Datasheet

PCA9538 All information provided in this document is subject to legal disclaimers. © NXP Semiconductors N.V. 2014. All rights reserved.
Product data sheet Rev. 7 — 26 November 2014 13 of 34
NXP Semiconductors
PCA9538
8-bit I
2
C-bus and SMBus low power I/O port with interrupt and reset
7.1 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 11
. 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 12
shows a high value resistor in parallel with the LED. Figure 13 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.
8. Limiting values
Fig 12. High value resistor in parallel with
the LED
Fig 13. Device supplied by a lower voltage
002aac660
LED
V
DD
IOn
100 kΩ
V
DD
002aac661
LED
V
DD
IOn
3.3 V 5 V
Table 9. 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
I
I
input current - 20 mA
V
I/O
voltage on an input/output pin V
SS
 0.5 5.5 V
I
O(IOn)
output current on pin IOn - 50 mA
I
DD
supply current - 85 mA
I
SS
ground supply current - 100 mA
P
tot
total power dissipation - 200 mW
T
stg
storage temperature 65 +150 C
T
amb
ambient temperature operating
all devices except PCA9538PW/Q900 40 +85 C
PCA9538PW/Q900 40 +125 C
T
j(max)
maximum junction temperature - +125 C