MITSUBISHI MITSUBISHI 〈DIGITAL 〈DIGITAL ASSP〉 ASSP〉 M66515FP M66515FP LASER-DIODE DRIVER/CONTROLLER LASER-DIODE DRIVER/CONTROLLER PIN CONFIGURATION (TOP VIEW) OUTPUT TO SWITCHING CURRENT SETTING LOAD OUTPUT TO BIAS CURRENT SETTING LOAD BIAS CURRENT SETTING VOLTAGE INPUT REFERENCE VOLTAGE OUTPUT REFERENCE VOLTAGE INPUT HOLDING CAPACITANCE LOAD INPUT/OUTPUT SAMPLE-HOLD CONTROL INPUT RS ← GND1 RB ← VB → Vref ← Vr → CH ← → S/H → VCC1 TEST PIN TEST 1 2 3 4 5 6 7 8 9 10 M66515FP DESCRIPTION The M66515 is a semiconductor laser-diode driver/controller. Its functions are the driving and laser power control of a specific type (Mitsubishi’s N type laser) of semiconductor laser diode, in which the anode of a semiconductor laser diode is connected in stem structure to the cathode of a monitoring photodiode. The IC has a laser drive current output pin of sink type and is capable of driving a laser diode on a maximum bias current of 30mA and a maximum switching current of 120mA, which is switched at a rate of 40Mbit/s. Since the M66515 has a built in sample-hold circuit, it is possible to realize an internal APC∗ system that requires no external device for laser power control. ∗: Automatic Power Control 20 19 18 17 16 15 14 13 12 11 VCC2 → RO LASER CURRENT LOAD OUTPUT NC → LD LASER CURRENT OUTPUT GND2 MONITORING DIODE ← PD INPUT ← DATA SWITCHING DATA INPUT CURRENT ← ENB LASER ENABLE INPUT ← 2RM MONITORING LOAD ← 1RM INPUT Outline 20P2N-A NC: No Connection FEATURES • Built-in sample-hold circuit for internal APC function • High speed switching (40Mbps) • Large drive current (150mA max.) • Capable of setting bias current (30mA max.) • 5V single power supply APPLICATION Semiconductor laser-diode applied equipment BLOCK DIAGRAM MONITORING LOAD INPUT 1RM 11 2RM 12 DIFFRENTIAL AMP REFERENCE VOLTAGE INPUT MONITORING DIODE INPUT PD 15 LASER CURRENT REFERENCE LASER CURRENT OUTPUT VOLTAGE OUTPUT LOAD RESISTOR Vref RO LD 17 19 5 REFERENCE VOLTAGE SOURCE (1.2V typ) IPD IB + ISW Vr 6 SAMPLE-HOLD S/H CONTROL INPUT HOLDING CAPACITANCE LOAD INPUT/OUTPUT CH OUTPUT TO SWITCHING CURRENT SETTING RS LOAD BIAS CURRENT SETTING VB VOLTAGE INPUT 8 CURRENT SWITCHING CIRCUIT SAMPLE-HOLD CIRCUIT IB 7 ISW SWITCHING CURRENT SOURCE (ISW) 120mA max. 1 14 DATA SWITCHING DATA INPUT 9 VCC1 20 VCC2 2 GND1 4 OUTPUT TO BIAS RB 3 CURRENT SETTING LOAD BIAS CURRENT SOURCE (IB) 30mA max. VCC1, GND1: For analog circuits in IC VCC2, GND2: For digital circuits in IC 16 GND2 13 ENB LASER CURRENT ENABLE CONTROL INPUT 1 MITSUBISHI 〈DIGITAL ASSP〉 M66515FP LASER-DIODE DRIVER/CONTROLLER FUNCTIONS The M66515 is a semiconductor laser-diode driver/controller. Its functions are the driving and laser power control of a specific type (Mitsubishi’s N type laser) of semiconductor laser diode, in which the anode of a semiconductor laser diode (LD) is connected in stem structure to the cathode of a monitoring photodiode (PD). The functions to drive LD and to control laser power are carried out by connecting an external capacitor to the CH pin and applying a reference voltage to the Vr pin. The PD current generated by LD illumination flows through the resistor connected between 1RM and 2RM, thereby gen- erating a potential difference (VM). VM is compared with the voltage applied to the Vr pin. If VM < Vr, a constant current is sourced through the CH pin so that the external capacitor is charged. If VM > Vr, a constant current sinks through the CH pin to discharge the external capacitor. The above operation occurs when the S/H input is “L” (sample). When the S/H input is “H,” the CH pin is maintained at high impedance state (hold), irrespective of the state of VM, Vr, and DATA input. The LD drive current is made up of the switching current, ISW, which is controlled by the DATA input, and IB, which is the bias current to LD independent of the state of the DATA input. PIN DESCRIPTIONS Pin LD PD RS RB Description Connect to cathode on semiconductor