4
dc2045af
DEMO MANUAL DC2045A
Quick start proceDure
Using short twisted pair leads for any power connections
and with all loads and power supplies off, refer to Figure 6
for the proper measurement and equipment setup. The
Power Supplies should not be connected to the circuit
until told to do so in the procedure below.
When measuring the input or output voltage ripple, care
must be taken to avoid a long ground lead on the oscil-
loscope probe.
The indicators for
PGD
,
V1GD
and
V2GD
are negative
logic.
PGD
indicates the output voltage is good if it is
pulled to ground and
V1GD
and
V2GD
indicate that the
input voltage on the respective sources are good if the
pins are pulled to ground.
1. JP1 and JP2 settings to start:
JP1 SELECT = IDEAL DIODE (V
CC
)
JP2 MODE = FIXED FREQ (V
CC
)
2. With power OFF connect the power supplies (PS1,
PS2) as shown in Figure 6. If accurate current mea-
surements are desired (for efficiency calculations for
example) then connect the ammeters in series with
the supplies as shown. The ammeters however, are
not required.
3. Connect the load, set at 50Ω, to V
OUT
as shown in
Figure 6. Again, connect an ammeter if accurate current
measurement or monitoring is desired.
4. Turn on the Power Supply, PS1, and slowly increase
the voltage. The converter will start at approximately
2.9V.
5. Verify V
OUT
is ~5.0V, and that
V2GD
is pulled high by
V
CC
and
PGD
and
V1GD
are pulled low.
6. PS1 can now be varied between 2.5V and 18.0V. V
OUT
will remain in regulation for load currents up to 2 amps
with V
IN
greater than V
OUT
. As V
IN1
falls below V
OUT
the
input current may increase to the maximum average
inductor current, depending on the load, which will
then limit the load current and the output voltage.
7. Turn off PS1 and repeat steps 3 to 6 with PS2. The part
will turn on with PS2 at approximately 4.5V. Once on,
PS2 can be varied between 3.8V and 18V. The voltage
measurements of step 5 will change where
V1GD
will
be at V
CC
and
V2GD
will be pulled low. Set the load to
50Ω.
8. Set PS2 to 7V and turn on PS1 slowly increasing the
voltage from 0V to 8V. Note that PS1 starts to supply
the power as the voltage of PS1 exceeds the voltage
on PS2 by at least 400mV.
9. Now decrease the voltage on PS1 and observe that
when the voltage on V
IN1
falls below the voltage on
PS2, PS1 stops supplying the power and PS2 takes
over. See Figure 2 for typical performance for steps
8 and 9.
10. Turn off PS1 and PS2. Change the SELECT jumper
(JP1) to V
CC
(the PRIORITY position). Turn on PS2
and adjust it to 14V.
11. By cycling the voltage on PS1 from 1V to 10V you can
observe the transition of power from PS2 to PS1 and
back as the voltage on V
IN1
goes through its startup
(approximately 2.9V) and shutdown (approximately
2.5V) thresholds. Typical response is shown in Figure 3.
Turn off PS1 and PS2.
Steps 12 and 13 are optional for looking at load step
response if desired.
12. With JP2 in the FIXED FREQ position and PS1 at 3.5V
switch the load from 100mA to 600mA and back. Note
the output voltage response. (Figure 4).
13. With JP2 in AUTOBURST and PS1 at 12V switch the
load from 50 mA to 600 mA and back. Note the output
voltage ripple. (Figure 5). See the data sheet for more
information.
Note: Remove D1 for V
OUT
> 5V to prevent damage to
the converter.