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IC-NZ
FAIL-SAFE LASER DIODE DRIVER
Rev B2, Page 1/20 FEATURES o Peak value controlled three level laser switch for operation from CW up to 155 MHz o Spike-free switching of laser currents of ca. 100 mA per channel (320 mA total) from 3.5 to 5 V supply voltage o Single-failure-proof o System-enable with self test o Separate setting of laser power for each channel via external resistors o Strong suppression of transients with very small external capacitors o Adjustable laser current monitor o Safety shutdown with overcurrent, overtemperature and undervoltage o Autonomous safety circuit for a second photo diode monitoring the laser power o All current LD types can be used (M/P/N configurations) o Error signal output at shutdown APPLICATIONS o Pulsed LD modules for safety applications o Distance measurement
PACKAGES
QFN28 5 mm x 5 mm
BLOCK DIAGRAM
SDIS +5 V VDD LDA LENL LENM LENH REGEN
Safety Monitor Diode RSI
RSI
Current Monitor
RVDD LDAOK RSIOV NSEN NTREN LDKH LDKM LDKL CIH MDOK CIOK
LD MD
EN ENCAL NERR NSF
FSM
LDKGND NSEN
CIM NPDR TEMPOK CIL MDL CIL CIM
CIH
Safety Monitor Diode
SMD + - RSMD VSH + - VSL SMD(0) SMD(1)
Laser Driver VBG and Reference VBG and Reference
AGND VREF
RMDM RMDH
RMH RGND
RMM
RML
GND
suitable laser diode configurations
N M LD LD MD MD P MD LD
Copyright (c) 2007 iC-Haus
http://www.ichaus.com
IC-NZ
FAIL-SAFE LASER DIODE DRIVER
Rev B2, Page 2/20 DESCRIPTION Three-channel laser diode pulse regulator IC-NZ enables the continuous wave operation of laser diodes and spike-free switching with defined current pulses in a frequency range of up to 155 MHz. The three channels can be accumulatively pulsed via inputs LENL, LENM and LENH. The peak optical power of the laser diodes is regulated separately for high, middle and low levels and adjusted using the three external resistors RMH, RMM and RML. The iC is activated via pin EN which triggers a selftest of the device. The system is enabled if no errors are detected. Any errors are signaled at pin NERR. The (average) current monitor can be set using external resistor RSI. Overcurrent is signalled at NERR, causing the iC to be shut down. To ensure that the selected laser class is maintained a second monitor input SMD (safety monitor diode) is needed. This optional photo diode monitors the laser power. Exceeding the monitor window, set-up by RSMD, triggers a permanent reset. This is reported at output NERR and can be deleted when the system is restarted at EN. For high pulse frequencies the device can be switched into controlled burst mode at input REGEN. A previously settled operating point is maintained throughout the burst phase. When the iC is switched on all safety-relevant signals pertinent to the current monitor, SMD and control unit are checked. These units are in turn monitored for the following: overcurrent, short circuits, open pins and whether the laser is switched off in terms of output power. With the exception of the latter these checks are carried out intermittently during operation. So that the device is single-failureproof various safety check routines are also implemented. To this end a second SMD (safety monitor diode) monitoring the laser power is required. The laser power must stay within a defined range during operation (thus maintaining the laser class). If this range is left, the system is shut down and an error message is generated.
IC-NZ
FAIL-SAFE LASER DIODE DRIVER
Rev B2, Page 3/20 PACKAGES QFN28 5 mm x 5 mm to JEDEC Standard (MO-220-VHHD-1)
PIN CONFIGURATION QFN28 5 mm x 5 mm (top view)
PIN FUNCTIONS No. Name Function 1 RMDH APC Setup, Monitor Input Hi 2 RVDD Reference (P-type laser diodes) 3 RMDM APC Setup, Monitor Input Mid 4 NSF No-Safety Signal
PIN FUNCTIONS No. Name Function 5 MDL APC Setup, Monitor Input Lo 6 ENCAL Enable Calibration 7 RGND Internal Ground 8 SMD Safety Monitor Diode 9 GND Ground 10 VREF Reference Voltage 11 CIL Power Control Capacitor Lo 12 REGEN Regulator Enable 13 CIM Power Control Capacitor Mid 14 LENL Enable Laser Channel Lo 15 LENM Enable Laser Channel Mid 16 GND Ground 17 LDKM Cathode Laser Diode Mid 18 AGND Analog Ground 19 LDKL Cathode Laser Diode Lo 20 LDKH Cathode Laser Diode Hi 21 LENH Enable Laser Channel Hi 22 NERR Error Output 23 EN Enable Input 24 CIH Power Control Capacitor Hi 25 LDA Anode Laser Diode 26 RSI Current Monitor Setup 27 SDIS External Current Limitation 28 VDD Power Supply
The Thermal Pad is to be connected to a Ground Plane (GND) on the PCB. Pins 9, 16 (GND) and 18 (AGND) must be connected externally, e.g. to a Ground Plane. Orientation of package label ( NZ CODE ...) may vary.
