BD95242MUV_10 Datasheet, PDF (10/21 Pages) Rohm – 2ch Switching Regulator for Desktop PC

●Timing Chart
• Soft Start Function
EN
TSS
SS
VOUT
IIN
・Timer Latch Type Short Circuit Protection
VOUT
REF×1.4
SCP
EN / UVLO
・Over Voltage Protection
150μs(typ)
or less
150μs(typ)
or more
REF×2.35
VOUT
OVP
150μs(typ)
Latch
EN / UVLO
Technical Note
Soft start is exercised with the EN pin set high. Current
control takes effect at startup, enabling a moderate
output voltage “ramping start.” Soft start timing and
incoming current are calculated with formulas (2) and
(3) below.
Soft start time
Tss= ^REF×Css [sec] ・・・(2)
2.5μA (typ.)
Incoming current
IIN= ^Co×VOUT
Tss
[A] ・・・(3)
(Css: Soft start capacitor; Co: Output capacitor)
Short protection kicks in when output falls to or below
REF × 1.4 (setting voltage ×0.7).
When the programmed time period (typ.=1ms) elapses,
output is latched OFF to prevent destruction of the IC.
Output voltage can be restored either by reconnecting
the EN pin or disabling UVLO.
When output rise to or above REF×2.35(output setting
voltage ×1.175), output over voltage protection is
exercised, and low side FET goes up maximum for
reducing output.(LG=High, HG=Low). When output falls
within the programmed time (typ=150μs), it returns to the
standard mode. When the programmed time period
elapses, output is latched OFF to prevent destruction of
the IC. Output voltage can be restored either by
reconnecting the EN pin or disabling UVLO.
・Over current protection circuit
tON
tON
HG
2.5μsec tON
LG
ILIMIT
IL
Vo
2×REF
increase Io
During the normal operation, when VOUT becomes less
than reference voltage, HG becomes High during the
time tON . However, when inductor current exceeds I_LIMIT
threshold, HG becomes OFF.
After 2.5μsec(typ), HG becomes ON again if the output
voltage is lower than the specific voltage level and I_L is
lower than I_LIMIT level.
www.rohm.com
© 2010 ROHM Co., Ltd. All rights reserved.
10/20
2010.03 - Rev.C