MITSUBISHI MITSUBISHI 〈DIGITAL 〈DIGITAL ASSP〉 ASSP〉 M66510P/FP M66510P/FP LASER-DIODE DRIVER LASER-DIODE DRIVER DESCRIPTION The M66510 is a semiconductor laser diode driver that drives a semiconductor laser of the type whose cathode and the anode of monitor photodiode are connected to the stem. Laser driving current of up to 120mA can be set by applying constant voltage from outside to drive the laser diode. It operates from a 5V single power supply, allowing switching of laser driving current at a speed of 20M bits/sec. *: Our semiconductor laser is of R type. 1 20 → 1RO VL1 → 2 19 → 2RO VCC1 CURRENT SETTING INPUT 1 CURRENT SETTING LOAD OUTPUT 1 CURRENT SETTING INPUT 2 CURRENT SETTING LOAD OUTPUT 2 LASER CURRENT FORCED OFF INPUT CURRENT SETTING LOAD OUTPUT 3 VL2 → 4 2RC ← 5 VOFF → 6 3RC ← 7 MONITOR LOAD INPUT 1 MONITOR LOAD INPUT 2 GND2 17 16 ← PD MONITOR DIODE INPUT 15 ← DATA DATA INPUT VCC2 14 8 13 → CO 1RM → 9 12 → MO 2RM → 10 11 ← CD GND1 LASER CURRENT LOAD OUTPUT 1 LASER CURRENT LOAD OUTPUT 2 LASER DIODE OUTPUT 18 → LD 1RC ← 3 M66510P/FP FEATURES • Built-in two outputs for monitoring laser power (comparator output and analog output) • With laser driving current forced off pin • High-speed switching (20M bits/s) • High driving current (120mA max.) • 5V single power supply PIN CONFIGURATION (TOP VIEW) MONITOR COMPARATOR OUTPUT MONITOR ANALOG OUTPUT DUTY CONTROL INPUT APPLICATION Laser beam printer Outline 20P4K BLOCK DIAGRAM MONITOR OUTPUT MO 12 COMPARATOR OUTPUT CO 13 LINEAR AMPLIFIER COMPARATOR (Vref = 1.2V) CURRENT SETTING VL1 2 INPUT 1 1RC 3 1RO 20 2RO 19 CONSTANT CURRENT SOURCE (IL1) Max. 60mA CURRENT SETTING VL2 4 INPUT 2 2RC 5 CONSTANT CURRENT SOURCE (IL2) Max. 30mA 3RC 7 CONSTANT CURRENT SOURCE (IL3) Max. 30mA VCC1 1 VCC2 14 GND2 17 DIFFERENTIAL AMPLIFIER CURRENT SWITCHING CIRCUIT GND1 8 IL = IL1 + IL2 + IL3 9 1RM 10 16 2RM PD MONITOR DIODE INPUT 18 11 LD LASER DIODE OUTPUT VL1, 1RC: LASER CURRENT (IL1) SETTING PIN VL2, 2RC: LASER CURRENT (IL2) SETTING PIN 3RC: LASER CURRENT (IL3) SETTING PIN CD DUTY CONTROL INPUT 15 6 DATA VOFF DATA INPUT LASER CURRENT FORCED OFF VCC1, GND1: IC INTERNAL ANALOG POWER SUPPLY PIN VCC2, GND2: IC INTERNAL DIGITAL POWER SUPPLY PIN 1 MITSUBISHI 〈DIGITAL ASSP〉 M66510P/FP LASER-DIODE DRIVER FUNCTION The 66510 is a semiconductor laser diode driver that drives a semiconductor laser of the type (our R type) whose cathode and the anode of monitor photodiode are connected to the stem. Using the R type laser allows direct fixing the laser on a device for easy installation, thus improving its radiation efficiency. Laser driving current is set by applying voltage from outside. The M66510 is equipped with two independent voltage applying pins to provide higher accuracy of setting the current value. It is also equipped with a laser current forced off pin to prevent overcurrent from flowing into the laser diode at the power-ON time. For detection of laser power, the monitor current of monitor photodiode built in the laser is converted into voltage by an external resistor to generate an analog output, and simultaneously the result of comparison with the internal reference voltage is output as TTL-level logic information. PIN DESCRIPTIONS Pin name LD PD VL1 1RC VL2 2RC 3RC DATA 1RM, 2RM MO CO VOFF 1RO Name Laser connecting pin Monitor diode connecting pin Voltage