ICHAUS IC

iC-WJ, iC-WJZ
LASER DIODE DRIVER
Rev C1, Page 1/12
FEATURES
APPLICATIONS
♦ Laser diode driver for continuous and pulsed operation (CW to
300 kHz) up to 250 mA
♦ Averaging control of laser power
♦ Simple adjustment of the laser power via external resistor
♦ Adjustable watchdog at the switching input to protect the laser
diode
♦ Soft-start after power-on
♦ Driver shutdown with overtemperature and undervoltage
♦ Single 5 V supply
♦ Simple circuitry
♦ iC-WJ for laser diodes with 50 to 500 µA monitor current
♦ iC-WJZ for laser diodes with 0.15 to 1.5 mA monitor current
♦ General purpose laser diode
driver
PACKAGES
SO8
MSOP8
BLOCK DIAGRAM
DRIVER STAGE
3
REF
VCC
5
+5 V
C1
1
100 µF
REFERENCE
C3
THERMAL
ISET
RSET
10 kΩ
2 nF
SHUTDOWN
KLD
4
6
INPUT
VCC
IN
8
LD MD
R1
12Ω
POWER DOWN
REF
AMD
7
74HCxx
2
4
1:1 iC−WJ
1:3 iC−WJZ
WATCHDOG
iC−WJ/WJZ
CWD
2
CWD
CI
3
GND
1
CI
100 nF..470 nF
usable LD models
Copyright © 2006 iC-Haus
http://www.ichaus.com
iC-WJ, iC-WJZ
LASER DIODE DRIVER
Rev C1, Page 2/12
DESCRIPTION
The iC-WJ and iC-WJZ devices are driver ICs for
laser diodes in continuous and pulsed operation up
to 300 kHz. The laser diode is activated via switching
input IN. A control to the mean value of the optical
laser power and integrated protective functions ensure nondestructive operation of the sensitive semiconductor laser.
The IC contains protective diodes to prevent destruction due to ESD, a protective circuit to guard against
overtemperature and undervoltage and a soft-start
for the laser diode driver to protect the laser diode
when switching on the supply voltage.
An external resistor at ISET is utilised to adapt the
power control to the laser diode being used. The capacitor at CI determines the recovery time constants
and the start-up time.
A watchdog circuit monitors the switching input IN.
If IN remains low longer than preset by the capacitor at CWD, the capacitor of the power control is
discharged at pin CI. This ensures that the current
through the laser diode during the next high pulse at
input IN is not impermissibly high.
PACKAGES SO8, MSOP8 to JEDEC Standard
PIN CONFIGURATION SO8
(top view)
PIN FUNCTIONS
No. Name Function
8
1
KLD
GND
2
7
AMD
CWD
CI
4
ISET
WJ
Code...
...yymm
3
6
IN
5
VCC
PIN CONFIGURATION MSOP8
(top view)
1
CWD
CI
ISET
iC−WJ
Code
GND
KLD
AMD
IN
VCC
1
2
3
4
5
6
7
8
GND
CWD
CI
ISET
VCC
IN
AMD
KLD
Ground
Capacitor for Watchdog
Capacitor for Power Control
Attachment for RSET
5 V Supply Voltage
Input
Anode Monitor Diode
Cathode Laser Diode
iC-WJ, iC-WJZ
LASER DIODE DRIVER
Rev C1, Page 3/12
ABSOLUTE MAXIMUM RATINGS
Beyond these values damage may occur; device operation is not guaranteed.
Item
No.
Symbol
Parameter
Conditions
Fig.
Unit
Min.
Max.
