Datasheet

BD9540EFV
Technical Note
9/17
www.rohm.com
2009.04 - Rev.B
© 2009 ROHM Co., Ltd. All rights reserved.
●Timing Chart
・Over current protection circuit
・Timer Latch Type Short Circuit Protection
・Output Over Voltage Protection
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 (1.7s) 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.
During normal operation, when FB falls below REF, HG
switches high during for the period of time t
ON (P8).
However, if the current of the low-side FET exceeds the
ILIMIT threshold, HG will switch off until it becomes belo
w
ILIMIT.
tON
tON
HG
LG
IL
tON
tON
Short protection engages when output falls to or belo
w
REF × 0.7. When the programmed time period (28s)
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.
FB
HG
LG
EN/UVLO
28s
REF×0.7
HG
LG
OVP threshod voltage
Switching
VOUT
1.7s
ILIMIT