MAX7321 Maxim, MAX7321 Datasheet - Page 14

• Manufacturer Part Number: MAX7321
• Description: The MAX7321 2-wire serial-interfaced peripheral features eight open-drain I/O ports with selectable internal pullups and transition detection
• Manufacturer: Maxim

The MAX7321 can be used to drive loads, such as
relays, that draw more than 20mA by paralleling out-
puts. 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 combi-
nation 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 induc-
tive loads (such as relays), by connecting a reverse-
biased diode across the inductive load. Choose the
peak current for the diode to be greater than the induc-
tive load’s operating current.
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 to the device as possible. For
the TQFN version, additionally connect the exposed
pad to GND.
I
14
2
C Port Expander with 8 Open-Drain I/Os
______________________________________________________________________________________
Driving Load Currents Higher than 20mA
TOP VIEW
Pin Configurations (continued)
SDA
AD0
RST
V+
*EXPOSED PADDLE, CONNECTED TO GND
13
14
15
16
Power-Supply Considerations
+
12
1
*EP
+
MAX7321
11
TQFN
2
10
3
9
4
8
7
6
5
P5
P4
GND
P3
μC
SCL
SDA
RST
INT
Typical Application Circuit
SCL
SDA
AD0
AD2
RST
INT
MAX7321
+3.3V
GND
V+
0.047μF
P7
P6
P5
P4
P3
P2
P1
P0
+5V
I/O
I/O
I/O
I/O