2
Rev. 0
QUICK START PROCEDURE
Refer to Figure 1 for the proper measurement equipment
setup and follow the procedure below:
NOTE: For accurate V
IN
, V
OUT
and efficiency measure-
ments, measure V
IN
at the VIN SNSE and GND SNSN
turrets, and measure V
OUT
at the VOUT SNSE and GND
SNSE turrets, as illustrated as VM1 and VM2 in Figure 1.
When measuring the input or output ripple, care must
be taken to avoid a long ground lead on the oscilloscope
probe. Measure the output voltage ripple by touching the
probe tip directly across the output turrets or to TP1 as
shown in Figure 2.
1. Set the JP1 Jumper to the HI position.
2. With power off, connect the input power supply to VIN
and GND. If the input EMI filter is desired, connect the
input power supply to VIN EMI and GND.
3. Set power supply PS1 current limit to 40A. Set the
electronic load LD1 to CC mode and 0A current. Slowly
increase PS1 to 1V. If PS1 output current reads less
than 20mA, increase PS1 to 3.3V. Verify that VM1 reads
3.3V and VM2 reads 1.2V. Check VM1, VM2, VM3,
PS1 output current, and LD1 input current. Connect
an oscilloscope voltage probe as shown in Figure 2.
Set Channel to AC-coupled, voltage scale to 20mV and
time base to 10µs. Check VOUT ripple voltage. Verify
that PGOOD voltage is above 3V.
4. Increase the load by 1A intervals up to full load and
observe the voltage output regulation, ripple voltage.
5. To test the transient response with a base load, add the
desired resistor to produce a minimum load between
VOUT and I_STEP turrets (RL shown on Figure 1).
Note that the total load resistance will be RL plus
R16 (10mΩ). The DC3186A uses a buffered signal
generator input to drive a source follower circuit, and
to control the slew rate and amplitude of the current
transient. The source follower FET, Q1, operates in the
linear region during the load step.
6. Connect PS2 to DRIVER BIAS and GND turrets. Turn
on and set PS2 to 8V.
7. Set a signal generator with a 1ms pulse width, a 10ms
period and an amplitude from 0V to 4V, and then
connect it to SG_INPUT turret.
NOTE: Do not allow the pulse generator to have more
than a 20% duty cycle. This can allow too much power
to be dissipated in Q1 and can damage the FET.
8. Connect an oscilloscope with a time scale of 200µs/
div with one channel having a vertical scale of 2V/div
on the SG_INPUT and another with a vertical scale of
50mV/div to the I_STEP turret.
9. Measure the I_STEP voltage to observe the current,
V
I_STEP
/10mΩ. Adjust the amplitude of the pulse to
provide the desired transient. Adjust the rising and
falling edge of the pulse to provide the desired ramp
rate. Figure 5 shows a load step from 10A to 20A in
1µs. Refer to the following equations:
I
OUT
=
V
I_STEP
10m
Ω
(1)
V
GS
= V
SG_INPUT
– V
I_STEP
(2)
10. When done, turn off SG1, PS1 and Load. Remove all
the connections to the demo board.
