PQ24018QGA25 Datasheet, PDF (9/13 Pages) SynQor Worldwide Headquarters – 25 Amp, No Heatsink, Isolated DC/DC Converter

referenced to the return terminal of the 24V input bus. There
are two versions of the PowerQor series converter that differ
by the sense of the logic used for the ON/OFF input. In the
PQxxyyyQGAzzPxx version, the ON/OFF input is active
high (meaning that a high turns the converter on). In the
PQxxyyyQGAzzNxx version, the ON/OFF signal is active
low (meaning that a low turns the converter on). Figure A
details five possible circuits for driving the ON/OFF pin.
Figure B shows detail of the internal ON/OFF circuitry.
Pins 7 and 5 (SENSE(+)): The SENSE(+) inputs correct
for voltage drops along the conductors that connect the con-
verter’s output pins to the load.
Pin 7 should be connected to Vout(+) and Pin 5 should be
connected to Vout(-) at the point on the board where regu-
lation is desired. That is,
[Vout(+) - Vout(-)] – [SENSE(+) - SENSE (-)] < 10%Vout
Pins 7 and 5 must be connected for proper regulation of the
output voltage. However, if these connections are not made,
nothing catastrophic will happen to the converter under nor-
mal operating conditions—the converter will simply deliver
an output voltage that is slightly higher than its specified
value.
Note: the output over-voltage protection circuit senses the
Technical Specification
Quarter
Brick
24Vin 1.8Vout 25A
voltage across the output (pins 8 and 4) to determine when
it should trigger, not the voltage across the converter’s sense
pins (pins 7 and 5). Therefore, the resistive drop on the
board should be small enough so that output OVP does not
trigger, even during load transients.
Pin 6 (TRIM): The TRIM input permits the user to adjust the
output voltage across the sense leads up or down. To lower
the output voltage, the user should connect a resistor
between Pin 6 and Pin 5, which is the SENSE(-) input. To
raise the output voltage, the user should connect a resistor
between Pin 6 and Pin 7, which is the SENSE(+) input.
A resistor connected between Pin 6 and Pin 5 will decrease
the output voltage. For a desired decrease of ∆ percent of
the nominal output voltage, the value of this resistor should
be
( ) ^{Rtrim-down =}
511
∆%
- 10.22
(kΩ)
where
( ) ∆ = VNOM – VDES x 100%
V_NOM
and
V_NOM = Nominal Voltage
V_DES = Desired Voltage
ON/OFF
ON/OFF
ON/OFF
Vin(^_)
Vin(^_)
Vin(^_)
Vin(+)
5V
Remote Enable Circuit
Negative Logic
Positive Logic
(Permanently Enabled)
(Permanently Enabled)
100k
ON/OFF
5V
TTL/
CMOS
ON/OFF
Vin(^_)
Open Collector Enable Circuit
Vin(^_)
Direct Logic Drive
Figure A: Various circuits for driving the ON/OFF pin.
ON/OFF
50k
TTL
100pF
50k
Vin(^_)
Figure B: Internal ON/OFF pin circuitry (detail)
Product # PQ24018QGA25
Phone [phone]
Doc.# 005-2QG218D_A
3/1/02
Page 9