Datasheet

Driving Load Currents Higher than 20mA
The MAX7321 can be used to drive loads, such as relays,
that draw more than 20mA by paralleling outputs. Use at
least one output per 20mA of load current; for example,
a 5V, 330mW relay draws 66mA, and therefore, requires
four paralleled outputs. Any combination of outputs can
be used as part of a load-sharing design because any
combination of ports can be set or cleared at the same
time by writing the MAX7321. Do not exceed a total sink
current of 100mA for the device.
The MAX7321 must be protected from the negative
voltage transient generated when switching off inductive
loads (such as relays), by connecting a reverse-biased
diode across the inductive load. Choose the peak cur-
rent for the diode to be greater than the inductive load’s
operating current.
Power-Supply Considerations
The MAX7321 operates with a supply voltage of +1.71V
to +5.5V over the -40°C to +125°C temperature range.
Bypass the supply to GND with a ceramic capacitor of
at least 0.047µF as close as possible to the device. For
the TQFN version, additionally connect the exposed pad
to GND.
Issue: I
2
C Flag Clearing Deassertion Anomaly
Description of Problem
The MAX7321 clears data stored in the interrupt flag and
deasserts the corresponding interrupt when an I
2
C mas-
ter reads any I
2
C slave on the same bus.
Workaround
To keep the interrupt flag data valid, the user must read
the MAX7321 device BEFORE any other device on the
I
2
C bus, after a pending interrupt. This limits the bus to
only one MAX7321 device.
PACKAGE
TYPE
PACKAGE
CODE
OUTLINE NO.
LAND
PATTERN NO.
16 QSOP E16+4 21-0055 90-0167
16 TQFN-EP T1633+4 21-0136 90-0031
15
16
14
13
5
6
7
P1 P2
8
AD2
P7 P6 SCL
1 3
V+
4
12 10 9
AD0
RST
P5
P4
GND
P3
MAX7321
P0 INT
2
11
SDA
TQFN
TOP VIEW
*EP
*EXPOSED PAD, CONNECTED TO GND
+
MAX7321
P2
P7
P6
P5
P4
V+
+3.3V
+5V
µC
SCL
SDA
SCL
AD0
P1
P0
SDA
P3
I/O
I/O
AD2
GND
I/O
I/O
RST
RST
INT INT
0.047µF
www.maximintegrated.com
Maxim Integrated │ 14
MAX7321 I
2
C Port Expander with 8 Open-Drain I/Os
Package Information
For the latest package outline information and land patterns
(footprints), go to www.maximintegrated.com/packages. Note
that a “+”, “#”, or “-” in the package code indicates RoHS status
only. Package drawings may show a different suffix character, but
the drawing pertains to the package regardless of RoHS status.
Pin Congurations (continued)
Typical Application Circuit