Using PWM Intensity Controls with Blink Disabled

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

isters specify 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.

Using PWM Intensity Controls with Blink Enabled

When blink is enabled (Table 7), the blink phase 0 regis-

ters and blink phase 1 registers specify each output’s

logic level during the PWM on-time during the respective

blink phases (Tables 8 and 9). The effect of setting an

output’s blink phase x register bit to 0 or 1 is shown in

Table 12. LEDs can be flipped between either directly on

and off, or between a variety of high/low PWM intensities.

Global/O16 Intensity Control

The 4 bits used for output O16’s PWM individual inten-

sity setting also double as the global intensity control

(Table 13). Global intensity simplifies the PWM settings

when the application requires them all to be the same,

such as for backlight applications, by replacing the 17

individual settings with 1 setting. Global intensity is

enabled with the Global Intensity flag G in the configu-

ration register (Table 4). When global PWM control is

used, the 4 bits of master intensity and 4 bits of global

intensity effectively combine to provide an 8 bit, 240-

step intensity control applying to all outputs.

It is not possible to apply global PWM control to a sub-

set of the ports, and use the others as logic outputs. To

mix static logic outputs and PWM outputs, individual

PWM control must be selected (Table 10).

16-Port I/O Expander with LED Intensity

Control, Interrupt, and Hot-Insertion Protection

20

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Table 12. PWM Intensity Settings (Blink Enabled)

EXAMPLES OF LED BLINK BEHAVIOR

(LED IS ON WHEN OUTPUT IS LOW)

PWM DUTY CYCLE

OUTPUT BLINK

PHASE X

REGISTER BIT = 0

PWM DUTY CYCLE

OUTPUT BLINK

PHASE X

REGISTER BIT = 1

OUTPUT

(OR

GLOBAL)

INTENSITY

SETTING

LOW

TIME

HIGH

TIME

LOW

TIME

HIGH

TIME

BLINK PHASE 0

REGISTER BIT = 0

BLINK PHASE 1

REGISTER BIT = 1

BLINK PHASE 0

REGISTER BIT = 1

BLINK PHASE 1

REGISTER BIT = 0

0x0

1/16

15/16

15/16

1/16

0x1

2/16

14/16

14/16

2/16

0x2

3/16

13/16

13/16

3/16

0x3

4/16

12/16

12/16

4/16

0x4

5/16

11/16

11/16

5/16

0x5

6/16

10/16

10/16

6/16

0x6

7/16

9/16

9/16

7/16

Phase 0: LED on at low intensity

Phase 1: LED on at high intensity

Phase 0: LED on at high intensity

Phase 1: LED on at low intensity

0x7

8/16

8/16

8/16

8/16

Output is half intensity during both blink phases

0x8

9/16

7/16

7/16

9/16

0x9

10/16

6/16

6/16

10/16

0xA

11/16

5/16

5/16

11/16

0xB

12/16

4/16

4/16

12/16

0xC

13/16

3/16

3/16

13/16

0xD

14/16

2/16

2/16

14/16

0xE

15/16

1/16

1/16

15/16

Phase 0: LED on at high intensity

Phase 1: LED on at low intensity

Phase 0: LED on at low intensity

Phase 1: LED on at high intensity

0xF

Static low

Static low

Static high

impedance

Static high

impedance

Phase 0: LED on continuously

Phase 1: LED off continuously

Phase 0: LED off continuously

Phase 1: LED on continuously