input pin for IL1 setting Load resistor connecting pin for IL1 setting Voltage input pin for IL2 setting Load resistor connecting pin for IL2 setting Load resistor connecting pin for IL3 setting Switching data input pin Monitor load resistor connecting pin VCC1 Monitor analog output pin Monitor comparator output pin Laser current forced off input pin Load resistor connecting pin for laser current IL1 Load resistor connecting pin for laser current IL2/IL3 Duty compensating capacitor connecting pin Power supply pin 1 VCC2 Power supply pin 2 GND1 GND2 GND pin 1 GND pin 2 2RO CD 2 Function Connects the anode of semiconductor laser diode. Connects the cathode of monitor photodiode. Voltage input for setting the output current (IL1) of current source 1. Connects IL1 setting load resistor between the pin and GND. Voltage input for setting the output current (IL2) of current source 2. Connects IL2 setting load resistor between the pin and GND. Connects IL3 setting load resistor between the pin and GND. If IL3 is not used, open the pin. Turns on the laser in the “L” position, and off in the “H” position. Connects between 1RM and 2RM the load resistor for converting monitor photodiode current into voltage. Analog output for monitoring laser power. Comparator output for monitoring laser power. Turns off all current source circuits in the “L” position. Connects load resistor for laser current IL1 between 1RO pin and VCC. Connects load resistor for laser current IL2 and IL3 between 2RO pin and VCC. Connects duty compensating capacitor of optical output switch waveforms between the pin and GND. If duty compensation is not required, open the pin. Power supply for internal analog circuits. Connected to positive power supply (+5V). Power supply for internal digital circuits. Connected to positive power supply (+5V). GND for internal analog circuits. GND for internal digital circuits. MITSUBISHI 〈DIGITAL ASSP〉 M66510P/FP LASER-DIODE DRIVER DESCRIPTION OF OPERATION 1. Setting laser driving current The M66510 is provided internally with three constant current sources IL1, IL2 and IL3, allowing setting of each independent output current. The methods of setting IL1 to IL3 are given below in (1) to (3). (2) The VM is output as an analog output from the MO pin through the buffer amplifier and compared to the internal reference voltage Vref (1.2V standard) by the comparator. Then the result of comparison is output from the CO pin on the TTL level. (1) Method of setting IL1 IL1 is approximated by the VL1 pin input voltage and the resistor (RC1) connected between 1RC pin and GND as follows: VL1[V] IL1[mA] = 12 × RC1[kΩ] However, 0 ≤ VL1 ≤ VCC – 1.8V, IL1(max.) = 60mA (2) Method of setting IL2 IL2 is approximated by the VL2 pin input voltage and the resistor (RC2) connected between 2RC pin and GND as follows: VL2[V] IL2[mA] = 6 × RC2[kΩ] However, 0 ≤ VL2 ≤ Vcc – 1.8V, IL2(max.) = 30mA (3) Method of setting IL3 IL3 is approximated by the internal reference voltage (V ref) and the resistor (RC3) connected between 3RC pin and GND as follows: Vref[V] IL3[mA] = 10 × RC3[kΩ] However, Vref = 1.2V (standard), IL3(max.) = 30mA – + VM MO output + RM – Differential amplifier LD + CO output – PD Buffer amplifier Comparator Vref Condition VM < Vref VM > Vref CO output “L” “H” Monitor circuit schematic drawing Note: The expressions for setting IL1 to IL3 are typical. Actually, the set values fluctuate several % depending on IC lot dispersion or operating ambient temperature (See the ELECTRICAL CHARACTERISTICS). 