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iC-WJB
2.7 V LASER DIODE DRIVER
Rev E1, Page 1/12 FEATURES o o o o o o o o Simple APC adjustment via an external resistor Continuous (CW) or pulsed operation of up to 300 kHz Laser diode current of up to 100 mA Adjustable watchdog for input signals Soft power-on and thermal protection Driver shutdown in case of overtemperature and undervoltage Operation at 2.7 to 6 V with two to four AA/AAA cells Protection against reverse polarity APPLICATIONS o Battery supplied LD modules o LD Pointers
PACKAGES
SO8
MSOP8
BLOCK DIAGRAM
DRIVER STAGE
REF
VCC
5
C1 47uF
R2 2
VB 2.7..6V
REFERENCE
C3 2nF RSET 2.7..330k 4 ISET THERMAL SHUTDOWN KLD 8 R1 0..2 POWER DOWN
REF
D1 Z6V8
LD
MD
INPUT
VCC
AMD IN 6 WATCHDOG 1 3
7
iC-WJB
CI 3 CI 470nF GND 1
alternative LD model LD MD (VCC > 4.5 )
CWD 2 CWD (..pF)
Copyright (c) 2008 iC-Haus
http://www.ichaus.com
iC-WJB
2.7 V LASER DIODE DRIVER
Rev E1, Page 2/12 DESCRIPTION The iC-WJB device is a driver IC for laser diodes in continuous or pulsed operation of up to 300 kHz. The wide power supply range of 2.7 to 6 V and the integrated reverse battery protection allows for batteryoperation with two to four AA/AAA cells. The laser diode is activated via switching input IN. A control to the average value of the optical laser power (APC) 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 circuit to protect the laser diode when switching on the power supply. Short-term reversed battery connection destroys neither the IC nor the laser diode. An external resistor at ISET is employed to adapt the APC to the laser diode being used. The capacitor at CI determines the recovery time constants and the starting 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 APC 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 PIN FUNCTIONS No. Name Function
8
1
GND
2 7
KLD AMD
CWD
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 Reference Current Input +2.7 to +6 V Supply Voltage Input Anode Monitor Diode Cathode Laser Diode
PIN CONFIGURATION MSOP8
1 GND CWD CI ISET KLD AMD IN VCC
Code... ...yymm
WJB
iC-WJB Code
iC-WJB
2.7 V LASER DIODE DRIVER
Rev E1, Page 3/12 ABSOLUTE MAXIMUM RATINGS
Beyond these values damage may occur; device operation is not guaranteed. Item No. Symbol Parameter Supply Voltage VCC Reverse Voltage at VCC Current in VCC 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 HBM, 100 pF discharged through 1.5 k -40 -40 IN = lo IN = hi IN = lo T < 10 s T < 10 s Conditions Min. -0.3 -3 -500 -4 0 -4 -4 -6 -10 -2 -2 50 4 9 400 4 6 2 2 2 1 150 150 Max. 6.5 V V mA mA V mA mA mA mA mA mA kV C C Unit
G001 VCC G002 VCC G003 I(VCC) G004 I(CI) G005 V(KLD) G006 I(KLD) G007 I(AMD) G008 I(IN) G009 I(ISET) G010 I(CWD) G011 Vd() G012 Tj G013 Ts
THERMAL DATA
Operating Conditions: VCC = 2.7...6 V 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 Min. -25 Typ. Max. 90 C Unit
T02
Rthja
170
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-WJB
2.7 V LASER DIODE DRIVER
Rev E1, Page 4/12 ELECTRICAL CHARACTERISTICS
