Command

entering

period

Blank

period

Command

execution

starts

CTRL

LED

9

LP5560

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SNVS873D – AUGUST 2012 – REVISED JUNE 2016

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7.3 Feature Description

7.3.1 LED Driver Headroom Voltage

The current source is connected internally between the VDD and LED output pins. The voltage across the

amount of headroom voltage to be present across it in order to regulate the output current properly. The LP5560

headroom voltage requirement is 40 mV (typical) and does not depend on the current setting.

7.3.2 Single-Wire Interface

The LP5560 has one digital control input (CTRL). Threshold levels of CTRL input are fixed to support control

from low-voltage controller. The CTRL signal is used to control the mode of the circuit. The rising edge of the

CTRL signal activates the circuit and starts a command entering period. During the command entering period all

rising edges are counted. After command entering period there is a blank period when no rising edges are

allowed. If there are any rising edges during blank period these are not detected. User must take care not to start

the training sequence before blank period has elapsed or the training sequence is corrupted.

If CTRL is left high after command entering period, the consequent command is performed right after the blank

period. In case of run once command CTRL pin can be set low after the command entering period and execution

of the command starts once CTRL pin is pulled high after blank period.

Figure 8. Single-Wire Interface

The LP5560 has four different commands. Command depends on the number of rising edges during command

entering period. If there are more than 4 rising edges during command entering period command is ignored. Note

that even in this case blank period needs to elapse before next command can be given.

Table 1. LP5560 Commands

COMMAND

NUMBER OF RISING EDGES DURING COMMAND

ENTERING PERIOD

Run

1

Training start

2

Training end

3

Run once

4