IC-HT Datasheet, PDF (15/42 Pages) IC-Haus GmbH – DUAL CW LASER DIODE DRIVER

iC-HT
DUAL CW LASER DIODE DRIVER
preliminary
Imon(min)
=
Vref (0x000,max)
Rmda(RMDx =0xFF ,min)
=
0.11
350000
= 0.31 uA
It is not recommended to configure iC-HT to have such
small Imon values, otherwise the leakage current at
MDAx may have an influence (cf. Electrical Charac-
teristics No. 204), especially at high temperatures. To
avoid this, Imon should be much greater than the leak-
age current.
For calculating the maximum value of Imon,
Vref(0x3FF, min value) (cf. Electrical Characteristics
No. 303) and Rmda(RMDx = 0x00, max vaule) (cf.
Electrical Characteristics No. 201) are used. Since
only the 4 MSB from PLR can be accessed at pin
MDAx, the following formula needs to be used for cal-
culating Rmda(RMDx = 0x00, max value):
Rmd
=
Rmd₀(1
+
∆
Rmd (%)
100
)ⁿ
+1
,
n
from
0
to
255
Rmda(RMDx
= 0x00, max)
=
Rmd₀(1
+
∆
Rmd (%)
100
)¹
6
286
=
Rmd₀(1
+
3.3
100
)¹⁶
Rmd₀ = 170Ω
Rev A1, Page 15/42
In each range, the particular overcurrent threshold
value can be set in register ILIMx.
ILIM1
0x00
...
0xFF
Addr. 0x11; bit 7:0
R/W 0xFF
Channel 1 overcurrent threshold set to minimum
current
Channel 1 overcurrent threshold set to
Ilim = (∆I(LDK ) · n), n from 0 to 255
Channel 1 overcurrent threshold set to maximum
current
Table 18: Overcurrent threshold configuration channel
1
ILIM2
0x00
...
0xFF
Addr. 0x16; bit 7:0
R/W 0xFF
Channel 2 overcurrent threshold set to minimum
current
Channel 2 overcurrent threshold set to
Ilim = (∆I(LDK ) · n), n from 0 to 255
Channel 2 overcurrent threshold set to maximum
current
Table 19: Overcurrent threshold configuration channel
2
Therefore:
Imon(max )
=
Vref (0x3FF ,min)
Rmd₀
=
1.00
170
= 5.88 mA
Any other Imon value can be calculated using Rmd for-
mula above. Due to its logarithmic characteristic, the
steps between two consecutive values is kept within
3.3 % typical value.
The programmable overcurrent shutdown can be set
to protect the laser by disabling the channel. The
overcurrent threshold is configurable in two different
ranges. The range is selected through register bit
RACCx. If RACCx = 1, the overcurrent threshold is
in the low range, up to 90 mA. If RACCx = 0, the over-
current threshold is in the high range, up to 750 mA (cf.
Electrical Characteristics No. 107 ).
An overcurrent event can be simulated using SOVCx.
If SOVCx = 1, the corresponding overcurrent error bit
OVCx will be set to 1, the error will be signaled at
NCHK and the corresponding laser channel will be dis-
abled. The overcurrent error will remain forced until
SOVCx = 0.
SOVC1
0
1
Addr. 0x1D; bit 5
R/W 0
No Overcurrent event at channel 1 is simulated.
Overcurrent event at channel 1 simulated.
Table 20: Simulate overcurrent channel 1
SOVC2
0
1
Addr. 0x1D; bit 6
R/W 0
No overcurrent event at channel 2 is simulated.
Overcurrent event at channel 2 simulated.
RACC1
0
1
Addr. 0x1A; bit 0
Current range high for channel 1
Current range low for channel 1
R/W 0
Table 16: RACC1 current range configuration channel
1
RACC2
0
1
Addr. 0x1A; bit 4
Current range high for channel 2
Current range low for channel 2
R/W 0
Table 17: RACC2 current range configuration channel
2
Table 21: Simulate overcurrent channel 2
ACC control mode
In this mode, the laser diode current is controlled and
no monitor diode is required. ACC mode is selected
setting EACCx register bit to 1.
EACC1
0
1
Addr. 0x10; bit 0
APC mode enabled for channel 1
ACC mode enabled for channel 1
R/W 0
Table 22: APC/ACC in channel 1