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

damage 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 nonexis-

tent, 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).

4-Wire-Interfaced, 2.5V to 5.5V, 20-Port and

28-Port I/O Expander

_______________________________________________________________________________________

5

PIN

36 SSOP

28 SSOP

TQFN

NAME

FUNCTION

11

36

ISET

39k

Ω to 120kΩ.

2, 3

2, 3

37, 38, 39

GND

Ground

44

40

DOUT

4-Wire Interface Serial Data Output Port

—

5–24

—

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.

5–32

—

1–10,

12–19,

21–30

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.

——

11, 20, 31

N.C.

No Connection. Not internally connected.

33

25

32

SCLK

4-Wire Interface Serial Clock Input Port

34

26

33

DIN

4-Wire Interface Serial Data Input Port

35

27

34

CS

4-Wire Interface Chip-Select Input, Active Low

36

28

35

V+

Positive Supply Voltage. Bypass V+ to GND with a minimum 0.047µF

——

PAD

Exposed

Pad

Exposed Pad on Package Underside. Connect to GND.

Pin Description