G001 VCC
Supply Voltage
0
6
V
G002 I(CI)
Current in CI
-4
4
mA
G003 V(KLD)
Voltage at KLD
IN = lo
0
6
V
G004 I(KLD)
G005 I(AMD)
Current in KLD
IN = hi
-4
600
mA
Current in AMD
iC-WJ
iC-WJZ
-4
-6
4
6
mA
mA
G006 I(IN)
Current in IN
-10
2
mA
G007 I(ISET)
Current in ISET
-2
2
mA
G008 I(CWD)
Current in CWD
IN = lo
-2
2
mA
G009 Vd()
ESD Susceptibility at CWD, CI, ISET,
IN, AMD, KLD
MIL-STD-883, HBM 100 pF discharged
through 1.5 kΩ
1.5
kV
G010 Tj
Junction Temperature
-40
150
°C
G011 Ts
Storage Temperature
-40
150
°C
THERMAL DATA
Operating Conditions: VCC = 5 V ±10 %
Item
No.
Symbol
Parameter
Conditions
Fig.
Unit
Min.
T01
Ta
Operating Ambient Temperature Range
(extended temperature range on
request)
T02
Rthja
Thermal Resistance Chip to Ambient
-25
surface mounted on PCB, without
special cooling
All voltages are referenced to ground unless otherwise stated.
All currents into the device pins are positive; all currents out of the device pins are negative.
Typ.
Max.
90
°C
140
K/W
iC-WJ, iC-WJZ
LASER DIODE DRIVER
Rev C1, Page 4/12
ELECTRICAL CHARACTERISTICS
Operating Conditions: VCC = 5 V ±10 %, RSET = 2.7...27 kΩ,
iC-WJ: I(AMD) = 50...500 µA, iC-WJZ: I(AMD) = 0.15...1.5 mA, Tj = -25...125 °C, unless otherwise noted.
Item
No.
Symbol
Parameter
Conditions
Tj
°C
Fig.
Unit
Min.
Typ.
Max.
Total Device
001
VCC
Permissible Supply Voltage
Range
4.5
002
Iav(VCC)
Supply Current in VCC (average Iav(KLD) = 100 mA,
value)
f(IN) = 200 kHz ±20 %
003
tp(IN-KLD) Delay Time Pulse Edge V(IN) to
I(KLD)
IN(hi ↔ lo), V(50 %) : I(50 %)
004
Vc()lo
Clamp Voltage lo at VCC, IN,
AMD, KLD, CI, CWD, ISET
I() = -2 mA, other pins open
005
Vc()hi
Clamp Voltage hi at IN, AMD,
KLD, GND, CI, CWD, ISET
Vc()hi = V() − VCC; I() = 2 mA,
other pins open
101
Vs(KLD)
Saturation Voltage at KLD
IN = hi, I(KLD) = 200 mA
102
103
I0(KLD)
Leakage Current in KLD
IN = lo, V(KLD) = VCC
I(KLD)
Current in KLD
IN = hi, I(AMD) = 0
104
V(AMD)
Voltage at AMD
iC-WJ: I(AMD) = 500 µA
iC-WJZ: I(AMD) = 1.5 mA
105
tr
Current Rise Time in KLD
106
tf
107
CR1()
5.5
V
15
mA
135
ns
-1.5
-0.3
V
0.3
1.5
V
1.3
V
Driver
108
CR2()
Input IN
201 Vt()hi
10
-25
27
70
125
225
250
250
250
Vt()lo
V
V
Imax(KLD) = 20...250 mA,
Ip(): 10 → 90 %
100
ns
Current Fall Time in KLD
Imax(KLD) = 20...250 mA,
Ip(): 90 % → 10 %
100
ns
Current Ratio I(AMD) / I(ISET)
I(CI) = 0, closed control loop;
iC-WJ
iC-WJZ
0.8
2.4
1
3
1.2
3.6
V(CI) = 1...3.5 V, ISET open;
iC-WJ
iC-WJZ
0.9
2.7
1
3
1.1
3.3
Threshold hi
1.60
Threshold lo
Vt()hys
1.50
Hysteresis
10
Rin
Pull-Down Resistor
V(IN) = -0.3...VCC + 0.3 V
205
206
V0()
Open-loop Voltage
I(IN) = 0
Vtwd()
Threshold for Watchdog
Reference und Thermal Shutdown
301 V(ISET)
Voltage at ISET
2.4
2.0
1.5
1.0
1.17
27
302
CR()
Current Ratio I(CI) / I(ISET)
V(CI) = 1...3.5 V, I(AMD) = 0
2.20
V
V
V
V
V
190
mV
mV
mV
mV
mV
80
90
90
100
4
-25
27
70
125
V
V
V
V
V
1.76
1.78
1.79
1.81
-25
27
70
125
204
2.40
1.84
1.87
1.88
1.91
-25
27
70
125
203
µA
mA
mA
mA
mA
1.5
1.5
Current Ratio I(AMD) / I(CI)
0.5
0.4
-25
27
70
125
202
250
16
kΩ
0.1
V
3.2
2.8
2.3
1.8
V
V
V
V
1.28
V
V
1.22
0.9
1
1.1
iC-WJ, iC-WJZ
LASER DIODE DRIVER
Rev C1, Page 5/12
ELECTRICAL CHARACTERISTICS
Operating Conditions: VCC = 5 V ±10 %, RSET = 2.7...27 kΩ,
iC-WJ: I(AMD) = 50...500 µA, iC-WJZ: I(AMD) = 0.15...1.5 mA, Tj = -25...125 °C, unless otherwise noted.
