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PCA9550D,112

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PCA9550_5 © NXP B.V. 2008. All rights reserved.
Product data sheet Rev. 05 — 13 October 2008 10 of 26
NXP Semiconductors
PCA9550
2-bit I
2
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
002aad268
0 0 AI 0 B2B1B00
command byte
A
acknowledge
from slave
12345678SCL 9
SDA DATA 1 A
write to register
data out from port
t
v(Q)
acknowledge
from slave
DATA 1 VALID
data to register
10000A01
Fig 12. Read from register
10000A00AS1
START condition R/W
acknowledge
from slave
002aad269
A
acknowledge
from slave
SDA
A P
acknowledge
from master
data from register
DATA (first byte)
slave address
STOP
condition
S
(repeated)
START condition
(cont.)
(cont.)
1 A
R/W
acknowledge
from slave
slave address
at this moment master-transmitter becomes master-receiver
and slave-receiver becomes slave-transmitter
NA
no acknowledge
from master
data from register
DATA (last byte)
command byte
0 0 AI 0 B2 B10B0
Auto-Increment
register address
if AI = 1
10000A01
Remark: This figure assumes the command byte has previously been programmed with 00h.
Fig 13. Read input port register
10000A01AS1
START condition R/W acknowledge
from slave
002aad270
A
acknowledge
from master
SDA NA
read from
port
data into
port
P
t
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
t
su(D)
DATA 1
PCA9550_5 © NXP B.V. 2008. All rights reserved.
Product data sheet Rev. 05 — 13 October 2008 11 of 26
NXP Semiconductors
PCA9550
2-bit I
2
C-bus LED driver with programmable blink rates
8. Application design-in information
8.1 Minimizing I
DD
when the I/Os are used to control LEDs
When the I/Os are used to control LEDs, they are normally connected to V
DD
through a
resistor as shown in Figure 14. Since the LED acts as a diode, when the LED is off the
I/O V
I
is about 1.2 V less than V
DD
. The supply current, I
DD
, increases as V
I
becomes
lower than V
DD
.
Designs needing to minimize current consumption, such as battery power applications,
should consider maintaining the I/O pins greater than or equal to V
DD
when the LED is off.
Figure 15 shows a high value resistor in parallel with the LED. Figure 16 shows V
DD
less
than the LED supply voltage by at least 1.2 V. Both of these methods maintain the I/O V
I
at or above V
DD
and prevents additional supply current consumption when the LED is off.
Fig 14. Typical application
PCA9550
LED0
LED1
SDA
SCL
RESET
5 V
I
2
C-BUS/SMBus
MASTER
SDA
SCL
V
DD
A0
V
SS
5 V
10 kΩ10 kΩ10 kΩ
002aad271
Fig 15. High value resistor in parallel with
the LED
Fig 16. Device supplied by a lower voltage
002aac189
LED
V
DD
LEDn
100 kΩ
V
DD
002aac190
LED
V
DD
LEDn
3.3 V 5 V
PCA9550_5 © NXP B.V. 2008. All rights reserved.
Product data sheet Rev. 05 — 13 October 2008 12 of 26
NXP Semiconductors
PCA9550
2-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 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 I
2
C-bus
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 PWM0–
256
--------------------------------
0.5=
Blink period 0.25
PSC1 1+
44
------------------------
==
256 PWM1–
256
--------------------------------
0.25=
Table 12. 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 - 50 mA
P
tot
total power dissipation - 400 mW
T
stg
storage temperature −65 +150 °C
T
amb
ambient temperature operating −40 +85 °C
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PCA9550D,112

Mfr. #:
Buy PCA9550D,112
Manufacturer:
NXP Semiconductors
Description:
LED Lighting Drivers 2-BIT I2C FM OD LED
Lifecycle:
New from this manufacturer.
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