Datasheet

PCA9551_8 © NXP B.V. 2008. All rights reserved.
Product data sheet Rev. 08 — 31 July 2008 12 of 26
NXP Semiconductors
PCA9551
8-bit I
2
C-bus LED driver with programmable blink rates
8.2 Programming example
The following example will show how to set LED0 to LED3 on. It will then set LED4 and
LED5 to blink at 1 Hz at a 50 % duty cycle. LED6 and LED7 will be set to blink at 4 Hz and
at a 25 % duty cycle.
9. Limiting values
Table 10. Programming PCA9551
Program sequence I
2
C-bus
START S
PCA9551 address with A0 to A2 = LOW C0h
PSC0 subaddress + Auto-Increment 11h
Set prescaler PSC0 to achieve a period of 1 second:
PSC0 = 37
25h
Set PWM0 duty cycle to 50 %:
PWM0 = 128
80h
Set prescaler PSC1 to achieve a period of 0.25 seconds:
PSC1 = 9
09h
Set PWM1 output duty cycle to 25 %:
PWM1 = 192
C0h
Set LED0 to LED3 on 00h
Set LED4 and LED5 to PWM0, and LED6 or LED7 to PWM1 FAh
STOP P
Blink period 1
PSC0 1+
38
------------------------
==
256 PWM0–
256
--------------------------------
0.5=
Blink period 0.25
PSC1 1+
38
------------------------
==
256 PWM1–
256
--------------------------------
0.25=
Table 11. Limiting values
In accordance with the Absolute Maximum Rating System (IEC 60134).
Symbol Parameter Conditions Min Max Unit
V
DD
supply voltage −0.5 +6.0 V
V
I/O
voltage on an input/output pin V
SS
− 0.5 5.5 V
I
O(LEDn)
output current on pin LEDn - ±25 mA
I
SS
ground supply current - 100 mA
P
tot
total power dissipation - 400 mW
T
stg
storage temperature −65 +150 °C
T
amb
ambient temperature operating −40 +85 °C