BD9540EFV Datasheet, PDF (9/18 Pages) Rohm – 2ch Switching Regulators for Desktop PC

BD9540EFV
●Timing Chart
・Over current protection circuit
tON
tON
tON
HG
LG
IL
Technical Note
tON
During normal operation, when FB falls below REF, HG
switches high during for the period of time tON (P8).
However, if the current of the low-side FET exceeds the
ILIMIT threshold, HG will switch off until it becomes below
ILIMIT.
ILIMIT
・Timer Latch Type Short Circuit Protection
FB
HG
LG
EN/UVLO
REF×0.7
28μs
Short protection engages when output falls to or below
REF × 0.7. When the programmed time period (28μs)
elapses, output is latched off to prevent damage to the
IC. Output voltage can be restored either by reconnecting
the EN pin or disabling UVLO.
・Output Over Voltage Protection
OVP threshod voltage
VOUT
1.7μs
HG
LG
Switching
When output voltage rises to or above the OVP threshold
voltage (1ch:1.02V, 2ch:0.9V), output over-voltage
protection engages after the set time (1.7μs) has
elapsed. During this protection period, the low-side
FET opens completely for maximum reduction of output
voltage (LG = high, HG = low). Output voltage can be
restored either by reconnecting the EN pin or disabling
UVLO.
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9/17
2009.04 - Rev.B