BD9206EFV_14 Datasheet, PDF (9/21 Pages) Rohm – Simple Structure Constant Current Backlight Driver for LCD panels

BD9206EFV
Datasheet
2. Rise Time and Fall Time of LED Driver’s Constant Current
For STBY=H, the rise time of the constant-current at the time of EN=L to H and the fall time at the time of EN=H to L are
shown in the following table.
As shown in Figure 12, 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 first one because the electrical charge of the
capacitor for phase compensation is reopened from the charged state.
First Time
Second Time or Later
Remarks
The time interval between the
Rise Time
2.9μs ± 7%
2.6μs ± 7%
moment of EN=L to H and the
moment at which the ILED
reaches 90% of the set value
The time interval between the
Fall Time
0.7μs ± 11%
0.7μs ± 11%
moment of EN=H to 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
(1) STBY, EN
When STBY=L, the IC enters the OFF mode. During OFF mode, only a portion of the circuit inside the IC is operating.
Thus, the circuit current is limited to 17μA (typ).
At the time of STBY=H, it enters the Standby mode. 5VREG block is triggered and UVLO is released before the LED
driver gets into the Ready-state
After that, if EN=L to H, then the current flows into the LED driver and the LED is turned ON.
Note: If STBY and EN are simultaneously turned from L to H, the rising edge of the LED driver will be late because of
the starting time of 5VREG.
If it is used after PWM dimming, set STBY=H first then input the CLK to EN before use.
(a) Operation Logic of LED Driver
EN
STBY
L
H
L
Stop
Stop
H
Stop Operation
STBY
EN
UVLO
TSD
LED
Driver
active : High
(b) Logic of LED Driver Protection Circuit
Function
Stop
Operation
UVLO
TSD
VREG < 2.9V(typ)
Ta > 175°C
VREG > 3.0V(typ)
Ta < 155°C
(2) TEST Terminal
TEST terminal is only used in ROHM’s testing process before delivery. Use the IC with the TEST terminal fixed at Low
in normal conditions.
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09.Dec.2014 Rev.002