laser diode. Connect to anode on monitoring photodiode. Connect a load resistor between this pin and GND for the setting of current (ISW) to be switched. Connect a load resistor between this pin and GND for the setting of bias current (IB). Leave this pin open if IB is not used. Bias current setting voltage input Bias current (IB) is set by applying a voltage at this pin. Leave this pin open if IB is not used. Switching data input For monitoring Load input Laser current enable input Laser current load output Sample hold control input If this pin is “L,” a current of ISW + IB flows through laser diode; if “H,” current IB flows. CH Holding capacitor load input/output Connect a holding capacitor between this pin and GND. Inside the M66515 this pin connects to the output of the sample-hold circuit and the current source input for I SW. Vref Reference voltage output Internal reference voltage (1.2 V typ.) output pin of M66515 Vr Reference voltage input A reference voltage is applied to this pin to operate the comparator in the sample-hold circuit. Connect this pin to the Vref pin if the internal reference voltage of the M66515 is to be used. TEST VCC1 VCC2 GND1 GND2 Test pin Power supply pin 1 Power supply pin 2 GND pin 1 GND pin 2 This pin is used to test the M66515 when shipped. Leave open. Power supply to internal analog circuits. Connect to a positive power source (+5 V). Power supply to internal digital circuits. connect to a positive power source (+5 V). GND for internal analog circuits. GND for internal digital circuits. VB DATA 1RM, 2RM ENB RO S/H 2 Name Laser current output Monitoring diode input Switching current Set load output Bias current Set load output A load resistor is connected between pins 1RM and 2RM for conversion of current generated by monitoring photodiode into changes in voltage. If this pin is “H” all current source circuits are turned off. Connect a laser current load resistor between this pin and Vcc. If this pin is “L,” sampling (APC) occurs, if “H,” holding (switching). MITSUBISHI 〈DIGITAL ASSP〉 M66515FP LASER-DIODE DRIVER/CONTROLLER OPERATION 1. Laser Drive Currents The approximate values of laser drive currents, ISW and IB, are obtained by the following equation, in which VC is the voltage of holding capacitor connected to the CH pin. (1) ISW (switching current) VC [V] ISW [mA] = 12 × RS [kΩ] provided that 0 ≤ VC ≤ VCC – 1.8V and ISW (max.) =120mA where RS is the resistance of the resistor connected between the RS pin and GND. (2) IB (bias current) VB [V] IB [mA] = 10 × RB [kΩ] provided that 0 ≤ VB ≤ Vcc – 2.7V and IB (max.) = 30mA where RB is the resistance of the resistor connected between the RB pin and GND. 2. Switching Operation If DATA = “L,” the LD drive current is ISW + IB; if DATA = “H,” IB . 3. ENB Input When the laser drive current is controlled by the DATA input, the M66515’s internal current source is maintained turned on. In contrast, the control by ENB is turning on and off at the current source. If ENB = “L” the current source turns on; if ENB = “H” off. When ENB = “H” the CH pin is compulsorily fixed to “L” in order to discharge the capacitor connected to the CH pin. 4. Internal Reset Function The M66515 has a reset circuit built in for the protection of laser from an excessive current flowing at the moment of power on. The internal current source goes off in the range Reference voltage input Vcc < 3.5V (typ.), and the CH pin is compulsorily fixed to “L” at the same time. 5. RO Pin A load resistor for laser drive current is connected to the RO pin, through which a current almost equal to ISW flows in (when DATA = “H”). The load resistor is connected between the RO pin and Vcc to reduce power dissipated in the IC. Due to reasons related to the operation of circuits, the voltage at this pin should be 2.5V or higher. Consequently, the maximum resistance, RO(max.), of load resistor RO is: Vcc(min.) –2.5 [V] RO(max.) [Ω] = ISW(max.) [A] where ISW(max.) is the maximum of ISW. If, for example, Vcc(min.) = 4.75V and ISW(max.) =120mA, RO(max.) =18.8Ω. Accordingly, if the resistance of RS is selected so as to gain maximum ISW of 120mA, RO should be 18.8Ω at the maximum. 