IC-HT datasheet(33/45 Pages) ICHAUS

33 / 45 page

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iC-HT

DUAL CW LASER DIODE DRIVER

Rev B1, Page 33/45

TEMPERATURE MONITOR AND PROTECTION

iC-HT includes an 8 bit temperature monitor that al-

lows to measure the internal chip temperature going

from -40 °C to 125 °C. The resolution is 1 °C/LSB. The

internal temperature can be obtained by reading TEMP

TEMP

Addr. 0x02; bit 7:0

0x00

Minimum temperature

. . .

0xFF

Maximum temperature

Table 64: Chip temperature

Absolute read values may differ from one chip to an-

other. An individual initial calibration of the temper-

ature monitor is recommended. The TEMP register

must be read at a known temperature. Using the reso-

lution value of 1 °C/LSB, the internal temperature can

be calculated.

The temperature monitor can be used to compensate

temperature effects on the laser diode. The microcon-

troller can use a laser diode characteristic formula or

a look-up table combined with the temperature value

measured through TEMP register. The reference volt-

age can be conﬁgured accordingly in order to compen-

sate temperature effects.

iC-HT is protected against overtemperature.

In iC-

WK mode, if the internal temperature value exceeds

the overtemperature threshold an OVT error event will

be triggered and signaled through pin NCHK. Both

laser channels will be disabled. Pin NCHK will keep

signaling the error although the internal temperature

goes down to a safe value below the overtemperature

threshold value. If the temperature has exceeded the

overtemperature threshold value, pins EC1 and EC2

have to be pulled lo in order to stop signaling the error.

Setting pin ECx back hi will re-enable the correspond-

ing channel.

In microcontroller mode, if the internal temperature

exceeds a safety value an overtemperature error bit

(OVT) will be set to 1. If OVT = 1, both channels will be

disabled and the error event will be signaled through

NCHK pin. If the internal temperature goes down to a

safe value below the overtemperature threshold value,

OVT will remain at value 1. Reading the OVT bit stop

signaling error through pin NCHK. Reading OVT bit will

set it back to 0. Setting ECx pin lo and then back hi will

allow re-enabling the corresponding channel.

The overtemperature threshold value can not be con-

ﬁgured.

OVT

Addr. 0x00; bit 3

No overtemperature event has occurred since last

read

Overtemperature event has occurred. Cleared on

read

Table 65: Overtemperature detection

In microcontroller mode it is possible to simulate an

overtemperature event using SOVT bit. Setting SOVT

to 1, the overtemperature error ﬂag OVT will be set to

1. iC-HT will remain in error state until SOVT is set

back to 0.

SOVT

Addr. 0x1D; bit 4

R/W 0

No overtemperature event is simulated.

Overtemperature event simulated.

Table 66: Simulate overtemperature

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