AN-149 Increased LITELINK™ II Transmit Power

```Application Note: AN-149
AN-149-R03
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1
Application Note: AN-149
1. Introduction
Some applications, such as voice computer telephony,
require higher power transmission from the host
equipment to the telephone network. This application
note describes changes to the standard LITELINK II
application circuits to provide the transmit gain needed
for a particular application.
Note: The recommended maximum drive level into the
line from LITELINK II is 6 mA peak, which is equivalent to about +10 dBm into a 600 Ω load. Datasheet
specifications for maximum current (IDDL) do not apply
with higher than specified output power. LITELINK II
will draw more current with higher output power.
3. Examples
3.1 PBX Example
To meet +3.18 dBm into 900 Ω, use the following calculations:
+3.18 dBm into 900 Ω = 1.935 VP.
1.935 V/1.1 V = 1.76.
The calculations work out as follows:
RZTX = 226 / 1.76 = 128.4
RZNT = 453 / 1.76 = 257
RNTF = 1M / 2.53 = 396683
2. Transmit Gain Design Procedure
1. Determine the peak transmit level needed for the
application.
2. If necessary, convert the required peak transmit
power into a voltage level. For example, 0 dBm
into 600 Ω = 1.1 VP.
3. Calculate the required linear voltage gain AV by
dividing the peak transmit voltage level from step
2 by 1.1.
4. Modify the following application circuit component vales:
The closest standard resistor values are 127 Ω for
RZTX, 255 Ω for RZNT, and 392 kΩ for RNTF.
3.2 +3 dBm into 600 Ohm Transmit Power Example
The following application circuit uses component values determined by the design procedure above for +3
dBm transmit power into 600 Ω.
Peak transmit power of +3 dBm into 600 Ω = 1.55 VP.
1.55/1.1 = 1.41. The calculations work out as follows:
RZTX = 150 / 1.41 = 106.4
ZZTX ← ZZTX / AV
RZNT = 301 / 1.41 = 213.5
ZZNT ← ZZNT / AV
RNTF ←
RNTF
((AV - 1)(RNTF / RNTS) + AV)
RNTF = 1M / 1.82 = 549000
These calculations result in a transmit (4-wire to 2wire) gain of AV, and a receive gain (2-wire to 4-wire)
of 1/AV. If necessary, the receive loss can be compensated with either the programmable input gain of a
CODEC or with a discrete op-amp gain stage between
the LITELINK RX output and the host system.
AN-149-R03
Standard resistor values have been substituted in the
circuit in Figure 1.
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Application Note: AN-149
Figure 1. +3 dBm Application Circuit
3.3 or 5 V
R23
10*
C1
1
FB1
600 Ω
200 mA
C16
10
C9
0.1
A
U1
A
1
R1 (RTX) 80.6K 1%
2
C13 0.1
3
TX-
C2 0.1
TX+
4
5
6
7
8
OH
REFL
VDD
TXSM
TXF
TX-
ZTX
TX+
ZNT
TX
TXSL
REFB
BR1-
GND
NTS
OH
GAT
9 RING
10 CID
RING
CID
C14 0.1 11
RX12 RX+
C4 0.1
13 SNP+
14 SNP-
RXRX+
15 RXF
16 RX
A
REFB
DCS1
DCS2
ZDC
BR2RPB
RXS
VDDL
32
31
C10
0.01
500V
-BR
R5 (RTXF)
49.9K
1%
C15
0.01
500V
30
28
27
-BR
Q1
CPC5602C
R13
(RNTS)
1M
1%
29
R22 (RDCS1A)
6.8 M 1%
R21 (RDCS1B)
6.2 M 1%
26
25
R14
(RGAT)
47
24
23
R12 (RNTF) 549 K 1%
C12 (CDCS)
0.027
-BR
22
21
R15 (RDCS2) 1.69 M 1%
R16 (RZDC) 8.2 1%
20
19
R20
(RVDDL)
2
-BR
18
+
DB1
SIZB60
600V_60A
17
R2
(RRXF)
127K
1%
R4
(RPB)
68.1
1%
-BR
Gain Setting
R8 (RHTX)
200K 1%
R9 (RHNT)
200K 1%
R18
(RZTX)
107
1%
-BR
R10
(RZNT)
215
1%
-BR
-
-BR
TIP
SP1
P3100SB 1
2
RING
AC Termination Setting
NOTE: Unless otherwise
noted, all resistors are in
Ohms, 5%. All capacitors
C7
(CSNP-)
220pF
2000V
R3
(RSNPD)
1.5M
1%
AN-149-R03
R6 (RSNP-2)
1.8M 1/10W 1%
R44 (RSNP-1)
1.8M 1/10W 1%
R7 (RSNP+2)
C8
(CSNP+) 1.8M 1/10W 1%
220pF
2000V
R45 (RSNP+1)
1.8M 1/10W 1%
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Application Note: AN-149
4.1 IXYS IC Division Design Resources
4.2 Third Party Design Resources
The IXYS ICD web site has a wealth of information
useful for designing with LITELINK, including application notes and reference designs that already meet all
sheets also contains additional application and design
The following also contain information useful for DAA
designs. All of the books are available on
www.amazon.com
Newton’s Telecom Dictionary, Harry Newton, CMP
Books; ISBN: 1578200695
Application note AN-107 LOCxx Series - Isolated Amplifier Design Principles
Application note AN-112, Ground-start Supervision Circuit Using IAA110
Application note AN-114 ITC117P
Application note AN-117 Customize Caller-ID Gain and
Ring Detect Voltage Threshold for CPC5610/11
Understanding Telephone Electronics, Stephen J. Bigelow, et. al., Butterworth-Heinemann; ISBN:
0750671750
Photodiode Amplifiers: Op Amp Solutions, Jerald
Graeme, McGraw-Hill Professional Publishing; ISBN:
007024247X
Teccor, Inc. Surge Protection Products
United States Code of Federal Regulations, CFR 47
Part 68.3
Application note AN-146, Guidelines for Effective
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and reser
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assumes no liability whatsoever, and disclaims any express or implied warranty, relating to its products including, but not limited to, the implied warranty
of merchantability
or a particular purpose, or infringement of any intellectual property right.
The products described in this document are not designed, intended, authorized or warranted for use as components in systems intended for surgical
implant into the body, or in other applications intended to support or sustain life, or where malfunction of IXYS Integrated Circuits Division’s product may
result in direct physical harm, injury, or death to a person or severe property or environmental damage. IXYS Integrated Circuits Division reserves the right
to discontinue or make changes to its products at any time without notice.
Specification: AN-149-R03