L3234 View Datasheet(PDF) - STMicroelectronics
Part Name
Description
Manufacturer
L3234 Datasheet PDF : 26 Pages
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L3234 - L3235
External components list for L3235
To set the SLIC into operation the following parameters have to be defined:
- The AC SLIC impedance at line terminals "Zs" to which the return loss measurements is referred. It can
be real (typ. 600Ω) or complex.
- The equivalent AC impedance of the line "Zl" used for evaluation of the trans-hybrid loss performance
(2/4 wire conversion). It is usually a complex impedance.
- The value of the two protection resistors Rp in series with the line termination.
Once, the above parameters are defined, it is possible to calculate all the external components using the
following table. The typical values has been obtained supposing: Zs = 600Ω; Zl = 600Ω; Rp = 50Ω
Name
RF
CF
RGF
CGF
RR
RLIM
CR
RP
RT
CAC
RPC
ZAC
CC
ZAS
RAS
ZB
CH
CTX
D1, D2
Text
CVSS; CVDD
CVB
Suggested Value
39KΩ
390nF
39KΩ
390nF
51KΩ
8.4KΩ to 33KΩ
4.7µF
6.3 V 30%
50
1MΩ 20%
100µF
6.3V 20%
2500Ω 1%
12500Ω 1%
220pF 20%
12500Ω 1%
2500Ω 1%
15KΩ 1%
220pF 20%
4.7µF 30%
1N4007
(3)
100nF
100nF/100V
Function
Delay Time
On-hook Off-hook
Delay Time
GK Detector
Bias Set
Ext. Current Limit. Progr.
Negative Battery
Filter
Protection Resistors
Termination Resistor
DC/AC current feedback splitting
RP insertion loss compensation
2W AC Impedance programmation
AC Feedback compensation
Slic Impedance Balancing Net.
Line impedance Balancing Net.
CC Transybrid loss Compensation
DC Decoupling Tx Output
Line Rectifier
External Transistor
±5V supply filter
VBAT supply filter
Formula
τ = 0.69 ⋅ CF ⋅ 39KΩ
(1)
τ = 0.69 ⋅ CGF ⋅ 39KΩ
RLIM
=
564
ILIM − 3mA
CAC
=
2π
⋅
1
16KΩ
⋅
fp
47 < RP < 100Ω (2)
CAC
=
2π
⋅
1
220Ω
⋅
fsp
RPC = 25 ⋅ (2RP)
ZAC = 25 ⋅ (ZS - 2RP)
f1 = 300KHz
CC
=
2πf1
1
⋅ 50RP
ZAS = 25 ⋅ (ZS - 2RP)
RAS = 25 ⋅ (2RP)
ZB = 25 ⋅ Zl
CH
=
CC
⋅
ZAC
ZAS
CTX
=
6.28
⋅
1
fp
⋅
Zload
PDiss > 2W, VCEO > 60V
HFE > 40, IC > 100mA
VBE < 0.8V @ 100mA
Notes:
1) For proper operation Cf should be selected in order to verify the following conditions:
A) cf > 150nF
B) τ < 1/2 • fRING
fRING: Ringing signal frequency
2) For protection purposes the RP resistor is usually splitted in two part RP1 and RP2, with RP1 > 30Ω.
3) 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. Depending on application enviroment an heatsink could be necessary.
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