4.3.2 PCMC Closed Loop Test

Below are the steps for testing the PCMC Closed Loop operation of the CIP Hybrid Power Starter Kit.

  1. Remove programming interface. Place CH1 oscilloscope probe to PWM_HS test point, CH2 oscilloscope probe to PWM_LS test point, CH3 oscilloscope probe to CT_CS test point, and CH4 oscilloscope probe to VOUT test point.
  2. Connect DC supply (set to 6V) and LOAD (set to 2A). Power-up the board. PWM_HS, PWM_LS and CT_CS signals and VOUT can be monitored.
  3. Increase VIN up to 16V. VOUT is regulated to 3.3V.
  4. Increase LOAD to 4A. VOUT is regulated to 3.3V.
    Figure 4-28. PWM_HS, PWM_LS, CT_CS and VOUT at VIN = 9V; LOAD = 2A
  5. Connect CH3 to VIN. Capture soft start by lowering the oscilloscope time base and setting positive edge trigger source to VOUT.
    Figure 4-29. Monitoring Soft Start at Start-up
  6. The control loop stability is observed by measuring the frequency response of the open loop gain in the closed loop system. This magnitude/phase measurement is commonly used to determine the three main stability criteria indicators phase margin, gain margin and gain slope at the crossover frequency of the gain.
    Figure 4-30. PCMC Loop Gain and Phase Measurements at VIN = 9V, LOAD = 4A