IC-HT Datasheet, PDF (16/42 Pages) IC-Haus GmbH – DUAL CW LASER DIODE DRIVER

iC-HT
DUAL CW LASER DIODE DRIVER
preliminary
Rev A1, Page 16/42
EACC2
0
1
Addr. 0x15; bit 0
APC mode enabled for channel 2
ACC mode enabled for channel 2
R/W 0
Table 23: APC/ACC in channel 2
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
In ACC mode the internal programmable logarithmic
monitor resistor (PLR) is not used. Instead the inter-
nal RACCx resistor is used set the current. Figure 5
shows an example of this configuration.
Two different current ranges can be set through regis-
ter bit RACCx, with RACCx = 1 for up to 90 mA and
with RACCx = 0 for up to 750 mA (cf. Electrical Char-
acteristics No. 114).
Table 26: 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 27: Overcurrent threshold configuration channel
2
ACC
DCO
8 Bit
D
A
10 Bit
D
A
10 Bit
A
D
LDK1
VDD
VB
OVC
RACC
+
-
ECIE1
LDK1
..750mA
CI1
CIL1
CI1
..10 nF..
AGND1
MDA1
ADSNF1
EM C
R
8 Bit
0
LASER CHANNEL 1
APC
DISP1
255
PLR1
MRL1
Figure 5: ACC mode simplified
An overcurrent event can be simulated using bit
SOVCx. If SOVCx = 1, the corresponding overcurrent
error bit OVCx will be set to 1, the error will be signaled
through NCHK and the corresponding laser channel
will be disabled. 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 28: 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
Table 24: RACC1 configuration
R/W 0
RACC2
0
1
Addr. 0x1A; bit 4
Current range high for channel 2
Current range low for channel 2
Table 25: RACC2 configuration
R/W 0
In each range, the particular overcurrent threshold
value can be set in register ILIMx.
Table 29: Simulate overcurrent channel 2
In ACC mode, the MDAx pin can be monitored through
a 10 bit A/D converter. This can be used for measur-
ing the laser light power, if a photodiode is connected
to pin MDAx, as it is shown in figure 6. This allows ad-
justing the voltage reference in order to set the laser
current and obtain the desired laser light power.
The internal programmable logarithmic monitor Resis-
tor (PLR), if enabled (DISPx = 0), gives feedback for
the current control through the 10 bit A/D converter.
Register bit ADSNFx must be set to 1 in order to mea-
sure the internal sense node. An external monitor
resistor can be used to measure the optical power,
achieved by setting DISPx to 1. Therefore register bit
ADSNFx must be set to 0 in order to measure directly
at pin MDAx.