IC-NZ
FAIL-SAFE LASER DIODE DRIVER
Rev B2, Page 4/20 ABSOLUTE MAXIMUM RATINGS
Beyond these values damage may occur; device operation is not guaranteed. Item No. Symbol Parameter Supply Voltage VDD Current Current in VDD Current in CIx Current in NSF Current in SMD Current in NERR Current in MDL Current in RMDx Current in LENL, LENM, LENH, REGEN, NEN, ENCAL Current in LDKx Current in LDA Current in RSI Current in SDIS Current in VREF Voltage at RMDH, RVDD, RMDM, NSF, MDL, ENCAL, SMD, VREF, REGEN, CIx, LENx, NERR, LDA, RSI, SDIS Voltage at LDKx ESD Susceptibility at all pins Operating Junction Temperature Storage Temperature Range HBM, 100 pF discharged through 1.5 k -40 -40 -0.7 V(LDA) = 0 Conditions Min. -0.7 Max. 6 400 5 20 20 20 20 20 20 300 400 20 20 50 6 V mA mA mA mA mA mA mA mA mA mA mA mA mA V Unit
G001 VDD G002 I(VDD) G003 I(CIx) G004 I(NSF) G005 I(SMD) G006 I(NERR) G007 I(MDL) G008 I(RMDx) G009 I()dig G010 I(LDKx) G011 I(LDA) G012 I(RSI) G013 I(SDIS) G014 I(VREF) G015 V()c
G016 V()h G017 Vd() G018 Tj G019 Ts
-0.7
15 2 150 150
V kV C C
THERMAL DATA
Operating Conditions: VDD = 3.5...5.5 V Item No. T01 T02 Symbol Ta Rthja Parameter Operating Ambient Temperature Range (extended range on request) Thermal Resistance Chip/Ambient surface mounted, thermal pad soldered to ca. 2 cm heat sink Conditions Min. -20 30 Typ. Max. 90 40 C K/W Unit
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-NZ
FAIL-SAFE LASER DIODE DRIVER
Rev B2, Page 5/20 ELECTRICAL CHARACTERISTICS
Operating Conditions: VDD = 3.5...5.5 V, Tj = -20...85 C; x: L, M, H, unless otherwise stated Item No. 001 002 003 004 005 006 Symbol Parameter Conditions Min. VDD Ioff(VDD) Idc(VDD) Tab VDDen Vc()hi Permissible Supply Voltage Supply Current in VDD Supply Current in VDD Thermal Shutdown Threshold Power-On Threshold Clamp Voltage hi at REGEN, LENH, LENM, LENL, EN, ENCAL, LDA, NERR, NSF Clamp Voltage hi at CIx, MDL, RMDH, RMDM SMD Clamp Voltage hi at LDKx Clamp Voltage hi at RSI, VREF Clamp Voltage hi at SDIS Clamp Voltage lo Voltage at MDL, VDD - V(MDL) for P-type LD Temperature Drift of Voltage at MDL Current in MDL, RMDM, RMDH Voltage at VREF, VDD - VREF for P-type LD Pull-Down Current in LENx, EN Pull-Down Current in REGEN Threshold Voltage at LENx, REGEN, ENCAL, EN Hysteresis Pull-Down Resistor at REGEN Pull-Down Resistor at ENCAL V(ENCAL) > Vt() 4 10 I() = 1 mA, other pins open, VDD = 0 EN = lo EN = hi, RSI > 780 110 2.1 0.3 3.5 460 6.4 Typ. Max. 5.5 600 10 150 2.95 1.5 V A mA C V V Unit
Total Device
007 008 009 010 011 101 102 103 104
Vc()hi Vc()hi Vc()hi Vc()hi Vc()lo V(MDL) dV(MDL) I() V(VREF)
I() = 1 mA, other pins open, VDD = 0 I() = 1 mA, other pins open I() = 1 mA, other pins open, VDD = 0 I() = 1 mA, other pins open I() = 1 mA, other pins open closed control loop closed control loop LENL, LENM, LENH = hi iC active
0.3 12 0.3 6 -1.5 440 -0.65 500 120 -500 405 480 0.9
1.6
V V
1.5 -0.3 550
V V V mV V/C
Reference
500 550
nA mV
Digital Inputs 201 202 203 204 205 206 Ipd() Ipd (REGEN) Vt() Vhys() Rpd (REGEN) Rpd (ENCAL) VSL VSH dVS VCHK I(RSMD) Ipd(SMD) V(LDA) = V(VDD) V(LDA) = V(VDD), V(ENCAL) < Vt() VDD = 5 V 1 1 0.75 4 4 1.8 800 20 30 10 10 2.2 A A V mV k k
Safety Monitor Diode 301 302 303 304 305 306 Monitor Threshold lo, Signal SMD(0) Monitor Threshold hi, Signal SMD(1) VSH - VSL Test Voltage for SMD Permissible Safety Monitor Diode Current Pull-Down-Current in SMD one channel only is activated; I(LDK) = 100 mA I(LDK) = 60 mA DC DC DC 100 760 0.2 0.6 265 615 350 300 680 390 325 750 430 120 5 3 mV mV mV %VSH mA A
Laser Driver LDKx, CI, RMDx 401 Vs(LDKx) Saturation Voltage at LDKx
1.2 0.8
2 1.3 120 100 100 12 900
V V mA mA mA V mV
402 403 404 405 406
Idc(LDKL) Permissible Current Idc(LDKM) Permissible Current Idc(LDKH) Permissible Current Vo() VCI() Permissible Voltage at LDKx REGOK Monitor Threshold
IC-NZ
FAIL-SAFE LASER DIODE DRIVER
