
8
Lucent Technologies Inc.
Advance Data Sheet
September 2000
18 Vdc to 36 Vdc or 36 Vdc to 75 Vdc Inputs
QC/QW030-Series Power Modules: dc-dc Converters;
Feature Descriptions
(continued)
Remote On/Off
(continued)
If not using the remote on/off feature, do one of the
following:
For positive logic, leave the ON/OFF pin open.
For negative logic, short the ON/OFF pin to V
I
(–).
8-758(C).a
Figure 4. QC/QW030-Series Remote On/Off
Implementation
Remote Sense
Remote sense minimizes the effects of distribution
losses by regulating the voltage at the remote-sense
connections. The voltage between the remote-sense
pins and the output terminals must not exceed the out-
put voltage sense range given in the Feature Specifica-
tions table, e.g., on the QW030A:
[V
O
(+) – V
O
(–)] – [SENSE(+) – SENSE(–)]
≤
0.5 V
The voltage between the V
O
(+) and V
O
(–) terminals
must not exceed the minimum output overvoltage pro-
tection value shown in the Feature Specifications table.
This limit includes any increase in voltage due to
remote-sense compensation and output voltage set-
point adjustment (trim). See Figure 5.
If not using the remote-sense feature to regulate the
output at the point of load, then connect SENSE(+) to
V
O
(+) and SENSE(–) to V
O
(–) at the module.
Although the output voltage can be increased by both
the remote sense and by the trim, the maximum
increase for the output voltage is not the sum of both.
The maximum increase is the larger of either the
remote sense or the trim. Consult your Lucent Technol-
ogies Account Manager or Application Engineer if you
need to increase the output voltage more than the
above limitation.
The amount of power delivered by the module is
defined as the voltage at the output terminals multiplied
by the output current. When using remote sense and
trim, the output voltage of the module can be
increased, which at the same output current would
increase the power output of the module. Care should
be taken to ensure that the maximum output power of
the module remains at or below the maximum rated
power.
8-651(C).m
Figure 5. QC/QW030-Series Effective Circuit
Configuration for Single-Module Remote-
Sense Operation
Output Voltage Set-Point Adjustment
(Trim)
Output voltage trim allows the user to increase or
decrease the output voltage set point of a module. This
is accomplished by connecting an external resistor
between the TRIM pin and either the SENSE(+) or
SENSE(–) pins. The trim resistor should be positioned
close to the module.
If not using the trim feature, leave the TRIM pin open.
With an external resistor between the TRIM and
SENSE(+) pins (R
adj-down
), the output voltage set point
(V
O, adj
) decreases (see Figure 6). The following equa-
tion determines the required external-resistor value to
obtain a change in output voltage from V
O, nom
to V
O, adj
.
The values of G, H, and L are shown in Table 5.
(
V
O nom
,
The QC/QW030 modules have a fixed current-limit set
point. As the output voltage is adjusted down, the avail-
able output power is reduced.
With an external resistor connected between the TRIM
and SENSE(–) pins (R
adj-up
), the output voltage set
point (V
O, adj
) increases (see Figure 7).
+
I
on/off
–
V
on/off
REMOTE
ON/OFF
V
I
(+)
V
I
(–)
V
O
(+)
SENSE(+)
SENSE(–)
V
O
(–)
V
I
(+)
V
I
(–)
I
O
LOAD
CONTACT AND
DISTRIBUTION LOSSES
SUPPLY
I
I
CONTACT
RESISTANCE
R
adj-down
,
---------------------------------------
V
O adj
,
–
)
H
–
=