ADP3210 datasheet(32/38 Pages) ONSEMI

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ADP3210

Rev. 0.3 | Page 32 of 38

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 RTTSET1

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 RTTSET1 = RTH1(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:

RATURE

ALARMTEMPE

REF

TTSET

−

(39)

where VFD 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

RTTSET = 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

Build the circuit based on compensation values computed

from Equation 1 to Equation 39.

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

Measure the output voltage at no load (VNL). Verify that it

is within tolerance.

Measure the output voltage at full load and at cold (VFLCOLD).

Let the board set for a ~10 minutes at full load and measure

the output (VFLHOT). If there is a change of more than a few

millivolts, then adjust RCS1 and RCS2 using Equation 40 and

Equation 41.

FLHOT

FLCOLD

OLD

NEW

−

)

(

)

(

(40)

Repeat Step 4 until cold and hot voltage measurements

remain the same.

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 (ROMEAS).

If ROMEAS is off from RO by more than 0.05 mΩ, use the

following to adjust the RPH values:

OMEAS

OLD

NEW

)

(

)

(

(41)

Repeat Step 6 and Step 7 to check load line and repeat

adjustments if necessary.

Once complete with dc load line adjustment, do not change

RPH, RCS1, RCS2, or RTH 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.

ADP3210 Datasheet(PDF) 32 Page - ON Semiconductor

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