6. Sample-Hold Circuit (1) Circuit Operation Overview The following is an overview of the operation of the samplehold circuit contained in the M66515. The PD current generated by LD illumination flows through the resistor connected between 1RM and 2RM, thereby generating a potential difference (VM). VM is compared with the voltage applied to the Vr pin. If VM < Vr, a constant current is sourced through the CH pin so that the external capacitor is charged. If VM > Vr, a constant current sinks through the CH pin to discharge the external capacitor.This operation occurs when the S/H input is “L” (sample). When the S/H input is “H,” the CH pin is maintained at high impedance state (hold), irrespective of the state of VM, Vr, and DATA input. Constant current source for charging Comparator − Vr + Potential difference on resistor RM VM SW1 Output CH Sample-hold control input S/H Control circuit SW2 Externat capacitor Constant current source for discharging ENB Tr1 Conceptual Diagram : Sample-Hold circuit 3 MITSUBISHI 〈DIGITAL ASSP〉 M66515FP LASER-DIODE DRIVER/CONTROLLER FUNCTION TABLE Input ENB H L S/H × H L L Switch condition VM, Vr × × VM < Vr VM > Vr SW1 OFF OFF ON OFF SW2 OFF OFF OFF ON Tr1 ON OFF OFF OFF Output Fixed to “L” High impedance state (hold) Constant current sourcing (sample) Constant current sinking (sample) ×: Don’t care (2) APC Timing Chart The following diagram is an APC timing chart, operation of which is based on sample hold control signals. Note that in the example it is assumed that the leak current occurring at the CH pin under hold condition flows out from the M66515 (in the negative direction). Power supply Hold Sample Hold Sample S/H input Sample ENB input Hold DATA input ∆ILD Laser drive current APC Timing Chart 7. Vcc and GND Pins Pins related to the power supply function are Vcc 1, Vcc 2, GND 1, and GND 2. The role of these pins in terms of the internal circuits are as follows. Vcc 1, GND 1: connected to analog circuits Vcc 2, GND 2: 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 GND 1. (3) Allocate by-pass capacitors near Vcc2 and GND 2. Notes on the Wiring for Peripheral Components Lay out peripheral components necessary for the M66515 to operate in closest possible proximity to the M66515. 4 Calculation Method for Power Dissipation The approximate power dissipation, P, of the M66515FP is determined by the following equation. P = Icc × Vcc + I (RO) × V (RO) + I (LD) × V (LD) where V (RO): voltage at RO pin V (LD) : voltage at LD pin I (RO) : load current at RO pin I (LD) : load current at LD pin If, for example, Vcc = 5.25V, V (RO) = V (LD) = 2.5V, and I (RO) = I (LD) = 150mA, power dissipation at times of turning laser on and off will be as follows. (1) Laser ON (DATA = “L” and Icc = 75mA) PON = 75 × 5.25 + 0 + 150 × 2.5 = 768.8 (mW) (2) Laser OFF (DATA = “H” and Icc = 74mA) POFF = 74 × 5.25 + 150 × 2.5 + 0 = 763.5 (mW) MITSUBISHI 〈DIGITAL ASSP〉 M66515FP LASER-DIODE DRIVER/CONTROLLER ABSOLUTE MAXIMUM RATINGS (Ta = –20 ~ 70°C unless otherwise noted) Symbol Parameter VCC Supply voltage VI Input voltage VO ISW IB CH, Vr DATE, ENB, S/H Output voltage RO Switching current Bias current Pd Power dissipation Tstg Storage temperature Conditions Ratings –0.5 ~ +7.0 –0.3 ~ VCC –0.3 ~ +7.0 –0.3 ~ +7.0 150 45 Unit V 1200 mW –65 ~ 150 °C Measured being mounted Ta = 25°C V V mA mA RECOMMENDED OPERATIONAL CONDITIONS (Ta = –20 ~ 70°C unless otherwise noted) Symbol VCC ISW IB Topr Parameter Supply voltage Switing current Bias current Operating ambient temperature Min. 4.75 Limits Typ. 5.0 Max. 5.25 120 30 70 –20 Unit V mA mA °C ELECTRICAL CHARACTERISTICS (Ta = –20 ~ 70°C, VCC = 5V±5% unless otherwise