Hello

Our customer will use ADN8834 and evaluating ADN8834CB-EVALZ.

At initial setting with his laser module including TEC and thermistor, OUT2 is oscillated.

So he aligned the C and R around OUT2.

As the result of alignment, OUT2 is stable at 25 degreeC and heating mode but OUT2 is oscillated at cooling mode.

I describes below about his alignment.

Please let me know your advice to avoid this problem.

About His alignment

Temperature condition: 25 degreeC

TEMPSET: fixed 1.544V

His board: ADN8834CB-EVALZ

Change by below method: Cl, Cd, Cf, Rl, Rd, Rp in datasheet P.13 figure 26.

Rl：51kΩ、Rd：100kΩ、Cd：100pF、Rp：100kΩ、Cl：22µF、Cf：0.01µF

He aligns as below method.

1: Short Cl and open Cd from condition of ADN8834CB-EVALZ.

2: The retio of Rl/Rp is increased and confirm the oscillation of OUT2. Then the retio of Rl/Rp is decreased by a factor of the two.

3: Add Cl and decreas its value until OUT2 starts oscillation. Then he increases Cl by a factor of the two.

4: Short Rd and add Cd. He increases Cd until OUT2 starts oscillation.Then Cd is decreased and Rd is added.

Now, OUT2 is oscillated at cooling mode only in above 4.

Please let me know your advice about the problem for above method and avoiding this problem.

If you need any other information ,please let me know it.

Regards,

Terumasa

The method is basically correct, just fine tune the PID a little and make it more conservative should solve the problem. When the load current is higher or the step change is larger, the circuit tend to oscillate easier. A fast compensation loop may not work under this scenario. Plus the load is usually heavier at cooling mode since there's more energy to dissipate.

I suggest try lower the RI/RP ratio, or CD a little more and see how things go.