ETALDOC 240/9

Page 1 of 5

January 2001

PRODUCT DATA SHEET

MICROPROFILE LINE

P2781

MATCHING TRANSFORMER

Features

Applications

∗

  Surface Mount

∗

  Telecommunications

∗

  7mm seated height

∗

  V.22bis and V.32bis modems

∗

  Vacuum encapsulated

∗

  Line matching

∗

  IEC 950, UL 1950 and EN 60950 certified

∗

  Portable computers

∗

  UL Recognized Component

∗

  Instrumentation

∗

  BABT Certificate of Recognition

∗

  CSA NRTL/C Certificate of Compliance

 
 

 

DESCRIPTION

P2781 is a  microprofile transformer for applications
where high performance and safety isolation to
international standards are required in an extremely
small case size.

Designed specifically as a surface mount device, the
P2781 features a 7mm seated height and is vacuum
encapsulated and tested to 6500VDC.

Despite the subminiature size, the performance is
the equal of that of much larger components.  The
P2781 offers reinforced insulation, is ideal for voice
telecommunications and for data communications to
medium speed, whilst capable of being matched to
both 600

Ω

 and complex impedance telephone lines.

At moderate transmit power levels (e.g. -10dBm)
performance to V.32bis may be achieved.

In instrumentation applications, the P2781 offers a
wideband frequency response from 50Hz to
40kHz.

P2781 is certified to IEC 950, EN 60950,
EN 41003,  and UL1950. P2781 is a UL
Recognized Component, and is supported by a
BABT Certificate of Recognition, a 

CSA

Certificate of Compliance and an IEC CB Test
Certificate.

E203175

to Electronic Techniques

(Anglia) Limited

P2781

ETALDOC 240/9

Page 2 of 5

January 2001

SPECIFICATIONS

Electrical

At T = 25ºC and as circuit Fig. 1 unless otherwise stated.

Parameter

Conditions

Min

Typ

Max

Units

Insertion Loss

f = 2kHz, R

L

 = 600

Ω

f = 2kHz, R

L

 = 430

Ω

-
-

-
-

2.0
4.0

dB
dB

Frequency response

-3dB LF cutoff
-3dB HF cutoff
200Hz - 4kHz

-
-
-

50
40

-

-
-

±0.2

Hz

kHz

dB

Return Loss

200Hz - 4kHz

18

-

-

dB

Distortion 

(1)

f = 450Hz
0dBm in line
3rd Harmonic

-

-60

-54

dBm

Balance

DC - 5kHz
Method TG25

80

-

-

dB

Saturation

Excitation 50Hz
250Vrms
Output voltage
across line

-
-

-
-

10
65

Vrms

Vpeak

Voltage
Isolation 

(2)

50Hz
DC

3.88

5.5

-

-

kVrms

kV

Operating range:
Functional
Storage
Humidity

Ambient temperature

-10
-40

-

-
-
-

+85

+125

95

ºC
ºC

%R.H.

Lumped equivalent circuit parameters as Fig. 1

DC resistance, R

DC

(3)

Sum of windings

205

-

245

Ω

Leakage
inductance 

∆

L

4.2

-

4.9

mH

Shunt
inductance Lp

(4)

-43dBm 200Hz
-43dBm 1kHz

1.4

-

-

1.8

3.5

-

H
H

Shunt loss Rp

(4)

-43dBm 200Hz
-43dBm 1kHz

5

-

-

10

15

-

k

Ω

k

Ω

Notes

1.  Third harmonic typically exceeds other

harmonics by 20dB.

2.  Components 100% tested at 6.5 kVDC.
3. 

Caution:

 do not pass DC through windings.

Telephone line current, etc. must be diverted
using choke or semiconductor line hold circuit.

4.  At signal levels greater than -20dBm,  Lp will

increase and  Rp will decrease slightly but the
effect is usually favourable to the return loss
characteristic.

5.  Excludes shipping materials.   Components are

dry-packed and sealed as shipped.   Refer to
Profec Technologies for appropriate storage
conditions for sealed consignments.

Equivalent Circuit

IDEAL

1:1

Fig 1

P2781

ETALDOC 240/9

Page 3 of 5

January 2001

PERFORMANCE

600    MATCH

Ω

-14

-22

-26

-30

100Hz

200 300

500

Typical

Worst Case

1kHz

2

Frequency

dB

3

4 5

10

-18

Return Loss

Fig 4

0

-0.2

-0.3

-0.4

100Hz

200 300

500

1kHz

2

Frequency

dB

3

4 5

10

-0.1

Typ

ica

l

W

or

st 

C

as

e

Frequency Response

Fig 3

Frequency response driven by terminal 
equipment (voltage scource with 430     series 
resistance)   measured  across  600       is    within
 ±0.2dB 200Hz to 4kHz

Ω

Ω

Note:
To obtain harmonic distortion power in dBm, add 
fundamental power in dBm to third harmonic in 
dBc e.g. at -10dBm power in line at 450Hz, third 
harmonic power is -10 + (-74) = -84dBm typical.

