iC-NZ FAIL-SAFE LASER DIODE DRIVER Rev B2, Page 1/20 FEATURES APPLICATIONS ♦ Peak value controlled three level laser switch for operation from CW up to 155 MHz ♦ Spike-free switching of laser currents of ca. 100 mA per channel (320 mA total) from 3.5 to 5 V supply voltage ♦ Single-failure-proof ♦ System-enable with self test ♦ Separate setting of laser power for each channel via external resistors ♦ Strong suppression of transients with very small external capacitors ♦ Adjustable laser current monitor ♦ Safety shutdown with overcurrent, overtemperature and undervoltage ♦ Autonomous safety circuit for a second photo diode monitoring the laser power ♦ All current LD types can be used (M/P/N configurations) ♦ Error signal output at shutdown ♦ Pulsed LD modules for safety applications ♦ Distance measurement PACKAGES QFN28 5 mm x 5 mm BLOCK DIAGRAM LENL SDIS LENM LENH REGEN +5 V LDA VDD Safety Monitor Diode Current Monitor RSI RVDD RSI LD MD NSEN RSIOV LDAOK NTREN EN LDKH MDOK LDKM CIOK ENCAL LDKGND FSM LDKL NSEN NERR CIH NSF CIH CIM NPDR TEMPOK CIL MDL Safety Monitor Diode SMD + SMD(1) − VSH RSMD + Laser Driver CIM CIL RMDM RMDH VBG and Reference SMD(0) RMH VBG and Reference − VSL AGND GND RMM RML RGND VREF suitable laser diode configurations N P M LD LD MD Copyright © 2007 iC-Haus MD LD MD 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 re- ported 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 Conditions Unit Min. Max. G001 VDD Supply Voltage VDD Current G002 I(VDD) Current in VDD -0.7 G003 I(CIx) Current in CIx G004 I(NSF) Current in NSF G005 I(SMD) Current in SMD 20 mA G006 I(NERR) Current in NERR 20 mA G007 I(MDL) Current in MDL 20 mA G008 I(RMDx) Current in RMDx 20 mA G009 I()dig Current in LENL, LENM, LENH, REGEN, NEN, ENCAL 20 mA G010 I(LDKx) Current in LDKx 300 mA G011 I(LDA) Current in LDA 400 mA G012 I(RSI) Current in RSI 20 mA G013 I(SDIS) Current in SDIS 20 mA G014 I(VREF) Current in VREF 50 mA G015 V()c Voltage at RMDH, RVDD, RMDM, NSF, MDL, ENCAL, SMD, VREF, REGEN, CIx, LENx, NERR, LDA, RSI, SDIS -0.7 6 V G016 V()h Voltage at LDKx -0.7 15 V G017 Vd() ESD Susceptibility at all pins 2 kV G018 Tj Operating Junction Temperature -40 150 °C G019 Ts Storage Temperature Range -40 150 °C V(LDA) = 0 HBM, 100 pF discharged through 1.5 kΩ 6 V 400 mA 5 mA 20 mA THERMAL DATA Operating Conditions: VDD = 3.5...5.5 V Item No. Symbol Parameter Conditions Unit Min. T01 Ta Operating Ambient Temperature Range (extended range on request) T02 Rthja Thermal Resistance Chip/Ambient Typ. -20 surface mounted, thermal pad soldered to ca. 2 cm² heat sink 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. 30 Max. 90 °C 40 K/W 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. Symbol Parameter Conditions Unit Min. Typ. Max. 5.5 V 460 600 µA Total Device 001 VDD Permissible Supply Voltage 002 Ioff(VDD) Supply Current in VDD EN = lo 3.5 003 Idc(VDD) Supply Current in VDD EN = hi, RSI > 780 Ω 10 mA 004 Tab Thermal Shutdown Threshold 110 150 °C 005 VDDen Power-On Threshold 2.1 2.95 V 006 Vc()hi Clamp Voltage hi at REGEN, LENH, LENM, LENL, EN, ENCAL, LDA, NERR, NSF I() = 1 mA, other pins open, VDD = 0 0.3 1.5 V 007 Vc()hi