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MITSUBISHI DIGITAL ASSP MITSUBISHI DIGITAL ASSP
M66512P/FP M66512P/FP
LASER-DIODE DRIVER LASER-DIODE DRIVER
DESCRIPTION The M66512 is a semiconductor laser-diode driver for driving a specific type* of semiconductor laser, in which the anode of a semiconductor laser diode is connected in stem structure to the cathode of a monitoring photodiode. The amplitude of laser drive current is set by applying a voltage from an external source. the M66512 is capable of driving laser diodes on a maximum current of 120 mA. It operates on a 5-V single power supply and switches laser drive current at a rate of 40 Mbit/s. *: The N type of Mitsubishi's semiconductor lasers. FEATURES * Two kinds of outputs for monitoring laser power built in. (comparator output and analog output) * Pin provided for forced OFF of current circuit. * High speed switching (40 Mbit/s) * Large drive current (120mA max.) * 5V single power supply APPLICATION Laser beam printers
PIN CONFIGURATION (TOP VIEW)
VCC1 CURRENT SETTING INPUT 1 VL1 CURRENT SETTING LOAD OUTPUT 1 1RC CURRENT SETTING INPUT 2 VL2 CURRENT SETTING LOAD OUTPUT 2 2RC LASER CURRENT FORCED OFF INPUT VOFF CURRENT SETTING LOAD OUTPUT 3RC GND1 MONITORING LOAD INPUT 1 1RM MONITORING LOAD INPUT 2 2RM
1 2 3 4 5 6 7 8 9 10
20 19 18 17 16 15 14 13 12 11
RO LOAD OUTPUT NC LD LASER DIODE OUTPUT GND2 PD MONITORING DIODE INPUT DATA DATA INPUT VCC2 MONITORING CO COMPARATOR OUTPUT MO MONITORING ANALOG OUTPUT NC
LASER CURRENT
Outline 20P4 20P2N-A
NC: No Connection
M66512P/FP
BLOCK DIAGRAM
MONITORING OUTPUT MO 12 Linear amp COMPARATOR OUTPUT CO 13 Comparator (Vref=1.4V)
PD 16
LD 18
RO 20
1RM 9 2RM 10 VL1 2 1RC 3 VL2 4 2RC 5
Differential amp
Current switching circuit
15 DATA DATA INPUT
IL=IL1+IL2+IL3 Constant current source(IL1) Max.60mA Constant current source(IL2) Max.30mA Constant current source(IL3) Max.30mA
6 VOFF LASER CURRENT FORCED OFF 1 VCC1 14 VCC2 8 GND1 17 GND2
3RC 7
VL1, 1RC : Laser current (IL1) setting pin VL2, 2RC : Laser current (IL2) setting pin 3RC : Laser current (IL3) setting pin
VCC1, GND1 : Power supply pin for analog circuits in IC VCC2, GND2 : Power supply pin for digital circuits in IC
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MITSUBISHI DIGITAL ASSP
M66512P/FP
LASER-DIODE DRIVER
FUNCTION The M66512 is a semiconductor laser-diode driver for driving a specific type (Mitsubishi's N type) of laser, in which the anode of a semiconductor laser diode is connected in stem structure to the cathode of a monitoring photodiode. The amplitude of laser drive current is set by applying a constant voltage from an external source. For that purpose, the M66512 has two voltage applying pins, which they are independent each other, This mechanism makes it possible to set a drive current with great accuracy.
As the IC is equipped with a pin to provide a forced OFF of current circuit, it is possible to prevent a large current flowing through laser diodes at the moment of power ON. Regarding the detection of laser power, a monitor current generated by a monitoring photodiode, which is incorporated in laser unit, is drawn and converted into changes in voltage by means of an external resistor, in order to output as an analog signal. Simultaneously, the converted voltage is compared with the internal reference voltage, thence the result is output in TTL level as logic information.
