LDS8868002-T2 Leadis Technology, LDS8868002-T2 Datasheet - Page 9

• Manufacturer Part Number: LDS8868002-T2
• Description: LED Drivers 6Ch Chrg Pump 1.5x Mode, PL Curr Reg
• Manufacturer: Leadis Technology

Specifications of LDS8868002-T2

• Number Of Segments: 6
• Operating Supply Voltage: 2.7 V to 5.5 V
• Maximum Supply Current: 450 mA
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Package / Case: TQFN EP
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

LDS8868
BLOCK DIAGRAM
BASIC OPERATION
At power-up, EN pin should be logic LOW. During
power-up device performs internal circuits reset that
requires less than 10µs. To start device, EN pin
should be set logic HIGH at least 10µs after V
applied. Device starts operating at 1x mode at which
the V
internal voltage losses). If the output voltage is
sufficient to regulate all LED currents, the device
remains in 1x operating mode.
. The low dropout PowerLite™ Current regulator
(PCR) performs well at input voltages up to 75 mV
above LED forward voltage V
driver’s efficiency. The LDS8868 monitors voltage
drop Vd across PCR at every channel in ON state. If
this voltage falls below 75 mV (typical) at any one
channel, (channel with LED with highest forward
voltage), the Mode Control Block changes charge
pump mode to the next multiplication ratio.
© 2008 Leadis Technology
Characteristics subject to change without notice
OUT
is approximately equal to V
F
significantly increasing
Figure 2. LDS8868 Functional Block Diagram
IN
(less any
IN
9
Vd (LEDX1/2) = V
is a Charge Pump Output Resistance at given mode,
Iout is sum of all LED currents, and M is a charge
pump’ multiplication ratio.
If the input voltage is insufficient or falls to a level
where Vd ≤75 mV, and the regulated currents cannot
be maintained, the low dropout PowerLite™ Current
Regulator switches the charge pump into 1.5x mode
(after a fixed delay time of about 800
mode,
approximately equal to 1.5 times the input supply
voltage (less any internal voltage losses).
This sequence repeats until driver enters the 2x
mode.
LED Current Setting
The current in each of the six LED channels is
programmed through the 1-wire EN/SET digital
the
charge
IN
x M – V
pump’
F
Doc. No. 8868_DS, Rev. 2.1
– Rcp x Iout, where Rcp
output
μ
voltage
s). In 1.5x
is