Rev B2, Page 6/20 ELECTRICAL CHARACTERISTICS
Operating Conditions: VDD = 3.5...5.5 V, Tj = -20...85 C; x: L, M, H, unless otherwise stated Item No. 407 408 409 410 411 Symbol C(CIx) |I(CIx)| I(CIx) Ipd(CIx) I(RMDx) Parameter Capacitance at CIx Charge Current from CIx Discharge Current in CIx Pull-Down Current in CIx Permissible Laser Monitor Diode Current iC active, control unit not yet settled iC inactive, V(CIx) > 1 V iC active, REGEN = lo active safety function; VDD = 5 V VDD = 3.3 V V(LDA) = V(VDD) = V(NERR), error state V(LDA) = V(VDD) = V(NERR), no error state, V(MDL) < 0.5 V V(LDA) = V(VDD) = V(NSF), V(NSF) > 0.8 V V(LDA) = V(VDD) = V(SDIS), V(SDIS) > 0.8 V Isat = 1 mA, NERR in error state 1.5 0.1 1.5 1.0 Conditions Min. 100 0.25 10 25 0.6 1 60 150 2.5 1 10 1 10 10 600 Typ. Max. nF mA mA nA mA mA mA mA mA mA mV Unit
Status Outputs 501 502 503 504 505 I(NERR) I(NERR) I(NSF) I(SDIS) Vsat() Current at Error Message Current in NERR Current at NSF Message Current at SDIS Message Saturation Voltage at NERR, NSF, SDIS Controlled Voltage at RSI Resistor at RSI LDAOK Monitor Threshold VDD - V(LDA) Current from LDA Pull-Down Resistor at LDA Overcurrent Shutdown Delay Current Ratio I(LDA)max / I(RSI) Pull-Down Current in RSI Propagation Time: EN lo hi system enable Laser Current Rise Time Laser Current Fall Time Propagation Time: LENx lo hi to Current lo hi Propagation Time: LENx hi lo to Current hi lo DC Reset I(LDA) > I(RSI) * 500 780 < RSI < 9000 V(RSI) > 0.5 V no error at self test, CLDA = 1 F see Fig. 2 see Fig. 2 see Fig. 3 see Fig. 3 400 1 500
Current Monitor RSI, LDA 601 602 603 604 605 606 607 608 701 702 703 704 705 706 V(RSI) RSI VLDA Idc(LDA) Rpd(LDA) td(SDIS) rILDA Ipd(RSI) ten tr tf tplh tphl ts0 EN = hi 430 0.78 440 490 490 560 9 550 320 1 10 650 10 300 1.5 1.5 10 10 A s ns ns ns ns mV k mV mA k s
Timing
Propagation Time: see Fig. 4 V(SMD) > VSL to SMD(0) lo hi Tj = 27 C Tj = 85 C Propagation Time: V(SMD) < VSL to SMD(0) hi lo Propagation Time: see Fig. 4 V(SMD) > VSH to SMD(1) lo hi Propagation Time: SMD(1) lo hi until shutdown Propagation Time: SMD(1) lo hi until error message see Fig. 4 see Fig. 4
220 240 220 220 10 500
ns ns ns ns ns ns
707 708 709 710
ts0off ts1 toff td
IC-NZ
FAIL-SAFE LASER DIODE DRIVER
Rev B2, Page 7/20 ELECTRICAL CHARACTERISTICS: DIAGRAMS
V VDD-0.45V Vt()hi Input/Output
Vt()lo 0.45V t
LENL LENM LENH
1 0
Figure 1: Reference levels
I(LDKL)
I(LED) tr I pk
90% I pk
tf
I(LDKM) I(LDKH)
t plh t plh t phl
t phl
t plh
t phl
10% I pk
V(MDL)
t
Zeit
Figure 2: Laser current pulse
Figure 3: Turn on/turn off behavior of the laser current
ENCAL LENL LENM LENH P(Laser)
Ph Pm Pl
Zeit Zeit
V(MDL)
0.5V
V(SMD)
VSH VSL
Zeit SMD(0) SMD(1)
t S0 t S1 t d
NERR NSEN NTREN
t off
Figure 4: Safety shutdown times with failure of the control unit, for example
IC-NZ
FAIL-SAFE LASER DIODE DRIVER
Rev B2, Page 8/20 CONTENTS DESCRIPTION OF FUNCTIONS Monitoring the laser current . . . . . . . . . . Demo board . . . . . . . . . . . . . . . . Switching up to three laser power levels . . . 1. Enabling the system . . . . . . . . . . . . . Demo board . . . . . . . . . . . . . . . . Possible sources of error . . . . . . . . . . . 2. Calibrating the low and middle channels . Setting the low output level . . . . . . . . . . Demo board . . . . . . . . . . . . . . . . Setting the middle channel . . . . . . . . . . Demo board . . . . . . . . . . . . . . . . 3. Calibrating the high channel . . . . . . . . Demo board . . . . . . . . . . . . . . . . Possible sources of error . . . . . . . . . . . Demo-Board . . . . . . . . . . . . . . . . . . 9 9 9 9 10 10 10 10 10 10 10 11 11 11 11 12 DEMO BOARD 19 OPERATION WITH ONE OR TWO CHANNELS SINGLE-FAILURE PROTECTION Calibrating the safety monitor diode . . . . . Demo-Board . . . . . . . . . . . . . . . Operation without a second monitor diode . . Demo-Board . . . . . . . . . . . . . . . MISCELLANEOUS Status outputs NERR, NSF and REGEN . . . Controlled burst mode . . . . . . . . . . . . . Extending the laser current . . . . . . . . . . Driving blue laser diodes . . . . . . . . . . . . 12 15 15 15 15 15 17 17 17 17 19 Warning! . . . . . . . . . . . . . . . . . . . . 12