Item
No.
Symbol
Parameter
Conditions
Tj
°C
Fig.
Unit
Min.
Max.
303
RSET
Permissible Resistor at ISET
(Control Set-up Range)
2.7
50
kΩ
304
Toff
Thermal Shutdown Threshold
125
150
°C
305
Thys
Thermal Shutdown Hysteresis
10
40
°C
4.3
V
V
Power-Down and Watchdog
401 VCCon
Turn-on Threshold VCC
3.5
27
402
403
VCCoff
Undervoltage Threshold at VCC
VCChys
Hysteresis
VCChys = VCCon − VCCoff
3.8
3.2
3.8
V
300
450
mV
mV
27
(*)
Typ.
400
404
Vs(CI)off
Saturation Voltage at CI with
undervoltage
I(CI) = 300 µA, VCC < VCCoff
1.6
V
405
Vs(CI)wd
Saturation Voltage at CI with
IN = lo
I(CI) = 300 µA, t(IN = lo) > tp (*)
1.5
V
406
Ipu(CWD)
Pull-Up Current at CWD
V(CWD) = 0, IN = lo
-15
-3
µA
407
tpmin
Min. Activation Time for
Watchdog
IN = lo, CWD open
10
45
µs
408
Kwd (*)
Constant for Calculating the
Watchdog Activation Time
IN = lo
0.57
µs/pF
tp = (C(CWD) ∗ Kwd) + tpmin
(see Applications Information)
0.19
0.38
iC-WJ, iC-WJZ
LASER DIODE DRIVER
Rev C1, Page 6/12
APPLICATIONS INFORMATION
Laser Power Adjustment
The iC-WJ and iC-WJZ devices can be adapted to CW
laser diodes from approximately 2 to 40 mW. N- and
M-type models can be used.
The pin ISET is used for the adjustment to the sensitivity of the monitor diode and to set the desired optical
laser power. The setpoint for the averaging control of
the monitor diode current is preset at this pin.
VCC
DRIVER
3
REF
+5 V
5
C1
100 uF
1
REFERENCE
C3
2 nF
THERMAL
4 ISET
SHUTDOWN
KLD
MD
8
RSET
LD
R1
12 Ω
VCC
INPUT
6 IN
POWER DOWN
REF
AMD
7
74HCxx
2
4
1:1 iC−WJ
1:3 iC−WJZ
WATCHDOG
iC−WJ/WJZ
CWD
CI
GND
2
3
1
CI
470 nF
Figure 1: Operation of a laser diode according to the example
To calculate the current required at ISET, the average
optical laser power is to determine:
Pav
Example iC-WJ
Laser diode with 5 mW maximum optical output, monitor diode with 0.13 mA/mW, pulse duty factor set to
20 % with Ppeak = 5 mW:
The resulting average optical power is 1 mW and the
average monitor diode current is 0.13 mA. The resistor
RSET is calculated as:
t
= Ppeak ∗ whi
T
RSET =
CR1 ∗ V (ISET ) 1 ∗ 1.22 V
=
= 9.4 k Ω
Iav (AMD)
0.13 mA
with peak value Ppeak and pulse/period duration
twhi /T .
twlo
T
Figure 2: Duty cycle
Ppeak
twhi
with the Electrical Characteristics No. 301 for V(ISET)
and No. 108 for current ratio CR1.
