Blink Phase Registers

When the blink function is disabled, the two blink phase

0 registers set the logic levels of the 16 ports (P0

through P15) when configured as outputs (Table 8). A

duplicate pair of registers called the blink phase 1 reg-

isters are also used if the blink function is enabled (Table

9). A logic high sets the appropriate output port high

impedance, while a logic low makes the port go low.

Reading a blink phase register reads the value stored

in the register, not the actual port condition. The port

output itself may or may not be at a valid logic level,

depending on the external load connected.

The 17th output, O16, is controlled through 2 bits in the

configuration register, which provide the same static or

blink control as the other 16 output ports.

PWM Intensity Control

The MAX7313 includes an internal oscillator, nominally

32kHz, to generate PWM timing for LED intensity con-

trol or other applications such as PWM trim DACs.

PWM can be disabled entirely for all the outputs. In this

case, all outputs are static and the MAX7313 operating

current is lowest because the internal PWM oscillator is

turned off.

The MAX7313 can be configured to provide any combi-

nation of PWM outputs and glitch-free logic outputs.

Each PWM output has an individual 4-bit intensity con-

trol (Table 14). When all outputs are to be used with the

same PWM setting, the outputs can be controlled

together instead using the global intensity control

(Table 13). Table 10 shows how to set up the MAX7313

to suit a particular application.

PWM Timing

The PWM control uses a 240-step PWM period, divided

into 15 master intensity timeslots. Each master intensity

timeslot is divided further into 16 PWM cycles (Figure 11).

The master intensity operates as a gate, allowing the indi-

vidual output settings to be enabled from 1 to 15 timeslots

per PWM period (Figures 12, 13, 14) (Table 13).

Each output’s individual 4-bit intensity control only

operates during the number of timeslots gated by the

master intensity. The individual controls provide 16

intensity settings from 1/16 through 16/16 (Table 14).

Figures 15, 16, and 17 show examples of individual

intensity control settings. The highest value an individ-

ual or global setting can be set to is 16/16. This setting

forces the output to ignore the master control, and fol-

low the logic level set by the appropriate blink phase

register bit. The output becomes a glitch-free static out-

put with no PWM.

16-Port I/O Expander with LED Intensity

Control, Interrupt, and Hot-Insertion Protection

______________________________________________________________________________________

17

Table 8. Blink Phase 0 Registers

REGISTER DATA

REGISTER

R/

W

ADDRESS

CODE

(HEX)

D7

D6

D5

D4

D3

D2

D1

D0

Write outputs P7–P0 phase 0

0

Read back outputs P7–P0 phase 0

1

0x02

OP7

OP6

OP5

OP4

OP3

OP2

OP1

OP0

Write outputs P15–P8 phase 0

0

Read back outputs P15–P8 phase 0

1

0x03

OP15

OP14

OP13

OP12

OP11

OP10

OP9

OP8

Table 9. Blink Phase 1 Registers

REGISTER DATA

REGISTER

R/

W

ADDRESS

CODE

(HEX)

D7

D6

D5

D4

D3

D2

D1

D0

Write outputs P7–P0 phase 1

0

Read back outputs P7–P0 phase 1

1

0x0A

OP7

OP6

OP5

OP4

OP3

OP2

OP1

OP0

Write outputs P15–P8 phase 0

0

Read back outputs P15–P8 phase 1

1

0x03

OP15

OP14

OP13

OP12

OP11

OP10

OP9

OP8