MIC23099 Datasheet, PDF(18/26 Page) Micrel Semiconductor – Single AA/AAA Cell Step-Up/Step-Down Regulators

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MIC23099 Datasheet, PDF (18/26 Pages) Micrel Semiconductor – Single AA/AAA Cell Step-Up/Step-Down Regulators

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Micrel, Inc.

Low-Battery Detection and Output Latch-Off

Figure 4 shows the low-battery power cycling operation. If

the battery voltage (VIN) drops below 0.85V for more than

100ms to 150ms, the PG de-asserts (goes low) and

outputs VOUT1 and VOUT2 are disabled. Then the 500â¦

active discharges resistors are enabled and discharges

VOUT1 and VOUT2 to ground, finally the MIC23099 enters a

cool off or sleep period. After a cool off period of about

1.3 sec, 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 15th 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.

MIC23099

Figure 5. 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 6. The outputs

are not re-enabled until the input power is recycled or the

enable pin is toggled.

Figure 4. Low-Battery Power Cycling

Output Fault and Power Cycling

If either VOUT1 or VOUT2 outputs are out of tolerance for

longer than the power good deglitch delay of between

60ms to 120ms, both outputs are disabled. The power

down procedure is the same as the low-battery fault

detection, as shown in Figure 5. 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 6. Power-Up into Short Circuit

May 27, 2014

Revision 1.2

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