lm9011 National Semiconductor Corporation, lm9011 Datasheet - Page 14

• Manufacturer Part Number: lm9011
• Description: Electronic Ignition Interface
• Manufacturer: National Semiconductor Corporation

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Circuit Description
Ground cannot be detected. The internal logic is unable to
discern which output pin is above the Fault Threshold Volt-
age, only that a pin is. Thus, the logical requirement of an Sx
pin voltage above the Fault Threshold voltage is met and no
fault is reported.
The output rise and fall times are basically a function of the
output current drive (source and sink) and the output load
characteristics. Due to the scaling of the output stages, and
variations in the value of S_HI, the fall time will typically be
two to ten times longer than the rise time for a given capaci-
tive load.
Since the output fault detection mode changes immediately
with the status of the ENB pin, and the voltage on the output
FIGURE 15. FAULT Pin Output During Normal Operation
(Continued)
14
pin cannot change instantly, the FAULT pin will go low during
the output transition times. The FAULT pin will stay low until
the output voltage rises above, or falls below, the active fault
threshold. See Figure 15.
When switching the outputs from the active mode to the
TRI-STATE mode the ENB should be taken low first. This will
take all of the outputs low. Then the RESET pin can be taken
low. This will eliminate false ’open’ faults that will be gener-
ated while waiting for the one output that was high, to
discharge any capacitance below the V
10126425
FAULT
threshold.