概觀
The IS32LT3953 is a DC-to-DC switching converter
that integrates an N-channel MOSFET to operate in a
buck configuration. The device can operate from a
wide input voltage between 4.5V and 38V and
provides a constant current of up to 3A for driving a
single LED or multiple series connected LEDs.
The external resistor, RISET, is used to set a constant
LED output current, while allowing the output voltage
to be automatically adjusted for a variety of LED
configurations.
The IS32LT3953 operates in a fixed frequency mode
during switching. There is an external resistor
connected between the VCC and TON pins used to
configure the on-time (switching frequency). The
switching frequency is dithered for spread spectrum
operation which will spread the electromagnetic
energy into a wider frequency band. This function is
helpful for optimizing EMI performance.
A logic input PWM signal applied to the enable (EN)
pin will adjust the average LED current. The LED
brightness is proportional to the duty cycle of the
PWM signal.
True average output current operation is achieved
with fast transient response by using cycle-by-cycle,
controlled on-time method.
The IS32LT3953 is available in an SOP-8-EP
package with an exposed pad for enhanced thermal
dissipation. It operates from 4.5V to 38V over the
temperature range of -40°C to +125°C.