LM3481QMMX/NOPB High efficiency controller for boost, SEPIC and flyback DC/DC converters

Product model: LM3481QMMX/NOPB

Product brand: TI/Texas Instruments

Product package: VSSOP10

Product function: efficient controller

LM3481QMMX/NOPB characteristics
● Comply with AEC-Q100 standards for automotive applications:
Device temperature level 1: - 40 ° C to+125 ° C, TA
10 pin VSSOP package
● Internal push-pull driver with 1A peak current capability
● Current limit and thermal shutdown
● Frequency compensation optimized by capacitors and resistors
● Internal soft start
● Current mode operation
● Adjustable undervoltage locking with hysteresis
● Pulse jump under light load
● Main specifications
2.97V to 48V wide supply voltage range
Adjustable and synchronous clock frequency range from 100kHz to 1MHz
± 1.5% (overheated) internal reference
10 µ A turn off current (overheat protection)
● Create customized design with LM3481-Q1 and WEBENCH Power Designer

LM3481QMMX/NOPB Description
LM3481QMMX/NOPB is a multi-functional low side N-FET high-performance controller for switching regulators. The device is designed for boost, SEPIC and flyback converters and topologies that require low side FETs as primary switches. LM3481-Q1 device can work at a very high switching frequency to reduce the size of the overall solution. The switching frequency of LM3481-Q1 can be adjusted to any value between 100kHz and 1MHz by using a single external resistor or synchronizing the device with the external clock. In addition to cycle by cycle current limiting, current mode control provides excellent bandwidth and transient response. Current limits can be programmed using a single external resistor.
LM3481QMMX/NOPB device has built-in protection functions, such as thermal shutdown, short circuit protection and overvoltage protection. The energy-saving shutdown mode can reduce the total power supply current to 5 µ A and support power timing control. Internal soft start will limit the surge current when starting. The integrated current slope compensation can simplify the design. If the specific application requires, a single resistor can be used to increase the current slope compensation.

LM3481QMMX/NOPB device adopts fixed frequency, pulse width modulation (PWM) current mode control architecture. In a typical application circuit, the peak current flowing through the external MOSFET is detected through the external detection resistance. The voltage on this resistor is fed to the ISEN pin. Then, the voltage will perform level conversion and be fed to the positive input of PWM comparator. The output voltage is also detected through the external feedback resistance voltage divider network and fed to the negative input terminal (feedback pin, FB) of the error amplifier (EA). The output of the error amplifier (COMP pin) is added to the slope compensation slope and then fed to the negative input terminal of the PWM comparator.
At the beginning of any switching cycle, the oscillator sets the RS latch using SET/blanking and switching logic blocks. This will force a high level signal on the DR pin (gate of the external MOSFET), and the external MOSFET will conduct. When the voltage on the positive input end of the PWM comparator exceeds the voltage on the negative input end, the RS latch will reset and the external MOSFET will turn off.
The voltage on the detection resistor usually contains spurious noise spikes, as shown in Figure 6-1. These spikes can force the PWM comparator to reset the RS latch prematurely. To prevent these spikes from resetting the latch, the blanking circuit inside the IC will prevent the PWM comparator from resetting the latch within a short time after the latch is set. This duration is called blanking time, usually 250ns, and is specified as tmin (on) in the electrical characteristics electrical characteristics section.
Under extremely light load or no-load conditions, when the external MOSFET is on, the energy supplied to the output capacitor within the blanking time will be greater than the energy supplied to the load. The overvoltage comparator in LM3481QMMX/NOPB prevents the output voltage from increasing under these conditions by detecting the feedback (FB pin) voltage and resetting the RS latch. The latch remains reset until the output decays to the nominal value. Therefore, the operating frequency will be reduced when the load is light, thus achieving excellent efficiency.

Package drawing