PCA9550_5

© NXP B.V. 2008. All rights reserved.

Product data sheet

Rev. 05 — 13 October 2008

12 of 26

NXP Semiconductors

PCA9550

8.2 Programming example

The following example will show how to set LED0 to blink at 1 Hz at a 50 % duty cycle.

LED1 will be set to blink at 4 Hz and at a 25 % duty cycle.

9.

Limiting values

Table 11.

Programming PCA9550

Program sequence

START

S

PCA9550 address with A0 = LOW

C0h

PSC0 subaddress + Auto-Increment

11h

Set prescaler PSC0 to achieve a period of 1 second:

PSC0 = 43

2Bh

Set PWM0 duty cycle to 50 %:

PWM0 = 128

80h

Set prescaler PSC1 to achieve a period of 0.25 seconds:

PSC1 = 10

0Ah

Set PWM1 output duty cycle to 25 %:

PWM1 = 192

C0h

Set LED0 to PWM0, and set LED1 to blink at PWM1

0Eh

STOP

P

Blink period

1

PSC0

1

+

44

------------------------

==

256

PWM 0

–

256

--------------------------------

0.5

=

Blink period

0.25

PSC1

1

+

44

------------------------

==

256

PWM 1

–

256

--------------------------------

0.25

=

Table 12.

Limiting values

In accordance with the Absolute Maximum Rating System (IEC 60134).

Symbol

Parameter

Conditions

Min

Max

Unit

supply voltage

−0.5

+6.0

V

voltage on an input/output pin

5.5

V

output current on pin LEDn

-

±25

mA

ground supply current

-

50

mA

total power dissipation

-

400

mW

storage temperature

−65

+150

°C

ambient temperature

operating

−40

+85

°C