HC55183ECM Intersil, HC55183ECM Datasheet - Page 19

• Manufacturer Part Number: HC55183ECM
• Manufacturer: Intersil

Specifications of HC55183ECM

• Number Of Channels: 1
• On-hook Transmission: Yes
• Polarity Reversal: Yes
• On-chip Ring Relay Driver: Yes
• Longitudinal Balanced: 45
• Operating Supply Voltage (typ): 5/-28V
• Operating Temp Range: 0C to 70C
• Package Type: PLCC
• Loop Current Limit: 45mA
• Operating Temperature Classification: Commercial
• Pin Count: 28
• Mounting: Surface Mount
• Operating Current: 8.5mA
• Operating Supply Voltage (max): 5.25/-75V
• Operating Supply Voltage (min): 4.75/-24V
• Lead Free Status / RoHS Status: Not Compliant

Additional Application Diagrams
Reducing Overhead Voltages
The transmission overhead voltage of the device is
internally set to 4V per side. The overhead voltage may be
reduced by injecting a negative DC voltage on the receive
input using a voltage divider (Figure 18). Accordingly, the
2-wire port overload level will decrease the same amount
as the injected offset.
The divider shunt resistance is the parallel combination of
the internal 160kΩ resistor and the external R
R
additional power dissipation of the divider. The DC gain
relationship from the divider voltage, V
outputs is shown below.
With a low battery voltage -24V and a divider voltage of
-0.5V, the Tip to Ring voltage is 17V. As a result, the
overhead voltage is reduced from 8V to 7V and the overload
level will decrease from 3.5V
CODEC Ringing Generation
Maximum ringing amplitudes of the device are achieved with
signal levels approximately 2.4V
receive output of the CODEC may serve as the low level ring
generator. The ringing input impedance of 480kΩ minimum
should not interfere with CODEC drive capability. A single
external capacitor is required to AC coupled the ringing
signal from the CODEC. The circuit diagram for CODEC
ringing is shown below.
Implementing Teletax Signalling
A resistor, R
injecting the teletax signal (Figure 19). For most
V
1
T R
and R
–
HC5518X
=
FIGURE 18. EXTERNAL OVERHEAD CONTROL
1:1
V
1:1
2
FIGURE 19. CODEC RINGING INTERFACE
BL
should be greater than 500kΩ to minimize the
T
–
, is required at the -IN input of the device for
8
HC5518X
–
160kΩ
(
2
480K
×
+
160kΩ
-
V
D
)
VRX
PEAK
19
VRX
VRS
P-P
VBL
V
to 3.0V
R
R
. Therefore the low pass
D
2
1
HC55180, HC55181, HC55183, HC55184
C
D
RX
, to the Tip and Ring
PEAK
2
RX OUT
CODEC
. The sum of
.
FROM
CODEC
(EQ. 38)
applications the synthesized device impedance (i.e., 600Ω)
will not match the 200Ω teletax impedance. The gain set by
R
to the teletax injection point. Therefore the device appears
as a low impedance source for teletax. The resistor R
calculated using the following equation.
The signal level across a 200Ω load will be twice the injected
teletax signal level. As the teletax level at VTX will equal the
injection level, set R
is based on the voice band transhybrid balance
requirements. The connection of the teletax source to the
transhybrid amplifier should be AC coupled to allow proper
biasing of the transhybrid amplifier input
Ringing With DC Offsets
The balanced ringing waveform consists of zero DC offset
between the Tip and Ring terminals. However, the linear
amplifier architecture provides control of the DC offset during
ringing. The DC gain is the same as the AC gain, 40V/V per
amplifier. Positive DC offsets applied directly to the ringing
input will shift both Tip and Ring away from half battery
towards ground and battery respectively. A voltage divider
on the ringing input may be used to generate the offset
(Figure 21). The reference voltage, V
CODEC 2.4V reference voltage or the 5V supply.
An offset during ringing of 30V, would require a DC shift of
15V at Tip and 15V at Ring. The DC offset would be created
by a +0.375V (V
should be selected to minimize the value of the AC coupling
capacitor C
voltage reference. The ringing input impedance should also
be accounted for in divider resistor calculations.
R
T
T
VFB
cancels the impedance matching feedback with respect
=
HC5518X
CFB
------------------------------------------------------------------ -
200
RT
FIGURE 21. EXTERNAL OVERHEAD CONTROL
+
RS
2
TELETAX
SOURCE
×
-IN
FIGURE 20. TELETAX SIGNALLING
480K
R
and the loading of the ring generator and
200
+
P
D
-
+
-
RS
) at the VRS input. The divider resistors
+
TA
(
C
R
VTX
S
= R
⁄
400
VRS
B
for cancellation. The value of R
)
×
R
V
R
R
REF
S
B
C
R
V
R
D
2
1
REF
R
C
F
RS
, can be either the
+2.4V
-
+
FROM
RING GEN.
TX IN
CODEC
(EQ. 39)
T
is
B