IC-NZ
FAIL-SAFE LASER DIODE DRIVER
Rev B2, Page 9/20 DESCRIPTION OF FUNCTIONS IC-NZ is a three-channel laser diode pulse regulator which is single-failure-proof and able to maintain a selected laser class. The device includes the following functions: * Monitoring of the laser current * Switching of three laser light intensity levels which are regulated separately * Single-failure-proof via laser light monitoring using a second monitor diode and shut-down of the laser in the event of error via three separate, independent switches * External error messaging * Pulses of up to 155 MHz in controlled burst mode, during which a previously set operating point is maintained * Extension of the laser current with few external components * Operation of blue laser diodes possible To simplify the initial operation of IC-NZ the following passage first outlines the basic steps involved and then goes on to provide details referring to the demo board available for evaluation. A HL6339G HITACHI laser diode has been used here by way of example. Monitoring the laser current IC-NZ monitors the laser current flowing from pin LDA (Figure 5). The DC current threshold is set using a resistor at pin RSI. If this threshold is exceeded, the device is shut down for safety reasons.
SDIS
VDD VDD CURRENT MONITOR x1 NEN VREF S2 NSEN S3 + - ILDA x500
SDIS
LDA
CLDA
0.5V
LD
RSI S1 IRS RSI LDAOK NSEN
MD
EN FINITE STATE MACHINE
Figure 5: Monitoring the laser current
When dimensioning resistor RSI the following applies: Imax (LDA) = 500 x 0.5 V RSI
current RSI is calculated as: RSI = 500 x 0.5 V = 3.5 k 70 mA
Short pulses with higher currents are also possible as the DC current is monitored. Capacitor CLDA supplies the current for short, higher pulses. Demo board According to the manufacturer's specifications laser diode HL6339G requires a maximum current of 70 mA for an optical power of 5 mW. For this maximum 70 mA
Switching up to three laser power levels The following steps must be taken to set the required optical power:
1. Enabling the system 2. Calibrating the low and middle channels 3. Calibrating the high channel
IC-NZ
FAIL-SAFE LASER DIODE DRIVER
Rev B2, Page 10/20 1. Enabling the system Before IC-NZ is put into operation for the first time the external circuitry should be checked for the following (see block diagram): * Resistor RSMD should be of low impedance. It may not, however, be lower than 250 , otherwise the internal iC check will generate an error message. * The resistors at pins RMDL, RMDM and RMDH should be of high impedance (low output). * Inputs LENL, LENM and LENH should be switched to low (the driver stages switched off). So that IC-NZ can be switched on pin EN must be set to high and pin ENCAL to low. A current in the milliampere range (Electrical Characteristics No. 501) now flows into pin NERR. This indicates that the device is now in its start-up phase. The voltage at pin RSI is set to 0.5 V and capacitor CLDA charged at pin LDA. Once voltage V(LDA) has reached its final value the control unit and safety monitor diode are checked, if the latter is in use (see also Operation without a second monitor diode). Following this check the current into pin NERR is lowered (Electrical Characteristics No. 502). The residual current still remaining (ca. 500 A) indicates that the control unit is not yet in operation (N-type: V(MDL) < 0.5 V, P-type: VDD - V(MDL) < 0.5 V). The entire process is described in Figure 6. Possible sources of error * V(NERR) remains at low: - Check the current in NERR. Is the impedance of the pull-up resistor too high? * Too high a current is flowing through pin NERR: An error has occurred during the device self-test. Check the following: - Is ENCAL lo? - Is RSMD of too low an impedance? RSMD may not be lower than 250 . - Is pin SMD open or has it directly shortcircuited with VCC? - Is there a direct connection between pin LDK and ground? - Is there a low-impedance connection between pin LDA and ground? - Have all CIx capacitors (x: L, M, H) been properly soldered and placed close to the iC? - Is VCC properly back upped? 