ROHM BD6586MUV Technical data

LED Drivers for LCD Backlights

White Backlight LED Driver for Medium to Large LCD Panels (Switching Regulator Type)

BD6586MUV

●Description

BD6586MUV is white LED driver IC with PWM step-up DC/DC converter that can boost max 24V and current driver that can drive max 25mA. The wide and precision brightness can be controlled by external PWM pulse. BD6586MUV has very accurate current drivers, and it has few current errors between each strings.So, it will be helpful to reduce brightness spots on the LCD.Small package type is suited for saving space.

●Features

1) High efficiency PWM step-up DC/DC converter (fsw=1MHz)

2) High accuracy & good matching (±3.0%) current drivers 4ch (MAX.25mA/ch)

3) 28V power Nch MOSFET

4) Soft Start

5) Drive up to 6

6) Rich safety functions  Over-voltage protection  Output Short protection  External SBD open detect  Over current limit  Thermal shutdown  UVLO

7) Small & thin package (VQFN024V4040) 4.0 × 4.0 × 1.0mm

●Applications

All middle size LCD equipments backlight of Notebook PC, portable DVD player, car navigation systems, etc.

●Absolute maximum ratings (Ta=25 ℃)

in series, 4 strings in parallel

No.11040ECT35

Parameter Symbol Ratings Unit Condition

Maximum applied voltage 1 VMAX1 7 V

Maximum applied voltage 2 VMAX2 25 V LED1, LED2, LED3, LED4,

Maximum applied voltage 3 VMAX3 30.5 V SW

Maximum applied voltage 4 VMAX4 50.5 V VDET

Power dissipation 1 Pd1 500 *1 mW

Power dissipation 2 Pd2 780 *2 mW

Power dissipation 3 Pd3 1510 *3 mW

Operating temperature range Topr -40 ~ +85 ℃

Storage temperature range Tstg -55 ~ +150 ℃

*1 Reduced 4.0mW/ ℃ With Ta>25 ℃ when not mounted on a heat radiation Board. *2 1 layer (ROHM Standard board) has been mounted. Copper foil area 0mm *3 4 layer (JEDEC Compliant board) has been mounted. Copper foil area 1layer 6.28mm

, Copper foil area 2~4layers 5655.04mm2, When it’s used by more than Ta=25 ℃, it’s reduced by 12.1mW/ ℃.

, When it’s used by more than Ta=25 ℃, it’s reduced by 6.2mW/ ℃.

VBAT, EN1, EN2, TRSW, PWM,TESTO, ISET, TEST

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2011.6 - Rev.C

BD6586MUV

●Recommended operating range (Ta=-40 ℃ ~ +85 ℃)

Parameter Symbol

Power supply voltage VBAT 2.7 3.6 5.5 V

●Electrical characteristic (Unless otherwise specified, VBAT=3.6V, Ta = +25 ℃)

Parameter Symbol

[EN1, EN2, PWM Terminal]

EN threshold voltage (Low) VthL 0 - 0.4 V

EN threshold voltage (High) VthH 1.4 - 5.5 V

EN terminal input current Iin - 8.3 16.0 µA Input=2.5V

[Under Voltage Lock Out]

Under Voltage Lock Out UVLO 2.05 2.35 2.65 V VBAT falling edge

[Switching Regulator]

Ratings

Min. Typ. Max.

Limits

Min. Typ. Max.

Unit Condition

Technical Note

Quiescent Current

Current Consumption

LED Control voltage

Over Current Limit

SBD Open Protect

Switching frequency

Duty cycle limit

Over voltage limit

SW Transistor On Resistance

[Current driver]

LED maximum current

LED current accuracy

LED current matching

ISET voltage

LED current limiter

LED Terminal Over Voltage Protect

*1 This parameter is tested with DC measurement.

Iq - 0.1 2.0 µA

Idd - 2.2 4.6 mA

VLED 0.4 0.5 0.6 V

Ocp 1.1 1.5 2.5 A

Sop - - 0.1 V

fSW 0.7 1.0 1.3 MHz

Duty 91 95 99 %

Ovl 25.0 25.5 26.0 V

RSW - 0.24 0.32 

ILMAX - - 25 mA

ILACCU - - ±5 %

ILMAT - - ±3 %

Iset 0.5 0.6 0.7 V

ILOCP 35 60 90 mA

LEDOVP 10.0 11.5 13.0 V

EN1=EN2=PWM=0V

VDET=0V,ISET=24k

Detect voltage of VDET pin

LED1-4=0.3V

Isw=100mA

ILED=20mA

Each LED current/Average (LED1- 4) ILED=20mA

Current limit value at ISET resistance 4.7k setting LED1, 2, 3, 4=0.5V

EN1=EN2=PWM=2.5V

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2011.6 - Rev.C

BD6586MUV

●Block diagram, I/O equivalent circuit diagram

VBAT

UVLO

VBAT

TRSW

PGND

N.C.

GND

TSD

Current SENCE

EN1

Reference

TEST

EN2

TESTO

Soft start

Pulse

Control

OSC

N.C.

