IC-HT_15 Datasheet, PDF (29/45 Pages) IC-Haus GmbH – DUAL CW LASER DIODE DRIVER

iC-HT
DUAL CW LASER DIODE DRIVER
preliminary
Rev B1, Page 29/45
The value in RDCO register needed in order to have
the desired output voltage can be calculated using the
following formula:
RDCO = = = ^Idco
2uA
IR2−IR1
2uA
0.5
6.7k
−
Vout −0.5
100k
2uA
The resulting value will vary slightly depending on the
tolerances of the selected resistors and DCO current.
The voltage is reduced from 8 V (RDCO = 0) to 2.5 V,
when RDCO = 27.
DC/DC step up operation: regulation at voltages
higher than power supply
A practical application of the present case is the con-
trol of blue lasers. This type of laser present a forward
voltage around 5 V, which demands an LDA voltage of
about 6 V. If the system is supplied with a 3 V LiPo bat-
tery, it is necessary to use a the DC/DC in order to step
up and drive the laser diode and driver with a sufficient
voltage. Figure 18 shows this application:
VB
3V
CVB
1μF
CVDD
1μF
GND
C3
2x10μF
C1
0.1μF
L1
1μH
L1
TPS63060
VIN
EN
VAUX
L2
VOUT
FB
PS/SYNC
GND
PG
PGND
6V
R1
100k
R3
1MEG
R2
6.7k
20μA
DUAL CW LASER DIODE DRIVER
VDD REGULATOR
VB
- ^REF
VDD
+
NCHK
EMC
NCS/A1
MOSI/A0
SCLK/SCL
MISO/SDA
INS/WKR
NSTBY
EC1
EC2
T.PAD
GND
VB UNDERVOLTAGE
VDD UNDERVOLTAGE
CFGTIMO
Check
PODO
OVC
MEMERR
WATCHDOG
OVT
IO DRIVERS
TEMPERATURE
MONITOR 8 Bit
RAM
INTEGRITY
CHECK
0x10 0x30
0x1F 0x3F
RAM
REGISTERS
0x11 ILIM1(7:0)
0x13
0x14
REF1(9:8)
REF1(7:0)
WATCHDOG
TIMER
OSCILLATOR
0x03
0x04
ADC1(9:8)
ADC1(7:0)
0x10 ADCC1(2:0)
SPI/I2C
SLAVE
0x12 RMD1(7:0)
LASER
CONTROL
0x05
0x06
ADC2(9:8)
ADC2(7:0)
0x16 ILIM2(7:0)
0x18
0x19
REF2(9:8)
REF2(7:0)
0x17 RMD2(7:0)
0x02 TEMP(7:0)
ACC
8 Bit
D
A
10 Bit
D
A
10 Bit
A
D
LDK1
VDD
VB
OVC1
+
-
ADSNF1
EM C
R
8 Bit
DISP1
0
255
LASER CHANNEL 1
DCO
LDK1
ECIE1
CI
CI1
CIL1
AGND1
MDA1
APC
PLR1
MRL1
LDK2
CI2
CIL2
AGND2
MDA2
LASER CHANNEL 2
MRL2
C2
3x22μF
N
Figure 18: Regulation at voltage greater than power supply
Setting register RDCO to 10 it delivers 20 µA and 6 V
are obtained at Vout.
Extension of system working voltage range
iC-HT must be supplied by a voltage within the thresh-
old values of 2.8 V and 8 V. It is possible to control the
DC/DC output in a voltage range of 2.5 V - 12 V if the
DC/DC converter, controlled by DCO output signal, is
included in the system, as it is shown in figure 19: