Tyco Electronics Power Systems 13
Data Sheet
August 22, 2006
36 Vdc to 75 Vdc Input; 1.2 Vdc to 5.0 Vdc Output; 10 A to 20 A
QW010/015/020 Series Power Modules: dc-dc Converters;
Design Considerations
Input Source Impedance
The power module should be connected to a low
ac-impedance input source. Highly inductive source imped-
ances can affect the stability of the power module. If the input
source inductance exceeds 4 µH, a 33 µF electrolytic capaci-
tor (ESR < 0.7 W at 100 kHz) mounted close to the power
module helps ensure stability of the unit.
Feature Descriptions
Remote On/Off
Two remote On/Off options are available. Positive logic
remote On/Off turns the module on during a logic-high volt-
age on the remote ON/OFF pin, and off during a logic low.
Negative logic remote On/Off, device code suffix "1", turns
the module off during logic-high voltage and on during a logic
low.
To turn the power module on and off, the user must supply a
switch to control the voltage between the
ON/OFF pin and the VI(–) terminal. The switch may be an
open collector or equivalent (see Figure 40). A logic low is
Von/off = –0.7 V to 1.2 V. The maximum Ion/off during a logic
low is 1 mA. The switch should maintain a logic-low voltage
while sinking 1 mA. During a logic high, the maximum Von/off
generated by the power module is 15 V. The maximum allow-
able leakage current of the switch at Von/off = 15 V is 50 µA.
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 VI(–).
Figure 40. 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 termi-
nals must not exceed the output voltage sense range given in
the Feature Specifications table:
[VO(+) – VO(–)] – [SENSE(+) – SENSE(–)] £ 0.5 V
The voltage between the VO(+) and VO(–) terminals must not
exceed the minimum output overvoltage protection 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
41). If not using the remote sense feature to regulate the out-
put at the point of load, then connect SENSE(+) to VO(+) and
SENSE
(–) to VO(–) 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.
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 volt-
age of the module can be increased, which at the same out-
put 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.
Figure 41. Effective Equivalent 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 accom-
plished 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 Rtrim-down between the TRIM and
SENSE(–) pins, the output voltage set point VO, set
decreases (see Figure 48). The following equation deter-
mines the required external-resistor value to trim-down the
output voltage:
Rtrim-down is the external resistor in kΩ
∆%
is the percentage change in voltage
A and B values are defined in Table 1 for various models.
+
Ion/off
-
Von/off
REMOTE
ON/OFF
V
I(+)
V
I(-)
VO(+)
SENSE(+)
SENSE(-)
V
O(-)
V
I(+)
V
I(-)
IO
LOAD
CONTACT AND
DISTRIBUTION LOSSE
SUPPLY
I
I
CONTACT
RESISTANCE
R
trim-down
A
F
----
B–
⎩⎭
⎨⎬
kΩ=
F
∆%
100
---------
=
