5
dc2215af
DEMO MANUAL DC2215A
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
PRIORITY
,
VALID1
and
VALID2
are
negative logic while the indicator for PGOOD is positive
logic. PGOOD indicates the output voltage is good if it is
pulled to V
CC
and
VALID1
and
VALID2
indicate that the
input voltage on the respective sources are good if the
pins are pulled to ground. With the unit enabled (JP4,
(ENA = ON) and JP2 (DIODE =
PRIORITY
)) the unit is
operating in PRIORITY mode. This means that if there is
enough voltage on V
IN1
then V
IN1
will be supplying power
to the converter independent of the voltage on V
IN2
and
VALID1
will be low.
If JP2 (DIODE) is connected to IDEAL DIODE the unit is
operating in IDEAL DIODE mode and power will be drawn
from whichever source has enough voltage to be enabled
and is the higher voltage. Both
VALID1
and
VALID2
will be
low if V
IN1
and V
IN2
are above their operating thresholds.
Turrets
Left side of board:
V
IN1
:
4.3V to 42V supply input: do not 42V.
GND:
Ground connection for input supply.
V
IN2
:
6V to 8.4V supply input: operational to +42V.
Right side of board:
GND:
Ground connection for LOAD.
V
OUT
:
3.3V/2.5A first of two terminals in parallel.
V
OUT
:
3.3V/2.5A second of two terminals in parallel.
GND:
Ground connection for LOAD.
Jumpers
JP1/PWM/SYNCH:
Selects PMW or Burst Mode opera-
tion. Leaving the jumper open and applying a square
wave signal to the SYNC pin allows the converter to
be synchronized. Default position is PWM which puts
the unit in fixed frequency PWM operation.
JP2/DIODE:
Selects PRIORITY or DIODE-OR mode.
JP3/EXTV
CC
:
connects EXTV
CC
to V
OUT
through a
diode or leaves EXTV
CC
open. If EXTV
CC
is open, the
LTC3126 derives bias from V
IN
. The default position
is V
OUT
.
JP4/ENA:
Selects ENA = ON/OFF. The default position
is “ON”.
1. JP1 through JP4 settings to start:
JP1
PWM/SYNC = PWM
JP2
DIODE
=
PRIORITY
JP3
EXTVcc = VOUT
JP4
ENA
= ON
2. With the power supplies (V
IN1
, V
IN2
) OFF connect them
as shown in Figure 6. If accurate current measurements
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 5Ω, (660mA) 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, V
IN1
, and increase the volt-
age. The converter will start at approximately 4.3V.
5. Verify V
OUT
is ~3.3V.
6. V
IN1
can now be varied between 4.3V and 42V. V
OUT
will remain in regulation for load currents up to 2.5A.
7. Set V
IN1
to 0V and turn off V
IN1
.