PWM COMP

SBD OPEN/ Output short PROTECT

Output Over Voltage PROTECT

ERRAMP

ISET

Resistor driver

ISET

PWM

GND

LED TERMINAL OPEN/SHORT DETECTOR

Current Drive

Fig.1 Block diagram Fig.2 I/O equivalent circuit diagram

●Pin assignment table

PIN Name In/Out PIN number Function

1 VBAT In Battery input G

2 EN1 In Power control pin A

3 EN2 In Power control pin A

4 GND - GND for DC/DC B

5 PWM In PWM input pin for power ON/OFF only driver A

6 ISET In Register connection for LED current setting D

7 GND - GND for ISET Register B

8 LED1 In Current sink for LED1 C

9 LED2 In Current sink for LED2 C

10 GND - GND for Current Driver B

11 LED3 In Current sink for LED3 C

12 LED4 In Current sink for LED4 C

13 TEST In TEST input (Pull down 100k to GND) A

14 TESTO Out TEST output D

15 N.C. - No connect pin E

16 SW Out Switching Tr drive Pin F

17 SW Out Switching Tr drive Pin F

18 SW Out Switching Tr drive Pin F

19 VDET In Detect input for SBD open and OVP C

20 N.C. - No connect pin E

21 PGND - PGND for switching transistor D

22 PGND - PGND for switching transistor D

23 N.C. - No connect pin E

24 TRSW Out The gate of Switching Tr D

RETURN

SELECT

LED

Technical Note

VDET

4ch

GND

LED1

LED2

LED3

LED4

VBAT

GND

VBAT

GND

PGND

VBAT

PGND

Terminal equivalent

circuit diagram

GND

PGND

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2011.6 - Rev.C

BD6586MUV

●Description of Functions

1) PWM current mode DC/DC converter While BD6586MUV is power ON, the lowest voltage of LED1, 2, 3, 4 is detected, PWM duty is decided to be 0.5V and output voltage is kept invariably. As for the inputs of the PWM comparator as the feature of the PWM current mode, one is overlapped with error components from the error amplifier, and the other is overlapped with a current sense signal that controls the inductor current into Slope waveform to prevent sub harmonic oscillation. This output controls internal Nch Tr via the RS latch. In the period where internal Nch Tr gate is ON, energy is accumulated in the external inductor, and in the period where internal Nch Tr gate is OFF, energy is transferred to the output capacitor via external SBD. BD6586MUV has many safety functions, and their detection signals stop switching operation at once.

2) Soft start BD6586MUV has soft start function. The soft start function prevents large coil current. Rush current at turning on is prevented by the soft start function. After EN1, EN2 are changed L H, soft start becomes effective for within 1ms and soft start doesn't become effective even if EN1, EN2 are changed L H after that. And, when the H section of PWM is within 1ms, soft start becomes invalid when PWM is input to H more than three times. The invalid of the soft start can be canceled by making EN1, EN2, PWM  L. And, a soft start function doesn't work after a protection function release.

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.).

Technical Note

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2011.6 - Rev.C

BD6586MUV

●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.

●Start control and select constant current driver

BD6586MUV can control the start conditions by EN1, 2 and PWM terminals, and sets 0.4V or below EN1, 2 terminals, so IC can power off. EN1,2 and PWM power on at more than 1.4V, constant current can select ON/OFF by the combination of EN as shown below table. When there is unused constant current driver, unused LED terminal is set “OPEN”.

Enable Constant current driver

EN1 EN2 PWM LED1 LED2 LED3 LED4

H H H OFF ON ON OFF ON

L H H OFF ON ON ON ON

H L H ON ON ON ON ON

L L H OFF OFF OFF OFF OFF

H H L OFF OFF OFF OFF ON

L H L OFF OFF OFF OFF ON

H L L OFF OFF OFF OFF ON

L L L OFF OFF OFF OFF OFF

IC POWER

Technical Note

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2011.6 - Rev.C

BD6586MUV

●Control Signal input timing

HI Voltage of

PWM, EN

2.7V

Technical Note

Stable voltage

VBAT

PWM

○

EN1,2

DC/DC VOUT

In case you input control signs, such as EN1, EN2 and PWM in the condition that the standup of supply voltage (VBAT) is not completed, be careful of the following point.

①Input each control signal after VBAT exceeds 2.7V. ②Please do not input each control sign until VBAT exceeds HI voltage of EN1, EN2 and PWM. ③When you input HI voltage to EN1, EN2 and PWM during the standup of VBAT, please give Min.100µs as the standup time

of VBAT from stable voltage to 2.7V.

There is no timing limitation at each input signal of EN1, EN2 and PWM. If each control sign changes into a condition lower than VBAT in (1) and (2), it goes via the ESD custody diode by the side of VBAT of each terminal. A power supply is supplied to VBAT and there is a possibility of malfunctioning. Moreover, when the entrance current to the terminal exceeds 50mA, it has possibility to damage the LSI. In order to avoid this condition, as shown in the above figure, please insert about 10k in a signal line, and apply current qualification.

●LED current setting range

LED current can set up Normal current by resistance value (RISET) connecting to ISET voltage. Setting of each LED current is given as shown below.

Normal current = 20mA(24k/RISET)

Also, Normal current setting range is 10mA~25mA. LED current becomes a leak current MAX 2µA at OFF setting.

ISET Normal current setting example

RISETH LED current

24k (E24) 20mA

25.5 k (E96) 18.8mA 27 k (E12) 17.8mA

28k (E96) 17.1mA

30k (E24) 16.0mA

33k (E6) 14.5mA

○

Fig.3 control Signal timing Fig.4 Voltage with a control sign higher than VBAT

Min. 100µs

○

HI Voltage of PWM

10k

Example corresponding to application of conditions

VBAT

300k

GND

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