BD6586MUV_12 Datasheet, PDF (5/24 Pages) Rohm – 4-Channel White LED Driver

BD6586MUV
Datasheet
˔Description of Functions - continued
3) External SBD open detect and over voltage protection
BD6586MUV has over boost protection by external SBD open and over voltage protection. It detects VDET voltage and is
stopped output Tr in abnormal condition. Details are as shown below.
▪ External SBD open detect
In the case of external SBD is not connected to IC, the coil or internal Tr may be destructed. Therefore, at such an error
as VOUT becoming 0.1V or below, the Under Detector shown in the figure works, and turns off the output Tr, and
prevents the coil and the IC from being destructed.
And the IC changes from activation into non-activation, and current does not flow to the coil (0mA).
▪ Over voltage protection
At such an error of output open as the output DC/DC and the LED is not connected to IC, the DC/DC will boost too much
and the VDET terminal exceed the absolute maximum ratings, and may destruct the IC. Therefore, when VDET becomes
sensing voltage or higher, the over voltage limit works, and turns off the output Tr, and the pressure up made stop.
At this moment, the IC changes from activation into non-activation, and the output voltage goes down slowly. And,
when the output voltage becomes the hysteresis of the over voltage limit or below, the output voltage pressure up to
sensing voltage once again and unless the application error is recovered, this operation is repeated.
4) Thermal shut down
BD6586MUV has thermal shut down function.
The thermal shut down works at 175°C or higher, and while holding the setting of EN1, EN2 control from the outside,
turns into non operation condition from operation condition. And at 175°C or below, the IC gets back to its normal
operation.
5) Over Current Limit
Over current flows the current detection resistor between switching transistor source and PGND, then the voltage of that
resistor turns more than detection voltage. Over current protection is operating and it is prevented from flowing more than
detection current by reducing ON duty of switching Tr without stopping boost.
As over current detector of BD6586MUV is detected peak current, current more than over current setting value does not
flow.
6) Under Voltage Lock Out(UVLO)
When VBAT declines in 2.35V (Typ.) from the condition of the power-on, DC/DC and a current driver are changed from a
state of movement to the condition at the time of the non-movement. And, it is returned in a state of movement when
VBAT is raised beyond 2.55V (Typ.).
˔Operating of the Application Deficiency
1) When 1 LED or 1parallel OPEN during the operating the LED parallel which became OPEN isn't lighting, but other LED
parallel is lighting.
Then, Output boosts up to the over voltage protection voltage 25.5V because LED terminal can be 0V.
After the over voltage protection is detected, LED terminal of 0V isn’t cut from feedback loop.
Then, Output voltage will become normal voltage automatically.
2) When LED short-circuited in the plural
All LED continue to be turned on, unless LED terminal voltage become more than “LED terminal over voltage protection (11.5V)”.
When it was more than 11.5V, the line which short-circuited is only turned on, and LED current of other lines decrease or turn
off.
3) When Schottky diode came off
All LED aren't turned on.
Also, IC isn't destroyed because boost operating stops by the Schottky diode coming off protected function.
4) When an output capacitor short.
All LED aren't turned on.
And, an IC isn't destroyed because boost stops by the SBD open protection function.
But, big electric current occurs, and a coil or SBD is likely to destroy it because the route of the GND short circuit of the
power supply → coil → output capacitor occurs.
5) When the resistance to connect it to the ISET terminal short,
All LED aren't turned on.
Because LED current limit works, all current drivers stop, and DC/DC maintains boost under the state without load.
And, it is returned in a state of normality by canceling a state of short.
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TSZ02201-0G3G0C400190-1-2
10.Dec.2012 Rev.001