LED1642GW datasheet(24/42 Pages) STMICROELECTRONICS

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Configuration register

LED1642GW

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DocID024395 Rev 6

8.3

Error detection conditions

During the error detection phases for each channel, the following checks have to be

performed:

–

The output current in open detection mode (digital key: 9 CLK rising edges when

LE is "1")

–

The output voltage in short detection (digital key: 10 CLK rising edges when LE is

"1")

–

Both parameters (output voltage and current) in combined error detection mode

(digital key: 11 CLK rising edges when LE is "1").

The thresholds for the error diagnostics are listed in Table 11:

8.4

Auto-wakeup/auto power shutdown (CFG-10)

This feature reduces the power consumption when all outputs are OFF. It is active when the

CFG -10 bit of configuration register is "1". The auto power shutdown (auto OFF) starts

when the data latched is "0" for all channels, and device is active again (wakeup) at the first

latched data string including at least one bit = "1" (at least one channel ON). Timings for

shutdown and wakeup are present in the dynamics feature table. While the auto power

shutdown is active, the device ignores any other command except the channel power-on.

8.5

Programmable turn-on/turn-off time (CFG-11/12)

The device gives the possibility to program the turn-on and turn-off time of the current

generators. Four different values can be selected using CFG -12 and CFG-11 bits of the

configuration register (see Table 8) to fit the application requirements: 30/20 ns (00), 100/40

ns (01), 140/80 ns (10) and 180/150 ns (11). The selected value refers to TON (current rise

time) and TOFF (current fall time).

Table 11. Diagnostic thresholds

Error detection

modes

Checked

malfunction

CFG-9

CFG-8

Thresholds (V)

Min.

Typ.

Max.

Open

detection

Open line or output

short to GND

IOUT ≤ 0.5 x IOUT

programmed

Short

detection

Short on LED or short

to V-LED

1.15

VOUT ≥ 1.8

2.05

2.25

VOUT ≥ 2.5

2.75

VOUT ≥ 3.0

3.25

VOUT ≥ 3.5

3.80

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