Recommended Circuit

Fig 2

Typical

Fundamental

450Hz

-65

-60

-70

-75

-80

-15

-10

Fundamental Power (dBm)

Th

ir

d

 

H

a

rm

o

n

ic

 

d

B

c

-5

0

Third Harmonic Distortion vs. Signal Level

Fig 5

LINE

600

* If return loss >16dB, 300Hz - 4kHz is acceptable, blocking
  capacitor may be relaxed to 4.7 F

6.8nF

6.8nF

5%

+

_

430

+ 2%

_

µ

+50%

20%

_

5%

+

_

*

20%

µ

6.8 F

Recommended Circuit

Fig 7

The circuit of Fig. 6 gives good TX and RX 
flatness (±0.3dBm 200Hz - 4kHz).   An 
alternative arrangement, using existing PCB 
sites, is shown in Fig. 7.  Note, however, that TX 
flatness will be degraded with the topology.

Recommended Circuit

Fig 6

P2781

ETALDOC 240/9

Page 4 of 5

January 2001

CONSTRUCTION

Dimensions shown are in millimetres (inches).
Geometric centres of outline and pad grid coincide within a tolerance circle of 0.3mm

Ø.

Observe correct orientation in circuit.

SAFETY

CERTIFICATION

Manufactured from materials conforming to
flammability requirements of UL94V-0 and

EN 60950:1992 (BS

 

7002:1992) sub-clause

1.2.13.2 (V-0).
Distance through reinforced insulation 0.4mm
minimum.
Creepage and clearances in circuit are 7mm
minimum where PCB pads do not exceed 3mmØ.
Constructed and fully encapsulated in accordance
with EN 60950:1992 (BS 7002:1992) IEC950:1991
and BS EN 41003:1997 (reinforced), 250Vrms
maximum working voltage.

Certified by BSI to IEC 950:1991/A4:1996
(IEC CB Test Certificate No. GB441W) sub-
clauses 1.5, 1.5.1, 1.5.3, 2.2, 2.2.2, 2.2.3, 2.2.4,
2.9.2, 2.9.3, 2.9.4, 2.9.6, 2.9.7, 4.4, 4.4.3.2 (class
V-0) and 5.3 for a maximum working voltage of
250Vrms, nominal mains supply voltage not
exceeding 250Vrms and a maximum operating
temperature of +85ºC in Pollution Degree 2
environment, reinforced insulation.

CAN/CSA C22.2 No.  950-95/UL1950, certified by
CSA, Third Edition, including revisions through to
revision date March 1, 1998, based on Fourth
Amendment of IEC 950, Second Edition, maximum
working voltage 250Vrms, Pollution Degree 2,
reinforced insulation.

UL File number E203175.
CSA Certificate of Compliance 1107696 (Master
Contract 1188107).
Certified by BABT to EN 60950.
BABT Certificate CR/0139.

Additionally, Profec Technologies certifies all
transformers as providing voltage isolation of
3.88kVrms, 5.5kV DC minimum.   All shipments
are supported by a Certificate of Conformity to
current applicable safety standards.

Tolerance  0.3mm
Terminals electroplated 60/40 solder 5  m  minimum

Terminal size : 1.5 (0.06) long, 1.32 (0.05) wide

±

Connections

Fig   9

1

2

3

4

5

6

µ

2.54 2.54

13.0 max

(0.51)

9.0 max

(0.36)

7.0 max

(0.28)

(0.1) (0.1)

NOTE:

Dimensions shown are in millimetres (inches)

Dimensions

Fig 8

(0.06)

1.5

1.32

1.77

(0.052)

(0.07)

P2781

ETALDOC 240/9

Page 5 of 5

January 2001

ABSOLUTE MAXIMUM RATINGS

COPYRIGHT

(Ratings of components independent of circuit).

Short term isolation voltage (2s)

DC current
Storage temperature

Soldering temperature
Profile peak - 

either
or
or

4.6 kVrms,
6.5kVDC
100

µ

A

-40ºC to
+125ºC

260ºC

10s

250ºC

30s

240ºC

60s

ETAL and P2781 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.

© 1997 and  2000  Profec Technologies Ltd.
Reproduction prohibited.

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

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FM 25326