Clamp Voltage hi at CIx, MDL, RMDH, RMDM SMD I() = 1 mA, other pins open, VDD = 0 0.3 1.6 V 008 Vc()hi Clamp Voltage hi at LDKx I() = 1 mA, other pins open 12 009 Vc()hi Clamp Voltage hi at RSI, VREF I() = 1 mA, other pins open, VDD = 0 0.3 010 Vc()hi Clamp Voltage hi at SDIS I() = 1 mA, other pins open 6 011 Vc()lo Clamp Voltage lo I() = 1 mA, other pins open 6.4 V 0.9 1.5 V -1.5 -0.65 -0.3 V 440 500 550 mV V Reference 101 V(MDL) Voltage at MDL, VDD − V(MDL) for P-type LD closed control loop 102 dV(MDL) Temperature Drift of Voltage at MDL closed control loop 103 I() Current in MDL, RMDM, RMDH LENL, LENM, LENH = hi -500 500 nA 104 V(VREF) Voltage at VREF, VDD − VREF for P-type LD iC active 405 480 550 mV 120 µV/°C Digital Inputs 201 Ipd() Pull-Down Current in LENx, EN V(LDA) = V(VDD) 1 4 10 µA 202 Ipd (REGEN) Pull-Down Current in REGEN V(LDA) = V(VDD), V(ENCAL) < Vt() 1 4 10 µA 203 Vt() Threshold Voltage at LENx, REGEN, ENCAL, EN VDD = 5 V 0.75 1.8 2.2 V 204 Vhys() Hysteresis 205 Rpd (REGEN) Pull-Down Resistor at REGEN 206 Rpd (ENCAL) Pull-Down Resistor at ENCAL 800 V(ENCAL) > Vt() mV 4 20 kΩ 10 30 kΩ Safety Monitor Diode 301 VSL Monitor Threshold lo, Signal SMD(0) 265 300 325 mV 302 VSH Monitor Threshold hi, Signal SMD(1) 615 680 750 mV 303 dVS VSH − VSL 350 390 430 mV 304 VCHK Test Voltage for SMD 120 %VSH 305 I(RSMD) Permissible Safety Monitor Diode Current 5 mA 306 Ipd(SMD) Pull-Down-Current in SMD 0.6 3 µA 1.2 0.8 2 1.3 V V Laser Driver LDKx, CI, RMDx 401 Vs(LDKx) Saturation Voltage at LDKx 0.2 one channel only is activated; I(LDK) = 100 mA I(LDK) = 60 mA 402 Idc(LDKL) Permissible Current DC 120 mA 403 Idc(LDKM) Permissible Current DC 100 mA 404 Idc(LDKH) Permissible Current DC 100 mA 405 Vo() Permissible Voltage at LDKx 406 VCI() REGOK Monitor Threshold 100 760 12 V 900 mV 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. Symbol Parameter Conditions Unit Min. Typ. Max. 0.6 1 mA 407 C(CIx) Capacitance at CIx 408 |I(CIx)| Charge Current from CIx iC active, control unit not yet settled 100 409 I(CIx) Discharge Current in CIx iC inactive, V(CIx) > 1 V 10 60 mA 410 411 Ipd(CIx) Pull-Down Current in CIx iC active, REGEN = lo 25 150 nA I(RMDx) Permissible Laser Monitor Diode Current active safety function; VDD = 5 V VDD = 3.3 V 2.5 1 mA mA 0.25 nF Status Outputs 501 I(NERR) Current at Error Message V(LDA) = V(VDD) = V(NERR), error state 1.5 10 mA 502 I(NERR) Current in NERR V(LDA) = V(VDD) = V(NERR), no error state, V(MDL) < 0.5 V 0.1 1 mA 503 I(NSF) Current at NSF Message V(LDA) = V(VDD) = V(NSF), V(NSF) > 0.8 V 1.5 10 mA 504 I(SDIS) Current at SDIS Message V(LDA) = V(VDD) = V(SDIS), V(SDIS) > 0.8 V 1.0 10 mA 505 Vsat() Saturation Voltage at NERR, NSF, SDIS Isat = 1 mA, NERR in error state 600 mV 560 mV Current Monitor RSI, LDA 601 V(RSI) Controlled Voltage at RSI 602 RSI Resistor at RSI EN = hi 0.78 430 603 VLDA LDAOK Monitor Threshold VDD – V(LDA) 440 604 Idc(LDA) Current from LDA DC 605 Rpd(LDA) Pull-Down Resistor at LDA Reset 606 td(SDIS) Overcurrent Shutdown Delay I(LDA) > I(RSI) * 500 607 rILDA Current Ratio I(LDA)max / I(RSI) 780 Ω < RSI < 9000 Ω 608 Ipd(RSI) Pull-Down Current in RSI V(RSI) > 0.5 V 400 