2. Switching operation The laser is turned on when DATA = “L”. At this time, the laser driving current is IL1 + IL2 + IL3. The laser is turned off when DATA = “H”. At this time, the laser driving current becomes almost 0 regardless of IL1 to IL3. 3. Usage of VOFF input The current which flows into the laser becomes 0 when DATA = “H”. And the laser is turned off but the internal current sources are active. Contrarily, the internal current sources are turned off when VOFF = “L”. It is therefore possible to prevent overcurrent from flowing into the laser by setting VOFF input to “L” until VCC reaches 3.5V (standard) at the power-ON time, for example (See 6. Internal reset). 4. Laser power monitor operation The M66510 outputs the information on monitor photodiode (PD) built in the laser from the MO and CO pins in the flow given below. (1) The current equal to the PD current produced through emission of the laser flows into the resistor (RM) connected between 1RM and 2RM. The potential difference (VM) produced on RM is converted into a level from GND by the internal differential amplifier. 3 MITSUBISHI 〈DIGITAL ASSP〉 M66510P/FP LASER-DIODE DRIVER 5. 1RO/2RO pin The 1RO pin is used to connect the load resistor (RO1) for current source 1 (IL1). The 2RO pin is used to connect the load resistor (RO2) for current sources 2 (IL2) and 3 (IL3). Connecting the load resistor between each pin and Vcc reduces IC internal power dissipation. Set a resistance value so that each pin voltage does not go down to 3.5V or less. In other words, set a value such as meets the following expression: RO1(RO2)[Ω] ≤ VCC – 3.5[V] Maximum load current [A] flowing into RO1(RO2) Ex: When VCC = 5V and maximum load current of each source is 60mA, RO1 and RO2 will be 25Ω or less. 6. Internal reset operation The M66510 is provided with an internal reset circuit to prevent overcurrent from flowing into the laser at the power-ON time. The reset circuit operates within the range of VCC < 3.5V (standard) to turn off all the current sources. 7. VCC/GND pin The power supply pins include VCC1 , V CC2, GND1 and GND2, each of which is as follows in terms of internal circuit: VCC1/GND1: Connected to an analog circuit. VCC2/GND2: Connected to a digital circuit. In actual wiring, pay attention to the following: (1) Make wiring width as wide as possible. Avoid redundant wiring. (2) Lay out an electrolytic capacitor for stabilizing voltage as close to VCC1/GND1 as possible. (3) Lay out a bypass capacitor as close to V CC2/GND2 as possible. Precaution for peripheral element wiring Lay out the peripheral elements required for M66510 operation as close to M66510 as possible. 