Feature Descriptions
Overcurrent Protection
To provide protection in a fault output overload condition, the
module is equipped with internal current-limiting circuitry and
can endure current limiting continuously. If the overcurrent
condition causes the output voltage to fall greater than 4.0V from
Vo,set, the module will shut down and remain latched off. The
overcurrent latch is reset by either cycling the input power or by
toggling the on/off pin for one second. If the output overload
condition still exists when the module restarts, it will shut down
again. This operation will continue indefinitely until the
overcurrent condition is corrected.
A factory configured auto-restart option (with overcurrent and
overvoltage auto-restart managed as a group) is also available.
An auto-restart feature continually attempts to restore the
operation until fault condition is cleared.
Remote On/Off
The module contains a standard on/off control circuit reference
to the VIN(-) terminal. Two factory configured remote on/off logic
options are available. Positive logic remote on/off turns the
module on during a logic-high voltage on the ON/OFF pin, and off
during a logic low. Negative logic remote on/off turns the module
off during a logic high, and on during a logic low. Negative logic,
device code suffix "1," is the factory-preferred configuration. The
On/Off circuit is powered from an internal bias supply, derived
from the input voltage terminals. To turn the power module on
and off, the user must supply a switch to control the voltage
between the On/Off terminal and the VIN(-) terminal (Von/off). The
switch can be an open collector or equivalent (see Figure 14). A
logic low is Von/off = -0.3V to 0.8V. The typical Ion/off during a logic
low (Vin=48V, On/Off Terminal=0.3V) is 147µA. The switch
should maintain a logic-low voltage while sinking 310µA. During a
logic high, the maximum Von/off generated by the power module is
8.2V. The maximum allowable leakage current of the switch at
Von/off = 2.0V is 10µA. If using an external voltage source, the
maximum voltage Von/off on the pin is 14.5V with respect to the
VIN(-) terminal.
If not using the remote on/off feature, perform one of the
following to turn the unit on:
For negative logic, short ON/OFF pin to VIN(-).
For positive logic: leave ON/OFF pin open.
Figure 14. Remote On/Off Implementation.
Output Overvoltage Protection
The module contains circuitry to detect and respond to output
overvoltage conditions. If the overvoltage condition causes the
output voltage to rise above the limit in the Specifications Table,
the module will shut down and remain latched off. The
overvoltage latch is reset by either cycling the input power, or by
toggling the on/off pin for one second. If the output overvoltage
condition still exists when the module restarts, it will shut down
again. This operation will continue indefinitely until the
overvoltage condition is corrected.
A factory configured auto-restart option (with overcurrent and
overvoltage auto-restart managed as a group) is also available.
An auto-restart feature continually attempts to restore the
operation until fault condition is cleared.
Overtemperature Protection
These modules feature an overtemperature protection circuit to
safeguard against thermal damage. The circuit shuts down the
module when the maximum device reference temperature is
exceeded. The module will automatically restart once the
reference temperature cools by ~25°C.
Input Under/Over voltage Lockout
At input voltages above or below the input under/over voltage
lockout limits, module operation is disabled. The module will
begin to operate when the input voltage level changes to within
the under and overvoltage lockout limits.
Load Sharing
For higher power requirements, the QBVW033A0 power module
offers an optional feature for parallel operation (-P Option code).
This feature provides a precise forced output voltage load
regulation droop characteristic. The output set point and droop
slope are factory calibrated to insure optimum matching of
multiple modules’ load regulation characteristics. To implement
load sharing, the following requirements should be followed:
▪ The VOUT(+) and VOUT(-) pins of all parallel modules must be
connected together. Balance the trace resistance for each
module’s path to the output power planes, to insure best load
sharing and operating temperature balance.
▪ VIN must remain between 40Vdc and 75Vdc for droop sharing to
be functional.
▪ It is permissible to use a common Remote On/Off signal to start
all modules in parallel.
▪ These modules contain means to block reverse current flow
upon start-up, when output voltage is present from other
parallel modules, thus eliminating the requirement for external
output ORing devices. Modules with the –P option may
automatically increase the Turn On delay, Tdelay, as specified in
the Feature Specifications Table, if output voltage is present on
the output bus at startup.
▪ When parallel modules startup into a pre-biased output, e.g.
partially discharged output capacitance, the Trise is automatically
increased, as specified in the Feature Specifications Table, to
insure graceful startup.