BD9420F Datasheet, PDF (23/31 Pages) Rohm – White LED Driver for large LCD Panels (DCDC Converter Type)

BD9420F
Datasheet
●List of Protection Functions
○List of protection detecting condition
Protection
names
Detection
Detection condition
pin
Detection pin
condition
PWM
SS
Release
condition
Timer
Protection
type
LED OPEN
LED SHORT
LED GND
SHORT
RT GND
SHORT
VCC UVLO
REG75
UVLO
OVP
SCP
BSx
CLx
BSx
BSx
CLx
RT
VCC
REG75
OVP
OVP
BSx < 0.1V
CLx < 0.1V
BSx > 9V
BSx < 0.1V
CLx < 0.1V
Under RT
x90%
VCC < 7.2V
REG75 < 4.0V
OVP>3.0V
OVP < 0.1V
H(Pulse
over 4CLK)
H(Pulse
over 4CLK)
H(Pulse
over 4CLK)
H(Pulse
over 4CLK)
H(Pulse
over 4CLK)
-
-
-
-
-
SS>4.0V
SS>4.0V
SS>4.0V
SS>4.0V
SS>4.0V
-
-
-
-
-
BSx > 0.1V
CLx > 0.1V
BSx < 9V
2¹⁵count
2¹⁵count
BSx > 0.1V
CLx > 0.1V
2¹⁵+2⁷coun
t
Canceled
RT=GND State
VCC>7.5V
REG75>4.5V
OVP<2.8V
OVP > 0.1V
Immediatel
y detect
Immediatel
y detect
Immediatel
y detect
2¹⁸count
2¹⁵count
Latch(Only
detected ch)
Latch(Only
detected ch)
Latch
Auto-restart
Auto-restart
Auto-restart
Latch
Latch
OCP
CS
CS>0.4V
-
-
・To clear the latch type, STB should be set to “L” once, and then to “H”.
・The count of Timer means “1count=1duty of switching frequency.”
○List of protection detecting operation
CS<0.4V
Immediatel
y detect
Pulse by Pulse
Protection
Functions
Operation when the hysteresis type protection is detected
DC/DC
LED Driver
Soft start
RT pin
LED OPEN
LED SHORT
LED GND
SHORT
RT GND
SHORT
VCC UVLO
REG75 UVLO
OVP
SCP
Stops operating
after CP counting
Stops operating
after CP counting
Stops operating
after CP counting
Instantaneously
stops operating
Instantaneously
stops operating
Instantaneously
stops operating
Instantaneously
stops operating
N output stops
Only detected LED stops
operating after CP counting
Only detected LED stops
operating after CP counting
Stops operating after CP
counting
Instantaneously stops
operating
Instantaneously stops
operating
Instantaneously stops
operating
Stops operating after CP
counting
Stops operating after CP
counting
Low after all ch
Latch
Low after all ch
Latch
Discharge after
CP counting
Not discharged
Discharge
Discharge
Discharge after
CP counting
Discharge after
CP counting
Low after all ch
Latch
Low after all ch
Latch
Low after CP
counting
-
Normal operation
Normal operation
Low after CP
counting
Low after CP
counting
OCP
Limits duty cycle
Normal operation
Not discharged
Normal operation
<Example>
Case FOSC=150kHz
○LED OPEN,LED SHORT,SCP
32768count→Latch after 218.5msec
○LED GND SHORT
32896count→Latch after 219.3msec
○OVP
262144count→Latch after 1.748sec
○Soft Start time
12480count→83.2msec
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TSZ02201-0F1F0C100300-1-2
31.Jan.2014 Rev.002