sx150x_89b-datasheet

ADVANCED COMMUNICATIONS & SENSING
Rev 4 – 26
th
April 2011 18 www.semtech.com
SX1508B/SX1509B
World’s Lowest Voltage Level Shifting GPIO
with LED Driver and Keypad Engine
t
t
1
0
Fade In
ON
Fade
Out
OFF
0
100%
TRiseX TFallX TOnX TOffX
IO[X] Intensity (PWM value)
RegData[X]
IOffX
IOnX
Figure 14 – LED Driver Overview
Each IO[X] has its own set of programmable registers (Cf §5 for more detailed information):
 RegTOnX (blinking capable I/Os only): TOnX, ON time of IO[X]
 RegIOnX (all I/Os): IOnX, ON intensity of IO[X]
 RegOffX (blinking capable I/Os only): TOffX and IOffX, OFF time and intensity of IO[X]
 RegTRiseX(breathing capable I/Os only): TRiseX, fade in time of IO[X]
 RegTFallX(breathing capable I/Os only): TFallX, fade out time of IO[X]
Please note that the LED driver mode is selectable for each IO bank between linear and logarithmic. (Cf §4.8.5)
All the figures assume normal IO polarity, for inverse polarity RegData control must be inverted (does not invert
the polarity of the IO signal itself).
4.8.2 Static Mode
Only mode available for non blinking capable IOs (with Off intensity = 0), else invoked when TOnX = 0.
If the I/O doesn’t support fading the LED intensity will step directly to the IOnX/IOffX value.
RegData(X)
IOLED(X) level
Off intensity(min) determined by
register RegIOffX
On intensity(max) determined by
register RegIOnX
Fade in rate determined by
register RegTRiseX
Fade out rate determined
by register RegTFallX
Figure 15 – LED Driver Static Mode
4.8.3 Single Shot Mode
Invoked when TOnX != 0 and TOffX = 0.
If the I/O doesn’t support fading the LED intensity will step directly to the IOnX/IOffX value.