IC-HT Datasheet, PDF (23/42 Pages) IC-Haus GmbH – DUAL CW LASER DIODE DRIVER

iC-HT
DUAL CW LASER DIODE DRIVER
preliminary
8 BIT INTERNAL PROGRAMMABLE LOGARITHMIC MONITOR RESISTORS
Rev A1, Page 23/42
In MCU mode internal 8 bit programmable logarithmic
monitor resistors (PLRx) are provided for APC.
The resistor value can be selected from 256 values,
ranging from 100 Ω to 500 kΩ, following logarithmic in-
crements with a typical step width of 3.3%. The resis-
tors are configured with registers RMDx(7:0).
RMD1
0x00
...
0xFF
Addr. 0x12; bit 7:0
R/W 0xFF
PLR1 set to the minimum resistance
PLR1 set to
Rmd
=
Rmd₀(1
+
∆
Rmd (%)
100
)ⁿ
+
1
,
n
from
0
to
255
PLR1 resistor set to the maximum resistance
Table 45: MDA resistor channel 1
DISP1
0
1
DISP2
0
1
Addr. 0x10; bit 2
PLR enabled for channel 1
PLR disabled for channel 1
Table 47: Disable PLR channel 1
R/W 0
Addr. 0x15; bit 2
PLR enabled for channel 2
PLR disabled for channel 2
R/W 0
Table 48: Disable PLR channel 2
RMD2
0x00
...
0xFF
Addr. 0x17; bit 7:0
R/W 0xFF
PLR2 resistor set to the minimum resistance
PLR2 set to
Rmd
=
Rmd₀(1
+
∆
Rmd (%)
100
)ⁿ
+
1
,
n
from
0
to
255
PLR2 resistor set to the maximum resistance
Table 46: MDA resistor channel 2
The following formular calculates the register RMDx in
order to set the desired resistor value:
Rmd
=
Rmd₀(1
+
∆
Rmd (%)
100
)ⁿ
+1
,
n
from
0
to
255
DCO
8 Bit
D
A
10 Bit
D
+
A
-
10 Bit
A
D
LDK1
VDD
VB
ADSNF1
EM C
R
8 Bit
0
255
LASER CHANNEL 1
ECIE1
LDK1
N
..750mA
CI1
CIL1
CI1
..10 nF..
AGND1
MDA1
APC
DISP1
PLR1
MRL1
Where Rmd₀ is the minimum resistor value (typically
100 Ω), ∆ Rmd(%) is the step between two consecu-
tive resistor values (typically 3.3%) and n is the value
of RMDx register in decimal.
Figure 12: PLR in APC
In APC mode the regulation node is the internal con-
nection to PLR, it is not MDAx pin. Voltage present at
pin MDAx may differ from the internal regulation node.
This regulation node can be sensed through the 10 bit
A/D converter and read at register ADCx. Register bit
ADSNFx must be set to 1 for this purpose. If ADSNFx
is set to 0, MDAx pin will be the input of the A/D con-
verter.
At pin MDAx only the 4 MSB of the RMDx configu-
ration from PLRx are measurable. The 8 bits of the
PLRx configuration RMDx can be measured with the
A/D converter setting ADSNFx to 1.
The PLRx can be disabled using register bit DISPx.
With DISPx = 0 the PLRx is enabled and DISPx = 1
disables the PLRx.
In ACC mode the PLR is not used in the control cir-
cuit. Instead, the internal RACCx resistor is used in
the control loop.
Even though the PLR is not in the control circuit, it
can be enabled (DISPx = 0) in order to give feedback
through the 10 bit A/D converter for the controlling light
power if a monitor diode is connected.
Register bit ADSNF is set to 1 to measure the internal
sense node. Alternatively, an external monitor resistor
can be used to measure the optical power, by setting
DISPx to 1. Then register bit ADSNF must be set to 0
in order to measure directly at pin MDAx.