ADP3208 ON Semiconductor, ADP3208 Datasheet - Page 35

• Manufacturer Part Number: ADP3208
• Description: 7-bit, Programmable, Dual-phase, Mobile, Cpu, Synchronous Buck Controller
• Manufacturer: ON Semiconductor

The number of hot spots monitored is not limited. The alarm
temperature of each hot spot can be individually set by using
different values for R
TUNING PROCEDURE FOR ADP3208
Set Up and Test the Circuit
1.
2.
3.
4.
Set the DC Load Line
1.
2.
3.
4.
5.
6.
7.
Set the AC Load Line
1.
2.
3.
4.
Build a circuit based on the compensation values
computed from the design spreadsheet.
Connect a dc load to the circuit.
Turn on the ADP3208 and verify that it operates properly.
Check for jitter with no load and full load conditions.
Measure the output voltage with no load (V
that this voltage is within the specified tolerance range.
Measure the output voltage with a full load when the
device is cold (V
minutes with a full load and then measure the output when
the device is hot (V
measured voltages is more than a few millivolts, adjust R
using Equation 44.
Repeat Step 2 until no adjustment of R
Compare the output voltage with no load to that with a full
load using 5 A steps. Compute the load line slope for each
change and then find the average to determine the overall
load line slope (R
If the difference between R
use the following equation to adjust the R
Repeat Steps 4 and 5 until no adjustment of R
Once this is achieved, do not change R
for the rest of the procedure.
Measure the output ripple with no load and with a full load
with scope, making sure both are within the specifications.
Remove the dc load from the circuit and connect a
dynamic load.
Connect the scope to the output voltage and set it to dc
coupling mode with a time scale of 100 μs/div.
Set the dynamic load for a transient step of about 40 A at
1 kHz with 50% duty cycle.
Measure the output waveform (note that use of a dc offset
on the scope may be necessary to see the waveform). Try to
use a vertical scale of 100 mV/div or finer.
R
R
CS2(NEW)
PH
(
NEW
)
=
=
TTSET1
FLCOLD
R
R
OMEAS
CS2(OLD)
PH
FLHOT
(
, R
OLD
). Allow the board to run for ~10
).
TTSET2
). If the difference between the two
)
OMEAS
×
×
V
R
V
, … R
NL
OMEAS
NL
R
and R
O
−
−
V
V
TTSETn
FLCOLD
FLHOT
O
is more than 0.05 mΩ,
CS2
PH
.
, R
is needed.
PH
CS1
NL
values:
) and verify
PH
, R
Rev. 1 | Page 35 of 38 | www.onsemi.com
is needed.
CS2
, or R
(44)
(45)
TH
CS2
5.
6.
7.
8.
9.
Set the Initial Transient
1.
The resulting waveform will be similar to that shown in
Figure 45. Use the horizontal cursors to measure V
V
shoot or overshoot that occurs immediately after the step.
If the difference between V
couple of millivolts, use Equation 46 to adjust C
be necessary to try several parallel values to obtain an
adequate one because there are limited standard capacitor
values available (it is a good idea to have locations for two
capacitors in the layout for this reason).
Repeat Steps 5 and 6 until no adjustment of C
Once this is achieved, do not change C
procedure.
Set the dynamic load step to its maximum step size (but do
not use a step size that is larger than needed) and verify
that the output waveform is square, meaning V
V
Ensure that the load step slew rate and the power-up slew
rate are set to ~150 A/μs to 250 A/μs (for example, a load
step of 50 A should take 200 ns to 300 ns) with no
overshoot. Some dynamic loads have an excessive
overshoot at power-up if a minimum current is incorrectly
set (this is an issue if a VTT tool is in use).
With the dynamic load set at its maximum step size,
expand the scope time scale to 2 μs/div to 5 μs/div. This
results in a waveform that may have two overshoots and
one minor undershoot before achieving the final desired
value after V
DCDRP
DCDRP
C
, as shown in Figure 45. Do not measure the under-
CS
are equal.
(
NEW
DROOP
Figure 45. AC Load Line Waveform
)
=
C
CS
(see Figure 46).
(
OLD
)
×
V
V
ACDRP
DCDRP
ACDRP
V
ACDRP
and V
DCDRP
CS
V
for the rest of the
DCDRP
is more than a
ADP3208
CS
ACDRP
CS
is needed.
ACDRP
. It may
and
and
(46)