SNVA881 November   2019 LP87521-Q1 , LP87522-Q1 , LP87523-Q1 , LP87524-Q1 , LP87525-Q1 , LP87561-Q1 , LP87562-Q1 , LP87563-Q1 , LP87564-Q1 , LP87565-Q1

 

  1.   Stability Considerations for LP8756x-Q1 and LP8752x-Q1
    1.     Trademarks
    2. 1 Introduction
    3. 2 Stability Target
    4. 3 Use Cases
    5. 4 Measurements
      1. 4.1 Measurement Setup
      2. 4.2 Measurement Results
    6. 5 Simulations
      1. 5.1 Simulation Model
      2. 5.2 Simulation Results
    7. 6 Summary
    8. 7 References

Summary

Figure 11, Figure 12, Figure 13, and Figure 14 summarize the measured phase margins for every phase configuration. The figures include all the measured combinations and are divided into different figures based on the phase configuration. These figures can be used when selecting point of load capacitors for the systems using the LP8756x-Q1 or LP8752x-Q1 PMICs.

To select the required point of load capacitor value which achieves a sufficient phase margin, do the following:

  1. Take a look at the figure corresponding to the phase configuration.
  2. Select the curve that matches the desired VOUT and VIN parameters the closest.
  3. Find the point on which the curve crosses the desired phase margin value and read the horizontal CPOL value on that point.

D009_SNVA881.gifFigure 11. Phase margins for 1-phase configurations

D011_SNVA881.gifFigure 13. Phase margins for 3-phase configurations

D010_SNVA881.gifFigure 12. Phase margins for 2-phase configurations

D012_SNVA881.gifFigure 14. Phase margins for 4-phase configurations

The minimum capacitor configurations that fulfilled the 45 degree phase margin requirement are listed in Table 12

Table 12. Minimum CPOL required for 45 degree phase margin

Phases VIN (V) VOUT (mV) CPOL (µF/phase) Bandwidth (kHz) Phase margin (deg)
1 (LP875x4/3/2-Q1) 3.3 860 91 101.7 48.5
1000 91 104.4 50.4
1800 44 167.4 46.0
5 860 91 114.6 52.0
1000 91 112.1 48.4
1800 44 181.4 45.4
3300 22 296.9 45.4
2 (LP875x3/5-Q1) 3.3 860 91 95.2 50.4
1000 91 99.6 50.7
1800 91 110.7 52.3
5 860 91 108.3 54.0
1000 91 105.7 52.2
1800 44 174.0 46.9
3300 44 194.2 50.3
3 (LP875x2-Q1) 3.3 860 91 100.5 48.3
1000 91 102.6 49.8
1800 91 111.4 51.5
5 860 44 183.1 45.6
1000 91 112.5 51.5
1800 44 175.8 46.2
3300 44 204.6 50.1
4 (LP875x1-Q1) 3.3 860 91 95.3 48.6
1000 91 99.5 49.4
1800 91 109.7 50.8
5 860 44 194.7 48.9
1000 44 170.7 45.7
1800 44 169.0 47.4
3300 44 197.2 50.1