PIN DESCRIPTIONS
Pin LD PD VL1 1RC VL2 2RC 3RC DATA 1RM, 2RM MO CO VOFF RO VCC1 VCC2 GND1 GND2 Name Laser connection pin Monitoring diode connection pin Voltage input pin for IL1 setting Load resistor connection pin for IL1 setting Voltage input pin for IL2 setting Load resistor connection pin for IL2 setting Load resistor connection pin for IL3 setting Switching data input pin Load resistor connection pins for monitoring function Analog output pin for monitoring function Comparator output pin for monitoring function Laser current forced OFF input pin Load resistor connection pin for laser current Power supply pin 1 Power supply pin 2 GND pin 1 GND pin 2 Functions Connect to cathode on semiconductor laser diode. Connect to cathode on monitoring photodiode. Voltage input to set output current (IL1) of current source 1. Connect load resistor between this pin and GND for IL1 setting. Voltage input to set output current (IL2) of current source 2. Connect load resistor between this pin and GND for IL2 setting. Connect load resistor between this pin and GND for IL3 setting. Leave this pin open if IL3 is not used. Laser turns on and off by "L" and "H", respectively. Connect resistor between pins 1RM and 2RM for conversion of current generated by monitoring photodiode into changes in voltage. Analog output for monitoring laser power Comparator output for monitoring laser power If this is "L", all current supply circuits are turned off. Connect load resistor between RO and VCC for laser current. Power supply for internal analog circuits. Connect to positive power source (+5V) Power supply for internal digital circuits. Connect to positive power source (+5V) GND for internal analog circuits GND for internal digital circuits
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MITSUBISHI DIGITAL ASSP
M66512P/FP
LASER-DIODE DRIVER
OPERATION 1. Setting for Laser Drive Current The M66512 has 3 built-in constant current sources, IL1, IL2, and IL3. Each output current can be controlled independently. The following (1) to (3) describe the method for how to set IL1,IL2, and IL3. (1) IL1 setting method The value of IL1 is determined by the voltage on the VL1 pin and the resistor (RC1) connected between the 1RC pin and GND. The following equation is used for approximation. VL1[V] IL1 [mA] = 12 x RC1 [k] provided that 0VL1VCC-1.8V and IL1(max.) =60mA (2) IL2 setting method The value of IL2 is determined by the voltage on the VL2 pin and the resistor (RC2) connected between the 2RC pin and GND. The following equation is used for approximation. VL2[V] IL2[mA] = 6 x RC2 [k] provided that 0VL2VCC-1.8V and IL2(max.) =30mA (3) IL3 setting method The value of IL3 is determined by the internal reference voltage (Vref) and the resistor (RC3) connected between the 3RC pin and GND. The following equation is used for approximation. IL3[mA] = 10 x Vref[V] RC3 [k] provided that Vref =1.4V (typ.) and IL3(max.) =30mA Note: Each of the above equations is a typical on for obtaining IL1-IL3. In practice values vary by a few percent due to some reasons such as differences of ICs from lot to lot and variations in operation temperatures. 2. Switching Operation The laser turns on if DATA ="L". The laser drive current at that moment is IL1 +IL2 + IL3. If DATA = "H" the laser is turned off, and the laser drive current is almost zero irrespective of the values of IL1 to IL3. 3. Use of the VOFF Input When DATA = "H" the current flowing through the laser is zero so the laser is turned off, but the internal current sources are in operation. When VOFF = "L" in contrast, the internal current sources are turned off. Accordingly, it is possible to prevent an excessive current from flowing through the laser by, for example, fixing the VOFF input to "L" until VCC, after turned on, reaches 3.5V(typ.). (See the section dealing with internal reset.) 4. Laser Power Monitoring Operation At the MO and CO pins, the M66512 outputs data obtained by the monitoring photodiode (PD) contained in the laser, in the sequence explained below.
(1) A current equal to the PD current generated by laser light flows through the resistor (RM) connected between 1RM and 2RM. Then, a potential difference (VM) proportional to the output of laser light occurs at RM. (2) The VM is output at the MO pin as an analog signal through a buffer amp. At the same time, VM is compared with the internal reference voltage Vref(1.4V typ.) by the comparator, thence the result of the comparison is output at the CO pin in TTL level.
