The IS32LT3175 is a single channel linear
programmable current regulator capable of up to
150mA. It integrates a debounce and latch circuit on
the channel enable pin (EN) to facilitate the use of a
low cost momentary contact switch. The PWM pin can
be interfaced to a logic level “courtesy light” signal to
directly drive the LED channel. The IS32LT3175P
accepts a positive polarity PWM signal while the
IS32LT3175N accepts a negative polarity PWM signal.
The device operates as a stand-alone LED driver
configurable with external resistors; no microcontroller
is required. A single external resistor programs the
current level, while two separate resistors
independently program the fade in and fade out ramp
rate for the channel.
The device integrates a 63 steps fade in and fade out
algorithm (Gamma correction) which causes the output
LED current to gradually ramp up to the full source
value after the EN pin is pulsed. The same controller
causes the LED current to gradually ramp down to
zero if the EN pin is pulsed while the output channel is
ON. The fade ramp can be interrupted mid-cycle
before completion of the ramp cycle. The EN pin will
accept either a momentary contact switch or logic level
signal pulsed low.
The IS32LT3175 is targeted at the automotive market
with end applications to include map and dome lighting
as well as exterior accent lighting. For 12V automotive
applications the low dropout driver can support 1 to 3
LEDs (VF = 3.2V) per channel. It is offered in a small
thermally enhanced SOP-8-EP package.