BD9673AEFJ Datasheet, PDF (6/23 Pages) Rohm – Flexible Step-down Switching Regulators with Built-in Power MOSFET

BD9673AEFJ
Datasheet
◇The case of not using the function of synchronization
Although the SYNC pin is pulled down by resistor in this device, if the function of the synchronization is not used, it is
recommended to connect SYNC pin to ground.
Figure 5. the method to disposal the SYNC pin without
synchronization
◇SOFT START
The soft start time of BD9673AEFJ is determined by the DCDC operating frequency (self-run mode 300 kHz ⇒10ms).
If synchronization is used at the time of EN=ON, The soft start time is restricted by SYNC pin input pulse frequency.
SYNC pin input pulse frequency is fosc_ex kHz, the soft start time is expressed by below equation.
300
Tss = _{fosc_ex}
× 10 [ms]
◇OCP operation
The device has the circuit of over current protection for protecting the FET from over current.
To detect OCP 2 times sequentially, the device will stop and after 13 msec restart.
VC
Lx
VOUT
OCP threshold
VC voltage rising by
output connect to GND
VC voltage discharged
by OCP latch
force the High side FET OFF
by detecting OCP current
(pulse by pulse protection)
output connect to GND
OCP
OCP_LATCH
set the OCP latch by detecting
the OCP current 2 times sequencially
OCP latch reset after 13 msec
(300ｋHz 4000 counts)
Figure 6. Timing chart at OCP operation
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TSZ22111・15・001
6/20
TSZ02201-0Q1Q0AJ00190-1-2
28.JAN.2014 Rev.003