LD PD
_ + + MO output Buffer amp
VM
RM Vref
_
CO output Comparator
Condition VMVref
CO output "L" "H"
A Schematic Diagram of Monitor Circuits
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MITSUBISHI DIGITAL ASSP
M66512P/FP
LASER-DIODE DRIVER P=ICC x VCC +I(RO) x V(RO) + I(LD) x V(LD) + IOL(CO) x VOL(CO) Where V(RO) : voltage at RO pin : voltage at LD pin V(LD) : load current at RO pin I(RO) I(LD) : load current at LD pin VOL(CO) : "L" output voltage at CO pin IOL(CO) : "L" output voltage at CO pin If, for example, VCC = 5.25V, V(RO) = V(LD) = 2.75V, I(RO) = I(LD) = 120mA, IOL(CO) = 8mA, and VOL(CO) = 0.5V, power dissipation at times of turning on and off of laser will be as follows. (1) Laser ON (DATA ="L" and ICC = 75mA) PON = 75 x 5.25 + 0 + 120 x 2.75 + 8 x 0.5 = 727.8(mW) (2) Laser OFF (DATA ="H" and ICC = 74mA) POFF = 74 x 5.25 + 120 x 2.75 + 0 = 718.5(mW)
5. RO Pin The RO pin is used to connect a load resistor (RO) for the current sources (IL1, IL2, and IL3). The load resistor is connected between the RO pin and VCC in order to reduce the power dissipated in the IC. The resistance of the load resistor should be such that does not generate a voltage equal to or lower than 2.5V at the RO pin. Accordingly, a value that satisfies the following equation should be chosen. VCC-2.5[V] RO () maximum load current flowing through RO [A] Example: If VCC =5V and the maximum load current is 120 mA, RO is 20 or under. 6. Internal Reset Function The M66512 has a reset circuit for the protection of laser from an excessive current flowing at the moment of power on. The reset circuit functions in the range VCC < 3.5V(typ.), letting all current sources turn off. 7. VCC and GND Pins Pins related to the power supply function are VCC1, VCC2, GND1, and GND2. The role of these pins in terms of the internal circuits are as follows. VCC1, GND1 : connected to analog circuits VCC2, GND2 : connected to digital circuits In practical wiring, the following should be noted. (1) Secure as much a width as possible for conductors and avoid lengthy wiring. (2) Allocate electrolytic capacitors for stable voltage near VCC1 and GND1. (3) Allocate by-pass capacitors near VCC2 and GND2. Notes on the Wiring for peripheral Components Lay out peripheral components necessary for the M66512 to operate in closest possible proximity to the M66512. Calculation Method for Power Dissipation The M66512's approximated power dissipation, P, is determined by the following equation.
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MITSUBISHI DIGITAL ASSP
M66512P/FP
LASER-DIODE DRIVER
OPERATING WAVEFORMS
P0
Laser output
Laser output
Laser current IL IL3 IL1 IL2
IL1 : 0~60mA IL2 : 0~30mA IL3 : 0~30mA
Drive current pulse
ABSOLUTE MAXIMUM RATINGS
Symbol VCC VI VO IL1 IL2 IL3 Pd Tstg Parameter Supply voltage VL1, VL2 Input voltage DATA, VOFF CO Output voltage RO Output current 1 Output current 2 Output current 3 DIP Power dissipation SOP Storage temperature Conditions Ratings -0.5 ~ +7.0 -0.3 ~ VCC -0.3 ~ + 7 -0.3 ~ + 5.5 -0.3 ~ + 7 90 45 45 1300 1200 -65 ~ 150 Unit V V V mA mA mA mW C
Output: "H"
For single integrated circuit; Ta=25C (Note 1) IC Measured being mounted; Ta=25C (Note 2)
Note 1: For operation above 25C free-air temperature, derating of 10.4mW/C is necessary. 2: For operation above 25C free-air temperature, derating of 9.6mW/C is necessary.