2. Calibrating the low and middle channels So that the optical power can be regulated pin REGEN must be set to high. The level at pin ENCAL is of no consequence when setting the low and middle channels. Setting the low output level Pin LENL is first switched from low to high. The integration capacitor at CIL is then charged. Until the control unit has settled a small amount of current flows in pin NERR. Following this the voltage at pin MDL is 0.5 V for an N-type diode and VDD - 0.5 V for a P-type diode. The required optical power can now be set at resistor RML. Demo board By way of example, three output levels of 1 mW, 3 mW and 5 mW are to be set. With an optical power of 1 mW laser diode HL6339G has a typical monitor current (IM) of 15 A. The following value is then obtained for the resistor at pin MDL (RMLn = PML + RML): RMLn = Figure 6: Signal pattern when the system is enabled Demo board Before the demo board is put into operation trimmers PSMDL, PML, PMM and PMH should be set to the left and trimmer PSMDH to its centre setting. V (MDL) 0.5 V = = 33.34 k IM 15 A
V(EN)
V(LDA)
VCHK
V(SMD)
VREF
V(MDL) V(NERR)
Setting the middle channel Pin LENL must remain at high and LENM be switched from low to high. Following the settling of the control unit at CIM (N-type: V(MDL) < 0.5 V; P-type: VDD - V(MDL) < 0.5 V) the required optical power can be set at resistor RMM.
IC-NZ
FAIL-SAFE LASER DIODE DRIVER
Rev B2, Page 11/20 Demo board With an optical power of 3 mW the monitor current (IM) is 43 A. This current must flow through the parallel connection of RMLn and RMMn (RMMn = PMM + RMM). The following then applies: RMLn||RMMn = V (MDL) 0.5 V = 11.62 k = IM 43 A
RMMn = RMMn =
RMLn||RMMn RMLn RMLn - RMLn||RMMn
11.62 k 33.34 k = 17.84 k 33.34 k - 11.62 k
3. Calibrating the high channel Here, pins REGEN and ENCAL must be high. This deactivates the monitoring of the optical power, thus enabling the calibration of the high output level. Pins
LENL and LENM must remain at high; pin LENH must also be switched from low to high. Following the settling of the control unit at CIH the required optical power can be set at resistor RMH.
Demo board With an optical power of 5 mW laser diode HL6339G has a typical monitor current (IM) of 80 A. The following value is then obtained for resistor RMHn = PMH + RMH: RMLn||RMMn||RMHn = V (MDL) 0.5 V = = 6.25 k IM 80 A
RMHn =
RMLn||RMMn||RMHn RMLn||RMMn RMLn||RMMn - RMLn||RMMn||RMHn 6.25 k 11.62 k = 13.52 k 11.62 k - 6.25 k
RMHn =
Possible sources of error * V(NERR) remains at low: - Check the current in NERR. Is the impedance of the pull-up resistor too high? * Too high a current is flowing at pin NERR (ERROR state): - Is the laser diode properly connected and the control unit functioning correctly? - Are RMDL, RMDM or RMDH of too low an impedance? (Possible shut-down due to overcurrent!) - Are all the capacitors at CIx (x: L, M, H) large enough and have they been properly soldered? - Is pin AGND connected to ground? * No laser light: - Is pin AGND connected to ground? - Is there a short circuit between CIx and ground? - Is the laser diode (type N or P) properly connected and the control unit functioning correctly? - The laser diode lights up for a few seconds and then turns off: * Is the laser diode too hot? With insufficient cooling the laser diode power consumption increases which can trigger an overcurrent shut-down.