4 Method of calculating power dissipation The power dissipation P of M66510 is given by the expression given below. P = ICC × VCC + I(1RO) × (V(1RO) – V(LD)) + I(2RO) × (V(2RO) – V(LD)) + IOL(CO) × VOL(CO) where, V(1RO) : 1RO pin voltage V(2RO) : 2RO pin voltage I(1RO) : 1RO pin load current I(2RO) : 2RO pin load current V(LD) : LD pin voltage IOL(CO) : CO pin “L” output current VOL(CO) : CO pin “L” output voltage For example, when V CC = 5.25V, V(1RO) = V(2RO) = 3.5V, I (1RO) = I (2RO) = 60mA, V (LD) = 2.5V, I OL(CO) = 8mA and VOL(CO) = 0.5V, the power dissipation at the laser-ON/OFF time is as follows: (1) Laser-ON time (DATA = “L”, ICC=26mA) PON = 26 × 5.25 + 60 × (3.5 – 2.5) + 60 × (3.5 – 2.5) + 8 × 0.5 = 260.5(mW) (2) Laser-OFF time (DATA = “H”, ICC = 44mA) POFF = 44 × 5.25 + 0 + 0 + 8 × 0.5 = 235(mW) MITSUBISHI 〈DIGITAL ASSP〉 M66510P/FP LASER-DIODE DRIVER OPERATING WAVEFORM Laser output P P0 Laser output lL1 : 0 ~ 60mA lL2 : 0 ~ 30mA lL3 : 0 ~ 30mA Laser current lL lL3 lL1 lL2 Driving current pulse ABSOLUTE MAXIMUM RATINGS Symbol VCC Supply voltage Parameter VI Input voltage VO Output current IL1 IL2 IL3 Output current 1 Output current 2 Output current 3 Pd Power dissipation Tstg Storage temperature Conditions VL1, VL2 DATA, VOFF CO 1RO, 2RO DIP SOP Ratings –0.5 ~ +7.0 –0.3 ~ VCC –0.3 ~ + 7 –0.3 ~ + 5.5 –0.3 ~ + 7 –90 –45 –45 1300 800 –65 ~ 150 When output is “H” IC unit, when Ta=25°C (Note 1) IC unit, when Ta=25°C (Note 2) Unit V V V mA mA mA mW °C Note 1: When Ta ≥ 25°C, do derating of 10.4mW/°C. 2: When Ta ≥ 25°C, do derating of 6.4mW/°C. RECOMMENDED OPERATINIG CONDITIONS Symbol VCC IL1 IL2 IL3 Topr Parameter Supply voltage Output current 1 Output current 2 Output current 3 Operating 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〉 M66510P/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 Upper limit of effective input voltage “H” output voltage DATA, VOFF DATA, VOFF VL1, VL2 CO VOL “L” output voltage CO VLD VOS Operating supply voltage Output offset voltage LD MO ∆VM Output voltage variance width Min. 2 Limits Typ.* Max. 0.8 IOH=–400mA IOL=4mA IOL=8mA VCC–1.8 2.7 VCC–1.4 0.4 0.5 2.5 0 IMO=±20mA, IPD=0mA (Note 3) IPD=–0.2~2.0mA, IMO=±20mA, MO RM=1kΩ (Note 4) Temperature coefficient RM=1kΩ, IPD=–1.2mA VI=2.7V DATA, VOFF VI=0.4V VL1, VL2 VI=0~VCC II Input current Vref Reference voltage IL1 Output current 1 (Note 5) Ta=–20~75°C Temperature coefficient Ta=25~75°C VL1=3V, RC1=560Ω, VLD=2V LD IL2 Output current 2 (Note 5) LD IL3 Output current 3 (Note 5) LD IOFF Off-state output current LD ICC Supply current VL2=3V, RC2=560Ω, VLD=2V RC3=360Ω, VLD=2V VOFF=DATA=2V VOFF=DATA=0.8V VCC=5.25V, VOFF=4.5V, DATA=0V VL1=VL2=3.0V, RC1=RC2=560Ω, RC3=360Ω, DATA=4.5V 1RO, 2RO, LD open V V mV 20 mV 20 –0.2 ±1 Temperature coefficient V V V V 30 0.05 Temperature coefficient Unit 1.2 –1.1 –0.7 –62 0.037 –31 0.017 –31 –0.2 –1 –1 –20 17 26 30 44 mV/°C mA mA mA V mV/°C mA mA/°C mA mA/°C mA mA mA mA Note 3: IMO: MO pin output current. IPD: PD pin input current 4: RM: Resistance connected between 1RM and 2RM pins. 5: This indicates the input voltage – output current conversion characteristic. Use IL1 to IL3 within the range of limits of the recommended operating conditions. *: The standard value is given on VCC = 5V and at Ta = 25°C. The items with Ta specified under test conditions are given on VCC = 5V. ELECTRICAL CHARACTERISTICS (VCC = 5V, Ta = 25°C) Symbol fOP tRP1 tRP2 Parameter Test pin Input Output Operating frequency Circuit response time 1 Circuit response time 2 VL1/VL2 voltage LD current PD current MO voltage CO voltage tRP3 Circuit response time 3 PD current tON tOFF Circuit ON time Circuit OFF time VOFF voltage LD current VOFF voltage LD current 6 Test conditions 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 (Note 8) ILD(H)=–60mA (Note 8) Min. Limits Typ. 20 