LP5569 datasheet(31/86 Pages) TI1

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DIMMING

CONTROL

STEP COUNT

STEP TIME

SPAN =

187.5 ms

TIME ELAPSED (ms)

375

750

1125

1500

140

141

142

143

144

145

146

147

148

RAMP

INSTRUCTION

LP5569

www.ti.com

SNVSAP8 – JULY 2017

Product Folder Links: LP5569

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PARAMETER

NAME

NUMERIC OR

VARIABLE

VALUE (d)

DESCRIPTION

prescale

Numeric

32.7 kHz / 16

≥ 0.488 ms cycle time

32.7 kHz / 512

≥ 15.625 ms cycle time

sign

Numeric

Increase PWM output

Decrease PWM output

step time

Numeric

1–31

One

ramp

increment

done

step

time

prescale

Value in the variable A, B, C, or D must be from 1 to 31 for correct

operation.

Variable

0–3

no. of

increments

Numeric

0–255

The number of ramp cycles. Variables A to D as input.

Variable

0–3

(1)

Valid for numerical operands

(2)

Valid for variables

8.5.2.4.2

Ramp Instruction Application Example

An example of generating a 1.5-s ramp from PWM value 140 (approximately 55%) to 148 (approximately 58%).

The ramp instruction uses relative values, so in this example we must ramp 8 steps up, as shown in Figure 18.

The parameters for the RAMP instruction are:

•

Positive ramp

→ sign = 0 (increase by 1)

•

Step from 140 to 148

→ no. of increments = 8

•

Ramp time 1.5 s

→ 1.5 s / 8 steps = 187.5 ms/step

•

Prescale = 1

→ 15.625 ms cycle time

•

187.5 ms / 15.625 ms = 12

→ step time = 12

Figure 18. Example of Ramp Instruction

8.5.2.4.3

Set_PWM

This instruction is used for setting the PWM value on outputs LED0 to LED8 without any ramps. Set the PWM

output value from 0 to 255 with PWM value bits [7:0]. Instruction execution takes 16 32-kHz clock cycles

(= 488 µs).

NAME

VALUE (d)

DESCRIPTION

PWM value(1)

0–255

PWM output duty cycle 0–100%

variable(2)

0–3

0 = local variable A

1 = local variable B

2 = global variable C

3 = global variable D

8.5.2.4.4

Wait

When a wait instruction is executed, the engine is set in wait status, and the PWM values on the outputs are

frozen. Note: A wait instruction with prescale and time = 0 is invalid and is executed as rst.

LP5569 Datasheet(PDF) 31 Page - Texas Instruments

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