Applications Information

Hot Insertion

I/O ports P0–P15, interrupt output INT/016, and serial

interface SDA, SCL, AD0–2 remain high impedance

with up to 6V asserted on them when the MAX7313 is

powered down (V+ = 0V). The MAX7313 can therefore

be used in hot-swap applications.

Output Level Translation

The open-drain output architecture allows the ports to

level translate the outputs to higher or lower voltages

than the MAX7313 supply. An external pullup resistor

can be used on any output to convert the high-imped-

ance logic-high condition to a positive voltage level.

The resistor can be connected to any voltage up to

5.5V. For interfacing CMOS inputs, a pullup resistor

value of 220k

Ω is a good starting point. Use a lower

resistance to improve noise immunity, in applications

where power consumption is less critical, or where a

faster rise time is needed for a given capacitive load.

Compatibility with MAX7311

The MAX7313 is pin compatible and software compatible

with the standard register structure used by MAX7311,

PCA9535, and PCA9555. However, some MAX7311 func-

tions are not implemented in the MAX7313, and the

MAX7313’s PWM and blink functionality is not supported

in the MAX7311. Software compatibility is clearly not

100%, but the MAX7313 was designed so the subset

(omitted) features default to the same power-up behavior

as the MAX7311, PCA9535, and PCA9555, and superset

features do not use existing registers in a different way. In

practice, many applications can use the MAX7313 as a

drop-in replacement for the MAX7311.

16-Port I/O Expander with LED Intensity

Control, Interrupt, and Hot-Insertion Protection

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21

Table 13. Master, O16 Intensity Register

REGISTER DATA

REGISTER

ADDRESS

CODE

(HEX)

D7

D6

D5

D4

D3

D2

D1

D0

MSB

LSB

MSB

LSB

MASTER AND GLOBAL INTENSITY

R/

W

MASTER INTENSITY

O16 INTENSITY

Write master and global intensity

0

Read back master and global intensity

1

M3

M2

M1

M0

G3

G2

G1

G0

Master intensity duty cycle is 0/15 (off);

internal oscillator is disabled;

all outputs will be static with no PWM

—

0000

—

—

—

—

Master intensity duty cycle is 1/15

—

0001

—

—

—

—

Master intensity duty cycle is 2/15

—

0010

—

—

—

—

Master intensity duty cycle is 3/15

—

0011

—

—

—

—

—

—

—

————

———

Master intensity duty cycle is 13/15

—

1101

—

—

—

—

Master intensity duty cycle is 14/15

—

1110

—

—

—

—

Master intensity duty cycle is 15/15 (full)

—

1111

—

—

—

—

O16 intensity duty cycle is 1/16

—

—

—

—

—

0

0

0

0

O16 intensity duty cycle is 2/16

—

—

—

—

—

0

0

0

1

O16 intensity duty cycle is 3/16

—

—

—

—

—

0

0

1

0

—

—

—

————

———

O16 intensity duty cycle is 14/16

—

—

—

—

—

1

1

0

1

O16 intensity duty cycle is 15/16

—

—

—

—

—

1

1

1

0

O16 intensity duty cycle is 16/16

(static output, no PWM)

—

0X0E

—

———

1

1

1

1