noted) VIH VIL Vr Test conditions Parameter Symbol “H” Input voltage “L” Input voltage Reference voltage input Vref Reference voltage output VLD VI VOH VOL Operating voltage range Maximum effective voltage “H” output voltage “L” output voltage II Input current DATA, ENB, S/H DATA, ENB, S/H Vr Vref Temprature coefficient LD CH CH CH ISW Switching current (Note) LD IB Icg Idg Bias current (Note) Load charging current Load discharging current LD CH CH Ioz Output current under off condition CH VO = 0 ~ VCC, Hold condition IOFF Output current under off condition LD ICC Supply current CH Temprature coefficient Limits Typ.∗ ENB = 0.8V, DATA = 2.0V ENB = 2.0V, DATA = 0.8V VCC = 5.25V, DATA = 0V ENB = 0V, CH = 3.0V, VB = 1.2V, RS = 300Ω, RB = 360Ω, DATA = 4.5V RO = LD = 5.0V Max. 0.8 2.0 0.4 IO = –10µA Ta = –20 ~ 25°C Ta = 20 ~ 70°C ENB = 0.8V, IOH = –2mA ENB = 0.8V, IOL = 2mA VI = 2.7V VI = 0.4V VI = 0 ~ VCC CH = 3.0V, RS = 300Ω, VLD = 2V Ta = 20 ~ 70°C VB = 1.2V, RB = 360Ω, VLD = 2V ENB = 0.8V, VO = 0.6 ~ 4.0V ENB = 0.8V, VO = 0.6 ~ 4.0V DATA, ENB Min. 2.0 1.2 –0.9 –0.9 2.5 VCC – 1.8 4.0 VCC 0.6 20 –0.2 ±1 120 0.11 30 –2.0 2.0 Test circuit V V V V mV/°C VCC – 1.4 –0.66 0.66 Unit V V V V µA mA µA mA mA/°C mA mA mA 1 1 1 2 2 3 3 ±5 µA 3 0.03 0.01 50 50 µA 2 54 75 mA 4 52 74 ∗ Typical values are gained under conditions of Ta = 25°C and Vcc = 5V. Note: This parameter indicates the conversion characteristics of the input voltage and output current. In actual use, ISW and IB shall be within the range specified as limits in the recommended operating conditions. 5 MITSUBISHI 〈DIGITAL ASSP〉 M66515FP LASER-DIODE DRIVER/CONTROLLER SWITCHING CHARACTERISTICS (Ta = 25°C, VCC = 5V) Symbol fop Test pin Parameter Input Output Limits Test condition Min. Operating frequency tRP1 Circuit response time 1 tRP2 Circuit response time 2 CH voltage PD current Typ. 40 Max. Mbps ILD (L) = 0mA ILD (H) = 60mA (Note 1) 7 ILD (L) = 55mA ILD (H) = 65mA (Note 1) 2 µs LD current CH voltage IPD (L) = 0mA IPD (H) = 2mA RM = 1kΩ Unit 15 (Note 2) µs |∆IPD| = 0.2mA RM = 1kΩ (Note 2) 8 tRP3 Circuit response time 3 S/H voltage CH voltage IPD = 0mA, 2mA, (Note 3) RM = 1kΩ,Vr = 1.2V 8 µs tON tOFF Circuit ON time Circuit OFF time ENB voltage ENB voltage LD current LD current ILD (H) = 60mA (Note 4) ILD (H) = 60mA (Note 4) 5 2 µs µs NOTE1: TEST CIRCUIT NOTE2: TEST CIRCUIT 18Ω Oscilloscope (Input) PD LD VCC VCC RO P.G. tr=tf=6ns CH 50Ω 300Ω RM Oscilloscope (Output) Oscilloscope (Output) 1RM 2RM Oscilloscope (Input) CH 18Ω PD 3kΩ ILD RS 18Ω RO LD LD RS Current probe IPD P.G. PD Current probe 50Ω Vr 1.2V S/H DATA RM GND ENB Other pins are opened t r=t f=6ns S/H 1RM DATA 2RM ENB GND Other pins are opened TIMING CHARTS TIMING CHARTS CH voltage VIH 50% PD current 50% 50% ∆IPD 50% ∆IPD VIL t RP1 t RP2 t RP1 LD current 90% t RP2 ILD(H) IPD0∗ IPD(L) VOH 1.2V 10% ILD(L) IPD(H) CH voltage 1.2V VOL ∗ : IPD gained at the moment CH output is inverted. 6 MITSUBISHI 〈DIGITAL ASSP〉 M66515FP LASER-DIODE DRIVER/CONTROLLER NOTE3: TEST CIRCUIT NOTE4: TEST CIRCUIT 18Ω VCC Oscilloscope (Output) PD LD VCC 18Ω RO RO CH Oscilloscope (Output) 18Ω 3kΩ LD RS 300Ω PD S/H Vr 1.2V Oscilloscope (Input) IPD 50Ω 1RM DATA P.G. tr=tf=6ns RM RM 2RM ENB GND Other pins are opened CH PD RS LD ILD Current probe S/H DATA 1RM 2RM Oscilloscope (Input) GND ENB Other pins are opened TIMING CHARTS 50Ω P.G. tr=tf=6ns TIMING CHARTS S/H voltage ENB voltage 3V 3V 1.5V 1.5V 1.5V 0V 0V VOH 3.0V CH voltage High impedance t OFF t ON t RP3 0.4V ILD(H) 90% 10% LD current VOL ILD(L) APPLICATION EXAMPLE 18Ω RM 1RM 11 Data stream 2RM 12 5 Vref PD Sample-hold signal Vr S/H 1µF CH 470Ω RB 1MΩ 300Ω VB Reference volttage source (1.2V typ) IB 6 8 7 3 17 LD 19 RO IB + ISW IPD Differential amp 15 Sample-hold circuit Current switching circuit 14 DATA 9 VCC1 Bias current source (IB) 30mA max. ISW 20 VCC2 2 GND1 16 GND2 4 1 Switching current source (ISW) 120mA max. RS 13 ENB Control signal 7