Answer:
A shorted SIMO output will not cause damage, but will cause all other SIMO channels to have unreliable output voltage regulation vs. load.
A shorted SIMO output will not cause damage, but will cause all other SIMO channels to have unreliable output voltage regulation vs. load.
Explanation:
The MAX77650/MAX77651 single-inductor multiple-output (SIMO) regulator has a robust switching state machine which protects the device and the inductor and IC from damage if an output is shorted.
SIMO inductor current will never ramp above IP_SBB (this is the peak inductor current level, ILIM, which is controlled on a pulse-by-pulse basis in the SIMO).
- The inductor positive ramp rate is determined only by inductor and VIN. It's not a function of VOUT in the MAX77650. A shorted output (SIMO VOUT = 0V) will not cause excessive inductor current ramp rate that violates the IP_SBB value.
- Reminder: This SIMO does not modulate inductor current to regulate output. It modulates pulse frequency. Therefore, the programmed value of IP_SBB is predictable and constant regardless of output voltage or output loading.
Since inductor current is strictly controlled in all modes of operation, a shorted output does not cause any danger to the inductor or the IC. However: A shorted SIMO output will request many inductor current pulses from the SIMO controller.
- The SIMO controller does not "know" that an output is shorted and will continue to give pulses.
- The shorted output will consume nearly 100% of the SIMO capacity. This deprives the other channels of capacity.
- The other SIMO outputs will still attempt to regulate output voltage, but the load regulation capability of the other outputs will become poor and unreliable due to one of the outputs being shorted.