2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or

28-Port I/O Expander

6

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Detailed Description

The MAX7300 general-purpose input/output (GPIO)

peripheral provides up to 28 I/O ports, P4 to P31, con-

trolled through an I

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 MAX7300 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 resis-

tor. Additionally, transition detection allows seven ports

(P24 to P30) to be monitored in any maskable combina-

tion for changes in their logic status. A detected transi-

tion is flagged through a status register bit, as well as an

interrupt pin (port P31), if desired.

The port configuration registers individually set the 28

ports, P4 to P31, as GPIO. A pair of bits in registers

0x09 through 0x0F sets each port’s configuration

(Tables 1 and 2).

The 36-pin MAX7300AAX and 40-pin MAX7300AGL

have 28 ports, P4 to P31. The 28-pin MAX7300ANI and

MAX7300AAI have only 20 ports available, P12 to P31.

The eight unused ports should be configured as out-

puts on power-up by writing 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 MAX7300 offers 20 or 28 I/O ports, depending on

package choice. Two addressing methods are avail-

able. 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 to P7,

P1 to P8, or P31 to P38 (P32 to P38 are nonexistent, so

the instructions to these bits are ignored).

Shutdown

When the MAX7300 is in shutdown mode, all ports are

forced to inputs, 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 MAX7300 is taken out of shutdown.

The MAX7300 can still be programmed while in shut-

down 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 con-

figuration register (Table 8).

PIN

SSOP/DIP

SSOP

QFN

NAME

FUNCTION

1

1

36

ISET

value of 39k

Ω to 120kΩ.

2, 3

2, 3

37, 38, 39

GND

Ground

4

4

40

AD0

Address Input 0. Sets device slave address. Connect to either GND,

V+, SCL, SDA to give four logic combinations. See Table 3.

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.

25

33

32

SDA

I

26

34

33

SCL

I

27

35

34

AD1

Address Input 1. Sets device slave address. Connect to either GND,

V+, SCL, SDA to give four logic combinations. See Table 3.

28

36

35

V+

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

capacitor.

Pin Description