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DIRECTED ENERGY, INC. PCO-7110 Laser Diode Driver Module
INSTALLATION and OPERATION NOTES
Directed Energy, Inc. An IXYS Company 2401 Research Blvd. Suite 108 Fort Collins, CO. 80526 TEL: 970-493-1901 FAX: 970-493-1903 EMAIL: deiinfo@directedenergy.com WEB: www.directedenergy.com
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Table of Contents Introduction ........................................................................................................2 Design Considerations.......................................................................................3 Circuit Operation ................................................................................................4 Current Measurement .............................................................................7 Specifications.....................................................................................................9 Mechanical Specifications.......................................................................10 Typical Output Waveforms......................................................................11 Warranty ............................................................................................................11
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Introduction The PCO-7110 is a compact, economical OEM pulsed laser diode driver module. It is designed to provide extremely fast, high current pulses to drive laser diodes in range finder, LIDAR, atmospheric communications and other applications requiring high current, nanosecond pulses. Six standard models are offered in the PCO-7110 product line, providing pulse currents ranging from 4A to 120A, and pulse widths from 4 nanoseconds to 65 nanoseconds, at frequencies as high as 50KHz. The PCO-7110 is designed to be an Original Equipment Manufacturer (OEM) style product in which the current pulse may be easily tailored to the diode type and application - contact DEI for more information. Mounting pads are provided to mount the laser diode directly to the driver. The four-hole mounting pattern accepts TO-18, TO-5, TO-52, 5.6MM, and 9MM packages (EG&G Optoelectronics R, S, T and U packages), as well as other packages of similar dimensions and lead spacing, mounted perpendicular to the driver circuit board. To facilitate different packages and mounting preferences, there are two solder pads on the end of the board to accept various laser diode packages mounted on axis to the driver. Furthermore, the diode can be connected remotely from the driver using a low-impedance stripline interconnection between the mounting pads and the leads of the laser diode. A current monitor output may be viewed with an oscilloscope, providing a straightforward means to observe the diode current waveform in real-time. The design is inherently temporally stable with large variations in ambient temperature and equally rugged with respect to mechanical parameters.
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Design Considerations Many elements and stray components may affect the PCO-7110 performance. One of the most important, which affects the performance greatly, is stray inductance. This is a combination of the output current loop's circuit elements and the physical inductance of that loop. The magnitude of this inductance has a great effect on the pulse width and the peak output current. The PCO-7110 design minimizes the stray inductance of the circuit components to approximately 2nH. However, the laser diode that it will drive and the means by which the diode is connected to the PCO-7110 also contribute to the stray inductance. This additional inductance, which is added to the system and will affect the output, is something that the user can minimize by appropriate diode package choice and interconnections between the diode and driver. Table 1 lists several laser diode package types and their Equivalent Series Inductance (ESL). Although many of the laser diode packages have the appearance of a good low inductance design, they are not. For example, the 832 STUD (line # 2) from all outward appearances is a low inductance package, however it has one of the largest ESL's of the devices listed. As shown in Table 1, this leaves the laser diode as the largest contributor of the total inductance.
