In case of U.S. application based on L3035 the

external components can be calculated suppo-

sing:

- Rfeed = 400

Ω

- Zs = 900

Ω + 2.12µF

- Zl = 1650

Ω// (100Ω + 5nF) Loaded Line

- Zl = 800

Ω// (100Ω + 50nF) Not Loaded Line

-Rp = 62

Ω

EXTERNAL COMPONENTS (for US. Application)

Name

Function

Formula

Typ. Value

CVB

Battery Filter

330nF 20% 63VI

CVDD

Positive Supply Filter

100nF 20%

CVSS

Negative Supply Filter

100nF 20%

RREF

Internal Current Reference

23.7K 1%

CSVR

Battery Ripple Rejection

CSVR = 1/(6.28 * fp * 150K)

@ fp = 1.6Hz

680nF

20% 60VI

CRT

Ring Trip & Ground-key Capacitor

⋅ 390nF

390nF 20% 6VI

RDC

DC Feeding Resistance

RDC = 10 * (Rfeed - 2Rp)

2.76K 1%

CAC

AC/DC Splitter

CAC = 1 / (6.28 * fsp * RDC)

@ fsp = 10Hz

4.7

µF

20% 15VI

RS

Protection Resistor Image

RS = 50 * 2RP

6.2K 1%

ZAC

2 Wire AC Impedance

ZAC = 50 * (Zs-2Rp)

(7)

39K + (180K//55nF)

ZA (1)

SLIC Impedance Balancing Network

ZA = 50 * (Zs-2Rp)

(7)

39K + (180K//55nF)

RA (1)

SLIC Impedance Balancing Network

RA = 50 * 2Rp

6.2K 1%

ZB (1)

Line Impedance Balancing Network

ZB = 50 * Zl

82.5K + (5K + 100pF) (3)

40K + (5K + 1nF) (4)

CCOMP

AC Feedback Compensation

CCOMP = 1 / [2

Πfo (100 Rp)]

@ fo = 250KHz

100pF

20%

CH (1)

Trans-hybrid Loss Freq. Comp.

CH = CCOMP

100pF 20%

RF

Feeding Resistance for Ring Inj.

≥ 200Ω (9)

200

Ω 2W

RT

Feeding Resistance for Ring Inj.

≥ 200Ω (9)

200

Ω 2W

RRG

Ring Input Resistor

180] (6)

CRG

Ring Input Capacitor

CRG = 25

180]

3.9nF 20%

100V

PTC (2)

Positive Temp. Coeff. Resistor

< 15

Ω

10

Ω

RST (2)

Tip Buffer Sensing Resistor

10 to 50K

Ω

33K 1W 5%(8)

RSR (2)

Ring Buffer Sensing Resistor

10 to 50K

Ω

33K 1W 5%(8)

QEXT

External Transistor (5)

(*)

Rp

Protection Resistor

30 to 80

Ω (10)

62

Ω

D1

Relay Kickback Clamp Diode

1N4148

Notes:

(1) These components can be removed and ZB pin shorted to GND when 2/4wire conversion is implemented with 2nd generation COMBO (EG.

TS5070FN)

(2) In case there is no necessity to recover the unbalance introduced by PTC tolerance pins TIP and STIP can be shorted togheter as pins

Ω between TIP/RING terminals and

protection connection. In this case PTC or fuse resistor (if used) can be placed in series to Rp.

(3) Loaded Line.

(4) Not Loaded Line.

T = 2.5ms.

(7) For details see AN496.

(8) RST and RSR wattage should be calculated according to the power cross test specification. (When PTC become open circuit the entire

power cross voltage will appear across RSR and RST).

(9) In order to optimize the component count it is also possible to use only one resistor in series to the ringing generator. In this case RT = 0

Ω;

RF

≥ 400Ω (RF typ. value = 400Ω).

(10) Suggested Rp type are 2W wire wound resistors or thick film resistors on ceramic substrate.

Fuse function should be included if PTC are not used.

(*) ex: BD140; MJE172;MJE350....(SOT32 or SOT82 package available also for surface mount).

For low power application (reduced battery voltage) BCP53 (SOT223 surface mount package) can be used.

4M

Ω 5%

L3037

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