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MITSUBISHI DIGITAL ASSP MITSUBISHI DIGITAL ASSP
M66515FP M66515FP
LASER-DIODE DRIVER/CONTROLLER LASER-DIODE DRIVER/CONTROLLER
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 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
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 Vref CH Vr VB
S/H VCC1
TEST PIN TEST
1 2 3 4 5 6 7 8 9 10
20 19 18 17 16 15 14 13 12 11
VCC2
RO
NC
LASER CURRENT LOAD OUTPUT LASER CURRENT OUTPUT
Outline 20P2N-A
NC: No Connection
M66515FP
LD
GND2
MONITORING DIODE PD INPUT DATA SWITCHING DATA INPUT ENB LASER CURRENT ENABLE INPUT 2RM MONITORING LOAD INPUT 1RM
BLOCK DIAGRAM

MONITORING LOAD INPUT 1RM 11
2RM 12
MONITORING DIODE INPUT PD 15 IPD
LASER CURRENT REFERENCE LASER CURRENT OUTPUT VOLTAGE OUTPUT LOAD RESISTOR Vref RO LD 17 19 5
REFERENCE VOLTAGE SOURCE (1.2V typ)
DIFFRENTIAL AMP REFERENCE VOLTAGE INPUT
IB + ISW Vr 6 8 SAMPLE-HOLD CIRCUIT IB 7 1 4 BIAS CURRENT SOURCE (IB) 30mA max. CURRENT SWITCHING CIRCUIT ISW SWITCHING CURRENT SOURCE (ISW) 120mA max. 14 DATA SWITCHING DATA INPUT 9 VCC1 20 VCC2 2 GND1 16 GND2 13 ENB LASER CURRENT ENABLE CONTROL INPUT
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
OUTPUT TO BIAS RB 3 CURRENT SETTING LOAD
VCC1, GND1: For analog circuits in IC VCC2, GND2: For digital circuits in IC
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 VB DATA 1RM, 2RM ENB RO S/H CH Vref Vr TEST VCC1 VCC2 GND1 GND2 Name Laser current output Monitoring diode input Switching current Set load output Bias current Set load output Bias current setting voltage input Switching data input For monitoring Load input Laser current enable input Laser current load output Sample hold control input Holding capacitor load input/output Reference voltage output Reference voltage input Test pin Power supply pin 1 Power supply pin 2 GND pin 1 GND pin 2 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 (IB) is set by applying a voltage at this pin. Leave this pin open if IB is not used. If this pin is "L," a current of ISW + IB flows through laser diode; if "H," current IB flows. 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). 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 ISW. Internal reference voltage (1.2 V typ.) output pin of M66515 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. 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.
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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 x RS [k] 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 x RB [k] 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
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.) [] = ISW(max.) [A] where ISW(max.) is the maximum of ISW. If, for example, Vcc(min.) = 4.75V and ISW(max.) =120mA, RO(max.) =18.8. Accordingly, if the resistance of RS is selected so as to gain maximum ISW of 120mA, RO should be 18.8 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.
Reference voltage input
Vr
Comparator - + Control circuit
Constant current source for charging
Potential difference on resistor RM VM Sample-hold control input
SW1 Output CH
S/H
SW2 Externat capacitor
Constant current source for discharging
ENB
Tr1
Conceptual Diagram : Sample-Hold circuit
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MITSUBISHI DIGITAL ASSP
M66515FP
LASER-DIODE DRIVER/CONTROLLER
FUNCTION TABLE
Input ENB H L L
x: Don't care
Switch condition VM, Vr x x VM < Vr VM > Vr SW1 OFF OFF ON OFF SW2 OFF OFF OFF ON
S/H x H L
Tr1 ON OFF OFF OFF
Output Fixed to "L" High impedance state (hold) Constant current sourcing (sample) Constant current sinking (sample)
(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
ENB input
Sample
Sample
S/H input
Hold
Hold
Sample
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.
