MSL2042GU Atmel, MSL2042GU Datasheet - Page 16

• Manufacturer Part Number: MSL2042GU
• Description: LED Lighting Drivers 4Str RGB or White LED Driver lighting
• Manufacturer: Atmel

Specifications of MSL2042GU

• Rohs: yes
• Input Voltage: 10.8 V to 13.2 V
• Maximum Supply Current: 31.5 mA
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Package / Case: SOP-32
• Minimum Operating Temperature: - 40 C
• Power Dissipation: 1576 mW
• Factory Pack Quantity: 1000

To select R
V
voltage limits, using:
V
and
V
where V
maximum forward voltage drops at the peak current set
by R
V
the total minimum and maximum voltage drop across a
string is 35V and 38V. Adding an allowance of 0.5V for
the string drive MOSFET headroom brings V
where I
of the Efficiency Optimizer outputs FBOn (280.5µA =
1.1µA * 255, the current per LSB of the FBO DAC times
the maximum DAC count). Finally, determine R
using:
where V
power supply. Place a diode (1N4148 or similar)
between FBOn and the supply’s feedback node to
protect the MSL2041/2 against current flow into FBOn.
Once configured, determine the change in power supply
output voltage in response to a change in FBOn output
current using:
35.5V and V
16
∆
R
R
OUT(MAX)
f(MAX)
OUT(MIN)
OUT(MAX)
V
TOP
BOTTOM
OUT
S
. For example, if the LED data are V
=
= 3.8V, and ten LEDs are used in a string, then
FBOn(MAX)
, the minimum and maximum string supply
=
f(MIN)
FB
V
= R
=
OUT
is the regulation feedback voltage of the
=
∆
TOP
OUT(MAX)
I
(
(
and V
TOP
FBOn
and R
V
(
V
MAX
I
is the 280.5µA maximum output current
f (MIN)
f (MAX)
FBOn
*
∗
)
f(MAX)
BOTTOM
to 38.5V. Then determine R
V
−
R
(
OUT(MAX)
MAX
* [#ofLEDs]
V
TOP
* [#ofLEDs]
OUT
are the LED’s minimum and
V
)
.
first determine V
FB
(
MIN
_ V
)
,
FB
)
)
+ 0.5 ,
,
+ 0.5 ,
f(MIN)
OUT(MIN)
OUT(MIN)
= 3.5V and
BOTTOM
TOP
and
using:
to
Assure that the power supply settling time for a voltage
step size of 1.1µA * R
Step-hold duration time.
Using Multiple EOs/Devices to
Control a Common Power Supply
Cascade multiple Efficiency Optimizers (EOs), either
within the same device or across multiple devices, into
a chain configuration (Figure 6), with the FBIn of one
EO connected to the FBOn of the next. Connect the
first FBOn to the power supply feedback resistor node
through a diode (1N4148 or similar) placed close to the
power supply feedback node, and unused FBIn inputs
to ground as close to the MSL2041/2 as possible. The
chained EOs work together to ensure that the system
operates at optimum efficiency. Note that the accuracy
of the feedback chain may degrade through each link
of the FBIn/FBOn chain by 2% (typical). Derate the
maximum FBOn current using:
I
where N is the number of EOs connected in series. Use
I
term I
Take care in laying out the traces for the Efficiency
Optimizer connections. Minimize the FBIn/FBOn trace
lengths as much as possible. Do not route the signals
close to traces with large variations in voltage or current,
because noise may couple into FBIn. If these traces must
be routed near noisy signals, shield them from noise by
using ground planes or guard traces. For clarity, Figure
6 shows Source and Drain connections only for unused
outputs 2 and 3 of device two. Note that because of the
interplay between EOs and the automatic fault response
behavior, when both strings monitored by a single EO
fault and turn off, that the string supply is forced to its
maximum value and all remaining active strings typically
detect short circuit faults and also turn off.
FBOn(MAX/MIN)
FBO(MAX / MIN)
FBOn(MAX)
in the above R
instead of using 280.5µA.
= 280.5µA* (0.98)
TOP
is less than the 4ms EO
TOP
resistor equation for the
Atmel LED Drivers-MSL2041/2042
N-1
,