TPS650365-Q1: Loop Test

Hello Xiaowei,

Are they wanting to test the loop stability using hardware or software? There is a SIMPLIS model available for the TPS65036x-Q1 in Secure Resources.

Best regards,
Jude Stehling

Hello Xiaowei,

In order to test this on hardware, you will need a spectrum analyzer or a bode analyzer. The test setup and process is described in the following document: www.ti.com/lit/an/sluaa51/sluaa51.pdf

What equipment do you have available to measure the frequency response? Internally, we have often used Bode 100 Network Analyzers for stability measurements with a similar test set up to the following:

Best regards,
Jude Stehling

Hello Xiaowei,

In order to inject the AC ripple on the output, it is necessary to break the feedback loop and provide the AC ripple to the Feedback (for Buck1, the pin name would be FB_B1). 

Please see the following document showing an example setup using a Bode 100 device: DC/DC Converter Stability Measurement

The feedback loop is broken so that the input and output can be measured separately while the AC signal is injected into the buck's feedback pin.

Best regards,
Jude Stehling

Hello Xiaowei,

Loop test results are not collected during the device's validation phase. For the typical values of passives and PMIC device conditions, stability of the individual regulators should not be an issue. For circumstances where a customer is concerned about the stability due to using higher POL capacitance, the SIMPLIS model would be useful for evaluating whether the regulator is approaching instability. 

Typically, more important effects of the phase/gain plot will be the load and line transient tests. These tests would be important to perform in order to evaluate the PMIC's voltage regulation to the specific device being powered.

Best regards,
Jude Stehling