IC-HT_15 Datasheet, PDF (33/45 Pages) IC-Haus GmbH – DUAL CW LASER DIODE DRIVER

iC-HT
DUAL CW LASER DIODE DRIVER
TEMPERATURE MONITOR AND PROTECTION
preliminary
Rev B1, Page 33/45
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
register. The TEMP register is a read-only register.
TEMP
Addr. 0x02; bit 7:0
R
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
0
1
Addr. 0x00; bit 3
R
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
0
1
Addr. 0x1D; bit 4
No overtemperature event is simulated.
Overtemperature event simulated.
R/W 0
Table 66: Simulate overtemperature