1 490 490 500 9 kΩ 550 mV 320 mA 1 kΩ 10 µs 650 10 µA Timing 701 ten Propagation Time: EN lo → hi system enable no error at self test, CLDA = 1 µF 300 µs 702 tr Laser Current Rise Time see Fig. 2 1.5 ns 703 tf Laser Current Fall Time see Fig. 2 1.5 ns 704 tplh Propagation Time: LENx lo → hi to Current lo → hi see Fig. 3 10 ns 705 tphl Propagation Time: LENx hi → lo to Current hi → lo see Fig. 3 10 ns 706 ts0 Propagation Time: see Fig. 4 V(SMD) > VSL to SMD(0) lo → hi Tj = 27 °C Tj = 85 °C 220 240 ns ns 707 ts0off Propagation Time: V(SMD) < VSL to SMD(0) hi → lo 220 ns 708 ts1 Propagation Time: see Fig. 4 V(SMD) > VSH to SMD(1) lo → hi 220 ns 709 toff Propagation Time: SMD(1) lo → hi until shutdown see Fig. 4 10 ns 710 td Propagation Time: SMD(1) lo → hi until error message see Fig. 4 500 ns iC-NZ FAIL-SAFE LASER DIODE DRIVER Rev B2, Page 7/20 ELECTRICAL CHARACTERISTICS: DIAGRAMS V Input/Output VDD−0.45V Vt()hi LENL Vt()lo 0.45V t 1 0 LENM LENH Figure 1: Reference levels I(LDKL) I(LED) tr I(LDKM) tf I pk I(LDKH) 90% I pk t phl t plh t plh t phl t phl t plh V(MDL) 10% I pk t Figure 2: Laser current pulse Zeit Figure 3: Turn on/turn off behavior of the laser current ENCAL LENL LENM LENH P(Laser) Ph Pm Pl Zeit V(MDL) 0.5V Zeit V(SMD) VSH VSL Zeit SMD(0) SMD(1) t S0 t S1 t d NERR NSEN t off NTREN 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 9 Warning! . . . . . . . . . . . . . . . . . . . . 12 OPERATION WITH ONE OR TWO CHANNELS 12 SINGLE-FAILURE PROTECTION 15 Monitoring the laser current . . . . . . . . . . 9 Demo board . . . . . . . . . . . . . . . . 9 Switching up to three laser power levels . . . 9 1. Enabling the system . . . . . . . . . . . . . 10 Demo board . . . . . . . . . . . . . . . . 10 Possible sources of error . . . . . . . . . . . 10 2. Calibrating the low and middle channels . 10 Setting the low output level . . . . . . . . . . 10 Demo board . . . . . . . . . . . . . . . . 10 Setting the middle channel . . . . . . . . . . 10 Status outputs NERR, NSF and REGEN . . . 17 Demo board . . . . . . . . . . . . . . . . 11 Controlled burst mode . . . . . . . . . . . . . 17 3. Calibrating the high channel . . . . . . . . 11 Extending the laser current . . . . . . . . . . 17 Demo board . . . . . . . . . . . . . . . . 11 Driving blue laser diodes . . . . . . . . . . . . 19 Possible sources of error . . . . . . . . . . . 11 Demo-Board . . . . . . . . . . . . . . . . . . 12 Calibrating the safety monitor diode . . . . . 15 Demo-Board . . . . . . . . . . . . . . . 15 Operation without a second monitor diode . . 15 Demo-Board . . . . . . . . . . . . . . . 15 MISCELLANEOUS DEMO BOARD 17 19 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: • Extension of the laser current with few external components • Operation of blue laser diodes possible • 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 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 SDIS VDD VDD x500 LDA NSEN CURRENT MONITOR ILDA S3 x1 S2 NEN + − CLDA 0.5V VREF LD MD RSI S1 IRS RSI LDAOK NSEN EN FINITE STATE MACHINE Figure 5: Monitoring the laser current When dimensioning resistor RSI the following applies: Imax (LDA) = 500 × 0.5 V RSI 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 current RSI is calculated as: RSI = 500 × 0.5 V = 3.5 k Ω 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 Ω, 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 µA) 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. V(EN) V(LDA) VCHK V(SMD) VREF V(MDL) V(NERR) 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 Ω. – 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 µA. 