MITSUBISHI MITSUBISHI 〈DIGITAL 〈DIGITAL ASSP〉 ASSP〉 M66512P/FP M66512P/FP LASER-DIODE DRIVER LASER-DIODE DRIVER 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 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 M66512P/FP 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. 20 19 18 17 16 15 14 13 12 11 LASER CURRENT RO LOAD OUTPUT NC LD LASER DIODE OUTPUT GND2 PD MONITORING DIODE INPUT DATA DATA INPUT VCC2 MONITORING CO COMPARATOR OUTPUT ANALOG MO MONITORING OUTPUT NC Outline 20P4 20P2N-A APPLICATION Laser beam printers NC: No Connection BLOCK DIAGRAM 1RM 9 2RM 10 MONITORING OUTPUT MO COMPARATOR OUTPUT CO 12 13 Linear amp Comparator (Vref=1.4V) PD 16 LD 18 RO 20 Current switching circuit Differential amp 15 DATA DATA INPUT IL=IL1+IL2+IL3 VL1 2 1RC 3 VL2 4 Constant current source(IL1) Max.60mA 2RC 5 Constant current source(IL2) Max.30mA 3RC 7 Constant current source(IL3) Max.30mA 6 VOFF LASER CURRENT FORCED OFF 1 VCC1 14 VCC2 VL1, 1RC : Laser current (IL1) setting pin VL2, 2RC : Laser current (IL2) setting pin 3RC : Laser current (IL3) setting pin 8 GND1 17 GND2 VCC1, GND1 : Power supply pin for analog circuits in IC VCC2, GND2 : Power supply pin for digital circuits in IC 1 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 1RC VL2 2RC 3RC 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 DATA 1RM, 2RM MO CO VOFF RO VCC1 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 VCC2 Power supply pin 2 GND1 GND2 GND pin 1 GND pin 2 LD PD VL1 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 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 × RC1 [kΩ] provided that 0≤VL1≤VCC–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 × RC2 [kΩ] provided that 0≤VL2≤VCC–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 × Vref[V] RC3 [kΩ] 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. (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 CO output Comparator Vref Condition VM<Vref VM>Vref CO output “L” “H” A Schematic Diagram of Monitor Circuits 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 V CC, 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. 3 MITSUBISHI 〈DIGITAL ASSP〉 M66512P/FP LASER-DIODE DRIVER 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 (Ω) ≤ maximum load current flowing through RO [A] Example: If VCC =5V and the maximum load current is 120 mA, RO is 20Ω 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. 4 P=ICC × VCC +I(RO) × V(RO) + I(LD) × V(LD) + IOL(CO) × 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 × 5.25 + 0 + 120 × 2.75 + 8 × 0.5 = 727.8(mW) (2) Laser OFF (DATA =“H” and ICC = 74mA) POFF = 74 × 5.25 + 120 × 2.75 + 0 = 718.5(mW) MITSUBISHI 〈DIGITAL ASSP〉 M66512P/FP LASER-DIODE DRIVER OPERATING WAVEFORMS Laser output P0 Laser output IL1 : 0~60mA IL2 : 0~30mA IL3 : 0~30mA Laser current IL IL3 IL1 IL2 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 Output: “H” For single integrated circuit; Ta=25˚C (Note 1) IC Measured being mounted; Ta=25˚C (Note 2) Unit V V V mA mA mA mW °C Note 1: For operation above 25°C free-air temperature, derating of 10.4mW/°C is necessary. 