MSL3086-IUR Atmel, MSL3086-IUR Datasheet - Page 18

• Manufacturer Part Number: MSL3086-IUR
• Description: LED Lighting Drivers 8-Str LED Driver Internal Boost Cntr
• Manufacturer: Atmel

Specifications of MSL3086-IUR

• Rohs: yes
• Input Voltage: 5 V
• Operating Frequency: 200 Hz
• Maximum Supply Current: 18 mA
• Output Current: 350 uA
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Package / Case: VQFN-24
• Minimum Operating Temperature: - 40 C
• Power Dissipation: 1850 mW

9.6 The Efficiency Optimizer (EO)
A voltage divider from the boost regulator output voltage to FB sets the regulation voltage (R
The EO improves power efficiency by dynamically adjusting the power supply output voltage to the minimum required to power the LEDs.
This ensures that there is sufficient voltage available for LED current control, and good power supply noise rejection, while minimizing
power dissipation. It does this by injecting a small current into the FB input over 256 steps (8-bit resolution).
When turned on, either by applying input voltage to VIN while EN is high, or by driving EN high with voltage applied to VIN, the EO
begins an initial calibration cycle by monitoring the external LED current regulators. If all the current regulators maintain LED current
regulation the EO output current is increased to reduce the boost output voltage. After the 4ms power supply settling time, it rechecks
the regulators, and if they are maintaining regulation the process repeats until one or more current regulator looses regulation. This
step requires that the strings are turned on for a minimum of 2µs to detect current regulation. The EO then decreases the output current
to increase boost output voltage, giving the regulator enough headroom to maintain regulation with minimal power dissipation. The
oscilloscope picture Figure 9.2 shows this procedure. The EO automatically re-calibrates VOUT every 1 second, and always increases
the string voltage when a string is detected with insufficient current.
Figure 9.2 Efficiency Optimizer (EO)
required to power the LEDs. This ensures that there is sufficient voltage available for LED current control,
supply noise rejection, while minimizing power dissipation. It does this my injecting a small current into the
256 steps (8-bit resolution).
When turned on, either by applying input voltage to VIN while EN is high, or by driving EN high with voltag
VIN, the EO begins an initial calibration cycle by monitoring the external LED current regulators. If all the c
regulators maintain LED current regulation the EO output current is increased to reduce the boost output v
4ms power supply settling time, it rechecks the regulators, and if they are maintaining regulation the proce
one or more current regulator looses regulation. This step requires that the strings are turned on for a min
detect current regulation. The EO then decreases the output current to increase boost output voltage, givi
enough headroom to maintain regulation with minimal power dissipation. The oscilloscope picture Figure 5
procedure. The EO automatically re-calibrates V
string is detected with insufficient current.
Figure 5. Efficiency Optimizer (EO)
S
Select the voltage divider resistors (R
ETTING THE
B
OOST
R
EGULATOR
TOP
O
UTPUT
and R
8-String 60mA LED Drivers with Integrated Boost Controller and Phase Shifted Dimming
BOTTOM
OUT
V
OLTAGE
every 1 second, and always increases the string volta
in Figure 3 on page 13) by first determining V
Atmel MSL3086/MSL3088 Datasheet
TOP
and R
BOTTOM
in Figure 8.1 on page 13).
18
OUT(MIN