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 Ω IM 15 µA 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 µA. This current must flow through the parallel connection of RMLn and RMMn (RMMn = PMM + RMM). The following then applies: RMLn||RMMn = RMMn = RMMn = V (MDL) 0.5 V = 11.62 k Ω = IM 43 µA RMLn||RMMn ∗ RMLn RMLn − RMLn||RMMn 11.62 k Ω ∗ 33.34 k Ω = 17.84 k Ω 33.34 k Ω − 11.62 k Ω 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 µA. The following value is then obtained for resistor RMHn = PMH + RMH: RMLn||RMMn||RMHn = RMHn = V (MDL) 0.5 V = = 6.25 k Ω IM 80 µA RMLn||RMMn||RMHn ∗ RMLn||RMMn RMLn||RMMn − RMLn||RMMn||RMHn RMHn = 6.25 k Ω ∗ 11.62 k Ω = 13.52 k Ω 11.62 k Ω − 6.25 k Ω 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. 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 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 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 short- circuited 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 LENL REGEN SDIS VDD LENM LENH RVDD VDD LDA C1 Safety Current Monitor RSI S1 Monitor Diode RSI LDAOK NSEN LD EN Finite State Machine NSEN MD NTREN LDKH VREF Safety Monitor Diode RMDH CIH + MDL − CIH Laser Driver RMDM APC LDKM SMD + VREF SMD(1) − MDL + − Monitor + RSMD CIM MDOK VSAH SMD(0) − LDKL VSAL VREF RGND + CIL − MDL AGND VREF GND RML CREF Figure 8: One-channel operation with safety function (N-type laser diode) VDD LENL REGEN SDIS LENM LENH VDD RVDD VDD LDA C1 Current Monitor RSI S1 RMDH CLDA RSI LDAOK NSEN MDL EN Finite State Machine RMDM NSEN NTREN RMDH LDKH SMD VREF Safety Monitor Diode + MDL CIH LD − CIH Laser Driver APC LDKM SMD + VREF SMD(1) − VSAH RSMD MDL + − Monitor + CIM MDOK SMD(0) − LDKL VSAL VREF RGND + CIL − AGND GND CREF Figure 9: One-channel operation with safety function (P-type laser diode) MD iC-NZ FAIL-SAFE LASER DIODE DRIVER Rev B2, Page 14/20 VDD REGEN SDIS LENM LENL LENH VDD RVDD VDD LDA C1 Safety Current Monitor S1 RSI CLDA Monitor Diode RSI LDAOK NSEN LD EN Finite State Machine RMDH NSEN MD NTREN RMH LDKH VREF Safety Monitor Diode CIH + MDL − CIH Laser Driver APC LDKM SMD + VREF SMD(1) − MDL + − Monitor + RSMD CIM MDOK VSAH SMD(0) − LDKL VSAL VREF RGND + CIL − CIL MDL AGND RML GND CREF Figure 10: Two-channel operation with safety function (N-type laser diode) VDD REGEN SDIS LENL LENM LENH VDD RVDD VDD LDA C1 RSI Current Monitor S1 RML CLDA RSI LDAOK NSEN MDL EN Finite State Machine RMDM RMH NSEN NTREN RMDH LDKH SMD VREF Safety Monitor Diode CIH + MDL LD − CIH Laser Driver APC LDKL SMD + − MDL + − Monitor + CIM MDOK VSAH RSMD VREF SMD(1) SMD(0) − VSAL LDKL VREF RGND + CIL − CIL AGND GND CREF Figure 11: Two-channel operation with safety function (P-type laser diode) MD 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. 