MSL3086-IU Atmel, MSL3086-IU Datasheet - Page 16

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

Specifications of MSL3086-IU

• 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

9.0 Application Information
9.1 Bypassing VIN and PVIN
9.2 Setting the LED Current
9.3 Fault Monitoring and Automatic Fault Handling
9.4 Setting the LED Short-Circuit Threshold on the MSL3086
Bypass VIN with a capacitor of at least 1µF. Bypass PVIN with at least 2µF. Place all bypass capacitors close to the device.
Set the on-current for all LED strings with a resistor from ILED to GND. Choose the resistor using:
where I
The maximum LED current per-string is 60mA. Driving all eight strings with 60mA at high duty cycles and elevated ambient temperatures
requires proper thermal management to avoid over-temperature shutdown. Connect the exposed pad (EP) to a large copper ground
plane for best thermal and electrical performance.
The MSL3086/88 monitor the LED strings to detect LED short-circuit, LED string open-circuit and Boost Over-voltage faults. String faults
latch the open drain fault output FLTB low. A boost over-voltage fault pulls FLTB low but is not latching.
When shorted LEDs are detected in a string the string is disabled and no longer monitored by the Efficiency Optimizer. The MSL3086/88
pulls FLTB low and recalibrates the LED power supply voltage. Set the short circuit voltage threshold with a resistor between SCTH
and GND, as explained in the section “Setting the LED Short-Circuit Threshold” beginning on page 16. Additionally, strings with shorted
LEDs are flagged in registers 0x05 through 0x08. For information about the fault registers and the I
MSL3040/41/50/60/80/86/87/88 Programming Guide.
When an open circuit occurs, the Efficiency Optimizer detects a loss of current regulation which must persist for greater than 2µs to be
detected therefore the minimum on-time for the strings is 2µs. In this case the Efficiency Optimizer keeps increasing the LED voltage
(boost regulator output voltage), in an attempt to bring the string back in to regulation. This continues until the voltage is at the maximum
level. The MSL3086/88 then determine that any LED strings that are not regulating current are open circuit. It disables those strings, pulls
FLTB low and recalibrates the LED power supply voltage. When the boost regulator is at its maximum value, fictitious LED short circuit
faults can occur when the LED short circuit threshold is set to a low value and/or the string LEDs exhibit excessive voltage mismatch.
Toggle EN low and then high to clear all faults and return the MSL3086/88 to controlling and monitoring all strings. Fault conditions
that persist re-establish fault responses. Additionally, strings with open circuits faults are flagged in registers 0x05 through 0x08. For
information about the fault registers and the I
When a given string, STRn, is sinking LED string current, the fault detection circuit monitors the STRn voltage. Typical optimized STRn
on-voltage is 0.5V. When one or more LED’s of a string are shorted out, the STRn voltage increases above the nominal. When the
voltage is above the Short-Circuit Threshold the fault circuit generates an LED short circuit fault. In most cases, two LEDs in a string must
be shorted to cause a short circuit fault, but because LED V
a fault varies. Set the LED short-circuit threshold with a resistor from SCTH to GND using:
Table 9.1 Short Circuit Threshold Resistor
R
input; the threshold is pre-set to 6.8V. Additionally, register 0x04 holds the Short Circuit Threshold level, changeable through
the I
“MSL3040/50/60/80/86/87/88/89 Programming Guide”.
SCTH
2
C compatible serial interface. For information about the Short Circuit Threshold register and the serial interface see the
is queried at power up, and when EN is taken high, to set the threshold level. The MSL3088 does not have an SCTH
LED
is the LED on-current in Amps.
330kΩ (or open)
1.0kΩ (or GND)
R
27kΩ
68kΩ
SCTH
2
C compatible serial interface see the MSL3040/41/50/60/80/86/87/88 Programming Guide.
Threshold Voltage
F
differs for different LEDs, the number of shorted LEDs required to generate
8-String 60mA LED Drivers with Integrated Boost Controller and Phase Shifted Dimming
4.9V
5.8V
6.8V
7.6V
Atmel MSL3086/MSL3088 Datasheet
2
C compatible serial interface see the
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