BD9206EFV Datasheet, PDF (6/13 Pages) Rohm – Simple Structure Constant Current Backlight Driver for LCD panels (Non-step type)

BD9206EFV
Technical Note
● Rise time and Fall time of LED Driver’s constant current
In the state of STBY=H, the rise time of constant current at the time of EN=L→H and the fall time at the time of EN=H→L
are as shown in the following table.
As shown in Fig.5, the constant current driver is formed in such a way that the NMOS of the driver output is made to be
operated or stopped by the EN signal.
Therefore, the rise time for the second time or later is shorter than the one for the first time because the electrical charge
of the capacitor for phase compensation is reopened from the charged state.
First time
Second time or later
Remarks
Rise time
2.9μs ± 7%
2.6μs ± 7%
The time interval between the
moment of EN=L→H and the
moment at which the ILED
reaches 90% of the set value
Fall time
0.7μs ± 11%
0.7μs ± 11%
The time interval between the
moment of EN=H→L and the
moment at which the ILED
reaches 10% of the set value
On the condition that VCC=Vo=24V, VF（LED）=3.2V 5-stage connection, RL=15Ω
■STBY, EN
At the time of STBY=L, it becomes the OFF mode, then only a portion of the circuit inside the IC is operating, so the circuit
current is restricted to 17μA (typ).
At the time of STBY=H, it becomes the Standby mode, then 5VREG is started and UVLO is released before the LED driver
gets into the state of Ready.
After that, if EN=L→H, then the current flows into the LED driver and the LED is lighted up.
Note: If STBY and EN are simultaneously made to be L→H, then the rising edge of the LED driver gets late because the
starting time of 5VREG is necessary.
If it is used after PWM dimming, then please let STBY=H beforehand and input the CLK to EN before using.
●Operation logic of LED driver
EN
STBY
L
H
L
Stop
Stop
H
Stop
Operation
STBY
EN
UVLO
TSD
LED
Driver
active : High
●Logic of LED driver protection circuit
Function
Stop
Operation
UVLO
VREG < 2.9V(typ)
VREG > 3.0V(typ)
TSD
Ta > 175℃
Ta < 155℃
■TEST terminal
TEST terminal is only used in ROHM’s testing process before delivery, so please use the IC with the terminal fixed at Low in
normal times.
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2009.07 - Rev.A