2: For operation above 25°C 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 –20 Limits Typ. 5 Max. 5.25 60 30 30 75 Unit V mA mA mA ˚C 5 MITSUBISHI 〈DIGITAL ASSP〉 M66512P/FP LASER-DIODE DRIVER ELECTRICAL CHARACTERISTICS (VCC = 5V ± 5%, Ta = –20 ~ 75˚C unless otherwise noted)) Symbol Parameter Test conditions VIH VIL VI VOH “H” input voltage “L” input voltage Maximum effective input voltage “H” output voltage DATA, VOFF DATA, VOFF VL1, VL2 CO VOL “L” output voltage CO VLD VOS Operating voltage range Output offset voltage LD MO ∆VM Output voltage fluctuation MO II DATA, VOFF VL1, VL2 Vref Reference voltage IL1 Output current 1 (Note 5) LD IL2 Output current 2 (Note 5) LD IL3 Output current 3 (Note 5) LD IOFF OFF state output current LD ICC Supply current Limits Typ.* Temperature coefficient Max. 0.8 IOH=–400µA IOL=4mA IOL=8mA VCC–1.8 2.7 VCC–1.4 0.4 0.5 VCC VCC–2.5 Temperature coefficient Input current Min. 2 IMO=±20µA, IPD=0mA (Note 3) IPD=0.2~2.0mA, IMO=±20µA RM=1kΩ (Note 4) RM=1kΩ, IPD=1.2mA VI=2.7V VI=0.4V VI=0~VCC VL2=3V, RC2=560Ω, VLD=2V Temperature coefficient RC3=360Ω, VLD=2V VOFF=DATA=2V VOFF=DATA=0.8V VCC=5.25V, VOFF=4.5V, DATA VL1=VL2=3.0V, =0V RC1=RC2=560Ω, RC3=360Ω, DATA RO=LD=5.0V =4.5V V V mV 20 mV 20 –0.2 ±1 Temperature coefficient V V V V 30 0.05 Ta=–20~25˚C Ta=25~75˚C VL1=3V, RC1=560Ω, VLD=2V Unit 1.4 –0.8 –0.5 61 0.111 31 0.050 34 0.03 0.01 50 50 60 75 59 74 mV/˚C µA mA µA V mV/˚C mA mA/˚C mA mA/˚C mA µA µA mA 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 =25˚C. Regarding parameters that Ta is specified as test condition, however, typical values are gained under the condition VCC = 5V. SWITCHING CHARACTERISTICS (VCC = 5V, Ta = –25˚C) Symbol fOP 6 Parameter Test pin Input Output Test conditions Operating frequency tRP1 Circuit response time 1 VL1, VL2 Voltage tRP2 Circuit response time 2 PD Current MO Voltage PD Current VOFF Voltage VOFF Voltage CO Voltage LD Current LD Current tRP3 Circuit response time 3 tON tOFF Circuit ON time Circuit OFF time 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=1kΩ (Note 7) |∆IPD|=0.2mA, RM=1kΩ (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) Min. Limits Typ. 40 4.5 0.5 Max. Unit Mbps 7 2 7 10 1 7 0.5 3 0.5 3 10 2 5 2 µs µs µs µs µs MITSUBISHI 〈DIGITAL ASSP〉 M66512P/FP LASER-DIODE DRIVER NOTE 6: MEASURING CIRCUIT NOTE 7: MEASURING CIRCUIT 5V 5V 20Ω Oscilloscope (input) VCC 50Ω 560Ω 560Ω Oscilloscope (input) RO VL1 RO VL2 VL2 P.G. tr=tf=6ns Oscilloscope (output) VCC VL1 20Ω Current probe PD 1RC 