bd9202efs ROHM Co. Ltd., bd9202efs Datasheet - Page 11

• Manufacturer Part Number: bd9202efs
• Description: White Backlight Led Drivers For Medium To Large Lcd Panels Swreg Type
• Manufacturer: ROHM Co. Ltd.

○Booster DC/DC Controller
○ Error Detection Output Function
© 2009 ROHM Co., Ltd. All rights reserved.
BD9202EFS
www.rohm.com
・ LED Series Numeric
・ Over voltage Protection Circuit OVP
・ Booster DC/DC Converter Oscillation Frequency and LED Driver PWM Standard Frequency
・ Internal Oscillation Frequency Output Terminal CT_SYNC_OUT and External Synchronous Terminal CT_SYNC_IN
・ Soft Start
・ Over-current Protection Circuit (OCP)
・ Outputs errors detected by protection circuits to FAIL1 and FAIL2 terminals. FAIL1 or FAIL2 switch to Low after the
It detects the LED cathode voltage, or the LED voltage, and controls the output voltage to be 0.75 (Typ.). The booster only
Furthermore, you must be aware that the LED inline numerics have the following limits. At open detection, 85% of
Inputs the output voltage to the OVP terminal with resistive divide.
When the output voltage side is ROVP1 and the GND side is ROVP2, the OVP detection voltage is:
VOVP=(ROVP1+ROVP2)/ROVP2×2.0V
When ROVP1=560kΩand ROVP2=20kΩ, OVP activates when VOUT=58V or more.
By attaching resistance to RT (BRT), it is possible to configure triangular wave oscillation frequency. The RT (BRT)
determines the charge and discharge current corresponding to the internal condenser, and the frequency changes.
Configure the RT (BRT) resistance by referring to the theoretical formula below. We recommend a range of 30kΩ
~300kΩ. Configurations outside of the frequency range in the chart below can result in stopping switching, and
operation cannot be guaranteed.
The internal oscillation frequency output terminal CT_SYNC_ OUT outputs the internal oscillator’s clock configured by the
RT terminal. However, there is no output when there is a CLK input in the external synchronous terminal CT_SYNC_IN.
The external synchronous terminal CT_SYNC_IN can be the operational frequency of the DC/DC converter by
There is no soft start function with this IC. At startup, stand-up occurs with control by the current value configured by
OCP (over-current detection).
The current flowing through the coil is changed to voltage by the sense resistance Rcs, and when the CS terminal is
over 0.2V (typ), the switching operation is stopped.
OCP detection is in pulse-by-pulse format, and is detected at every switching cycle and reset at the next clock.
When detection continues longer than the time configured at tCP1, FAIL1=L and it latches with the switching operation
in the stopped position.
filter time configured at CP1 or CP2, when they detect OVP or OCP (FAIL1) or LED open/short (FAIL2). (Because
FAIL1 terminal is open collector output, it is used with external pull-up.)
The filter time for CP1 and CP2 is expressed as:
operates when the LED output is operating. When multiple LED outputs are operating, the LED VF controls the LED output
of the highest line to be 0.75V (Typ.). Therefore, the voltages of other LED outputs are higher by the variation of VF.
the OVP configured voltage becomes the trigger, so the maximum value of output voltage during normal operation is
51V=60×0.85, and 51V/VF>maximum N.
determined by the series numeric of the LED and the VF variance. When determining the OVP configured voltage,
the open detection trigger, OVP×0.85 should be considered. The switching operation stops when OVP is detected.
Furthermore, if the output voltage falls to 80% of the OVP configuration voltage within the filter time tcp1 determined
by CP1, OVP is released. If OVP continues for over tcp1, the error detection flag FAIL1 turns to Low, it latches with
the switching operation in the stopped position.
externally inputting CLK. At this time, the external input frequency should be configured to be higher than the internal
oscillation frequency. Furthermore, there should be no switching between the external synchronous and internal oscillator
during operation.
1200
1000
800
600
400
200
0
0
100
(Actual Line)
Calculated
計 算 値
( 実 線 ）
Value
RT(BRT)-FOSC Characteristics
200
R T(B R T)-FOSC特 性
( マ ー カー ）
実 測 値
Measured
(Marker)
R T(BR T)[kΩ ]
Value
300
11/19
400
Tcp
1
(
cp
2
500
)

Ccp
1
μ
The configured value of OVP should be
1
600

A
2
V
fosc

RT
3
(
.
04
BRT
Technical Note
2009.04 - Rev.A

10
)[
k
4
Ω
]
[
kHz
]