lm9072 National Semiconductor Corporation, lm9072 Datasheet - Page 10

• Manufacturer Part Number: lm9072
• Description: Dual Tracking Low-dropout System Regulator
• Manufacturer: National Semiconductor Corporation

www.national.com
Application Information
Safety Latch-OFF
To address a system FMEA (Failure Mode Effects Analysis)
issue the Keep-Alive high level should be derived from the
Tracking output regulator as shown in Figure 6 . The issue
stems from the “what-if” scenario whereby the system is in
the Keep-Alive state and there is a short to ground on the
Tracking Output regulator. If this output is powering remote
sensors or systems, this becomes a more highly possible
fault condition. Since a short on the Tracking output does not
affect the Main output, which, if used to provide the
FIGURE 5. Simple Logic Configuration to Provide ON/OFF Sensing
(Continued)
10
Keep-Alive input signal, would remain ON and draw 120 mA,
the short circuit current of the Tracking regulator, from the
input supply.
Using the Tracking output supply for Keep-Alive would pre-
vent Keep-Alive operation during a short to ground fault and
the excessive drain on the input supply. The inversion by the
transistor will require a low level from the controller to allow
Keep-Alive operation. The 24 k
current limiting in the event of a Tracking output short to the
unregulated/battery input supply.
DS012906-21
pull-up resistor provides