LP5569 datasheet(30/86 Pages) TI1

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LP5569

SNVSAP8 – JULY 2017

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(1)

This opcode is used with numerical operands.

(2)

This opcode is used with variables.

8.5.2.4 LED Driver Instructions

Table 8. LP5569 LED Driver Instructions

INST.

Bit

[15]

Bit

[14]

Bit

[13]

Bit

[12]

Bit

[11]

Bit

[10]

Bit

[9]

Bit

[8]

Bit

[7]

Bit

[6]

Bit

[5]

Bit

[4]

Bit

[3]

Bit

[2]

Bit

[1]

Bit

[0]

ramp(1)

pre-

scale

step time

sign

no. of increments

ramp(2)

pre-

scale

sign

step time

no. of

increments

set_pwm(1)

PWM value

set_pwm(2)

PWM value

wait

pre-

scale

time

(1)

Compatible with LP5523 and LP55231

8.5.2.4.1

Ramp

This is the instruction useful for smoothly changing from one PWM value into another PWM value on the LED0 to

LED8 outputs — in other words, generating ramps with a negative or positive slope. The LP5569 device allows

the programming of very fast and very slow ramps using only a single instruction. Full ramp 0 to 255 ramp time

ranges from 124 ms to 4 s.

The ramp instruction generates a PWM ramp, using the effective PWM value as a starting value. At each ramp

step the output is incremented or decremented by 1, unless the number of increments is 0. The time span for

one ramp step is defined with the prescale bit [14] and step-time bits [13:9]. The ramp instruction controls the

eight most significant bits (MSB) of the PWM values and the remaining bits are interpolated as ramp mid-values

internally for smoother transition.

Prescale = 0 sets a 0.49-ms cycle time and prescale = 1 sets a 15.6-ms cycle time; so the minimum time span

for one step is 0.49 ms (prescale × step time span = 0.49 ms × 1) and the maximum time span is 15.6 ms × 31 =

484 ms/step. If all the step-time bits [13:9] are set to zero, the output value is incremented or decremented during

one prescale on the whole time cycle.

The number-of-increments value defines how many steps are taken during one ramp instruction: the increment

maximum value is 255, which corresponds to an increment from zero value to the maximum value. If PWM

reaches the minimum or maximum value (0 or 255) during the ramp instruction, the ramp instruction is executed

to the end regardless of saturation. This enables ramp instruction to be used as a combined ramp-and-wait

instruction. Note: the ramp instruction is a wait instruction when the increment bits [7:0] are set to zero.

Programming ramps with variables is very similar to programming ramps with numerical operands. The only

difference is that step time and number of increments are captured from variable registers when the instruction

execution is started. If the variables are updated after starting the instruction execution, it has no effect on

instruction execution. Again, at each ramp step the output is incremented or decremented by one unless the step

time is 0 or the number of increments is 0. The time span for one step is defined with the prescale and step-time

bits. The step time is defined with variable A, B, C, or D. Variable A is set by an I2C write to the engine 1, 2, or 3

variable A register or the ld instruction, variables B and C are set with the ld instruction, and variable D is set by

an I2C write to the variable D register.

Setting the EXP_EN bit of registers 07h–0Fh high or low sets the exponential (1) or linear ramp (0). By using the

exponential ramp setting, the visual effect appears like a linear ramp to the human eye.

Table 9. Ramp Instructions

INST.

Bit

[15]

Bit

[14]

Bit

[13]

Bit

[12]

Bit

[11]

Bit

[10]

Bit

[9]

Bit

[8]

Bit

[7]

Bit

[6]

Bit

[5]

Bit

[4]

Bit

[3]

Bit

[2]

Bit

[1]

Bit

[0]

ramp(1)

pre-

scale

step time

sign

no. of increments

ramp(1)

pre-

scale

sign

step-time

variable

no.-of-

increments

variable

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