MC34653EF 데이터 시트보기 (PDF) - Freescale Semiconductor
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MC34653EF Datasheet PDF : 24 Pages
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TYPICAL APPLICATIONS
TYPICAL APPLICATIONS
The 34653 resides on the plug-in board (see Figures 18
and 19), allowing the board to be safely inserted or removed
without damaging electrical equipment. The 34653 can be
operated with no external components other than the power
good output signal pull-up resistor if the default mode was
selected for all the programmable features. This is one of the
great advantages of the 34653: it operates with minimal user
interface and minimal external component count and still
offers complete hot swapping functionality with all the
necessary protection features, from undervoltage/
overvoltage detection, to current limiting, to short circuit
protection and power good output signaling. The default
values were chosen to be sufficient for many standard
applications.
Figure 18 is a typical application diagram depicting the
default mode and using the power good output signal pullup
resistor. Refer to the static and dynamic electrical
characteristics tables on pages 5 through 7 for the various
default values.
GND
PLUG-IN CARD
33653
VPWR
PG
PG
VIN
ICHG
VOUT
ILIM
44 kΩ
Application
Dependent
Enable/Enable
CLOAD
DC/DC
Converter
-48 V
Figure 18. Typical Application Diagram with Default
Settings and Minimal External Components
The 34653 can be also programmed for different values of
the Overcurrent Limit and the Charging Current Limit using
external components connected to the device. Figure 19
shows the 34653 with the required external components that
allow access to all programmable features in the device.
GND
PLUG-IN CARD
33653
VPWR
PG
DISABLE
PG
VIN
ICHG
VOUT
ILIM
44 kΩ
Application
Dependent
Enable/Enable
CLOAD
DC/DC
Converter
-48 V
Figure 19. Typical Application Diagram with External
Components Necessary to Program the Device
UNDERVOLTAGE AND OVERVOLTAGE
DETECTION
The 34653 monitors the input voltage to ensure that it is
within the operating range and that there are no overvoltage
or undervoltage conditions, and to quickly turn off the Power
MOSFET if there are. Internal comparators connected to an
internal resistor divider between the VPWR and VIN input
pins compare the supply voltages with a reference voltage.
The typical default values of 37 V for the UV turn-off threshold
(falling threshold) and 78 V for the OV turn-off threshold
(rising threshold) will give a typical operating range of 38 V to
76 V. This range is suitable for telecom industry standards.
When the device passes the UVLO threshold, it uses the
UV/OV detection circuits to check the input supply levels
before turning on the Power MOSFET during the start-up
Timer delay and thereafter. As long as the voltage is above
the undervoltage falling threshold and below the overvoltage
rising threshold, the supply is within operating range and the
Power MOSFET is allowed to turn on and stay on. If the input
voltage falls below its undervoltage falling threshold or rises
above its overvoltage rising threshold, then one of the start-
up conditions (list on page 10) is violated and the Power
MOSFET turns off, the power good signal deactivates, and a
new start-up timer initiates. The undervoltage and
overvoltage detection circuits are equipped with a 1.0 ms
filter to filter out momentary input supply dips.
TIMER
The Timer function on the 34653 provides the time base
used to generate the timing sequences at start-up. The same
timer controls the retry delay when the device experiences
any fault. The Timer function has a default timer value of
Analog Integrated Circuit Device Data
Freescale Semiconductor
34653
17
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