CPC7593ZC IXYS, CPC7593ZC Datasheet - Page 19

• Manufacturer Part Number: CPC7593ZC
• Manufacturer: IXYS

Specifications of CPC7593ZC

• Lead Free Status / RoHS Status: Supplier Unconfirmed

2.5 T
The T
internal pull up sourced from V
pin indicates the status of the thermal shutdown
circuitry. Typically, during normal operation, this pin will
be pulled up to V
create excess thermal loading the CPC7593 will enter
thermal shutdown and a logic low will be output.
As an input, the T
CPC7593 into the “All-Off” state by simply pulling the
input low via an open collector type buffer. Using a
standard output with an active drive logic high
capability may disable the thermal shutdown
mechanism. Without the ability to enter thermal
shutdown during a fault condition, permanent damage
to the CPC7593 will occur.
Under no circumstances should the T
high via an external device. The CPC7593’s internal
pull up has a nominal value of 16µA.
2.6 Ringing Switch Zero-Cross Current Turn Off
After the application of a logic input to turn SW4 off,
the ringing switch is designed to delay the change in
state until the next zero-crossing. Once on, the switch
requires a zero-current cross to turn off, and therefore
should not be used to switch a pure DC signal. The
switch will remain in the on state no matter the logic
input until the next zero crossing. These switching
characteristics will reduce and possibly eliminate
overall system impulse noise normally associated with
ringing switches. See Clare application note
Impulse Noise Benefits of Line Card Access Switches
more information. The attributes of ringing switch SW4
may make it possible to eliminate the need for a
zero-cross switching scheme. A minimum impedance
of 300 Ω in series with the ringing generator is
recommended.
2.7 Power Supplies
Both a +5 V supply and battery voltage are connected
to the CPC7593. Switch state control is powered
exclusively by the +5 V supply. As a result, the
CPC7593 exhibits extremely low power consumption
during active and idle states.
Although battery power is not used for switch control, it
is required to supply trigger current for the integrated
internal protection circuitry SCR during fault
conditions. This integrated SCR is designed to
activate whenever the voltage at T
to 4 V below the applied voltage on the V
R02
SD
SD
Pin Description
pin is a bi-directional I/O structure with an
DD
SD
but under fault conditions that
pin can be utilized to place the
DD
. As an output, this
BAT
SD
or R
pin be pulled
BAT
BAT
AN-144,
pin.
drops 2
for
www.clare.com
Because the battery supply at this pin is required to
source trigger current during negative overvoltage
fault conditions at tip and ring, it is important that the
net supplying this current be a low impedance path for
high speed transients such as lightning. This will
permit trigger currents to flow enabling the SCR to
activate and thereby prevent a fault induced negative
overvoltage event at the T
2.8 Battery Voltage Monitor
The CPC7593 also uses the V
battery voltage. If the system battery voltage is lost,
the CPC7593 immediately enters the all-off state. It
remains in this state until the system battery voltage is
restored. The device also enters the all-off state if the
battery voltage rises more positive than about –10 V
and remains in the all-off state until the battery voltage
drops below –15 V. This battery monitor feature draws
a small current from the battery (less than 1 µA
typical) and will add slightly to the device’s overall
power dissipation.
This monitor function performs properly if the
CPC7593 and SLIC share a common battery supply
origin. Otherwise, if battery is lost to the CPC7593 but
not to the SLIC, then the V
biased by the potential applied at the T
pins via the internal protection circuitry SCR trigger
current path.
2.9 Protection
The CPC7593 uses a combination of current limited
break switches, a diode bridge/SCR clamping circuit,
and a thermal shutdown mechanism to protect the
SLIC device or other associated circuitry from damage
during line transient events such as lightning. During a
positive transient condition, the fault current is
conducted through the diode bridge to ground via
F
ground. During a negative transient of 2 to 4 V more
negative than the voltage source at V
conducts and faults are shunted to F
or the diode bridge.
In order for the SCR to crowbar or foldback, the SCR’s
on-voltage (see
Specifications” on page
applied voltage at the V
less negative than the SCR on-voltage, or if the V
supply is unable to source the trigger current, the SCR
will not crowbar.
GND
2.9.1 Diode Bridge/SCR
. Voltage is clamped to a diode drop above
“Protection Circuitry Electrical
13) must be less than the
BAT
BAT
BAT
pin. If the V
or R
BAT
pin will be internally
BAT
pin to monitor
GND
BAT
nodes.
BAT
BAT
, the SCR
via the SCR
or R
CPC7593
voltage is
BAT
BAT
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