Datasheet

Any of the four open-drain ports can be configured as a
logic input by setting the port output logic-high (logic-high
for an open-drain output is high impedance). When the
MAX7323 is read through the serial interface, the actual
logic levels at the ports are read back.
The four ports offer latching transition detection
functionality. All input ports are continuously monitored for
changes. An input change sets 1 of 4 flag bits that identify
changed input(s). All flags are cleared upon a subsequent
read or write transaction to the MAX7323.
A latching interrupt output, INT, automatically flags data
changes on any of the I/O ports used as inputs. The
interrupt output INT, and all transition flags are
deasserted when the MAX7323 is next accessed through
the serial interface.
Internal pullup resistors to V+ are selected by the address
select inputs, AD0 and AD2. Pullups are enabled on the
input ports in groups of two (see Table 3).
Use the slave address selection to ensure that I/O ports
used as inputs are logic-high on power-up. I/O ports with
internal pullups enabled default to a logic-high output
state. I/O ports with internal pullups disabled default to a
logic-low output state. Output port power-up logic states
are selected by the address select inputs AD0 and AD2.
Ports default to logic-high or logic-low on power-up in
groups of two (see Table 3).
Initial Power-Up
On power-up, the transition detection logic is reset, and
INT is deasserted. The interrupt mask register is set to
0x3C, enabling the interrupt output for transitions on
all four input ports. The transition flags are cleared to
indicate no data changes. The power-up default state of
the four push-pull outputs is set according to the I
2
C slave
address selection inputs, AD0 and AD2 (see Table 3).
Power-On Reset
The MAX7323 contains an integral power-on-reset (POR)
circuit that ensures all registers are reset to a known state
on power-up. When V+ rises above V
POR
(1.6V max), the
POR circuit releases the registers and 2-wire interface
for normal operation. When V+ drops to less than V
POR
,
the MAX7323 resets all ports to the POR defaults (see
Table 3).
RST Input
The active-low RST input operates as a reset that voids
any current I
2
C transaction involving the MAX7323,
forcing the MAX7323 into the I
2
C STOP condition. The
reset action does not clear the interrupt output (INT).
Standby Mode
When the serial interface is idle, the MAX7323
automatically enters standby mode, drawing minimal
supply current.
PART
I
2
C
SLAVE
ADDRESS
INPUTS
INPUT
INTERRUPT
MASK
OPEN-
DRAIN
OUTPUTS
PUSH-
PULL
OUTPUTS
APPLICATION
MAX7323 110xxxx Up to 4 — Up to 4 4
4 I/O, 4 output-only versions:
4 open-drain I/O ports with latching transition
detection interrupt and selectable pullups.
4 push-pull outputs with selectable power-up default
levels.
MAX7328
MAX7329
0100xxx
0111xxx
Up to 8 — Up to 8 —
8 open-drain I/O ports with nonlatching transition
detection interrupt and pullups on all ports.
All ports power up as inputs (or logic-high outputs).
Any port can be used as an input by setting the
open-drain output to logic-high.
16-PORT EXPANDERS
MAX7324
101xxxx
and
110xxxx
8 Yes — 8 Software equivalent to a MAX7320 plus a MAX7319.
MAX7325 Up to 8 — Up to 8 8 Software equivalent to a MAX7320 plus a MAX7321.
MAX7326 4 Yes — 12 Software equivalent to a MAX7320 plus a MAX7322.
MAX7327 Up to 4 — Up to 4 12 Software equivalent to a MAX7320 plus a MAX7323.
Table 1. MAX7319–MAX7329 Family Comparison (continued)
www.maximintegrated.com
Maxim Integrated │ 6
MAX7323 I
2
C Port Expander with 4 Push-Pull
Outputs and 4 Open-Drain I/Os