RECOMMENDED OPERATIONAL CONDITIONS
Symbol VCC IL1 IL2 IL3 Topr Parameter Supply voltage Output current 1 Output current 2 Output current 3 Operational ambient temperature Conditions Min. 4.75 Limits Typ. 5 Max. 5.25 60 30 30 75 Unit V mA mA mA C
-20
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MITSUBISHI DIGITAL ASSP
M66512P/FP
LASER-DIODE DRIVER
ELECTRICAL CHARACTERISTICS (VCC = 5V 5%, Ta = -20 ~ 75C unless otherwise noted))
Symbol VIH VIL VI VOH VOL VLD VOS VM Parameter "H" input voltage "L" input voltage Maximum effective input voltage "H" output voltage "L" output voltage Operating voltage range Output offset voltage Output voltage fluctuation DATA, VOFF DATA, VOFF VL1, VL2 CO CO LD MO MO Temperature coefficient DATA, VOFF VL1, VL2 Vref Reference voltage Test conditions Min. 2 VCC-1.8 2.7 Limits Typ.* Max. 0.8 VCC-1.4 0.4 0.5 VCC 30 20 0.05 20 -0.2 1 1.4 -0.8 -0.5 61 0.111 31 0.050 34 0.03 0.01 60 59 IOH=-400A IOL=4mA IOL=8mA IMO=20A, IPD=0mA (Note 3) IPD=0.2~2.0mA, IMO=20A RM=1k (Note 4) RM=1k, IPD=1.2mA VI=2.7V VI=0.4V VI=0~VCC Ta=-20~25C Ta=25~75C VL1=3V, RC1=560, VLD=2V VL2=3V, RC2=560, VLD=2V Temperature coefficient RC3=360, VLD=2V VOFF=DATA=2V VOFF=DATA=0.8V VCC=5.25V, VOFF=4.5V, DATA VL1=VL2=3.0V, =0V RC1=RC2=560, RC3=360, DATA RO=LD=5.0V =4.5V Unit V V V V V V mV mV mV/C A mA A V mV/C mA mA/C mA mA/C mA A A
VCC-2.5
II
Input current
Temperature coefficient LD LD LD LD
IL1 IL2 IL3 IOFF
Output current 1 (Note 5) Output current 2 (Note 5) Output current 3 (Note 5) OFF state output current
Temperature coefficient
50 50 75
ICC
Supply current
mA 74
Note 3. IMO: Output current at MO pin. IPD: Input current at PD pin 4. RM: Resistor connected between 1RM and 2RM pins 5. These parameters indicate the conversion characteristics of the input voltage and output current. In actual use, IL1 - IL3 shall be within the range specified as limits in the recommended operating conditions. * Typical values are gained under conditions of VCC =5V and Ta =25C. Regarding parameters that Ta is specified as test condition, however, typical values are gained under the condition VCC = 5V.
SWITCHING CHARACTERISTICS (VCC = 5V, Ta = -25C)
Symbol fOP tRP1 Parameter Operating frequency Circuit response time 1 VL1, VL2 Voltage PD Current PD Current VOFF Voltage VOFF Voltage LD Current MO Voltage CO Voltage LD Current LD Current ILD(L)=0mA, ILD(H)=60mA (Note 6) ILD(L)=55mA, ILD(H)=65mA (Note 6) IPD(L)=0mA, IPD(H)=2mA, RM=1k (Note 7) |IPD|=0.2mA, RM=1k (Note 7) |IPD|=1mA (Note 7) |IPD|=0.2mA (Note 7) ILD(H)=60mA, ILD(L)=0mA (Note 8) ILD(H)=60mA, ILD(L)=0mA (Note 8) Test pin Input Output Test conditions Min. Limits Typ. 40 4.5 0.5 7 1 7 0.5 3 0.5 Max. 7 2 10 3 10 2 5 2 Unit Mbps s s s s s
tRP2 tRP3 tON tOFF
Circuit response time 2 Circuit response time 3 Circuit ON time Circuit OFF time
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MITSUBISHI DIGITAL ASSP
M66512P/FP
LASER-DIODE DRIVER
NOTE 6: MEASURING CIRCUIT
NOTE 7: MEASURING CIRCUIT
5V Oscilloscope (input) VL1 P.G. tr=tf=6ns 50 560 560 VL2 1RC 2RC PD LD ILD
RM
5V 20 VCC VL1 VL2 560 560 RO Oscilloscope (input) Current probe P.G. IPD CO 2RM MO GND 50 tr=tf=6ns
20 VCC RO
Oscilloscope (output)
Current probe
1RC DATA 2RC 1RM PD
1RM DATA
2RM GND
Oscilloscope (output) Other pins are opend
Other pins are opend
TIMING CHART
TIMING CHART
VL1, VL2
VIH 50% tRP1 50% VIL tRP1 90% 10% ILD(H) ILD(L)
IPD
50% tRP2, tRP3
50% tRP2, tRP3
| IPD| | IPD|
IPD(H) IPD(T)( V ) IPD(L) VOH VOL
ILD
MO,CO
MO=10% MO=90% CO=1.5V CO=1.5V
( V ): IPD gained at the moment CO output is inverted.
