1s)

3.0kVdc
2.12kVrms

Storage temperature

-25ºC to +85ºC

Lead temperature (10s)

260ºC

Short circuit duration (pins 6-7)

OUT

≤

30mA

Indefinite

30mA < I

OUT

≤

40mA

10s

40mA <I

OUT

≤

45mA

ETAL and P3143 are Trade Marks of Profec
Technologies Ltd.
The Trade Mark ETAL is registered at the UK
Trade Marks Registry.

Profec Technologies Ltd. is the owner of the
design right under the Copyright Designs and
Patents Act 1988 and no rights or licences are
hereby granted or implied to any third party.

T R A N S F O R M I N G T H E F U T U R E

Profec Technologies Ltd., 10 Betts Avenue, Martlesham Heath, Ipswich, IP5 3RH, England

Telephone: +44 (0) 1473 611422

Fax: +44 (0) 1473 611919

Websites: www.etal.ltd.uk

www.profec.com

Email:

info@etal.ltd.uk

sales@profec.com

ISO 9001

FM 25326