BD6581GU-E2 Rohm Semiconductor, BD6581GU-E2 Datasheet - Page 16

• Manufacturer Part Number: BD6581GU-E2
• Description: IC LED DVR WHT BCKLGHT VCSP85H2
• Manufacturer: Rohm Semiconductor
• Series: -r

Specifications of BD6581GU-E2

• Constant Current: -
• Constant Voltage: -
• Topology: PWM, Step-Up (Boost)
• Number Of Outputs: 6
• Internal Driver: Yes
• Type - Primary: Backlight
• Type - Secondary: White LED
• Frequency: 800kHz ~ 1.2MHz
• Voltage - Supply: 2.7 V ~ 22 V
• Voltage - Output: 44.7 V
• Mounting Type: *
• Package / Case: *
• Operating Temperature: -30°C ~ 85°C
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

●The Coil Selection
●Layout
BD6581GU
© 2010 ROHM Co., Ltd. All rights reserved.
www.rohm.com
The DC/DC is designed by more than 4.7µH. When L value sets to a lower value, it is possibility that the specific
sub-harmonic oscillation of current mode DC / DC will be happened.Please do not let L value to 3.3µH or below.
And, L value increases, the phase margin of DC / DC becomes to zero. Please enlarge the output capacitor value when you
increase L value.
Example)
This value is just examples, please made sure the final judgment is under an enough evaluation.
In order to make the most of the performance of this IC, its layout pattern is very important. Characteristics such as efficiency
and ripple and the likes change greatly with layout patterns, which please note carefully.
Connect the input bypath capacitor CIN(10µF) nearest to coil L, as shown in the upper diagram.
Wire the power supply line by the low resistance from CIN to VBAT pin. Thereby, the input voltage ripple of the IC can be
reduced. Connect smoothing capacitor CREG of the regulator nearest to between VREG and GND pin, as shown in the
upper diagram. Connect schottky barrier diode SBD of the regulator nearest to between coil L and switching transistor Tr.
And connect output capacitor COUT nearest to between CIN and GND pin. Thereby, the output voltage ripple of the IC can
be reduced.
Connect switching transistor Tr nearest to SW pin. Wire coil L and switching transistor Tr, current sensing resistor R
the low resistance. Wiring to the SENSP pin isn't Tr side, but connect it from R
low when wiring from Tr side. Connect R
wiring from R
the possibility that restricts the current drive performance by the influence of the noise when other GND is connected to this GND.
Connect LED current setting resistor RISET nearest to ISET pin. There is possibility to oscillate when capacity is added
to ISET terminal, so pay attention that capacity isn't added. And, RISET of GND side must be wired directly to GND pin.
When those pins are not connected directly near the chip, influence is given to the performance of BD6581GU, and may limit
the current drive performance. As for the wire to the inductor, make its resistance component small so as to reduce electric
power consumption and increase the entire efficiency.
4.7µH
6.8µH
10µH
SENSE
=
=
=
pin to GND pin. And R
output capacitor
output capacitor
output capacitor
Reset
PWM
C
C
BAT
IN
2.2µF/50V
2.2µF/50V
2.2µF/50V
SENSE
SENSE
E
D
C
B
A
L
of GND side isolated to SENS pin. Don’t wire between R
RSTB
VDET
LED6
VBAT
1
GND line must be wired directly to GND pin of output capacitor. It has
to Cathode of LED
PWMPOW
Fig. 43 Layout
LED5
GND
2
16/26
to Anode of each LED
SBD
1pcs
2pcs
3pcs
FAILSEL
VREG
TEST
LED4
SW
3
Tr
C
OUT
SENSP
ISETH
ISETL
LED3
GND
4
PWMDRV
R
SENSN
LED2
LED1
SENSE
GND
5
to GND
C
REG
SENSE
side. Over current value may become
SENSE
2010.03 - Rev.A
Technical Note
and SNESN pin
SENSE
by