# 1 Dip 14 Leads out top 2 3 4 5 6 Long Horn 14 Pin 7 8 9 10
.200 KOVAR Gold Plate .060 Hight .200 COPPER .039 Hight .078 COPPER
PACKAGE STYLE
PACKAGE INDUCTANCE 15.7nH
8-32 STUD 10-32 STUD TO-5 (2 lead) TO-52
12nH 11nH 9.6nH 6.8nH 6.4nH
CD9mm
.060 Hight
5.2nH 5.0nH 3.6nH 1.56nH
.014 lead diameter
.014 lead diameter
.014 lead diameter
Table 1 Package Style Vs Package Inductance
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Circuit Operation Table 2 below provides the pin outs of connectors JP1 and J1. Figure 1 provides the component side silk of the PCO-7110 to facilitate locating the various components mentioned in this section
PIN 1 PIN 2 PIN 3 PIN 4 PIN 5 PIN 6 PIN 7 PIN 8 PIN 9 PIN 10 PIN 1 PIN 2 PIN 3 Connector JP1 GND 15V @ 1mA +/-0.5mA GND GATE 5V into 50 GND NC NC NC NC HV IN, 0-195/495V @ IPS(see eq. 1) Connector J1 GND NC CONDUCTOR
Table 2. PCO-7110 Connector Pin Out
Figure 1. Component side silk
Referring to the above pin outs, there are three inputs: Trigger (GATE), Support Power (+15V) and DC High Voltage input (HV IN) on JP1. The trigger should be +5V into 50, with a pulse width of 50ns to 100ns. The current requirement for the +15V power supply is very low, on the order of 1mA. Connector J1 is the output of the current monitor. Connector JP1 is a DuPont/Berg #65611-172 two-row header on 0.1" centers. The header mates with a DuPont/Berg Mini-Latch Housing, part #65043-032 or equivalent, using DuPont/Berg mating receptacles #48236-000 or equivalent. Connector J1 is a DuPont/Berg #65500-236 one-row header on 0.1" centers. The header mates with a DuPont/Berg Mini-Latch Housing, part #65039-034 or equivalent, using DuPont/Berg mating receptacles #48236-000 or equivalent. A connector kit with the housings and receptacles for JP1 and J1 are available through DEI, as part #PCA-9210. The high voltage DC power supply is either 195V, 400V or 495V maximum voltage, depending upon the PCO-7110 model (see the Specifications section for power specific maximum DC input voltages for each model. The maximum
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average current that the high voltage supply must provide is determined by the pulse recurrence frequency required for the user's application. Equation 1 has been derived in order to approximate (20%) the current requirement (IPS) of the high voltage power supply. It is a function of the total input capacitance (the Pulse Forming Network CPFN, the FET capacitance CFET, and the stray CSTRAY), the high voltage input (VIN), and the frequency of each application (f). 1. I PS = (C PFN + C FET + C STRAY ) VIN f , where the various capacitances are given in Table 3. PCO-7110 MODEL 40-4 CPFN 1100pF CFET CSTRAY 120pF 200pF 50-15 4000pF 120pF 430pF 100-7 1100pF 150pF 550pF 120-15 4080pF 150pF 600pF 90-30 10800pF 150pF 100pF 45-65 7000pF 450pF 100pF
Table 3. CPFN values of the different PCO-7110 models
The output current of the PCO-7110 is adjusted by varying the applied voltage (VIN). The output current depends upon the available charge of the CPFN. This charge is directly proportional to the applied voltage. Therefore, varying the applied voltage will cause the output current to vary respectively. If the PCO7110 driver is operated at less than maximum output current, the maximum DC input voltage specified may not be required.
HV IN
R1 CHARGE RESISTOR
C PFN
R PFN
CLAMPING DIODES D2 D1 CATHODE (NEG) D3 LASER DIODE
0
J1 3 2 1 CVR MONITOR
ELECTRON FLOW
R CVR
-VOUT
Figure 2. Equivalent Circuit Diagram and Output Waveform
Figure 2 is the equivalent circuit diagram of the PCO-7110. It shows the location of the CPFN mentioned previously and the location of the laser diode in respect to the entire circuit. When monitoring the output waveform through J1, the waveform should approximate the one in Figure 2. For more details about
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current monitoring and output waveforms refer to sections "Current Measurement" and "Typical Output Waveforms." D3 is the laser diode mounting location. It is marked on the silkscreen, and is separated in the middle with a line. The right-most two holes are negative (NEG) for the cathode while the other two are positive (POS) for the anode.
Cathode
Anode
Figure 3. Cathode and Anode Pads on the PCB
TOP SIDE
ANODE CATHODE
BOTTOM SIDE
ANODE
POS POS
CATHODE
POS
NEG
Figure 4. Detailed View of Cathode and Anode Pads on the PCB
Figures 3 and 4 show where the cathode and anode are located on the board. It is very important to mount the diode properly to avoid damaging it. To facilitate different packages and user preferences, there are two strips of copper exposed; one on the top (component) side and one on the bottom (circuit) side of the PCB. The one on top is marked NEG and is for the cathode of the diode, while the one on the bottom is marked POS for the anode. These pads are provided to facilitate mounting the diode perpendicular to the edge of the board (axial mount) as shown in Figure 5, rather than using the mounting holes. A stripline interconnect may also be soldered to these pads. The laser diode can then be soldered to the opposite end of the stripline, allowing remote mounting or installation of the laser diode. These pads have no soldermask. If the diode case is connected to the anode of the diode, it is necessary to use an insulator when mounting the diode radially. This insulator should be for a TO-18 package, and will prevent the diode case from shorting to one of the pads. The driver is provided with kapton insulators. For higher average power applications, beryllium oxide (BeO) insulators are available upon request from DEI. The BeO insulators have lower thermal
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impedance than the kapton insulators, and will therefore help to better dissipate heat in the laser diode package.