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. 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 LENL REGEN SDIS VDD LENM LENH RVDD VDD LDA C1 RSI Current Monitor S1 CLDA RSI RMDH LDAOK NSEN EN RMDM RMDL MDL Finite State Machine NSEN NTREN RMDM RMDH SMD VREF Safety Monitor Diode LDKH + MDL − LD CIH MD CIH Laser Driver APC SMD + − MDL LDKL + MDOK VSAH RSMD2 VREF SMD(1) − CIM Monitor + CIM SMD(0) − CSMD VSAL RSMD1 VREF LDKL + RGND − CIL CIL iC−NZ AGND 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). 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. 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. 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 REGEN SDIS VDD LENL LENM LENH VDD C1 LDA Current Monitor RSI Laser Driver RSI RSIOV LDAOK NSEN CLDA EN LD MD NTREN LDKH MDOK ENCAL LDKM CIOK LDKGND Finite State Machine NERR LDKL NSEN CIH NSF CIH CIM NPDR TEMPOK CIM CIL CIL MDL Safety Monitor Diode VBG and Reference SMD + RMDH VBG and Reference RMDM SMD(1) − VSH + RMH SMD(0) RMM RML RGND − VSL VREF Figure 13: Operation without a second monitor diode (N-type laser diode) REGEN SDIS VDD LENL LENM LENH VDD LDA RVDD C1 Current Monitor RSI Laser Driver RSI RSIOV LDAOK NSEN RMH CLDA RML RMM NTREN EN MDOK ENCAL CIOK Finite State Machine RMDH LDKGND NERR RMDM NSEN MDL NSF NPDR TEMPOK LD Safety Monitor Diode VBG and Reference SMD + MD LDKH VBG and Reference LDKM LDKL SMD(1) − CIH VSH + CIH CIM SMD(0) − CIL CIM VSL CIL 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 I(NERR) > 1.5 mA 0 < I(NERR) < 1.5 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 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 µA Ipd(REGEN) > 100 µA 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. again be regulated after 500 µs, with this rising to 1 ms with 200 nF. EN REGEN LENL 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 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: 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. VDD Q1 RLDA LENL R1 LENM REGEN LENL SDIS LENH LENM CLDA LENH RVDD MD LD LDA LDKH LDKM LDKL LDK CIH VDD VDD CI CIH Safety Monitor Diode LDK RSI CIM CIM LDK CIL VDD EN1 iC−HK GND CI AGND1 EN1 LENL iC−HK GND AGND1 EN2 LENM LENL AGND2 MDL RMDM RSMD RMM RMDH RGND RMH GND CREF AGND Figure 16: Extending the laser current AGND1 EN2 AGND2 LENH EN2 AGND2 CIL iC−NZ iC−HK GND CI EN SMD EN1 VDD RML 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 lev- 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. 5..12 V CLDA VDD REGEN SDIS LENL LENM LD LENH RVDD VDD MD VDD LDA Safety Monitor Diode RSI Current Monitor S1 RMDM LDAOK NSEN EN Finite State Machine RMM RMDH NSEN NTREN RMH LDKH VREF Safety Monitor Diode MDL + − CIH + − CIM CIH Laser Driver APC LDKM SMD + VREF SMD(1) MDL − MDOK VSAH Monitor + RSMD CIM SMD(0) − LDKL VSAL VREF RGND + − CIL CIL iC−NZ MDL AGND RML GND CREF 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 Package Order Designation iC-NZ QFN28 5 mm x 5 mm iC-NZ QFN28 Evaluation Board 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: [email protected] Appointed local distributors: http://www.ichaus.de/support_distributors.php