NOTE 8: MEASURING CIRCUIT
TIMING CHART
5V 20 VCC VL1 VL2 560 560 Oscilloscope (input) 1RC 2RC PD LD ILD
ILD 10%
Oscilloscope (output)
VOFF 3V 1.5V tOFF 1.5V 0V tON 90% ILD(H) ILD(L)
RO
Current probe
1RM DATA 2RM
P.G. tr=tf=6ns 50
VOFF GND
Other pins are opend
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MITSUBISHI DIGITAL ASSP
M66512P/FP
LASER-DIODE DRIVER
APPLICATION EXAMPLE
Controller M66512 RO MO 12 CO 13 PD 16 LD 18 20 RO
Linear amp. 1RM
Comparator (Vref=1.4V)
RM
9 10 2 3 4 5
Differential amp. Consttant current source(IL1) Max.60mA Consttant current source(IL2) Max.30mA Consttant current source(IL3) Max.30mA
Current switching circuit IL=IL1+IL2+IL3
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DATA STREAM DATA DATA INPUT
2RM RC1 VL1 1RC RC2 VL2 2RC RC3 3RC
6
CONTROL SIGNAL VOFF LASER CURRENT FORCED OFF
7
1 VCC1 14 VCC2 8 GND1 17 GND2
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MITSUBISHI DIGITAL ASSP
M66512P/FP
LASER-DIODE DRIVER
TYPICAL CHARACTERISTICS (VCC=5V, Ta=25C)
LASER CURRENT VS. CURRENT SETTING VOLTAGE
LASER CURRENT VS. RC3 RESISTANCE
100 LASER CURRENT IL1, IL2 (mA) IL1 +IL2 80 IL1(RC1=560)
50
LASER CURRENT IL3 (mA)
40
60 IL2(RC2=560) 40 20 0 0
30
20 10 0 0.2
1
2
3
4
5
0.4
0.6
0.8
1.0
1.2
CURRENT SETTING INPUT VOLTAGES VL1, VL2 (V)
RC3 RESISTANCE (k)
MO OUTPUT VS. MONITORING CURRENT
CO OUTPUT VS. MONITORING CURRENT
MONITORING COMPARATOR OUTPUT VCO (V)
MONITORING ANALOG OUTPUT VMO (V)
5
5
4 VMO 3
4
3
2 RM=1k 1 0 0
2 RM=1k 1 0 1.0
1
2
3
4
5
1.2
1.4
1.6
1.8
2.0
MONITORING CURRENT IPD (mA)
MONITORING CURRENT IPD (mA)
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MITSUBISHI DIGITAL ASSP
M66512P/FP
LASER-DIODE DRIVER
EVALUATION OF SWITCHING OPERATION WAVEFORMS
ML44114N Connector 0.1F 22F GND 2 VL1 3 VL2 4 VOFF 5 GND 6 JP CO 7 MO 8 DATA 9 PD 10 RM 3k RC1 680 RC2 680 RC3 680 2 VL1 3 1RC 4 VL2 5 2RC 6 VOFF 7 3RC 8 GND1 9 1RM 10 2RM NC 19 LD 18 GND2 17 PD 16 DATA 15 VCC2 14 CO 13 MO 12 NC 11 0.1 F ( V ): Optimum values of RLD and CLD may vary depending on the kind of the laser in use and the pattern of the printed board. Oscilloscope (laser light output) (V) CLD VCC=5V Ta=25C 1 VCC1 RO 20 1RO 20 Light intensity meter (V) RLD 100 RD 300pF 2 50
VCC 1
Oscilloscope (data input) P.G. (Note 9) 50 Evaluation Circuit
Note 9. tr=tf=6ns, VO=3VP-P, duty=50% SWITCHING OPERATION WAVEFORMS
10Mbit/s (t : 50ns/div) 3V 20Mbit/s (t : 20ns/div)
DATA input (2V/div)
0V 3mW
Laser light output (1mW/div)
0mW
25Mbit/s (t : 20ns/div)
40Mbit/s (t : 10ns/div)
Note: The delay from the DATA input to the laser light output contains the delay occurring in measuring systems.
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