AXIAL MOUNT
CATHODE ANODE
RADIAL MOUNT LASER DIODE INSULATOR PCB
PCB
LASER DIODE
Figure 5. Axial and Radial Mounting Positions
Figure 6: PCO-7110 Photos Showing Axially And Radially Mounted Laser Diodes
It is possible to mount the laser diode remotely using a strip line. It is imperative that this strip line be of low inductance. As mentioned in the "Design Considerations" section, inductance can greatly affect the circuit performance. Strip line material designed for use with the PCO-7110 is available from DEI (DEI stock #1820-0030). Current Measurement The current monitor signal provided on the PCO-7110 is available through connector J1. The output waveform will look very similar to that in Figure 2. Waveform photographs from an oscilloscope through the driver's internal monitor are included in the "Typical Output Waveforms" section. The physical topology of the PCO-7110's current monitor resistors yields a Current Viewing Resistor (CVR) with a bandwidth of approximately 500MHz. Since the resistance value of the CVR is low as compared to a 50 scope input, the CVR can be directly coupled to an oscilloscope with 50 cable. Ground loops are eliminated by wrapping several (3-10) turns of the coaxial cable around and through a high ferrite torroid or pot core, forming a common mode choke. This technique provides an accurate (3%), DC-500MHz current monitor, determined by 2. ILD =
VCVR RCVR
,
where ILD is the output current, VCVR is the value from the scope and RCVR is the equivalent resistance of the 10 chip resistors that make up the driver's CVR (0.1). In this case, the corresponding current is 10A per 1V.
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DEI provides an optional cable assembly (Part Number PCA-9140) with connectors to connect the current monitor output J1 to an oscilloscope input. This assembly is an RG-316 coax with a series termination of 50 Ohms at the CVR end, and a BNC connector on the other end. This in combination with the 50 Ohm terminator at the oscilloscope end will cause the above formula to become: V 3. I LD = 2 * CVR , RCVR The series termination eliminates any current signal reflections. Using the DEI CVR monitor cable, because of the series 50 Ohm termination, the current monitor becomes 10A = 500mV from 10A = 1V.
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Specifications The specifications in Table 4 below are for the six standard models. For OEM applications, the PCO-7110 can be configured to specific pulse width and output current levels to meet individual customer requirements - contact DEI for more information.
SPECIFICATIONS PCO-7110 MODEL 40-4 50-15 100-7 120-15 90-30 45-65 Pulse Output Current Range (Controlled by input high 4A to 40A 5A to 50A voltage amplitude) Maximum DC Input Voltage Pulse Width (FWHM at maximum output current)
5A to 5A to 5A to 4A to 45A 100A* 120A* 95A* +195V +495V +400V +495V 4ns 1ns 15ns 2ns 7ns 1ns 15ns 2ns 30ns 3ns 65ns 3ns 2.5ns 11KHz 2.5ns 5KHz** 2.5ns 2KHz 0.003% <3ns 1KHz 0.003% 35ns 1.5KHz 0.01% <2ns 55ns Typ.
Rise Time (10% - 90%, Typical) <2ns Maximum PRF (Pulse Recurrence Frequency), CW at 50KHZ maximum output current, controlled by input trigger Maximum Duty Cycle (CW at maximum output 0.02% current) Jitter (1st Sigma) Throughput Delay (Delay from input trigger to output pulse) Maximum Overshoot at maximum output current Output Current Monitor Trigger In Support Power MECHANICAL Length Width Height Weight (Approximate) Operating Temperature
0.0165% 0.0035% <1ns 33ns Typical
5% 10A/V into 50 Ohms +5V/50, 50-100ns pulse width +15V at 2mA 2.45 in. (62.2mm) 1.0 in. (25.4mm) 0.3 in. (7.5mm) 10 grams
o
12 grams -20 C to+85 C
o
0.5 in. (12.7mm) 14 grams
ALL SPECIFICATIONS MEASURED INTO A SHORTED OUTPUT AND MEASURED WITH THE INTERNAL CURRENT MONITOR SPECIFICATIONS SUBJECT TO CHANGE WITHOUT NOTICE * LASER DIODE NOT INCLUDED * Maximum output current must be derated by 15% at operating temperatures above 60oC ** Maximum current must be limited to 90A at frequencies above 2.5KHz.
