MAX7314 데이터 시트보기 (PDF) - Maxim Integrated

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MAX7314

18-Port GPIO with LED Intensity Control, Interrupt, and Hot-Insertion Protection

Maxim Integrated 

18-Port GPIO with LED Intensity Control,

Interrupt, and Hot-Insertion Protection

Table 12. PWM Intensity Settings (Blink Enabled)

OUTPUT

(OR

GLOBAL)

INTENSITY

SETTING

0x0

0x1

0x2

0x3

0x4

0x5

0x6

0x7

0x8

0x9

0xA

0xB

0xC

0xD

0xE

0xF

PWM DUTY CYCLE

OUTPUT BLINK

PHASE X

REGISTER BIT = 0

PWM DUTY CYCLE

OUTPUT BLINK

PHASE X

REGISTER = 1

EXAMPLES OF LED BLINK BEHAVIOR

(LED IS ON WHEN OUTPUT IS LOW)

BLINK PHASE 0

REGISTER BIT = 0

BLINK PHASE 0

REGISTER BIT = 1

LOW

TIME

1/16

2/16

3/16

4/16

5/16

6/16

7/16

8/16

9/16

10/16

11/16

12/16

13/16

14/16

15/16

Static low

HIGH

TIME

LOW

TIME

HIGH

TIME

BLINK PHASE 1

REGISTER BIT = 1

BLINK PHASE 1

REGISTER BIT = 0

15/16

15/16

1/16

14/16

13/16

12/16

11/16

14/16

13/16

12/16

11/16

2/16

3/16

4/16

Phase 0: LED on at low intensity Phase 0: LED on at high intensity

Phase 1: LED on at high intensity Phase 1: LED on at low intensity

5/16

10/16

9/16

8/16

7/16

6/16

10/16

9/16

8/16

7/16

6/16

6/16

7/16

8/16

9/16

10/16

Output is half intensity during both blink phases

5/16

5/16

11/16

4/16

4/16

12/16

Phase 0: LED on at high intensity Phase 0: LED on at low intensity

Phase 1: LED on at low intensity Phase 1: LED on at high intensity

3/16

3/16

13/16

2/16

2/16

14/16

1/16

1/16

15/16

Static low

Static high Static high

impedance impedance

Phase 0: LED on continuously

Phase 1: LED off continuously

Phase 0: LED off continuously

Phase 1: LED on continuously

Applications Information

Hot Insertion

I/O ports P0–P15, interrupt output INT/O16, RST input,

BLINK input, and serial interface SDA, SCL, AD0 remain

high impedance with up to 6V asserted on them when

the MAX7314 is powered down (V+ = 0V). The MAX7314

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 MAX7314 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 220kΩ 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.

Driving LED Loads

When driving LEDs, a resistor in series with the LED

must be used to limit the LED current to no more than

50mA. Choose the resistor value according to the fol-

lowing formula:

RLED = (VSUPPLY - VLED - VOL) / ILED

where:

RLED is the resistance of the resistor in series with the

LED (Ω).

VSUPPLY is the supply voltage used to drive the LED (V).

VLED is the forward voltage of the LED (V).

VOL is the output low voltage of the MAX7314 when

sinking ILED (V).

ILED is the desired operating current of the LED (A).

For example, to operate a 2.2V red LED at 14mA from a

5V supply, RLED = (5 - 2.2 - 0.25) / 0.014 = 182Ω.

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