LDS8620-002-T2 IXYS, LDS8620-002-T2 Datasheet - Page 7

• Manufacturer Part Number: LDS8620-002-T2
• Description: IC LED DRIVER FLASH 16WQFN
• Manufacturer: IXYS
• Series: PowerLite™r
• Type: Photo Flash LEDr

Specifications of LDS8620-002-T2

• Topology: Linear (LDO), Switched Capacitor (Charge Pump)
• Number Of Outputs: 2
• Internal Driver: Yes
• Type - Primary: Flash/Torch
• Frequency: 1.1MHz
• Voltage - Supply: 2.7 V ~ 5.5 V
• Mounting Type: Surface Mount
• Package / Case: 16-WQFN Exposed Pad, 16-DQFN
• Operating Temperature: -40°C ~ 85°C
• Current - Output / Channel: 96mA
• Internal Switch(s): Yes
• Efficiency: 95%
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Voltage - Output: -
• Lead Free Status / Rohs Status: Details
• Other names: LDS8620-002-T2-2

LDS8620
BLOCK DIAGRAM
BASIC OPERATION
At power-up, EN/SET pin should be logic LOW. The
LDS8620 starts operating in 1-x mode when EN/SET
pin is asserted logic high and at least one channel is
enabled.
approximately equal to the input supply voltage (less
any internal voltage losses). If the output voltage is
sufficient to regulate all LED currents, the device
remains in 1-x operating mode.
The low dropout PowerLite™ Current regulator
(PCR) performs well at input voltages up to 50 mV
above LED forward voltage significantly increasing
driver’s efficiency. The LDS8620 monitors voltage
drop Vd across PCR at every channel in ON state. If
this voltage falls below 50 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.
Vd = V
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 ≤50 mV, and the regulated currents cannot
be maintained, the low dropout PowerLite™ Current
© 2009 IXYS Corp.
Characteristics subject to change without notice
IN
x M – V
At
1-x
F
– Rcp x Iout, where Rcp is a
mode,
the
Figure 2. LDS8620 Functional Block Diagram
output
will
be
7
Regulator switches the charge pump into 1.5-x mode
(after a fixed delay time of about 800 μ s). In 1.5-x
mode,
approximately equal to 1.5 times the input supply
voltage (less any internal voltage losses).
This sequence repeats at every mode until driver
enters the 2-x mode.
If the device detects a sufficient input voltage is
present to drive all LED currents in 1-x mode, it will
change automatically back to 1-x mode. This only
applies for changing back to the 1-x mode. The
difference between the input voltage when exiting 1-x
mode and returning to 1-x mode is called the 1-x
mode transition hysteresis (about 600 mV).
LED Current Setting
The current in each of the LED is programmed
through the 1-wire EN/SET digital control input. By
pulsing this signal according to a IXYS 1-wire
protocol, a set of internal registers can be addressed
and written into allowing to configure each of LEDs
with the desired current. There are five registers: the
first is 2 bits long, while registers 2 – 4 are six bits
long, and the fifth is one bit long. The registers are
the
charge
pump’
Doc. No. 8620DS, Rev. N1.1
output
voltage
is