PCA9531 Datasheet, PDF (8/27 Pages) NXP Semiconductors – 8-bit I2C LED dimmer

NXP Semiconductors
PCA9531
8-bit I²C-bus LED dimmer
6.3.6 LS0 to LS1 - LED selector registers
The LSn LED select registers determine the source of the LED data.
00 = output is set high-impedance (LED off; default)
01 = output is set LOW (LED on)
10 = output blinks at PWM0 rate
11 = output blinks at PWM1 rate
Table 9. LS0 to LS1 - LED selector registers bit description
Legend: * default value.
Register Bit
Value
Description
LS0 - LED0 to LED3 selector
LS0
7:6
00*
LED3 selected
5:4
00*
LED2 selected
3:2
00*
LED1 selected
1:0
00*
LED0 selected
LS1 - LED4 to LED7 selector
LS1
7:6
00*
LED7 selected
5:4
00*
LED6 selected
3:2
00*
LED5 selected
1:0
00*
LED4 selected
6.4 Pins used as GPIOs
LED pins not used to control LEDs can be used as General Purpose I/Os (GPIOs).
For use as input, set LEDn to high-impedance (00) and then read the pin state via the
Input register.
For use as output, connect external pull-up resistor to the pin and size it according to the
DC recommended operating characteristics. LEDn output pin is HIGH when the output is
programmed as high-impedance, and LOW when the output is programmed LOW through
the ‘LED selector’ register. The output can be pulse-width controlled when PWM0 or
PWM1 are used.
6.5 Power-on reset
When power is applied to V_DD, an internal Power-On Reset (POR) holds the PCA9531 in
a reset condition until V_DD has reached V_POR. At that point, the reset condition is released
and the PCA9531 registers are initialized to their default states, all the outputs in the
OFF state. Thereafter, V_DD must be lowered below 0.2 V to reset the device.
6.6 External RESET
A reset can be accomplished by holding the RESET pin LOW for a minimum of t_w(rst). The
PCA9531 registers and I²C-bus state machine will be held in their default states until the
RESET input is once again HIGH.
This input requires a pull-up resistor to V_DD if no active connection is used.
PCA9531_6
Product data sheet
Rev. 06 — 19 February 2009
© NXP B.V. 2009. All rights reserved.
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