PCA9551BS,118 Datasheet PCA9551PW,118, PCA9551BS,118, PCA9551D,118 | P10-P12

Product data sheet Rev. 08 — 31 July 2008 10 of 26

NXP Semiconductors

PCA9551

8-bit I

C-bus LED driver with programmable blink rates

7.4 Bus transactions

Fig 11. Write to register

0 AS

slave address

START condition R/W acknowledge

from slave

002aac507

0 0 AI 0 B2B1B00

command byte

acknowledge

from slave

12345678SCL 9

SDA DATA 1 A

write to register

data out from port

v(Q)

acknowledge

from slave

DATA 1 VALID

data to register

1 0 0 A2 A1 A01

Fig 12. Read from register

1 0 0 A2 A1 A0 0 AS1

START condition R/W

acknowledge

from slave

002aac508

acknowledge

from slave

SDA

A P

acknowledge

from master

data from register

DATA (first byte)

slave address

STOP

condition

(repeated)

START condition

(cont.)

1 A

R/W

acknowledge

from slave

slave address

at this moment master-transmitter becomes master-receiver

and slave-receiver becomes slave-transmitter

no acknowledge

from master

data from register

DATA (last byte)

command byte

0 0 AI 0 B2 B10B0

Auto-Increment

if AI = 1

1 0 0 A2 A1 A01

Remark: This ﬁgure assumes the command byte has previously been programmed with 00h.

Fig 13. Read Input Port register

1 0 0 A2 A1 A0 1 AS1

START condition R/W acknowledge

from slave

002aac509

acknowledge

from master

SDA NA

read from

port

data into

port

h(D)

data from port

no acknowledge

from master

data from port

DATA 4

slave address

DATA 1

STOP

condition

DATA 2 DATA 3 DATA 4

su(D)

Product data sheet Rev. 08 — 31 July 2008 11 of 26

NXP Semiconductors

PCA9551

8-bit I

C-bus LED driver with programmable blink rates

8. Application design-in information

8.1 Minimizing I

when the I/Os are used to control LEDs

When the I/Os are used to control LEDs, they are normally connected to V

through a

resistor as shown in Figure 14. Since the LED acts as a diode, when the LED is off the

I/O V

is about 1.2 V less than V

. The supply current, I

, increases as V

becomes

lower than V

and is speciﬁed as ∆I

in Table 12 “Static characteristics”.

Designs needing to minimize current consumption, such as battery power applications,

should consider maintaining the I/O pins greater than or equal to V

when the LED is off.

Figure 15 shows a high value resistor in parallel with the LED. Figure 16 shows V

less

than the LED supply voltage by at least 1.2 V. Both of these methods maintain the I/O V

at or above V

and prevents additional supply current consumption when the LED is off.

LED0 to LED5 are used as LED drivers.

LED6 and LED7 are used as regular GPIOs.

Fig 14. Typical application

PCA9551

LED0

LED1

SDA

SCL

RESET

5 V

C-BUS/SMBus

MASTER

002aac510

SDA

SCL

5 V

10 kΩ

LED2

LED3

LED4

LED5

LED6

LED7

GPIOs

10 kΩ10 kΩ

Fig 15. High value resistor in parallel with

the LED

Fig 16. Device supplied by a lower voltage

002aac189

LED

LEDn

100 kΩ

002aac190

LED

LEDn

3.3 V 5 V

Product data sheet Rev. 08 — 31 July 2008 12 of 26

NXP Semiconductors

PCA9551

8-bit I

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

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+

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

256 PWM0–

256

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

0.5=

Blink period 0.25

PSC1 1+

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

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

supply voltage −0.5 +6.0 V

I/O

voltage on an input/output pin V

− 0.5 5.5 V

O(LEDn)

output current on pin LEDn - ±25 mA

ground supply current - 100 mA

tot

total power dissipation - 400 mW

stg

storage temperature −65 +150 °C

amb

ambient temperature operating −40 +85 °C

P1-P3 P4-P6 P7-P9 P10-P12 P13-P15 P16-P18 P19-P21 P22-P24 P25-P26

PCA9551BS,118

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Manufacturer:

NXP Semiconductors

Description:

LED Lighting Drivers 8-BIT I2C FM OD LED

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PCA9551BS,118

PCA9551BS,118

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