BD9B400MUV Datasheet, PDF (18/34 Pages) Rohm – Integrated MOSFET Single Synchronous Buck DC/DC Converter

BD9B400MUV
2. Protection
The protective circuits are intended for prevention of damage caused by unexpected accidents. Do not use them
for continuous protective operation
(1) Over Current Protection (OCP) / Short Circuit Protection (SCP)
Setting (Typ) of over current protection are 7A (lower MOSFET) and 9.5A (upper MOSFET). When OCP is triggered,
over current protection is realized by restricting On / Off Duty of current flowing in upper and lower MOSFET by each
switching cycle. Also, if Over current protection operates 512 cycles in a condition where FB terminal voltage
reaches below 70% of internal standard voltage, Short Circuit protection (SCP) operates and stops switching for
1msec (Typ) before it initiates restart. However, during startup, Short circuit protection will not operate even if the IC
is still in the SCP condition.
Table 1. Over Current Protection / Short Circuit Protection Function
EN terminal PGD
Startup
Over current
protection
L
More than 2.0V
While start up
Startup completed
Valid
Valid
H
＊
Valid
Less than 0.8V ＊
＊
Invalid
Short circuit
protection
Invalid
Valid
Invalid
Invalid
VOUT
FB
High side
MOSFET gate
Low side
MOSFET gate
High side OCP threshold
Low side OCP threshold
Coil current
Inside IC OCP signal
(Low side)
Inside IC OCP signal
(High side)
PGD
1ms(Typ)
512 Cycle
Figure 46. Short Circuit Protection (SCP) Timing Chart
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TSZ02201-0J3J0AJ01200-1-2
22.Apr.2016 Rev.002