pca9557bs NXP Semiconductors, pca9557bs Datasheet - Page 13

• Manufacturer Part Number: pca9557bs
• Description: 8-bit I2c And Smbus I/0 Port With Reset
• Manufacturer: NXP Semiconductors

NXP Semiconductors
9. Application design-in information
PCA9557_5
Product data sheet
Fig 18. Typical application
V
DD
(5 V)
Device address configured as 0011 100x for this example.
IO0, IO2, IO3 configured as outputs.
IO1, IO4, IO5 configured as inputs.
IO6, IO7 are not used.
CONTROLLER
MASTER
V
V
DD
SS
RESET
9.1 Minimizing I
SDA
SCL
When the I/Os are used to control LEDs, they are normally connected to V
resistor as shown in
I/O V
lower than V
Designs needing to minimize current consumption, such as battery power applications,
should consider maintaining the I/O pins greater than or equal to V
Figure 19
than the LED supply voltage by at least 1.2 V. Both of these methods maintain the I/O V
at or above V
1.8 k
I
is about 1.2 V less than V
1.8 k
shows a high value resistor in parallel with the LED.
DD
DD
.
DD
2 k
and prevents additional supply current consumption when the LED is off.
when the I/Os are used to control LEDs
Figure
Rev. 05 — 12 September 2007
2 k
SCL
SDA
RESET
A2
A1
A0
18. Since the LED acts as a diode, when the LED is off the
PCA9557
V
V
SS
DD
DD
. The supply current, I
IO0
IO1
IO2
IO3
IO4
IO5
IO6
IO7
620
8-bit I
2
C-bus and SMBus I/O port with reset
DD
100 k
( 5)
, increases as V
enable
Figure 20
DD
INT
RESET
ALARM
(e.g., alarm system)
(e.g., temp. sensor)
A
B
when the LED is off.
SUBSYSTEM 1
SUBSYSTEM 2
SUBSYSTEM 3
PCA9557
(e.g., counter)
© NXP B.V. 2007. All rights reserved.
shows V
controlled switch
(e.g., CBT device)
DD
I
002aad285
becomes
through a
V
DD
DD
13 of 26
less
I