Operating Conditions: VCC = 2.7...6 V, RSET = 2.7...27 k, I(AMD) = 0.15...1.5 mA, Tj = -25...125 C, unless otherwise noted. Item No. 001 002 003 004 005 006 007 Symbol Parameter Conditions Min. VCC Idc(VCC) I0(VCC) Iav(VCC) Permissible Supply Voltage Range Supply Current in VCC Standby Supply Current in VCC RSET = 5 k, IN = hi, Idc(KLD) = 40 mA REST= 5 k, IN = lo, Tj = 27 C 2.7 4 7 5 9 65 50 6.2 7.5 0.3 0.11 0.4 10 0.4 0.84 100 30 100 20 2.4 2.4 2.7 3 3.6 3 0.01 -0.1 45 40 20 Tj = 27 C 204 205 Rin V0() Pull-Down Resistor Open-loop Voltage V(IN) = -0.3 V...VCC Tj = 27 C I(IN) = 0 1.16 Tj = 27 C 302 303 304 305 CR() RSET Toff Thys Current Ratio I(CI)/I(ISET) Permissible Resistor at ISET (Control Set-up Range) Thermal Shutdown Threshold Thermal Shutdown Hysteresis V(CI) = 1...2 V, I(AMD) = 0 0.9 2.7 125 10 2.4 Tj = 27 C 402 403 404 VCCoff VCChys Vs(CI)off Undervoltage Threshold at VCC Tj = 27 C Hysteresis Saturation Voltage at CI with undervoltage VCChys = VCCon - VCCoff I(CI) = 300 A, VCC < VCCoff 70 2.3 2.5 100 150 1.5 2.6 2.63 1.22 1 1.12 330 150 40 2.7 k C C V V V V mV V 4 10 0.1 1.28 65 16 3.8 5.4 3.3 % / C % / C %VCC %VCC mV mV k k V V V 1.0 10 15 135 Typ. Max. 6 13 V mA mA mA ns mW V V V V V A V V ns ns ns ns Unit
Total Device
Supply Current in VCC (average Ipk(KLD) = 80 mA, f(IN) = 200 kHz 20 %, value) twhi / twlo = 1 IN(hi lo), V(50 %) : I(50 %) VCC = 3 V, V(KLD) 0.6 V, RSET = 5 k, Idc(KLD) = 40 mA I() = 2 mA, other pins open Tj = 27 C IN = hi, I(KLD) = 80 mA Tj = 27 C IN = hi, I(KLD) = 100 mA IN = lo, V(KLD) = VCC I(AMD) = 1.5 mA Tj = 27 C Imax(KLD) = 20...80 mA, Ip(): 10 90 % Tj = 27 C Imax(KLD) = 20...80 mA, Ip(): 90 % 10 % Tj = 27 C I(CI) = 0, closed control loop; RSET = 2.7..27 k RSET = 27..330 k V(CI) = 1...2 V, ISET open I(CI) = 0, closed control loop; RSET = 2.7...27 k RSET = 27...330 k
tp(IN-KLD) Delay Time Pulse Edge V(IN) to I(KLD) Pcon Vc()hi Power Consumption Clamp Voltage hi at VCC, IN, AMD, KLD, CI, CWD, ISET Saturation Voltage at KLD Saturation Voltage at KLD Leakage Current in KLD Voltage at AMD Current Rise Time in KLD Current Fall Time in KLD Current Ratio I(AMD)/I(ISET)
Driver 101 Vs(KLD) 102 103 104 105 106 107 Vs(KLD) I0(KLD) V(AMD) tr tf CR1()
108 109
CR2() TC1()
Current Ratio I(AMD)/I(CI) Temperature Coefficient of Current Ratio I(AMD)/I(ISET)
-0.25 70 65
Input IN 201 202 203 Vt()hi Vt()lo Vt()hys Threshold hi Threshold lo Hysteresis
Reference und Thermal Shutdown 301 V(ISET) Voltage at ISET
Power-Down and Watchdog 401 VCCon Turn-on Threshold VCC
iC-WJB
2.7 V LASER DIODE DRIVER
Rev E1, Page 5/12 ELECTRICAL CHARACTERISTICS
Operating Conditions: VCC = 2.7...6 V, RSET = 2.7...27 k, I(AMD) = 0.15...1.5 mA, Tj = -25...125 C, unless otherwise noted. Item No. 405 406 407 408
(*)
Symbol Vs(CI)wd Isc(CWD) tpmin Kwd (*)
Parameter Saturation Voltage at CI with IN = lo Pull-Up Current at CWD Min. Activation Time for Watchdog Constant for Calculating the Watchdog Activation Time
Conditions Min. I(CI) = 300 A, t(IN = lo) > tp (*) V(CWD) = 0, IN = lo IN = lo, CWD open Tj = 27 C IN = lo Tj = 27 C 2 10 25 0.19 0.25 0.57 Typ. Max. 1.5 15 45
Unit V A s s s/pF s/pF
tp = (C(CWD) Kwd) + tpmin
(see Applications Information)
iC-WJB
2.7 V LASER DIODE DRIVER
Rev E1, Page 6/12 APPLICATIONS INFORMATION Laser Power Adjustment The iC-WJB device can be adapted to CW laser diodes of up to 40 mW. When the supply voltage is higher than approx. 4.5 V, LD models in common cathode configuration 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 pre-set at this pin.