Example iC-WJZ
Laser diode with 5 mW maximum optical output, monitor diode with 0.75 mA at 3 mW, CW operation (pulse
duty factor 100 %) with Pcw = 1 mW:
iC-WJ, iC-WJZ
LASER DIODE DRIVER
Rev C1, Page 7/12
For the monitor diode current of 0.25 mA the resistor
RSET is calculated as:
RSET =
CR1 ∗ V (ISET ) 3 ∗ 1.22 V
=
= 14.6 k Ω
Iav (AMD)
0.25 mA
with Electrical Characteristics No. 301 for V(ISET) and
No. 108 (iC-WJZ) for current ratio CR1.
Averaging control
The control of the average optical laser power requires
a capacitor at pin CI. This capacitor is used for averaging and must be adjusted to the selected pulse repetition frequency and the charging current preset with
RSET. The ratios are linear in both cases, i.e. the capacitor CI must be increased in size proportionally as
the pulse repetition frequency slows or the current from
ISET increases:
Figure 4 shows the corresponding signals for a pulse
duty factor of 20 %. The influence of the pulse duty
factor on the peak value of the monitor current proportional to the laser current is apparent. The average
kept constant by the control (RSET unchanged) means
a peak value increased by the factor 2.5. The pulse
duty factor for which RSET was dimensioned should
therefore be kept constant if possible.
5.0 V
V(IN)
0V
3.120 V
V(CI)
3.118 V
600 uA
I(AMD)
440 ∗ I(ISET )
440
CI ≥
=
f ∗ V (ISET )
f ∗ RSET
0A
Example
Pulse repetition frequency 100 kHz, RSET = 10 kΩ:
CI = 440 nF, chosen 470 nF.
Otherwise the charging of the capacitor CI during the
pulse pauses (with I(ISET) = 1.22 V / RSET) will create
an excessive mean value potential and may destroy
the laser diode during the next pulse. The capacitor CI
is correctly dimensioned when the current through the
laser diode and the optical output signal do not show
any overshots following the rising edge.
Time
Figure 4: Steady-state averaging, f(IN) = 100 kHz
(1:4), CI = 470 nF, RSET = 10 kΩ
3.0 V
2.0 V
V(CI)
1.0 V
0V
I(KLD)
5.0 V
V(IN)
0A
0s
0V
2.552 V
2 ms
4 ms
6 ms
8 ms
10 ms
12 ms
Figure 5: Turn-on behavior, f(IN) = 100 kHz (1:1), CI
= 470 nF, RSET = 10 kΩ
V(CI)
2.550 V
250 uA
0A
I(AMD)
Time
Figure 3: Steady-state averaging control, f(IN) =
100 kHz (1:1), CI = 470 nF, RSET = 10 kΩ
In steady-state condition and for a pulse duty factor of
50 % (pulse/pause 1:1), signals as shown in Figure 3
are present at the IC pins.
Turn-on and turn-off behavior
Capacitor CI also determines the starting time from
switching on the supply voltage VCC to steady-state
laser pulse operation or after a discharge of CI by
the watchdog. The following applies to estimating the
starting time (Figure 5):
Ton =
2.5 V ∗ CI 2.5 V ∗ CI ∗ RSET
=
I(ISET )
1.22 V
iC-WJ, iC-WJZ
LASER DIODE DRIVER
Rev C1, Page 8/12
Example
CI = 470 nF, RSET = 10 kΩ: Ton = 9.6 ms
Figure 6 shows a detailed view of the start of laser operation; Figure 7 shows the shut-down behavior. The
decline in the voltage at CI and the absence of the
laser pulses are signs that the undervoltage detector
is active.
