Micrel, Inc.
MIC23099 Evaluation Board
Low-Battery Detection and Output Latch-Off
Figure 3
shows the low-battery power cycling operation. If
the battery voltage (V
IN
) drops below 0.85V for more than
100ms to 150ms, the PG de-asserts (goes low) and
outputs V
OUT1
and V
OUT2
are disabled. Then the 500
Ω
active discharges resistors are enabled, discharges V
OUT1
and V
OUT2
to ground and finally the MIC23099 enters a
cool off or sleep period. After a cool off period of about 1.3
seconds, if the battery voltage is above the 0.85V
threshold, then the outputs will power up again. This cycle
repeats itself until the end of the 15
th
cycle when both
outputs are latched off for the last time.
The outputs can be turned back on by recycling the input
power or by toggling the enable pin. If the battery voltage
is still low, the MIC23099 will turn itself off again after 15
power-up cycles.
Figure 3. Low-Battery Power Cycling
Output Fault and Power Cycling
If either V
OUT1
or V
OUT2
outputs are out of tolerance for
longer than the power good deglitch delay of between
60ms to 120ms, then both outputs are disabled. The
power-down procedure is the same as the low-battery fault
detection, as shown in
Figure 3
. The outputs can be turned
back on by recycling the input power or by toggling the
enable pin. The latch-off feature eliminates the thermal
stress on the MIC23099 and the external inductors during
a fault event.
Figure 4. Output Fault Power Cycling
Boost Short-Circuit Protection
The low-side current limit protects the IC from transient-
overload conditions, but not from a direct short-to-ground.
The high-side MOSFET current limit provides the
protection from a short-to-ground. In this fault condition,
the high-side PMOS switch operates in linear mode and
limits the current to approximately 80mA. If the short-circuit
condition last for more than 30ms, the PMOS switch is
latched off as shown in
Figure 5
. The outputs are not re-
enabled until the input power is recycled or the enable pin
is toggled.
Figure 5. Power-Up into Short Circuit
May 30, 2014
3
Revision 1.0