2RC 560Ω LD 2RC ILD 1RM DATA P.G. PD IPD 1RM RM 2RM GND Current probe 1RC DATA 560Ω CO tr=tf=6ns Oscilloscope (output) 2RM MO GND Other pins are opend 50Ω Other pins are opend TIMING CHART VL1, VL2 TIMING CHART VIH 50% 50% IPD 50% VIL tRP1 tRP2, tRP3 tRP1 ILD(H) 90% ILD 10% MO,CO | IPD| 50% | tRP2, tRP3 MO=10% MO=90% CO=1.5V CO=1.5V IPD| IPD(H) IPD(T)( ✽ ) IPD(L) VOH VOL ILD(L) ( ✽ ): IPD gained at the moment CO output is inverted. NOTE 8: MEASURING CIRCUIT TIMING CHART 5V 20Ω Oscilloscope (output) VCC VL1 RO VOFF VL2 560Ω 560Ω Oscilloscope (input) 1RC 1.5V 0V Current probe PD tOFF 2RC 1RM DATA VOFF GND tON LD ILD 90% ILD 10% 2RM P.G. tr=tf=6ns 50Ω 3V 1.5V ILD(H) ILD(L) Other pins are opend 7 MITSUBISHI 〈DIGITAL ASSP〉 M66512P/FP LASER-DIODE DRIVER APPLICATION EXAMPLE Controller M66512 RO MO CO 12 Linear amp. RM 1RM 2RM RC1 VL1 1RC RC2 VL2 2RC RC3 3RC 8 9 10 2 3 4 13 PD 16 LD 18 20 RO Comparator (Vref=1.4V) Differential amp. Consttant current source(IL1) Max.60mA 5 Consttant current source(IL2) Max.30mA 7 Consttant current source(IL3) Max.30mA Current switching circuit DATA STREAM 15 DATA DATA INPUT IL=IL1+IL2+IL3 6 CONTROL SIGNAL VOFF LASER CURRENT FORCED OFF 1 VCC1 14 VCC2 8 GND1 17 GND2 MITSUBISHI 〈DIGITAL ASSP〉 M66512P/FP LASER-DIODE DRIVER TYPICAL CHARACTERISTICS (VCC=5V, Ta=25˚C) LASER CURRENT VS. RC3 RESISTANCE LASER CURRENT VS. CURRENT SETTING VOLTAGE 50 IL1 +IL2 LASER CURRENT IL3 (mA) LASER CURRENT IL1, IL2 (mA) 100 IL1(RC1=560Ω) 80 60 IL2(RC2=560Ω) 40 20 0 0 1 2 3 4 40 30 20 10 0 0.2 5 0.4 0.6 0.8 1.0 1.2 MO OUTPUT VS. MONITORING CURRENT CO OUTPUT VS. MONITORING CURRENT 5 4 VMO 3 2 RM=1kΩ 1 0 0 1 2 3 4 MONITORING CURRENT IPD (mA) 5 MONITORING COMPARATOR OUTPUT VCO (V) RC3 RESISTANCE (kΩ) MONITORING ANALOG OUTPUT VMO (V) CURRENT SETTING INPUT VOLTAGES VL1, VL2 (V) 5 4 3 2 RM=1kΩ 1 0 1.0 1.2 1.4 1.6 1.8 2.0 MONITORING CURRENT IPD (mA) 9 MITSUBISHI 〈DIGITAL ASSP〉 M66512P/FP LASER-DIODE DRIVER EVALUATION OF SWITCHING OPERATION WAVEFORMS ML44114N Connector VCC=5V Ta=25°C RO 20Ω 0.1µF VCC 1 1 VCC1 1RO 20 Light intensity meter (✽) RLD 22µF RD GND 2 RC1 VL1 3 680Ω VL2 4 RC2 VOFF 5 680Ω GND 6 RC3 JP CO 7 680Ω MO 8 DATA 9 PD 10 100Ω RM 3kΩ 2 VL1 NC 19 3 1RC LD 18 4 VL2 (✽) CLD GND2 17 5 2RC PD 16 6 VOFF DATA 15 7 3RC VCC2 14 8 GND1 CO 13 9 1RM MO 12 10 2RM NC 11 2Ω 50Ω 300pF Oscilloscope (laser light output) 0.1 µF ( ✽ ): 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 (data input) P.G. (Note 9) 50Ω Evaluation Circuit Note 9. tr=tf=6ns, VO=3VP-P, duty=50% SWITCHING OPERATION WAVEFORMS 10Mbit/s (t : 50ns/div) 20Mbit/s (t : 20ns/div) 25Mbit/s (t : 20ns/div) 40Mbit/s (t : 10ns/div) 3V DATA input (2V/div) Laser light output (1mW/div) 0V 3mW 0mW Note: The delay from the DATA input to the laser light output contains the delay occurring in measuring systems. 10