IC-NZ
FAIL-SAFE LASER DIODE DRIVER
Rev B2, Page 12/20 Demo-Board When using an N-type laser diode jumper J2 must be placed between pins 2 and 3 on the demo board. If a P-type laser diode is used the jumper must be connected between pins 1 and 2. Warning! Following calibration pin EN has to be briefly set to low before actual operation may start with EN set to high again. The following explains why. When the low channel (LENL hi) is switched on capacitor CIL is charged. When the middle channel is switched in the internal control unit switches to CIM and starts to charge it. The voltage at CIL is then no longer regulated. As residual current could boost the voltage at CIL, which in turn would increase the current in the low channel, thus the capacitor at CIL is actively discharged with a maximum of 100 nA. The current in the low channel slowly decreases. As the control unit endeavours to keep the optical power constant, the capacitor at CIM is charged at the same rate as CIL is gradually discharged. If the middle channel is now switched off, the control unit switches back to the low channel. Capacitor CIL is regulated again; CIM, however, remains charged. If the middle channel were then again to be switched on, far too much current would flow; this could destroy the laser diode. The same happens if the low and middle channels are regulated and the high channel switched on for a lengthy period of time. In this instance CIL and CIM are slowly discharged and the voltage at CIH rises in order to maintain a constant optical power. The entire process is illustrated in Figure 7.
EN
CIL CIM
LENL LENM
Overcurent
I(Laser)
Figure 7: Behavior with very long power-on times
OPERATION WITH ONE OR TWO CHANNELS It is of course also possible to operate IC-NZ with one or two levels of light intensity. To make use of the safety functions of the system in one- or two-channel mode, pins LDKx (x: L, M) on the unused channels must be kept unconnected. Nodes CIx should be directly shortcircuited with AGND. To use the safety functions of the safety monitor diode the high channel must always be in use in one- or two-channel mode. Figures 8 to 11 give the configuration of IC-NZ for one- or two-channel operation for both N- and P-type laser diodes.
IC-NZ
FAIL-SAFE LASER DIODE DRIVER
Rev B2, Page 13/20
VDD
VDD VDD
SDIS
REGEN
LENL
LENM
LENH RVDD
LDA Safety Monitor Diode RSI EN Finite State Machine NSEN NTREN NSEN LDAOK C1 RSI Current Monitor S1
LD
MD
LDKH Safety Monitor Diode MDL Laser Driver APC SMD + - VSAH + RSMD VSAL VREF RGND + - MDL CIL - SMD(0) LDKL SMD(1) MDOK
Monitor MDL
VREF + -
RMDH CIH CIH
RMDM LDKM VREF + - CIM
AGND GND VREF CREF RML
Figure 8: One-channel operation with safety function (N-type laser diode)
VDD
SDIS VDD
REGEN
LENL
LENM
LENH RVDD
VDD LDA C1 RSI Current Monitor S1 CLDA RMDH
RSI EN
NSEN Finite State Machine NSEN
LDAOK
MDL RMDM
NTREN
RMDH
SMD Safety Monitor Diode MDL Laser Driver APC VREF + -
LDKH
CIH
LD
CIH
MD
LDKM SMD + - RSMD VSAH + - VSAL VREF RGND + - CIL SMD(0) LDKL SMD(1) MDOK
Monitor MDL
VREF + - CIM
AGND
GND
CREF
Figure 9: One-channel operation with safety function (P-type laser diode)
IC-NZ
FAIL-SAFE LASER DIODE DRIVER
Rev B2, Page 14/20
VDD
SDIS VDD
REGEN
LENL
LENM
LENH RVDD
VDD LDA Safety Monitor Diode RSI EN Finite State Machine NSEN NTREN RMH LDKH Safety Monitor Diode MDL Laser Driver APC LDKM SMD + - VSAH + RSMD VSAL VREF RGND + - MDL CIL CIL - SMD(0) LDKL SMD(1) MDOK
Monitor MDL
C1 RSI
Current Monitor S1 CLDA
NSEN
LDAOK RMDH
LD
MD
VREF + - CIH CIH
VREF + - CIM
AGND RML GND CREF
Figure 10: Two-channel operation with safety function (N-type laser diode)
VDD REGEN LENL LENM LENH RVDD VDD LDA C1 RSI Current Monitor S1 CLDA RSI EN Finite State Machine NSEN NTREN RMDM RMH RMDH RML
SDIS VDD
NSEN
LDAOK
MDL
SMD Safety Monitor Diode MDL Laser Driver APC VREF + -
LDKH
CIH
LD
CIH
MD
LDKL SMD + - RSMD VSAH + - VSAL RGND VREF + - CIL AGND CIL SMD(0) LDKL SMD(1) MDOK
Monitor MDL
VREF + - CIM
GND
CREF
Figure 11: Two-channel operation with safety function (P-type laser diode)
IC-NZ
FAIL-SAFE LASER DIODE DRIVER
Rev B2, Page 15/20 SINGLE-FAILURE PROTECTION Maintaining the laser class and the single-failure protection feature are achieved by means of a second monitor diode and by monitoring the laser current. Further safety is provided by the layout of the laser driver stages. The output stages consist of several identical driver cells where each cell can discharge the integration capacitor CIx (x: L, M, H) and shut down the laser current. So that the laser can be switched off in the event of error IC-NZ has three completely separate circuits. The second diode monitors whether the laser light is within a predetermined power range or not. Calibrating the safety monitor diode To calibrate the safety monitor diode IC-NZ is first activated via EN (low high) with ENCAL at low. Once the device self-test has been successfully carried out (NERR is high) pin ENCAL must be set to high and the system switched to maximum optical power (pins LENL, LENM and LENH switched to high). Resistor
VDD
RSMD at pin SMD is now set so that voltage V(SMD) is inside the monitor window between 0.3 V and 0.7 V. ENCAL can now be switched back to low.
