MAX7301_15 Datasheet, PDF (5/17 Pages) Maxim Integrated Products – 4-Wire-Interfaced, 2.5V to 5.5V,20-Port and 28-Port I/O Expander

MAX7301
4-Wire-Interfaced, 2.5V to 5.5V,
20-Port and 28-Port I/O Expander
Pin Description
PIN
36 SSOP 28 SSOP
TQFN
1
1
36
2, 3
2, 3
37, 38, 39
4
4
40
—
5–24
—
5–32
—
33
34
35
36
—
1–10,
—
12–19,
21–30
—
11, 20, 31
25
32
26
33
27
34
28
35
—
—
NAME
FUNCTION
ISET
Bias Current Setting. Connect ISET to GND through a resistor (R_ISET) value of
39kW to 120kW.
GND Ground
DOUT 4-Wire Interface Serial Data Output Port
P12–P31
I/O Ports. P12 to P31 can be configured as push-pull outputs, CMOS logic
inputs, or CMOS logic inputs with weak pullup resistor.
P4–P31
I/O Ports. P4 to P31 can be configured as push-pull outputs, CMOS logic inputs,
or CMOS logic inputs with weak pullup resistor.
N.C.
SCLK
DIN
CS
V+
EP
No Connection. Not internally connected.
4-Wire Interface Serial Clock Input Port
4-Wire Interface Serial Data Input Port
4-Wire Interface Chip-Select Input, Active-Low
Positive Supply Voltage. Bypass V+ to GND with a minimum 0.047µF capacitor.
Exposed Pad on Package Underside. Connect to GND.
Detailed Description
The MAX7301 GPIO peripheral provides up to 28 I/O
ports, P4 to P31, controlled through an SPI-compatible
serial interface. The ports can be configured to any
combination of logic inputs and logic outputs, and
default to logic inputs on power-up.
Figure 1 is the MAX7301 functional diagram. Any I/O
port can be configured as a push-pull output (sinking
10mA, sourcing 4.5mA), or a Schmitt-trigger logic
input. Each input has an individually selectable internal
pullup resistor. Additionally, transition detection allows
seven ports (P24 through P30) to be monitored in any
maskable combination for changes in their logic status.
A detected transition is flagged through an interrupt pin
(port P31).
The port configuration registers set the 28 ports, P4
to P31, individually as GPIO. A pair of bits in registers
0x09 through 0x0F sets each port’s configuration
(Tables 1 and 2).
The 36-pin MAX7301AAX and 40-pin MAX7301ATL
have 28 ports, P4 to P31. The 28-pin MAX7301AAI is
offered in 20 ports, P12 to P31. The eight unused ports
should be configured as outputs on power-up by writ-
ing 0x55 to registers 0x09 and 0x0A. If this is not done,
the eight unused ports remain as floating inputs and
quiescent supply current rises, although there is no dam-
age to the part.
Register Control of I/O Ports
Across Multiple Drivers
The MAX7301 offers 20 or 28 I/O ports, depending on
package choice.
Two addressing methods are available. Any single
port (bit) can be written (set/cleared) at once; or, any
sequence of eight ports can be written (set/cleared) in
any combination at once. There are no boundaries; it is
equally acceptable to write P0 through P7, P1 through P8,
or P31 through P38 (P32 through P38 are nonexistent,
so the instructions to these bits are ignored).
Shutdown
When the MAX7301 is in shutdown mode, all ports are
forced to inputs (which can be read), and the pullup
current sources are turned off. Data in the port and
control registers remain unaltered so port configuration
and output levels are restored when the MAX7301 is
taken out of shutdown. The display driver can still be
programmed while in shutdown mode. For minimum
supply current in shutdown mode, logic inputs should
be at GND or V+ potential. Shutdown mode is exited by
setting the S bit in the configuration register (Table 6).
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