Table 4
PCO-7110 Specifications
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Mechanical Specifications Figure 7 contains the dimensions for the mounting holes of the standard PCO7110, and Figure 8 is a detailed mechanical dimensional drawing. The mounting holes in the four corners are 0.125" through-holes, to clear a #4 screw. These drawings facilitate the design of the mechanics of the supporting system.
1.00in. 0.80in.
2.25in. 2.45in.
Figure 7: Mounting Hole Locations
Figure 8: Detailed Mechanical Dimensions
(Mounting holes in corners are 0.125" through-holes)
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Typical Output Waveforms Below are typical output waveforms for the various PCO-7110 models. All waveforms are shown driving a short in place of the laser diode.
Model 40-4-Typical Output Waveform 4ns Pulse Width, 45A Output
(10ns/Div horizontal scale, 10A/Div vertical scale)
Model 45-65-Typical Output Waveform 65ns Pulse Width, 48A Output
(50ns/Div horizontal scale, 10A/Div vertical scale)
Model 50-15 Typical Output Waveform 15ns Pulse Width, 56A Output
(10ns/Div horizontal scale, 10A/Div vertical scale)
Model 100-7 Typical Output Waveform 6ns Pulse Width, 120A Output
10ns/Div horizontal scale, 20A/Div vertical
Model 120-15 Typical Output Waveform 15ns Pulse Width, 120A Output
10ns/Div horizontal scale, 20A/Div vertical
Model 90-30 Typical Output Waveform 30ns Pulse Width, 99A Output
25ns/Div horizontal scale, 20A/Div vertical
Warranty There are no warranties, express or implied, including any implied warranty of fitness for a particular purpose nor any IMPLIED WARRANTY OF MERCHANTIBILITY made by Directed Energy, Inc. (DEI) except as follows: DEI warrants equipment manufactured by it to be free from defects in materials and/or workmanship under conditions of normal use for a period of one year from the date of shipment to the purchaser. DEI will repair or replace, at DEI's option, any product manufactured by it which is shown to be defective or fails to perform within specifications within one year from the date of shipment to the purchaser. OEM, modified and custom items of equipment are similarly warranted, for a period of ninety (90) days from date of shipment to the purchaser. Equipment claimed to be defective must be returned, transportation prepaid, to DEI's factory in Fort Collins, Colorado within the warranty period. Returns must be preauthorized by contact with DEI's customer service department. Written documentation of such preauthorization shall be included with the returned item. At DEI's discretion, DEI may elect to repair or replace the equipment claimed to be defective or refund the original purchase price, plus taxes and transportation charges incurred by the purchaser.
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This Warranty shall not apply to any product that has been: 1. Repaired, worked on, or altered by persons unauthorized by DEI; 2. Subjected to misuse, neglect, or damage by others; or 3. Connected, installed, adjusted, or used in a manner not authorized in the instructions or specifications furnished by DEI. This warranty is the purchaser's sole remedy for claimed defects in the equipment sold or manufactured by DEI. DEI's liability to the purchaser is limited to the repair or replacement of the claimed defective equipment or, at DEI's option, refund of the purchase price, taxes and transportation charges incurred by the purchaser. DEI will not be responsible for or liable to the purchaser for consequential losses or damages asserted to be attributable to a claimed defect in the equipment provided. Changes made by DEI in the design or manufacture of similar equipment which are effected subsequent to the date of shipment of the warranted equipment to the purchaser are reflective of DEI's program of constant product development and improvement and shall not be construed as an acknowledgement of deficiency in the product shipped to purchaser. DEI will be under no obligation to make any changes to product previously shipped.
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