IC-HT_15 Datasheet, PDF (17/45 Pages) IC-Haus GmbH – DUAL CW LASER DIODE DRIVER

iC-HT
DUAL CW LASER DIODE DRIVER
preliminary
Rev B1, Page 17/45
ACC (Automatic Current 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
Table 22: APC/ACC in channel 1
R/W 0
EACC2
0
1
Addr. 0x15; bit 0
APC mode enabled for channel 2
ACC mode enabled for channel 2
Table 23: APC/ACC in channel 2
R/W 0
In ACC mode the internal programmable logarithmic
monitor resistor (PLR) is not used. Instead the inter-
nal RACCx resistor is used to set the current. For
fine-tuning the regulated current, the reference volt-
age can be set with a 10 bit logarithmic D/A converter,
which is configurable through the register REFx. This
converter has a voltage range that goes typically from
0.1 V to 1.1 V, allowing an operation resolution of typi-
cally 0.235%. More information on the logarithmic D/A
converter can be found on page 26. Figure 8 shows an
example of this configuration.
Two different current ranges can be set through reg-
ister bit RACCx, with RACCx = 1 for up to 75 mA and
with RACCx = 0 for up to 650 mA. The programmable
overcurrent shutdown protects against over regula-
tions during the laser power-on. Table 44 shows some
typical current settings. For detailed limits, please refer
to Electrical Characteristics No. 114
ACC typical current settings
REFx
RACCx=0 RACCx=1
0x000
77.0 mA 9.06 mA
0x001
77.2 mA 9.08 mA
0x010
77.4 mA 9.10 mA
...
...
...
0x200
256.2 mA 30.14 mA
0x201
256.8 mA 30.21 mA
0x202
257.4 mA 30.28 mA
...
...
...
0x3FD 846.0 mA 99.53 mA
0x3FE 848.0 mA 99.77 mA
0x3FF 850.0 mA 100 mA
Table 24: ACC typical current settings
ACC
DCO
8 Bit
D
A
OVC
RACC
LDK1
10 Bit
D
+
A
-
10 Bit
A
D
LDK1
VDD
VB
ECIE1
CI1
CIL1
AGND1
MDA1
ADSNF1
EM C
R
8 Bit
0
LASER CHANNEL 1
APC
DISP1
255
PLR1
MRL1
I LDK
CI1
..10 nF..
Figure 8: ACC mode simplified
RACC1
0
1
Addr. 0x1A; bit 0
Current range high for channel 1
Current range low for channel 1
Table 25: 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 26: RACC2 configuration
R/W 0
In each range, the particular overcurrent threshold
value can be set in register ILIMx. The regulator does
differ the two current ranges in ACC.
ILIM1
0x0A
...
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 10 to 255
Channel 1 overcurrent threshold set to maximum
current
Table 27: Overcurrent threshold configuration channel
1
ILIM2
0x0A
...
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 10 to 255
Channel 2 overcurrent threshold set to maximum
current
Table 28: Overcurrent threshold configuration channel
2
An overcurrent event can be simulated using bit
SOVCx. If SOVCx = 1, the corresponding overcurrent