ZHCSKX0 February 2020 TPS59632-Q1
PRODUCTION DATA.
Once the the ROSR value is fixed, then the USR level can be set by the voltage on the O-USR pin. The resistor RUSR (between the O-USR pin and the VREF pin) sets the voltage.
LEVEL | VO-USR SELECTION
VOLTAGE (V) |
VUSR
UNDERSHOOT REDUCTION LEVEL (mV) |
|
---|---|---|---|
MIN | MAX | ||
1 | 0.25 | 60 | |
2 | 0.35 | 0.45 | 90 |
3 | 0.55 | 0.65 | 120 |
4 | 0.75 | 0.85 | 180 |
5 | 0.95 | 1.05 | 240 |
6 | 1.15 | 1.25 | 420 |
7 | 1.35 | 1.45 | 480 |
8 | 1.55 | VVREF | 540 |
The USR level is also selected similar to the OSR setting. First, begin with least undershoot reduction and lower the level until pulse-overlap between two phases happens sufficiently to meet the load insertion transient requirement. The USR level can be approximately estimated by multiplying one-third of the droop voltage for the specified load transient with the ADROOP determined in Step 8: Set the Load-Line Slope. The actual level needs to be tuned based on measurement. In this design, OSR is set to OFF and USR is set to 90-mV level. Therefore ROSR = 150k and RUSR = 487k.