HC55180 Datasheet, PDF (14/19 Pages) Intersil Corporation – Extended Reach Ringing SLIC Family

HC55180, HC55181, HC55182, HC55183, HC55184
Tip Open
Overview
The tip open mode (110) is intended for compatibility for
PBX type interfaces. Used during idle line conditions, the
device does not provide transmission. Loop supervision is
provided by either the switch hook detector (E0 = 1) or the
ground key detector (E0 = 0). The ground key detector will
be used in most applications. The device may be operated
from either high or low battery.
Functionality
During tip open operation, the Tip amplifier is disabled and
the Ring amplifier is enabled. The minimum Tip impedance
is 30kΩ. The only active path through the device will be the
Ring amplifier.
In keeping with the MTU characteristics of the device, Ring
will not exceed -56.5V when operating from the high battery.
Though MTU does not apply to tip open, safety requirements
are satisfied.
On Hook Power Dissipation
The on hook power dissipation of the device during tip open
is determined by the operating voltages and quiescent
currents and is calculated using Equation 37.
P_TO= V_BH × I_BHQ + V_BL × I_BLQ + V_CC × I_CCQ
(EQ. 37)
The quiescent current terms are specified in the electrical
tables for each operating mode. Load power dissipation is
not a factor since this is an on hook mode.
Power Denial
Overview
The power denial mode (111) will shutdown the entire device
except for the logic interface. Loop supervision is not
provided. This mode may be used as a sleep mode or to
shut down in the presence of a persistent thermal alarm.
Switching between high and low battery will have no effect
during power denial.
Functionality
During power denial, both the Tip and Ring amplifiers are
disabled, representing high impedances. The voltages at
both outputs are near ground.
Thermal Shutdown
In the event the safe die temperature is exceeded, the ALM
output will go low and DET will go high and the part will
automatically shut down. When the device cools, ALM will
go high and DET will reflect the loop status. If the thermal
fault persists, ALM will go low again and the part will shut
down. Programming power denial will permanently
shutdown the device and stop the self cooling cycling.
Battery Switching
Overview
The integrated battery switch selects between the high
battery and low battery. The battery switch is controlled
with the logic input BSEL. When BSEL is a logic high, the
high battery is selected and when a logic low, the low
battery is selected. All operating modes of the device will
operate from high or low battery except forward loop back.
Functionality
The logic control is independent of the operating mode
decode. Independent logic control provides the most
flexibility and will support all application configurations.
When changing device operating states, battery switching
should occur simultaneously with or prior to changing the
operating mode. In most cases, this will minimize overall
power dissipation and prevent glitches on the DET output.
The only external component required to support the battery
switch is a diode in series with the V_BH supply lead. In the
event that high battery is removed, the diode allows the
device to transition to low battery operation.
Low Battery Operation
All off hook operating conditions should use the low battery.
The prime benefit will be reduced power dissipation. The
typical low battery for the device is -24V. However this may
be increased to support longer loop lengths or high loop
current requirements. Standby conditions may also operate
from the low battery if MTU compliance is not required,
further reducing standby power dissipation.
High Battery Operation
Other than ringing, the high battery should be used for
standby conditions which must provide MTU compliance.
During standby operation the power consumption is typically
50mW with -100V battery. If ringing requirements do not
require full 100V operation, then a lower battery will result in
lower standby power.
High Voltage Decoupling
The 100V rating of the device will require a capacitor of
higher voltage rating for decoupling. Suggested decoupling
values for all device pins are 0.1µF. Standard surface mount
ceramic capacitors are rated at 100V. For applications driven
at low cost and small size, the decoupling scheme shown
below could be implemented.
0.22µ 0.22µ
VBL VBH
HC5518X
FIGURE 11. ALTERNATE DECOUPLING SCHEME
As with all decoupling schemes, the capacitors should be as
close to the device pins as physically possible.
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