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iC-WJ, iC-WJZ
LASER DIODE DRIVER
Rev C1, Page 1/12 FEATURES o Laser diode driver for continuous and pulsed operation (CW to 300 kHz) up to 250 mA o Averaging control of laser power o Simple adjustment of the laser power via external resistor o Adjustable watchdog at the switching input to protect the laser diode o Soft-start after power-on o Driver shutdown with overtemperature and undervoltage o Single 5 V supply o Simple circuitry o iC-WJ for laser diodes with 50 to 500 A monitor current o iC-WJZ for laser diodes with 0.15 to 1.5 mA monitor current APPLICATIONS o General purpose laser diode driver
PACKAGES
SO8
MSOP8
BLOCK DIAGRAM
3 REF REFERENCE
DRIVER STAGE 1
VCC
5
+5 V
100 F
C1
C3
ISET 4 INPUT IN VCC REF AMD
74HCxx
THERMAL SHUTDOWN KLD 8
2 nF
LD MD R1 12
RSET 10 k
6
POWER DOWN 7
2
4 WATCHDOG
1:1 iC-WJ 1:3 iC-WJZ
iC-WJ/WJZ
CWD 2 CWD CI 3 CI 100 nF..470 nF usable LD models GND 1
Copyright (c) 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)
1 8
PIN FUNCTIONS No. Name Function
KLD
GND
2 7
CWD
AMD
3
6
CI
4
IN
5
ISET
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
PIN CONFIGURATION MSOP8 (top view)
1 GND CWD CI ISET KLD AMD IN VCC
Code... ...yymm
WJ
iC-WJ Code
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 Supply Voltage Current in CI Voltage at KLD Current in KLD Current in AMD Current in IN Current in ISET Current in CWD ESD Susceptibility at CWD, CI, ISET, IN, AMD, KLD Junction Temperature Storage Temperature IN = lo MIL-STD-883, HBM 100 pF discharged through 1.5 k -40 -40 IN = lo IN = hi iC-WJ iC-WJZ Conditions Fig. Min. 0 -4 0 -4 -4 -6 -10 -2 -2 Max. 6 4 6 600 4 6 2 2 2 1.5 150 150 V mA V mA mA mA mA mA mA kV C C Unit
G001 VCC G002 I(CI) G003 V(KLD) G004 I(KLD) G005 I(AMD) G006 I(IN) G007 I(ISET) G008 I(CWD) G009 Vd() G010 Tj G011 Ts
THERMAL DATA
Operating Conditions: VCC = 5 V 10 % Item No. T01 Symbol Ta Parameter Operating Ambient Temperature Range (extended temperature range on request) Thermal Resistance Chip to Ambient surface mounted on PCB, without special cooling Conditions Fig. Min. -25 Typ. Max. 90 C Unit
T02
Rthja
140
K/W
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.
iC-WJ, iC-WJZ
LASER DIODE DRIVER
Rev C1, Page 4/12 ELECTRICAL CHARACTERISTICS
Operating Conditions: VCC = 5 V 10 %, RSET = 2.7...27 k, iC-WJ: I(AMD) = 50...500 A, iC-WJZ: I(AMD) = 0.15...1.5 mA, Tj = -25...125 C, unless otherwise noted. Item No. 001 002 003 004 005 Driver 101 102 103 Vs(KLD) I0(KLD) I(KLD) Saturation Voltage at KLD Leakage Current in KLD Current in KLD IN = hi, I(KLD) = 200 mA IN = lo, V(KLD) = VCC IN = hi, I(AMD) = 0 -25 27 70 125 225 250 250 250 0.5 0.4 250 1.3 10 V A mA mA mA mA 1.5 1.5 100 100 V V ns ns Symbol Parameter Conditions Tj C Fig. Min. 4.5 Typ. Max. 5.5 15 135 -1.5 0.3 -0.3 1.5 V mA ns V V Unit