The capacitor CWD should be dimensioned such that
the response time tp of the watchdog is slightly longer
than the pulse pause twlo of the input signal. As a result, the watchdog is just short of being activated.
For response times tp longer than tpmin applies:
CWD =
2.55 V
V(CI)
tp − tpmin
Kwd
2.45 V
with tpmin and Kwd from Electrical Characteristics
No. 407, 408.
I(KLD)
V(IN)
5.0 V
0A
Time
0V
5V
Figure 6: Turn-on behavior, detailed view f(IN) =
100 kHz (1:1), CI = 470 nF, RSET = 10 kΩ
V(CWD)
0V
3V
V(CI)
5.0 V
2V
VCC
I(AMD)
300 uA
0V
3.0 V
0A
V(CI)
Time
Figure 8: Watchdog, CWD open, f(IN) = 100 kHz
(1:1), CI = 470 nF, RSET = 10 kΩ
0V
I(KLD)
0A
V(IN)
5.0 V
Time
Figure 7: Turn-off behavior, f(IN) = 100 kHz (1:1), CI
= 470 nF, RSET = 10 kΩ
0V
5.0 V
V(CWD)
0V
Watchdog
In order for the watchdog to function correctly, the input
IN must be activated with a CMOS output (e.g. with an
HCMOS gate: see Figure 1).
The watchdog ensures that the capacitor CI is discharged during protracted pulse pulses at IN. During
the pulse pauses the potential at CI increases by ∆V
(Figure 3):
3.0 V
V(CI)
2.0 V
300 uA
I(AMD)
0A
Time
Figure 9: Watchdog, CWD open, f(IN) = 100 kHz →
10 kHz (1:1), CI = 470 nF, RSET = 10 kΩ
I(ISET ) ∗ twlo
∆V =
CI
Figure 8 shows the signals during normal operation,
without the watchdog being activated. The potential at
CWD rises during pulse pauses but does not reach the
watchdog activation threshold.
The discharge of capacitor CI by the watchdog protects
the laser diode from being destroyed by an excessive
turn-on current during the next pulse.
Figure 9 shows the watchdog behavior when the input frequency is reduced from 100 kHz to 10 kHz. The
pulse pauses are longer than the watchdog’s response
iC-WJ, iC-WJZ
LASER DIODE DRIVER
Rev C1, Page 9/12
time. The watchdog begins to discharge the capacitor
CI current limited. The remaining charge time during
the pulse pauses before further watchdog intervention
is not sufficient to maintain the initial potential at CI.
The potential is thus gradually reduced until it reaches
the saturation voltage Vs(CI)wd (Electrical Characteristics No. 405).
The watchdog therefore protects the laser diode from
destruction when the input signal change in such a
manner that the capacitor CI is not longer adequate
for averaging.
Furthermore, the introduction of the watchdog permits
long pulse pauses and activation of the laser diode with
pulse packets.
C1
10 uF
1
GND
KLD
8
C3
5 nF
R1
12 Ω
LD
MD
AMD
2
7
CWD
CI
100 nF
RSET
10 kΩ
3
4
CI
WDOG
IN
6
REF
ISET
VCC
iC−WJ/WJZ
5
+5 V
C2
100 nF
Figure 10: CW operation via cable
CW Operation
In case of CW operation, the input IN can be connected to the power supply VCC. The pin CWD may
be left open, because the capacitor for the watchdog
is not necessary. The capacitor CI for the averaging
control can be reduced to 100 nF.
Operation of laser diode via cable
It is recommended to connect a capacitor of 1 to 10 nF
across the laser diode in order to protect the laser
diode against destruction due to ESD or transients.
This capacitor should be placed close to the laser
diode and not at the beginning of the LD supply line.
An approx. 12 Ω series resistor at pin KLD reduces
the IC power consumption and damps possible resonances of the load circuit caused by the inductive LD
supply line. This resistor is useful for many applications, also for those which do not operate via cable.
