MAX7315 Просмотр технического описания (PDF) - Maxim Integrated

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MAX7315

8-Port I/O Expander with LED Intensity Control, Interrupt, and Hot-Insertion Protection

Maxim Integrated 

8-Port I/O Expander with LED Intensity

Control, Interrupt, and Hot-Insertion Protection

Table 5. Ports Configuration Register

REGISTER

Ports configuration

(1 = input, 0 = output)

Read-back ports configuration

ADDRESS

R/W CODE

REGISTER DATA

(HEX)

D7

D6

D5

D4

D3

D2

D1

D0

0

0x03

OP7 OP6 OP5 OP4 OP3 OP2 OP1 OP0

1

Table 6. Input Ports Register

REGISTER

Read input ports

ADDRESS

R/W CODE

REGISTER DATA

(HEX)

D7

D6

D5

D4

D3

D2

D1

D0

1

0x00

IP7 IP6 IP5 IP4 IP3 IP2 IP1 IP0

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 9th output, O8, is controlled through 2 bits in the

configuration register, which provide the same static or

blink control as the other 8 output ports.

PWM Intensity Control

The MAX7315 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 MAX7315 operating cur-

rent is lowest because the internal PWM oscillator is

turned off.

The MAX7315 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 MAX7315

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.

Using PWM Intensity Controls with Blink Disabled

When blink is disabled (Table 7), the blink phase 0 reg-

ister specifies each output’s logic level during the PWM

on-time (Table 8). The effect of setting an output’s blink

phase 0 register bit to 0 or 1 is shown in Table 11. With

its output bit set to zero, an LED can be controlled with

16 intensity settings from 1/16th duty through fully on,

but cannot be turned fully off using the PWM intensity

control. With its output bit set to 1, an LED can be con-

trolled with 16 intensity settings from fully off through

15/16th duty.

Table 7. Blink Controls

BLINK

ENABLE

FLAG E

BLINK

FLIP

FLAG B

BLINK

FUNCTION

0

X

Disabled

0

1

1

X = Don’t care.

Enabled

OUTPUT

REGISTERS

USED

Blink phase 0

register

Blink phase 0

register

Blink phase 1

register

16 ______________________________________________________________________________________

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