Max. 4.5 7 0.5 2 7 10 1 3 7 0.5 3 0.5 10 2 5 2 Unit Mbps ms ms ms ms ms MITSUBISHI 〈DIGITAL ASSP〉 M66510P/FP LASER-DIODE DRIVER NOTE 6: TEST CIRCUIT NOTE 7: TEST CIRCUIT 5V Oscilloscope (input) 20Ω P.G. tr = tf = 6ns 50Ω 560Ω 560Ω VL1 VCC 1RO VL2 2RO lLD LD 1RC 20Ω 560Ω Current probe 560Ω Oscilloscope (output) PD 2RC 5V 20Ω VL1 VCC 1RO VL2 2RO 1RC DATA 2RC PD 20Ω Oscilloscope (input) Current probe P.G. lPD 1RM DATA 50Ω 1RM CO RM 2RM GND TIMING CHART Oscilloscope (output) 2RM MO GND Other pins are open. tr = tf = 6ns Other pins are open. TIMING CHART VIH 50% VL1, VL2 50% VIL tRP1 50% IPD 50% tRP2, tRP3 tRP1 ILD(H) 90% MO, CO ILD 10% tRP2, tRP3 MO=10% CO=1.5V MO=90% CO=1.5V | IPD | | IPD | IPD(H) IPD(T)( ✽ ) IPD(L) VOH VOL ILD(L) ✽ : IPD when CO output is inverted. NOTE 8: TEST CIRCUIT 5V 20Ω 560Ω 560Ω Oscilloscope (input) VL1 VCC 1RO VL2 2RO 1RC LD 2RC PD 20Ω ILD Current probe Oscilloscope (output) 1RM DATA 2RM P.G. tr = tf = 6ns VOFF GND 50Ω Other pins are open. TIMING CHART 1.5V 3V 1.5V VOFF 0V tOFF tON 90% ILD(H) ILD 10% ILD(L) 7 MITSUBISHI 〈DIGITAL ASSP〉 M66510P/FP LASER-DIODE DRIVER APPLICATION EXAMPLE Control circuit 5V M66510 MO VL1 RC1 560Ω 1RC VL2 5V RC2 560Ω 2RC RC3 360Ω 3RC VCC1 0.1mF 0.22mF VCC2 GND2 GND1 RO1 1RO CO 12 13 Linear amplifier Comparator (Vref = 1.2V) 2 RO2 20Ω 20Ω 2RO 19 20 Constant current source (IL1) Max. 60mA 3 4 Constant current source (IL2) Max. 30mA 5 7 Constant current source (IL3) Max. 30mA 1 14 17 Power supply switching circuit Differential amplifier 8 1RM IL = IL1 + IL2 + IL3 9 2RM 10 16 18 PD LD CD 11 15 DATA 6 VOFF 91pF RM 3kΩ Data stream ML4403R 8 Control signal MITSUBISHI 〈DIGITAL ASSP〉 M66510P/FP LASER-DIODE DRIVER STANDARD CHARACTERISTICS (VCC = 5V, Ta = 25°C) LASER CURRENT - CURRENT SETTING VOLTAGE CHARACTERISTIC LASER CURRENT - RC3 RESISTANCE CHARACTERISTIC –50 IL1 + lL2 IL1(RC1=560Ω) –80 –60 IL2(RC2=560Ω) –40 LASER CURRENT IL3 (mA) LASER CURRENT IL1, IL2 (mA) –100 –40 –30 –20 –10 –20 0 0.2 0 0 1 2 3 4 5 0.4 0.6 0.8 1.0 1.2 MO OUTPUT - MONITOR CURRENT CHARACTERISTIC CO OUTPUT - MONITOR CURRENT CHARACTERISTIC MONITOR COMPARATOR OUTPUT VCO (V) RC3 RESISTANCE (kΩ) MONITOR ANALOG OUTPUT VMO (V) CURRENT SETTING INPUT VOLTAGE VL1, VL2 (V) 5 4 VMO 3 2 RM=1kΩ 1 0 0 –1 –2 –3 –4 MONITOR CURRENT IPD (mA) –5 5 4 3 2 RM=1kΩ 1 0 –0.8 –1.0 –1.2 –1.4 –1.6 –1.8 MONITOR CURRENT IPD (mA) 9 MITSUBISHI 〈DIGITAL ASSP〉 M66510P/FP LASER-DIODE DRIVER EVALUATION OF SWITCHING OPERATION WAVEFORM Connector RO 12Ω 0.1mF VCC 1 22mF GND 2 1 VCC1 1RO 20 2 VL1 2RO 19 (✽) (✽) RLD CLD 500Ω 75pF RC1 3 1RC VL1 3 VCC = 5V Ta = 25°C LD 18 680Ω 4 VL2 VL2 4 GND 17 RC2 VOFF 5 5 2RC PD 16 6 VOFF DATA 15 7 3RC VCC2 14 Laser beam output 680Ω GND 6 JP CO 7 (Open) 390Ω MO 8 8 GND1 DATA 9 RM 3kΩ PD 10 Laser power meter RC3 CO 13 9 1RM MO 12 10 2RM CD 11 0.1 mF ML4403R Directly mounted on PC board 91pF Oscilloscope (data input) P.G. (Note 9) 50Ω Note 9: tr = tf = 6ns, VO = 3Vp-p, duty = 50% 50Ω Oscilloscope (laser beam output) ✽ : The RLD and CLD optimum values depend on a type of laser used and a PCB pattern. EVALUATION CIRCUIT SWITCHING OPERATION WAVEFORM 2Mbit/s (t: 200ns/div) 5Mbit/s (t: 100ns/div) 10Mbit/s (t: 50ns/div) 20Mbit/s (t: 20ns/div) 3V DATA input (2V/div) 0V 3mW Laser beam output (1mW/div) 0mW Note: The delay from DATA input to laser beam output includes a measurement delay. 10