In applications with a low duty cycle both the peak and average laser power must be monitored to maintain the laser class. To this end the resistor at RSMD is split into RSMD1 and RSMD2 and a capacitor (CSMD) connected in parallel to RSMD1 (see Figure 12). With short laser light pulses capacitor CSMD behaves as if it is a short circuit and bypasses RSMD1. In this instance only RSMD2 is active (higher shutdown threshold). With longer pulses resistors RSMD1 and RSMD2 are in series (lower shutdown threshold). This setup dynamically alters the monitor window. An excess of the maximum permissible laser power through both too high a pulse power or too long a pulse duration is equally detected.
LENL LENM LENH RVDD
SDIS
REGEN
VDD LDA C1 RSI Current Monitor S1 CLDA RSI EN Finite State Machine NSEN NTREN RMDH MDL RMDM RMDH SMD Safety Monitor Diode MDL Laser Driver APC SMD + - RSMD2 VSAH + - CSMD RSMD1 VSAL VREF + RGND - CIL CIL AGND LDKL SMD(0) SMD(1) MDOK
Monitor MDL
NSEN
LDAOK
RMDM
RMDL
VREF + -
LDKH CIH CIH
LD
MD
VREF + -
LDKL CIM CIM
IC-NZ
GND
Figure 12: Dynamic adaptation of the monitor window Demo-Board So that the second monitor diode can be used jumper J1 must be placed between pins 1 and 2 on the demo board. The voltage at SMD is set using the two potentiometers PSMDH (peak) and PSMDL (average). Operation without a second monitor diode The monitoring function can be disabled for applications which do not require a second monitor diode. To this end pins SMD and ENCAL must be set to high. This no safety function (NSF) is signalled at pin NSF. The overcurrent monitor at LDA is, however, still active in this mode. This ensures safe operation with so called low-power applications - even without a second monitor diode. Figures 13 and 14 give the circuitry for N- and P-type laser diodes.
Demo-Board So that the demo board can be operated without a second monitor diode, jumper J1 must be placed between pins 2 and 3.
IC-NZ
FAIL-SAFE LASER DIODE DRIVER
Rev B2, Page 16/20
VDD
SDIS VDD
REGEN
LENL
LENM
LENH LDA
C1
RSI
Current Monitor Laser Driver
RSI
LDAOK EN
RSIOV
NSEN
CLDA
LD MD
NTREN MDOK CIOK LDKGND NSEN LDKH LDKM LDKL CIH CIM CIH CIM CIL
ENCAL NERR NSF
Finite State Machine
NPDR
TEMPOK
CIL MDL
Safety Monitor Diode VBG and Reference + VSH - + - VSL RMH RGND RMM RML SMD(1) VBG and Reference RMDH RMDM
SMD
SMD(0)
VREF
Figure 13: Operation without a second monitor diode (N-type laser diode)
VDD VDD SDIS REGEN LENL LENM LENH
LDA RVDD
C1
RSI
Current Monitor Laser Driver
RSI LDAOK EN ENCAL NERR NSF Finite State Machine RSIOV NSEN CLDA NTREN MDOK CIOK LDKGND NSEN
RMH
RMM
RML
RMDH RMDM MDL
NPDR
TEMPOK
LD
Safety Monitor Diode VBG and Reference + - VSH + - VSL CIL SMD(0) CIH CIM CIL CIM CIH SMD(1) VBG and Reference LDKH LDKM LDKL
MD
SMD
VREF
Figure 14: Operation without a second monitor diode (P-type laser diode)
IC-NZ
FAIL-SAFE LASER DIODE DRIVER
Rev B2, Page 17/20 MISCELLANEOUS Status outputs NERR, NSF and REGEN Pin NERR is an open-collector output with three states: I(NERR) = 0 mA Pin EN is low or the control unit is operational (no error) N-type laser diode: V(MDL) = 0.5 V P-type laser diode: V(MDL) = VDD - 0.5 V Error or IC-NZ is still undergoing its self-test No error, the control unit is not yet settled or not enough laser light N-type laser diode: V(MDL) < 0.5 V P-type laser diode: V(MDL) < VDD - 0.5 V
I(NERR) > 1.5 mA 0 < I(NERR) < 1.5 mA
Pin NSF is also an open-collector output and signals the no safety mode: I(NSF) > 1.5 mA I(NSF) = 0 mA IC-NZ is in safety mode IC-NZ is in no safety mode operation with a second monitor diode operation without a second monitor diode
Pin REGEN, in addition to its mode select input function (regulated output power burst mode), also signals the condition of Pin ENCAL by its pull-down current: Ipd(REGEN) < 10 A Ipd(REGEN) > 100 A ENCAL = low ENCAL = high cf. Item No. 202 cf. Item No. 205
Controlled burst mode In controlled burst mode IC-NZ can pulse with up to 155 MHz, thus making it suitable for use in laser projection or data transmission. Controlled here means that a preset operating point is maintained during fast pulsing or the burst phase. A low power level is first regulated, for which REGEN and LENL must be high. Following this the middle or high power level can be set (LENx high). The control unit then switches over to the middle or high channel. As only one channel can be regulated at any one time and as the voltage at CIL must not increase by residual current (this could destroy the laser diode) the capacitor at CIL is discharged with a maximum of 100 nA. Once CIx has been regulated LENx can return to low. REGEN at low switches into burst mode and thus turns the control unit off. The preset operating point is maintained. To prevent the laser current rising due to residual current the capacitors for the three channels are discharged with a maximum of 100 nA. This process is illustrated in Figure 15. As the capacitors are discharged gradually the output levels must be regulated again after a certain period. With an integration capacitance (CIx) of 100 nF, for example, the level must
again be regulated after 500 s, with this rising to 1 ms with 200 nF.