3 REF
DRIVER STAGE
1
VCC
5
C1 47uF
+5V
REFERENCE
C3 2nF 4 RSET 24k INPUT
2 VCC REF
LD MD
ISET
THERMAL SHUTDOWN KLD 8 R1 0..2 POWER DOWN 7
AMD 6 IN
4 1 3
WATCHDOG
iC-WJB
CI GND 3 CI 470nF 1
CWD 2
Figure 1: Circuit diagram for LD models with a common cathode
To calculate the current required at ISET, the average optical laser power is to determine: Pav = Ppeak twhi T
At Pav = Pcw = 1 mW, the monitor diode current is 0.25 mA and RSET is calculated to:
with peak value Ppeak and pulse/period duration twhi /T.
twhi twlo Ppeak
RSET =
CR1 V (ISET ) 3 1.22 V = = 14.64 k Iav (AMD) 0.25 mA
with Electrical Characteristics No. 301 for V(ISET) and No. 107 for current ratio CR1. Example for pulse operation Pulse duty factor twhi /T set to 20 % at Ppeak = 3 mW, laser diode as above with maximum optical output of 3 mW, monitor diode with 0.75 mA at 3 mW. The average optical power is set to 0.6 mW by the pulse duty factor; the average monitor diode current IAV is then 0.15 mA. The resistor RSET is calculated to:
T
Figure 2: Duty cycle Example for CW operation Pcw = 1 mW (pin IN at VCC, pin CWD open), laser diode maximum optical output of 3 mW, monitor diode with 0.75 mA at 3 mW.
iC-WJB
2.7 V LASER DIODE DRIVER
Rev E1, Page 7/12 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
RSET =
CR1 V (ISET ) 3 1.22 V = = 24.4 k Iav (AMD) 0.15 mA
with the Electrical Characteristics No. 301 for V(ISET) and No. 108 for current ratio CR1. Averaging control (APC) 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:
V(IN)
0V
3.120 V
V(CI)
3.118 V 600 uA
I(AMD)
0A Time
CI
440 I(ISET ) 440 = f V (ISET ) f RSET
Figure 4: Steady-state APC, f(IN) = 100 kHz (1:4), CI = 470 nF, RSET = 10 k
3.0 V
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 average 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. In steady-state condition and for a pulse duty factor of 50 % (pulse / pause = 1:1), wave forms as shown in Figure 3.
5.0 V
2.0 V
V(CI)
1.0 V
0V
I(KLD)
0A 0s
2 ms
4 ms
6 ms
8 ms
10 ms
12 ms
Figure 5: Turn-on behaviour, f(IN) = 100 kHz (1:1), CI = 470 nF, RSET = 10 k Turn-on and turn-off behaviour 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):
V(IN)
0V 2.552 V
V(CI)
2.550 V
250 uA 0A
I(AMD)
Time
Ton
1.7 V CI 1.7 V CI RSET = I(ISET ) 1.22 V
Figure 3: Steady-state APC, f(IN) = 100 kHz (1:1), CI = 470 nF, RSET = 10 k Figure 4 shows the corresponding signals for a pulse duty factor of 20 %. The influence of the pulse duty
Example CI = 470 nF, RSET = 10 k: Ton 6.5 ms Figure 6 shows a detailed view of the start of laser operation; Figure 7 shows the shut-down behaviour. The decline in the voltage at CI and the absence of the
iC-WJB
2.7 V LASER DIODE DRIVER
Rev E1, Page 8/12 laser pulses indicate that the undervoltage detector is active.
2.55 V
V(CI)
2.45 V
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.
