ADP3208C ON Semiconductor, ADP3208C Datasheet - Page 38

• Manufacturer Part Number: ADP3208C
• Description: 7-bit,programmable,dual- Phase,mobile,cpu,synchronous Buck Controller
• Manufacturer: ON Semiconductor

ADP3208C
capacitor bank is formed by eight pieces of 10 μF, 25 V MLC
capacitors, with a ripple current rating of about 1.5 A each.
Selecting Thermal Monitor Components
To monitor the temperature of a single-point hot spot, set
R
temperature. For example, if the alarm temperature for VRTT is
100°C and a Vishey thermistor (NTHS-0603N011003J) with a
resistance of 100 kΩ at 25°C, or 6.8 kΩ at 100°C, is used, the
user can set R
To monitor the temperature of multiple-point hot spots, use the
configuration shown in Figure 40. If any of the monitored hot
spots reaches the alarm temperature, the VRTT signal is
asserted. The following calculation sets the alarm temperature:
where V
Because the forward current is very small, the forward drop
voltage is very low, that is, less than 100 mV. Assuming the same
conditions used for the single-point thermal monitoring
example—that is, an alarm temperature of 100°C and use of an
NTHS-0603N011003J Vishay thermistor—solving Equation 42
gives a R
7.32 kΩ (1%).
TTSET1
R
TTSET1
equal to the NTC thermistor’s resistance at the alarm
FD
TTSET
is the forward drop voltage of the parallel diode.
=
Figure 40. Multiple-Point Thermal Monitoring
of 7.37 kΩ, and the closest standard resistor is
TTSET1
Figure 39. Single-Point Thermal Monitoring
1
1
2 /
2 /
+
−
equal to 6.8 kΩ (the R
V
V
V
V
REF
REF
FD
FD
×
R
TH1AlarmTe
mperature
TH1
at 100°C).
Rev. 1 | Page 38 of 41 | www.onsemi.com
(34)
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 ADP3208C
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 ADP3208C 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 35.
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
V
R
, … 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
is needed.
CS2
, or R
(35)
(36)
TH
CS2