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XC9263/XC9264

Series

■

OPERATIONAL EXPLANATION (Continued)

<Current limiting>

The current limiting circuit of the XC9263/64 series monitors the current that flows through the High-side driver transistor and Low-side driver

transistor, and when over-current is detected, the current limiting function activates.

①

Low-side driver Tr. current limiting

The current in the Low-side driver Tr. is detected to equivalently monitor the bottom value of the coil current. The Low-side driver Tr. current

limiting function prohibits the High-side driver Tr. from turning on in an over-current state where the bottom value of the coil current is higher

is released, normal operation resumes.

②

High-side driver Tr. current limiting

The current in the High-side driver Tr. is detected to equivalently monitor the peak value of the coil current. The High-side driver Tr. current

limiting function forcibly turns off the High-side driver Tr. when the peak value of the coil current reaches the High-side driver current limit value

at this time. When the over-current state is released, normal operation resumes.

③

Over-current latch (Type A)

Type A turns off the High-side and Low-side driver Tr. when state ① or ② continues for 1.0ms (TYP.). The LX pin is latch-stopped at the GND

level (0V).

The latch-stopped state only stops the pulse output from the Lx pin; the internal circuitry of the IC continues to operate. To restart after

latch-stopping, L level and then H level must be input into the EN/SS pin, or VIN pin re-input must be performed (after lowering the voltage

below the UVLO detection voltage) to resume operation by soft start.

The over-current latch function may occasionally be released from the current limit detection state by the effects of ambient noise, and it may

also happen that the latch time becomes longer or latching does not take place due to board conditions. For this reason, place the input

capacitor as close as possible to the IC.

Type B is an automatic recovery type that performs the operation of ① or ② until the over-current state is released.

Type A only

1.0ms(TYP.)

0A

0V

0V

Current limiting timing chart