EN REGEN
LENL LENx
CIL
CIx
I(Laser)
Figure 15: Controlled burst mode Extending the laser current IC-NZ also has a high-current mode. Here, the laser current no longer flows through the iC but passes instead through the external circuitry (RLDA, Q1, iC-HK); pin RSI is switched to VDD. The current monitor is still active and the shutdown threshold can be set us-
IC-NZ
FAIL-SAFE LASER DIODE DRIVER
Rev B2, Page 18/20 ing RLDA. iC-HK is a fast, spike-free laser switch with which up to 1.4 A can be driven in pulsed operation. An iC-HK can be connected to each channel on IC-NZ so that a maximum laser pulse current of 4.2 A can be achieved (depending on pulse frequency, duty cycle and thermal dissipation). To this end pins CIx (x:
VDD
L, M, H) on IC-NZ must be connected to the CI inputs of the relevant iC-HK and IC-NZ inputs LENx to iC-HK inputs EN1 and EN2 (Figure 16). Individual levels are set as described above in Switching up to three laser power levels.
Q1
RLDA
R1
SDIS
LENL
LENM
LENH
CLDA
REGEN LENL
LENM
LENH
RVDD LDA LDKH LDKM LDKL
LDK VDD
LD
MD
VDD
CIH CIH
CI
Safety Monitor Diode
RSI CIM CIM EN CIL
CI CI
LDK
VDD
EN1
iC-HK
GND AGND1
EN2
AGND2
LDK
VDD
EN1
iC-HK
GND AGND1
EN2
LENH
AGND2
SMD
IC-NZ
CIL
EN1
iC-HK
GND AGND1
EN2
LENM LENL
LENL MDL RMDM
AGND2
RSMD
RMDH RGND
RMM RMH
GND
CREF
AGND
RML
Figure 16: Extending the laser current
IC-NZ
FAIL-SAFE LASER DIODE DRIVER
Rev B2, Page 19/20 Driving blue laser diodes It is also possible to drive blue laser diodes with iCNZ. The laser diode is then directly powered by a second, higher voltage. The laser power is set as described above in Switching up to three laser power lev5..12 V
els. Figure 17 shows IC-NZ connected up to a blue laser diode. It is important to note that here the laser diode supply voltage should be as low as possible to keep iC power dissipation to a minimum.
VDD
SDIS VDD REGEN LENL LENM LENH
CLDA
LD MD
RVDD VDD LDA Current Monitor S1 RMDM NSEN EN Finite State Machine NSEN NTREN LDAOK RMDH
Safety Monitor Diode
RSI
RMM RMH
LDKH Safety Monitor Diode MDL Laser Driver APC LDKM SMD VREF
+ -
CIH CIH
+ -
VSAH
SMD(1) MDOK
VREF
MDL
Monitor
+ -
CIM CIM
RSMD
VSAL RGND
+ -
SMD(0) LDKL VREF
+ -
CIL CIL MDL AGND
IC-NZ
GND CREF
RML
Figure 17: Driving blue laser diodes
DEMO BOARD The IC-NZ device is equipped with a Demo Board for test purposes. A description of the demo board is available as a separate document.
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-NZ
FAIL-SAFE LASER DIODE DRIVER
Rev B2, Page 20/20 ORDERING INFORMATION
Type IC-NZ Evaluation Board
Package QFN28 5 mm x 5 mm
Order Designation IC-NZ QFN28 IC-NZ EVAL NZ1D
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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