On a PCB the forward path VCC to the laser diode
should be arranged in parallel with the return path to
KLD even when the line is only a few centimeters in
length.
iC-WJ, iC-WJZ
LASER DIODE DRIVER
Rev C1, Page 10/12
+5 V
C1
100 uF
C3
2 nF
1
GND
LD
KLD
8
MD
R1
12Ω
AMD
2
CI
22 nF
VMOD
0..1.5 V
R2
10 kΩ
WDOG
3
7
CWD
CI
IN
6
+5 V
REF
4
ISET
iC−WJ/WJZ
RSET
10 kΩ
VCC
5
C2
100 nF
Figure 11: Analogue modulation during CW operation
Analogue modulation during CW operation
The modulation cut-off frequency is determined by the
capacitor CI as well as by the operating point set with
the resistor RSET. With CI = 100 nF and RSET = R2 =
10 kΩ the cut-off frequency is approx. 40 kHz, with CI
= 22 nF and the same resitor value of about 230 kHz.
The laser power can also be modulated by adapting a
current source, e.g. by using an operational amplifier
with a current output (OTA). To limit the current at pin
ISET while turning on the power supply for the OTA circuitry, however, RSET should be connected to the OTA
output (instead of to GND). The maximum current possible at ISET must be taken into consideration when
dimensioning the capacitor CI.
PC board layout
The ground connections of the external components
CI, CWD and RSET have to be directly connected at
the IC with the GND terminal.
DEMO BOARD
For the devices iC-WJ/WJZ/WJB a Demo Board is
available for test purposes. The following figures show
the schematic diagram and the component side of the
test PCB.
iC-WJ, iC-WJZ
LASER DIODE DRIVER
Rev C1, Page 11/12
ALD
J1
VCC
LD
C1
C3
2 nF
100 uF
MONITOR
IN
LASER
IC1
GND
1
GND
KLD
8
R1
12Ω
KLD
AMD
2
AMD
7
CWD
WDOG
3
IMOD
RMOD
10 kΩ (15 kΩ )
6
VCC
5
I
II
REF
4
CWD
...
AGND
IN
CI
ISET
iC−WJ/WJZ/WJB
CI
470 nF
RSET
10 kΩ (15 kΩ )
C2
100nF
Figure 12: Schematic diagram of the Demo Board
Figure 13: Demo Board (components side)
This specification is for a newly developed product. iC-Haus therefore reserves the right to change or update, without notice, any information contained herein,
design and specification; and to discontinue or limit production or distribution of any product versions. Please contact iC-Haus to ascertain the current data.
Copying – even as an excerpt – is only permitted with iC-Haus approval in writing and precise reference to source.
iC-Haus does not warrant the accuracy, completeness or timeliness of the specification on this site and does not assume liability for any errors or omissions
in the materials. The data specified is intended solely for the purpose of product description. No representations or warranties, either express or implied, of
merchantability, fitness for a particular purpose or of any other nature are made hereunder with respect to information/specification or the products to which
information refers and no guarantee with respect to compliance to the intended use is given. In particular, this also applies to the stated possible applications or
areas of applications of the product.
iC-Haus conveys no patent, copyright, mask work right or other trade mark right to this product. iC-Haus assumes no liability for any patent and/or other trade
mark rights of a third party resulting from processing or handling of the product and/or any other use of the product.
iC-WJ, iC-WJZ
LASER DIODE DRIVER
Rev C1, Page 12/12
ORDERING INFORMATION
Type
Package
Order Designation
iC-WJ
SO8
MSOP8
iC-WJ SO8
iC-WJ MSOP8
iC-WJ EVAL WJ1D
SO8
MSOP8
iC-WJZ SO8
iC-WJZ MSOP8
iC-WJZ EVAL WJ1D
WJ Evaluation Board
iC-WJZ
WJZ Evaluation Board
For information about prices, terms of delivery, other packaging options etc. please contact:
iC-Haus GmbH
Am Kuemmerling 18
D-55294 Bodenheim
GERMANY
Tel.: +49 (61 35) 92 92-0
Fax: +49 (61 35) 92 92-192
Web: http://www.ichaus.com
E-Mail: [email protected]