LDS8865 IXYS Corporation, LDS8865 Datasheet - Page 9

• Manufacturer Part Number: LDS8865
• Description: Lds8865 6-channel Ultra Low Dropout Led Driver
• Manufacturer: IXYS Corporation

LDS8865
LED Selection
LEDs with forward voltages (V
3.6 V may be used. Charge pumps operate in highest
efficiency when V
multiplied by switching mode, i.e. V
and so on. If the power source is a Li-ion battery,
LEDs with VF = 2.7V - 3.3V are recommended to
achieve highest efficiency performance and extended
operation on a single battery charge.
External Components
The driver requires two external 1 µF ceramic capa-
citors (C
citors (C1 and C2) X5R or X7R type. Capacitors C1
and C2 may be increased up to 1 µF to improve
charge pump efficiency by 3%. In all charge pump
modes, the input current ripple is very low, and an
input bypass capacitor of 1µF is sufficient.
In 1x mode, the device operates in linear mode and
does not introduce switching noise back onto the
supply.
Recommended Layout
In charge pump mode, the driver switches internally
at a high frequency. It is recommended to minimize
trace length to all four capacitors. A ground plane
should cover the area under the driver IC as well as
the bypass capacitors. Short connection to ground on
© 2009 IXYS Corp.
Characteristics subject to change without notice
IN
and C
OUT
F
) and two 0.22 µF ceramic capa-
voltage is close to V
F
) ranging from 1.6 V to
IN
x 1, V
IN
IN
voltage
x 1.5,
9
capacitors C
use of multiple via. A copper area matching the
TQFN exposed pad (TAB) must be connected to the
ground plane underneath. The use of multiple via
improves the package heat dissipation.
Figure 5. Recommended layout
IN
and C
OUT
can be implemented with the
Doc. No. 8865DS, Rev. N2.1