Total Device VCC Iav(VCC) Permissible Supply Voltage Range Supply Current in VCC (average Iav(KLD) = 100 mA, value) f(IN) = 200 kHz 20 % IN(hi lo), V(50 %) : I(50 %) I() = -2 mA, other pins open Vc()hi = V() - VCC; I() = 2 mA, other pins open
tp(IN-KLD) Delay Time Pulse Edge V(IN) to I(KLD) Vc()lo Vc()hi Clamp Voltage lo at VCC, IN, AMD, KLD, CI, CWD, ISET Clamp Voltage hi at IN, AMD, KLD, GND, CI, CWD, ISET
104 105 106 107
V(AMD) tr tf CR1()
Voltage at AMD Current Rise Time in KLD Current Fall Time in KLD Current Ratio I(AMD) / I(ISET)
iC-WJ: I(AMD) = 500 A iC-WJZ: I(AMD) = 1.5 mA Imax(KLD) = 20...250 mA, Ip(): 10 90 % Imax(KLD) = 20...250 mA, Ip(): 90 % 10 % I(CI) = 0, closed control loop; iC-WJ iC-WJZ V(CI) = 1...3.5 V, ISET open; iC-WJ iC-WJZ
0.8 2.4 0.9 2.7 1.60 -25 27 70 125
1 3 1 3
1.2 3.6 1.1 3.3 2.40 V V V V V V V V V V mV mV mV mV mV k V V V V V V V
108
CR2()
Current Ratio I(AMD) / I(CI)
Input IN 201 Vt()hi
Threshold hi
1.84 1.87 1.88 1.91 1.50 2.20 1.76 1.78 1.79 1.81 10 190 80 90 90 100 4 16 0.1 3.2 2.8 2.3 1.8 1.28 1.22 0.9 1 1.1
202
Vt()lo
Threshold lo -25 27 70 125
203
Vt()hys
Hysteresis -25 27 70 125
204 205 206
Rin V0() Vtwd()
Pull-Down Resistor Open-loop Voltage Threshold for Watchdog
V(IN) = -0.3...VCC + 0.3 V I(IN) = 0 -25 27 70 125
2.4 2.0 1.5 1.0 1.17
Reference und Thermal Shutdown 301 V(ISET) Voltage at ISET 27 302 CR() Current Ratio I(CI) / I(ISET) V(CI) = 1...3.5 V, I(AMD) = 0
iC-WJ, iC-WJZ
LASER DIODE DRIVER
Rev C1, Page 5/12 ELECTRICAL CHARACTERISTICS
Operating Conditions: VCC = 5 V 10 %, RSET = 2.7...27 k, iC-WJ: I(AMD) = 50...500 A, iC-WJZ: I(AMD) = 0.15...1.5 mA, Tj = -25...125 C, unless otherwise noted. Item No. 303 304 305 Symbol RSET Toff Thys Parameter Permissible Resistor at ISET (Control Set-up Range) Thermal Shutdown Threshold Thermal Shutdown Hysteresis Conditions Tj C Fig. Min. 2.7 125 10 3.5 27 402 403 404 405 406 407 408
(*)
Unit Typ. Max. 50 150 40 4.3 3.8 3.2 3.8 450 400 1.6 1.5 -15 10 0.19 0.38 -3 45 0.57 300 k C C V V V mV mV V V A s s/pF
Power-Down and Watchdog 401 VCCon Turn-on Threshold VCC VCCoff VCChys Vs(CI)off Vs(CI)wd Ipu(CWD) tpmin Kwd (*) Undervoltage Threshold at VCC Hysteresis Saturation Voltage at CI with undervoltage Saturation Voltage at CI with IN = lo Pull-Up Current at CWD Min. Activation Time for Watchdog Constant for Calculating the Watchdog Activation Time VCChys = VCCon - VCCoff 27 I(CI) = 300 A, VCC < VCCoff I(CI) = 300 A, t(IN = lo) > tp (*) V(CWD) = 0, IN = lo IN = lo, CWD open IN = lo
tp = (C(CWD) Kwd) + tpmin
(see Applications Information)
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.
