ADP3210 Datasheet, PDF (32/38 Pages) ON Semiconductor – 7-Bit Programmable Multiphase Mobile CPU Synchronous

ADP3210
fSwitching is the switching frequency.
PSnubber is the power dissipated in RSnubber.
SELECTING THERMAL MONITOR COMPONENTS
For single-point hot spot thermal monitoring, simply set R_TTSET1
equal to the NTC thermistor’s resistance at the alarm
temperature (see Figure 26). For example, if the VRTT alarm
temperature is 100°C using a Vishey thermistor (NTHS-
0603N011003J) with a resistance of 100 kΩ at 25°C, and 6.8 kΩ
at 100°C, simply set R_TTSET1 = R_TH1(100°C) to 6.8 kΩ.
Figure 26. Single-Point Thermal Monitoring
Multiple-point hot spot thermal monitoring can be
implemented as shown in Figure 27. If any of the monitored hot
spots reaches alarm temperature, the VRTT signal is asserted.
The following calculation sets the alarm temperature:
½ + ^VFD
R_TTSET1
=
V_REF
½ − ^VFD
R_{TH1ALARMTEMPERATURE}
V_REF
(39)
where V_FD is the forward drop voltage of the parallel diode.
Because the forward current is very small, the forward drop
voltage is very low (100 mV). Assuming the same 100°C alarm
temperature used in the single-spot thermal monitoring example,
and the same Vishay thermistor, then Equation 39 leads to
R_TTSET = 7.37 kΩ, whose closest standard resistor is 7.32 kΩ (1%).
Figure 27. Multiple-Point Thermal Monitoring
The number of hot spots monitored is not limited. The alarm
temperature of each hot spot can be set differently by playing
different RTTSET1, RTTSET2, RTTSETn.
TUNING PROCEDURE FOR ADP3210
1. Build the circuit based on compensation values computed
from Equation 1 to Equation 39.
2. Hook-up the dc load to the circuit. Turn the circuit on and
verify operation. Check for jitter at no load and full load.
DC Loadline Setting
3. Measure the output voltage at no load (V_NL). Verify that it
is within tolerance.
4. Measure the output voltage at full load and at cold (V_FLCOLD).
Let the board set for a ~10 minutes at full load and measure
the output (V_FLHOT). If there is a change of more than a few
millivolts, then adjust R_CS1 and R_CS2 using Equation 40 and
Equation 41.
R_{CS2(NEW )}
=
R_CS2(OLD)
×
V_NL
V_NL
− V_FLCOLD
− V_FLHOT
(40)
5. Repeat Step 4 until cold and hot voltage measurements
remain the same.
6. Measure output voltage from no load to full load using 5 A
steps. Compute the load line slope for each change and
then average it to get the overall load line slope (R_OMEAS).
7. If R_OMEAS is off from R_O by more than 0.05 mΩ, use the
following to adjust the R_PH values:
R_{PH(NEW )}
=
R _{PH (OLD )}
×
R_OMEAS
R_O
(41)
8. Repeat Step 6 and Step 7 to check load line and repeat
adjustments if necessary.
9. Once complete with dc load line adjustment, do not change
R_PH, R_CS1, R_CS2, or R_TH for the rest of procedure.
10. Measure output ripple at no load and full load with a scope
to make sure it is within specification.
Rev. 0.3 | Page 32 of 38