IC-LO datasheet(13/25 Pages) ICHAUS

13 / 25 page

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iC-LO

TRIANGULATION SENSOR

Rev B3, Page 13/25

The effect of the individual parameters is shown in fig-

ure 2.

I(LCC)

t(PW)

1/freq(PER)

Figure 2: Light pulse

NEAR/FAR CHANNEL PARTITION AND AMPLIFICATION

The typical spectral sensitivity is shown in figure 3.

Wave Length [nm]

Figure 3: Spectral sensitivity of the photodiode

The diode array is partitioned into two channels (one

near and one far channel). The channelwise received

photocurrents are added, converted to voltages and

amplified. Afterwards a differential comparator decides

whether the signal of the near or far channel is greater.

A greater signal in the near channel indicates an object

within the defined near range and the switching output

is activated.

Current/voltage conversion

The transimpedance of the current/voltage conversion

can be configured according to the expected photocur-

rents. In the static transimpedance setting modes

this configuration is not altered by iC-LO. If the tran-

simpedance amplifier exceeds a high set point it contin-

ues with a logarithmic characteristic. In the logarithmic

range the parametrized switching point can shift if the

digital potentiometer is used (table 13). iC-LO thus has

an automatic mode which selects the transimpedance

depending on the received sum light current. The tran-

simpedance set in the automatic modes represents the

start value in operating mode STARTUP/RESET. Two

comparators monitor the sum light current and switch

up or down one transimpedance step when the fixed

thresholds are either overshot or undershot. If the tran-

simpedance setting is to be changed during operation,

after programming the device must be reset (operating

mode STARTUP/RESET).

TIM

Addr. 0x04; bit 7:5

Code

Mode

R Tran-

simpedance

Rac

Transimpedance

0x0

static

50 kΩ

112.5 kΩ

0x1

static

7765 Ω

17.5 kΩ

0x2

static

600 Ω

1350 Ω

0x3

static

45 Ω

101 Ω

0x4

auto

50 kΩ

112.5 kΩ

0x5

auto

7765 Ω

17.5 kΩ

0x6

auto

600 Ω

1350 Ω

0x7

auto

45 Ω

101 Ω

Table 11: Transimpedance Mode

Channel partitioning

The block diagram on page 1 depicts the signal chain.

There are two ways in which the differential comparator

input signals and thus the necessary sensing distance

can be configured in iC-LO. The two setting parameters

are implemented in two sets of parameters twice. One

of these sets of parameters is active when the switching

state is off - i.e. the object was in the far range during

the last measurement (parameter set OBF). The other

is used in switching state on (parameter set OBN). De-

pending on the difference of the switching points of the

two sets of parameters, a freely selectable switching

hysteresis can be set.

Setting parameters for the near/far channel Diodes

are partitioned to the near and far channels using pa-

rameters SPF and SPN. SPF belongs to parameter set

OBF and SPN to parameter set OBN. Diodes from 0

(near diode) to the set value are assigned to the near

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