3 REF REFERENCE
DRIVER 1
VCC
5
+5 V
C1 100 uF
C3 4 ISET THERMAL SHUTDOWN KLD 8 R1 12 6 IN INPUT VCC REF POWER DOWN AMD 7 2 nF
LD MD
RSET
74HCxx 2 4 WATCHDOG 1:1 iC-WJ 1:3 iC-WJZ
iC-WJ/WJZ
CWD 2 CI 470 nF CI 3 GND 1
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:
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:
Pav
t = Ppeak whi T
RSET = with peak value Ppeak and pulse/period duration
twhi twlo Ppeak
CR1 V (ISET ) 1 1.22 V = = 9.4 k Iav (AMD) 0.13 mA
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:
twhi /T .
T
Figure 2: Duty cycle
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 Iav (AMD) 0.25 mA 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
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: 440 I(ISET ) 440 CI = f V (ISET ) f RSET Example Pulse repetition frequency 100 kHz, RSET = 10 k: 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.
5.0 V
V(IN)
0V
3.120 V
V(CI)
3.118 V 600 uA
I(AMD)
0A Time
Figure 4: Steady-state averaging, f(IN) = 100 kHz (1:4), CI = 470 nF, RSET = 10 k
3.0 V
2.0 V
V(CI)
1.0 V
0V
I(KLD)
V(IN)
0V 2.552 V
0A 0s
2 ms
4 ms
6 ms
8 ms
10 ms
12 ms
V(CI)
Figure 5: Turn-on behavior, f(IN) = 100 kHz (1:1), CI = 470 nF, RSET = 10 k 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):
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 k 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.
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 k: 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.
2.55 V
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: tp - tpmin Kwd
CWD =
V(CI)
2.45 V
I(KLD)
with tpmin and Kwd from Electrical Characteristics No. 407, 408.
5.0 V
V(IN)
0A Time
0V 5V
Figure 6: Turn-on behavior, detailed view f(IN) = 100 kHz (1:1), CI = 470 nF, RSET = 10 k
5.0 V
V(CWD)
0V 3V
V(CI) I(AMD)
VCC
0V 3.0 V
2V 300 uA
0A
Time
V(CI)
0V
Figure 8: Watchdog, CWD open, f(IN) = 100 kHz (1:1), CI = 470 nF, RSET = 10 k
I(KLD)
5.0 V
V(IN)
0A
Time
0V 5.0 V
Figure 7: Turn-off behavior, f(IN) = 100 kHz (1:1), CI = 470 nF, RSET = 10 k 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):
V(CWD)
0V 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 k 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. 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
I(ISET ) twlo V = CI
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.
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 R1 12 C3 5 nF
1
GND
KLD AMD
8
LD
MD
2 CWD CI 100 nF 3 CI
WDOG
7
IN
REF
6
RSET 10 k
4
ISET
iC-WJ/WJZ
VCC
5 C2 100 nF
+5 V
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 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 C3 2 nF C1 100 uF
LD
MD
1
GND
KLD AMD
8
R1 12
2 CI 22 nF
CWD
WDOG
7 IN
3
CI
REF
6 +5 V
VMOD 0..1.5 V
R2 10 k
4
ISET
VCC
5 C2 100 nF
iC-WJ/WJZ
RSET 10 k
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 k 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
VCC J1 ALD
LD C1 100 uF IN
LASER
C3 2 nF
MONITOR
IC1
GND 1 GND KLD AMD 2 CWD
WDOG
8
R1 12
KLD
7
AMD
3 RMOD 10 k (15 k )
CI
REF
IN
6
I
II
IMOD
4 CWD ... CI 470 nF RSET 10 k (15 k )
ISET
VCC
5
iC-WJ/WJZ/WJB
C2 100nF
AGND
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 iC-WJ WJ Evaluation Board iC-WJZ WJZ Evaluation Board
Package SO8 MSOP8
Order Designation iC-WJ SO8 iC-WJ MSOP8 iC-WJ EVAL WJ1D iC-WJZ SO8 iC-WJZ MSOP8 iC-WJZ EVAL WJ1D
SO8 MSOP8
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: sales@ichaus.com

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