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KTZ8866

January 2022 - Revision 04b

Page 18 of 37

Company Confidential

When PWM dimming is enabled and a non-zero PWM duty cycle is detected, the KTZ8866 multiplies the duty

cycle with I2C brightness settings. Figure 2 and Figure 3 describe the start-up timing for operation with I2C

controlled current and with PWM controlled current.

I2C Registers in

Reset

I2C Data Valid

I2C Brightness Data

Sent

I2C LED String

Enable

TI2C_RESET

VIN

HWEN

I2C

ILED

Figure 2. Enable of KTZ8866 via I2C

I2C Registers in

Reset

I2C Data Valid

I2C PWM Dimming

Enable

I2C LED String

Enable

TI2C_RESET

VIN

HWEN

I2C

ILED

PWM

TPWM_STBY

Figure 3. Enable of KTZ8866 via PWM

Operating Mode Description

The KTZ8866 backlight can operate in different modes, see Table 1 below

Table 1. Backlight Operating Modes

HWEN

BL_EN

0x08[6]

PWM

INPUT

I

2C

BRIGHTNESS

0X05[7:0]

0X04[2:0]

CURRENT

SINKs

ENABLEs

0x08[5:0]

PWM_EN

0x02[0]

FEEDBACK

DISABLEs

0x10[6:1]

MAPPING MODE

0x02[3]

ACTION

0

X

X

X

X

X

X

X

Shutdown

1

0

X

X

X

X

X

X

Standby7

1

1

X

0x000

000000

X

X

X

Standby7

1

1

X

≥0x001

≥000001

0

<111111

0 = Exp. Mode

1 = Lin. Mode

-Backlight boost enabled

-Selected current sink(s) enabled

-I2C control only

1

1

Duty = 0

X

≥000001

1

<111111

X

Standby7

1

1

Duty > 0

≥0x001

≥000001

1

<111111

0 = Exp. Mode

1 = Lin. Mode

-Backlight boost enabled

-Selected current sink(s) enabled

-I2C × PWM control

1

1

Duty > 0

≥0x001

≥000001

1

111111

0 = Exp. Mode

1 = Lin. Mode

-Backlight boost disabled

-Selected current sink(s) enabled

-I2C × PWM control

7. Standby signifies that the backlight boost and current sinks are shut down. Register writes are still possible. Shutdown signifies that that

the device was reset and no I2C communication is accepted.