LTM4641
APPENDICES
regulator can witnesses transient excursions above its
ideal DC voltage operating point routinely, owing to:
short-circuit testing (shorting V to SW on evaluation
INH
hardware such as DC1543, for example) does not clamp
the output voltage to one’s satisfaction, be aware that
increasing output capacitance can reduce the maximum
output voltage excursion. The reason follows: the larger
the output capacitance, the longer it takes for the output
voltage to be ramped up, even in the extreme case of
•ꢀ ControlꢀICꢀbandgapꢀreferenceꢀaccuracy
•ꢀ Outputꢀvoltageꢀrippleꢀandꢀnoise
•ꢀ Loadꢀcurrentꢀstep-downꢀtransientꢀevents—includingꢀ
recovery from a short-circuit condition
deliberately short circuiting V to SW. The capacitance
INH
•ꢀ Steepꢀlineꢀvoltageꢀstep-up
on V
is mainly what prevents the output voltage from
shooting up to V —until CROWBAR turns on MCB.
OUT
•ꢀ Start-upꢀovershootꢀ(littleꢀorꢀnoꢀsoft-startingꢀofꢀV ),
INH
OUT
or rail-tracking a fast master rail
Multimodule parallel applications also have better output
voltage overshoot during high side MOSFET short-circuit
testing, owing to the fact that the sibling modules whose
high side MOSFETs are not short circuited are able to help
pull the output voltage down by turning on their low side
power MOSFETs. Examples of paralleled LTM4641 power-
ing and protecting loads are shown in Figures 56 and 66.
The Linear Technology LTpowerCAD design tool can help
quantify some of these dynamic values; LTM4641’s total
DC error (including bandgap reference variation) is better
than 1.5%, over temperature.
If OV
has been decreased to its lowest practical level
PGM
and output voltage overshoot during high side MOSFET
4641f
61
Linear [ Linear ]
