MSL2042GU Atmel, MSL2042GU Datasheet - Page 18

• 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

Choosing the Drain Resistor R
The drain resistor R
the Drain of the external MOSFET. Choose R
where V
section “Connecting the Efficiency Optimizer to an LED
String Power Supply and Selecting Resistors” beginning
on page12, N is the number of LEDs in the string, I
is the maximum allowable string off current and V
is the LED forward voltage drop at I
calculated for R
LED manufacturers typically do not publish I
V
numbers is to use the following method.
Figure 7. Test Circuit for Determining V
18
Figure 7. Test Circuit for Determining
F(DARK)
Set up the test circuit of Figure 7. Adjust R1
until the current meter indicates I
I
the voltage at the anode of the LED (A),
and then at the cathode of the LED (B).
Subtract the voltage measured at B from that
measured at A to determine V
typical values determined using this method
are listed in Table 2.
DARK
information. One way to determine these
OUT(MAX)
< 1mA). Use a volt meter to measure
D
is the value calculated above in the
< 0 use 0Ω.
D
connects the MSL2041/2 to
Ω
F(DARK)
DARK
F(DARK)
D
DARK
. When the value
. Some
(choose
DARK
D
using:
and
F(DARK)
DARK
Ω,
Table 2. Some Typical I
Using Figure 7
Large values of R
faults. Discharge of the parasitic capacitance at the Dn
node through a large R
string fault threshold for longer than the LED short
circuit verification time. The addition of a feed-forward
capacitor, C
value for C
capacitance at the Dn node and the size of R
= 15pF is an appropriate first approximation.
MEDIUM
POWER
POWER
POWER
TYPE
HIGH
LOW
Figure 8. Feed Forward Capacitor
LED
Figure 8. Feed Forward Capacitor
FF
FF
depends upon the amount of parasitic
in Figure 8, mitigates this issue. The
LXLW-PWC1
LW Y1SG
LW G6SP
PART #
D
LED
may cause false LED short circuit
DARK
D
and V
holds the node above the
F(DARK)
I
DARK
1.72
1.67
1.72
Atmel LED Drivers-MSL2041/2042
Values Determined
(µA)
V
D
F(DARK)
2.285
2.276
2.195
, but C
(V)
FF