Name

Function

Formula

Typ. Value

CRD (6)

High frequency noise filter

100nF 10% 15VL

Q1

DC/DC converter switch P ch.

MOS transistor

RDS(ON)

≤1.2Ω,VDS = -100V

Total gate charge=20nC max.

with VGS=4.5V and VDS=1V

ID>500mA

Possible choiches:

IRF9510 or IRF9520 or

IRF9120 or equivalent

D1

DC/DC converter series diode

≤ 50ns

SMBYW01-200

or equivalent

RSENSE

DC/DC converter peak current

limiting

110m

Ω

L (8)

DC/DC converter inductor

DC Resistance

≤ 0.1Ω (9)

L=125

µH RFP1304PV

(Manuf.: All Inductive)

or SUMIDA CDRH125

or equivalent

CF1

DC/DC converter feedback loop

stability

220pF to 470pF (10)

RF1

Negative battery programming

level

250K

Ω<RF1<300KΩ (7)

300kW 1%

RF2

Negative battery programming

level

9.1k

Ω 1%

(1) In case Zs=Zl, ZA and ZB can be replaced by two resistors of same value: RA=RB=|Zs|.

(2) In this case CTTX is just operating as a DC decoupling capacitor (fp=100Hz).

(3) Defining ZTTX as the impedance of RTTX in series with CTTX, RTTX and CTTX can also be calculated from the following formula:

ZTTX=50*(Zlttx+2Rp+18

Ω).

(4) CVpos should be defined depending on the power supply current capability and maximum allowable ripple.

(5) For low ripple application use 2x47

µF in parallel.

(6) Can be saved if proper PCB layout avoid noise coupling on RD pin (high impedance input).

(7) RF1 sets the self generated battery voltage in RING and ACTIVE(Il=0) mode as follows:

267k

Ω

280k

Ω

294kW

300k

Ω

-46V

-48V

-49V

-50V

-62V

-65V

-68V

-70V

VBATR should be defined considering the ring peak level required (Vringpeak=VBATR-6V typ.).

The above relation is valid provided that the Vpos power supply current capability and the RSENSE programming allow to source all the

current requested by the particular ringer load configuration.

(8) Core: MICROMETALS T50-26C IRON POWDER, AL-VALUE 61nH/N2

Current rating: 2A (50/60Hz)

Operating Temperature -25

° to +60° Centigrades

Inductance: 14

µH +/-15% at 1KHz, 1mA

DC resistance of winding: MAX.100 mOhm

Code: RFY1303

Wire: UEW2, 0,60 mm

Turns: 50

Inductance (f=1KHz): >125

µH

(9) For high efficiency in HI-Z mode coil resistance @125kHz must be <3ohm

(10) Function of this capacitor is to introduce a zero at the resonance frequency for loop stability. In case some parasitic resistance are already

present in the loop (Coil, CVBAT, PCB layout), the presence of this capacitor can degrade the device noise performances; in this case CF1

should be removed being the loop stability already guaranteed by the parasitic resistance.

EXTERNAL COMPONENTS (continued)

STLC3055

11/22