2
dc1687af
DEMO MANUAL DC1687A
Quick start proceDure
Using short twisted pair leads for any power connections
and with all loads and power supplies off, refer to Figure 3
for the proper measurement and equipment setup. The
battery/power supply (PS1) 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. Measure the input or output voltage ripple
by touching the probe tip directly across the V
IN
or V
OUT
and GND terminals (see Figure 4), or by using an oscil-
loscope probe tip jack.
1. Jumper and PS1 settings to start:
PS1 = OFF
JP1 (PWM) = fixed frequency
JP2 (RUN) = ON
2. With power OFF connect the power supply (PS1) as
shown in Figure 3. If accurate current measurements
are desired (for efficiency calculation for example) then
connect an ammeter in series with the supply as shown.
The ammeter is not required however.
3. Connect a 500mA load to V
OUT
as shown in Figure 3
(10Ω for V
OUT
= 5V). Connect an ammeter if accurate
current measurement or monitoring is desired.
4. Turn on PS1 and slowly increase voltage until the volt-
age at V
IN
is 4.0V.
5. Verify V
OUT
is ~5.0V.
6. V
IN
can now be varied between 2.7V and 40.0V. I
OUT
may
need to be reduced for V
IN
< 4V. V
OUT
should remain in
regulation.
7. Load current (I
OUT
) can also be varied. The maximum
I
OUT
is a function of V
IN
and the current limit. Consult
the data sheet for more information on I
OUT
vs V
IN
. In
general for V
IN
> 3.6V I
OUT
can be increased to 1A. For
V
IN
> 6V I
OUT
can be increased to 2A.
8. For operation in Burst Mode operation move Jumper
JP1 to burst. I
OUT
is limited in Burst Mode operation.
See the data sheet for more information.
9. NOTE: If V
OUT
drops out of regulation, check to be sure
the maximum load has not been exceeded, or that V
IN
is not below the minimum value for regulation (see data
sheet)
0
100
90
80
70
60
50
5
10
15
20
25
30
35
40
EFFICIENCY (%)
V
IN
(V)
LOAD = 1A
LOAD = 500mA
0
100
90
80
70
60
50
5
10
15
20
25
30
35
40
EFFICIENCY (%)
V
IN
(V)
LOAD = 300mA
LOAD = 200mA
LOAD = 100mA
Figure 1. DC1687A Efficiency in PWM Mode
Figure 2. DC1687A Efficiency in Burst Mode Operation
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