V(IN)
I(KLD)
5.0 V
0V 5V
0A Time
V(CWD)
0V 3V
Figure 6: Turn-on behaviour, detailed view f(IN) = 100 kHz (1:1), CI = 470 nF, RSET = 10 k
5.0 V
V(CI) I(AMD)
2V 300 uA
VCC
0V 3.0 V
0A
Time
Figure 8: Watchdog, CWD open, f(IN) = 100 kHz (1:1), CI = 470 nF, RSET = 10 k
V(CI)
0V
5.0 V
V(IN)
I(KLD)
0A Time
0V 5.0 V
V(CWD)
0V 3.0 V
Figure 7: Turn-off behaviour, f(IN) = 100 kHz (1:1), CI = 470 nF, RSET = 10 k Watchdog The watchdog ensures that the capacitor CI is discharged during protracted pulses at IN. During the pulse pauses the voltage at CI increases by V (Figure 3). 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. 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
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 9 shows the watchdog behaviour when the input frequency is reduced from 100 kHz to 10 kHz. The pulse pauses are longer than the watchdog's response 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.
CWD =
with tpmin and Kwd from Electrical Characteristics No. 407, 408.
iC-WJB
2.7 V LASER DIODE DRIVER
Rev E1, Page 9/12 Furthermore, the introduction of the watchdog permits long pulse pauses and activation of the laser diode with pulse packets.
2.7..6V
S1
R2 2
D1 ZD6V8
C1 47uF
VCC
1
GND
KLD AMD
8
R1 0..2
KLD LD supply cord AMD
C3 4.7nF
LD
MD
2 CI 100nF
CWD
WDOG
7
3
CI
REF
IN
6 C2 100nF
RSET 15k
4
ISET
VCC
5
iC-WJB
Figure 10: CW operation via cable plus protective circuitry
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. 2 series resistor at pin KLD reduces the IC power consumption and damps possible reso-
nances 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. Additional protective components for clipping of strong positive and negative spikes can be useful, in particular when contact bouncing occurs in an inductive accumulator power supply line. Elements which come into question here are D1 and R1 as in Figure 10.
iC-WJB
2.7 V LASER DIODE DRIVER
Rev E1, Page 10/12
2.7..6V C1 47uF
1
GND
KLD AMD
8
R1 0..2
C3 2nF
LD
MD
2 CI 22nF
CWD
WDOG
7
3
CI
REF
IN
6 C2 100nF
RSET 27k 4 VMOD 0..1.3V R3 27k
ISET
VCC
5
iC-WJB
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 = R3 = 15 k the cut-off frequency is approx. 30 kHz, with CI = 22 nF and the same resitor value of about 150 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 purpose. The following figures show the schematic diagram and the component side of the test PCB.
iC-WJB
2.7 V LASER DIODE DRIVER
Rev E1, Page 11/12
VCC J1 ALD
LD C1 47uF IN
LASER
C3 2nF
MONITOR
IC1
GND 1 GND KLD AMD 2 CWD
WDOG
8
R1 2
KLD
7
AMD
3 RMOD 15k
CI
REF
IN
6
I
II
IMOD
4
ISET
VCC
5
CWD ....... AGND
CI 470nF
RSET 15k
iC-WJ/WJZ/WJB
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. As a general rule our developments, IPs, principle circuitry and range of Integrated Circuits are suitable and specifically designed for appropriate use in technical applications, such as in devices, systems and any kind of technical equipment, in so far as they do not infringe existing patent rights. In principle the range of use is limitless in a technical sense and refers to the products listed in the inventory of goods compiled for the 2008 and following export trade statistics issued annually by the Bureau of Statistics in Wiesbaden, for example, or to any product in the product catalogue published for the 2007 and following exhibitions in Hanover (Hannover-Messe). We understand suitable application of our published designs to be state-of-the-art technology which can no longer be classed as inventive under the stipulations of patent law. Our explicit application notes are to be treated only as mere examples of the many possible and extremely advantageous uses our products can be put to.
iC-WJB
2.7 V LASER DIODE DRIVER
Rev E1, Page 12/12 ORDERING INFORMATION
Type iC-WJB WJB Evaluation Board
Package SO8 MSOP8
Order Designation iC-WJB SO8 iC-WJB MSOP8 iC-WJB EVAL WJ1D
For technical support, information about prices and terms of delivery 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
Appointed local distributors: http://www.ichaus.de/support_distributors.php

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