Datasheet

Data Sheet ADM1073
Rev. B | Page 19 of 24
An undervoltage glitch is dealt with in a similar way. When V
UV
falls below the undervoltage threshold of 0.868 V, th e G AT E
voltage is pulled low. V
UV
begins to rise back toward the
operating voltage window, and the GATE drive is restored when
the undervoltage rising threshold (0.868 V plus preset UV
hysteresis level) is reached. Figure 39 illustrates the ADM1073’s
operation in an undervoltage situation.
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Figure 39. Timing Waveforms Associated with an Undervoltage Fault
(Ch1 = GATE; Ch2 = UV; Ch3 =
PWRGD
; Ch4 =
SPLYGD
)
SOFT START
The ADM1073 offers a variable soft start feature. The value of
the capacitor on the SS pin sets the ramp rate of the inrush
current profile at startup. Figure 40 to Figure 42 show different
inrush current ramp rates for three SS capacitors.
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Figure 40. Soft Start Profile with a 0.1 nF Capacitor
(Ch1 = GATE; Ch2 = SENSE)
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Figure 41. Soft Start Profile with a 1.5 nF Capacitor
(Ch1 = GATE; Ch2 = SENSE)
04488-042
Figure 42. Soft Start Profile with an 8.2 nF Capacitor
(Ch1 = GATE; Ch2 = SENSE)