Data Sheet
March 27, 2008
QBW018A0B Series Power Modules, DC - DC Converters:
36 – 75Vdc Input; 12Vdc Output; 18A Output Current
Feature Description
Remote On/Off
Two remote on/off 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. 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 Vi (-)
terminal (Von/off). The switch can be an open
collector or equivalent (see Figure 12). A logic low is
Von/off = 0.0V to 0.8V. The typical Ion/off during a
logic low is 10 µA. The switch should maintain a logic-
low voltage while sinking 10µA. During a logic high,
the maximum Von/off generated by the power module
is 5.0V. The maximum allowable leakage current of
the switch at Von/off = 2.0V is 6.0µA. If using an
external voltage source, the maximum voltage V
on/off on the pin is 14.0V with respect to the Vi (-)
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 VI(-).
For positive logic: leave ON/OFF pin open.
An auto-restart option is also available. An auto-
restart feature continually attempts to restore the
operation until fault condition is cleared.
Input Undervoltage 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.
Overtemperature Protection
These modules feature an overtemperature protection
circuit to safeguard against thermal damage. The
circuit shuts down and latches off the module when
the maximum device reference temperature is
exceeded. The module can be restarted by cycling
the dc input power for at least one second or by
toggling the remote on/off signal for at least one
second.
Output Overvoltage Clamp
The output overvoltage clamp consists of a control
circuit, independent of the primary regulation loop,
that monitors the voltage on the output terminals and
clamps the voltage when it exceeds the overvoltage
set point. The control loop of the clamp has a higher
voltage set point than the primary loop. This provides
a redundant voltage control that reduces the risk of
output overvoltage.
I
on/off
+
V
on/off
–
ON/OFF
V
O
(+)
LOAD
V
I
(+)
V
I
(–)
V
O
(–)
Figure 12. Remote On/Off Implementation
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 for a few mili-seconds. If the overcurrent
condition persists beyond a few milliseconds, 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.
LINEAGE
POWER
9
LINEAGEPOWER [ LINEAGE POWER CORPORATION ]
