MSL3088-IUR Atmel, MSL3088-IUR Datasheet - Page 13

• Manufacturer Part Number: MSL3088-IUR
• Description: LED Lighting Drivers 8-Str LED Driver Intrnl Bst Cntr/Phas
• Manufacturer: Atmel

Specifications of MSL3088-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

8.3 Boost Regulator Overview
8.4 Error Amplifier
The MSL3086/88 boost regulator boosts the input voltage up to the regulated output voltage. For design details see the section “Boost
Regulator” beginning on page 17, the following text presents an overview of the boost regulator controller.
The boost regulator uses an external switching MOSFET, current sense resistor, inductor, rectifier, and input and output capacitors for
this purpose (Figure 8.1). Because the MOSFET and current sense resistor are external, the boost regulator operates over a wide range
of input and output voltage, and LED current configurations. It includes a 2.5V reference voltage, fixed slope compensation and external
voltage regulator compensation to optimize the control loop for each configuration. Because the boost regulator components are external,
it is useful for a number of topologies such as SEPIC, flyback, and single-switch forward converters. The boost regulator includes soft-
start, adjustable cycle-by-cycle current limiting, and output over-voltage fault detection.
Figure 8.1. Power section of MSL3086/MSL3088
The internal error amplifier compares the external divided output voltage at FB to the internal 2.5V reference voltage to set the regulated
output voltage. The error amplifier output voltage at COMP is externally accessible and is used in conjunction with an external RC
network to compensate the voltage regulator. FB also drives the integrated boost over-voltage comparator that detects if the output
voltage exceeds the regulation voltage, to generate a fault condition. The error amplifier internally controls the current mode PWM
regulator.
Figure 3. Power section of MSL3086/MSL3088
E
The internal error amplifier compares the external divided output voltage at FB to the internal 2.5V reference voltage to set
the regulated output voltage. The error amplifier output voltage at COMP is externally accessible and is used in
conjunction with an external RC network to compensate the voltage regulator. FB also drives the integrated boost over-
voltage comparator that detects if the output voltage exceeds the regulation voltage, to generate a fault condition. The
error amplifier internally controls the current mode PWM regulator.
G
The gate driver drives the gate of the external boost regulator switching MOSFET. The drain of the switching MOSFET in
turn drives the boost inductor and rectifier to boost the input voltage to the regulated output voltage. The gate driver
sources and sinks up to 1A allowing fast switching speed and allows the use of MOSFETs with high gate capacitance.
The gate driver power is separated from the internal circuitry power to reduce internal noise and to allow separate gate
driver bypassing for optimal performance.
S
The boost regulator includes a built in soft-start to prevent excessive input current overshoot at turn-on. The soft-start
ramps the output regulation voltage from 0V at turn-on to the as-configured regulation output voltage over 1.6ms. Note
that the boost regulator only controls output voltages greater than the input voltage; when the soft-start sets the regulation
voltage below the input voltage, the actual output voltage remains at approximately the input voltage.
RROR
OFT
ATE
-S
D
A
TART
RIVER
MSL3086
MPLIFIER
SLOPE
COMP
0.4V
1.5V
1.1V
REF
+
CURRENT
MSL3086/MSL3087/MSL3088 Datasheet
GATE DRIVE
A = 11
START
DROPOUT DETECT
SOFT
5V
EFFICIENCY
CURRENT
OPTIMIZER
PVIN
SENSE
LIMIT
SINK
LED
0.1 V
8-String 60mA LED Drivers with Integrated Boost Controller and Phase Shifted Dimming
GATE
CS
GND
FB
COMP
STRn
C
COMPENSATION:
C
C
R
COMP1
COMP2
COMP1
COMP
V
, R
= POLE
PWR
COMP
Q1
R
L1
CS
C
= ZERO
D1
COMP2
C
IN
Atmel MSL3086/MSL3088 Datasheet
R
R
BOTTOM
TOP
C
R
OUT
ESR
V
LED
13