Calculation Method for Power Dissipation The approximate power dissipation, P, of the M66515FP is determined by the following equation. P = Icc x Vcc + I (RO) x V (RO) + I (LD) x 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 x 5.25 + 0 + 150 x 2.5 = 768.8 (mW) (2) Laser OFF (DATA = "H" and Icc = 74mA) POFF = 74 x 5.25 + 150 x 2.5 + 0 = 763.5 (mW)
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MITSUBISHI DIGITAL ASSP
M66515FP
LASER-DIODE DRIVER/CONTROLLER
ABSOLUTE MAXIMUM RATINGS (Ta = -20 ~ 70C unless otherwise noted)
Symbol VCC VI VO ISW IB Pd Tstg Supply voltage CH, Vr DATE, ENB, S/H Output voltage RO Switching current Bias current Input voltage Power dissipation Storage temperature Measured being mounted Ta = 25C Parameter Conditions Ratings -0.5 ~ +7.0 -0.3 ~ VCC -0.3 ~ +7.0 -0.3 ~ +7.0 150 45 1200 -65 ~ 150 Unit V V V mA mA mW C
RECOMMENDED OPERATIONAL CONDITIONS (Ta = -20 ~ 70C 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 Unit V mA mA C
-20
ELECTRICAL CHARACTERISTICS (Ta = -20 ~ 70C, VCC = 5V5% unless otherwise noted)
Symbol VIH VIL Vr Vref VLD VI VOH VOL II Parameter "H" Input voltage "L" Input voltage Reference voltage input Reference voltage output Operating voltage range Maximum effective voltage "H" output voltage "L" output voltage Input current DATA, ENB, S/H DATA, ENB, S/H Vr Vref Temprature coefficient LD CH CH CH DATA, ENB CH ISW IB Icg Idg Ioz IOFF Switching current (Note) Bias current (Note) Load charging current Load discharging current Output current under off condition Output current under off condition LD LD CH CH CH LD Temprature coefficient Test conditions Min. 2.0 0.4 IO = -10A Ta = -20 ~ 25C Ta = 20 ~ 70C 2.5 VCC - 1.8 4.0 1.2 -0.9 -0.9 VCC VCC - 1.4 0.6 20 -0.2 1 120 0.11 30 -0.66 0.66 -2.0 2.0 5 0.03 0.01 54 52 50 50 75 mA 74 4 Limits Typ. Max. 0.8 2.0 Unit V V V V mV/C V V V V A mA A mA mA/C mA mA mA A A 1 Test circuit
ENB = 0.8V, IOH = -2mA ENB = 0.8V, IOL = 2mA VI = 2.7V VI = 0.4V VI = 0 ~ VCC CH = 3.0V, RS = 300, VLD = 2V Ta = 20 ~ 70C VB = 1.2V, RB = 360, VLD = 2V ENB = 0.8V, VO = 0.6 ~ 4.0V ENB = 0.8V, VO = 0.6 ~ 4.0V VO = 0 ~ VCC, Hold condition 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 = 300, RB = 360, DATA = 4.5V RO = LD = 5.0V
1 1
2 2 3 3 3 2
ICC
Supply current
Typical values are gained under conditions of Ta = 25C 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.
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MITSUBISHI DIGITAL ASSP
M66515FP
LASER-DIODE DRIVER/CONTROLLER
SWITCHING CHARACTERISTICS (Ta = 25C, VCC = 5V)
Symbol fop Parameter Operating frequency ILD (L) = 0mA ILD (H) = 60mA (Note 1) tRP1 Circuit response time 1 CH voltage LD current ILD (L) = 55mA ILD (H) = 65mA (Note 1) IPD (L) = 0mA IPD (H) = 2mA RM = 1k 2 Test pin Input Output Test condition Limits Min. Typ. 40 Max. Unit Mbps 7 s
15 (Note 2) 8 8 5 2 s s s s
tRP2
Circuit response time 2
PD current
CH voltage
|IPD| = 0.2mA RM = 1k (Note 2) tRP3 tON tOFF Circuit response time 3 Circuit ON time Circuit OFF time S/H voltage ENB voltage ENB voltage CH voltage LD current LD current IPD = 0mA, 2mA, (Note 3) RM = 1k,Vr = 1.2V ILD (H) = 60mA (Note 4) ILD (H) = 60mA (Note 4)
NOTE1: TEST CIRCUIT
NOTE2: TEST CIRCUIT
18 Oscilloscope (Input) VCC RO P.G. tr=tf=6ns CH 50 300 RS 1RM 2RM PD
PD
LD
VCC 18 RO CH 18 3k LD RS Vr RM PD 50 1.2V S/H 1RM DATA 2RM ENB GND Current probe P.G. tr=tf=6ns IPD Oscilloscope (Input)
Oscilloscope (Output) ILD
Oscilloscope (Output)
LD S/H DATA
Current probe
RM
GND ENB Other pins are opened
Other pins are opened
TIMING CHARTS
TIMING CHARTS
CH voltage 50% 50%
VIH VIL t RP1 t RP1 90% 10% ILD(L) ILD(H)
PD current 50% t RP2 50% t RP2
IPD IPD
IPD(H) IPD0 IPD(L)
LD current
VOH 1.2V CH voltage 1.2V VOL : IPD gained at the moment CH output is inverted.
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MITSUBISHI DIGITAL ASSP
M66515FP
LASER-DIODE DRIVER/CONTROLLER
NOTE3: TEST CIRCUIT
NOTE4: TEST CIRCUIT
18 VCC Oscilloscope (Output) CH 18 3k 1.2V RM LD RS Vr IPD PD S/H 50 P.G. tr=tf=6ns RM Oscilloscope (Input) 300 CH RS 1RM 2RM PD RO 18 VCC RO
PD
LD
Oscilloscope (Output) ILD LD S/H DATA 50 Current probe Oscilloscope (Input) P.G. tr=tf=6ns
1RM DATA 2RM ENB GND Other pins are opened
GND ENB Other pins are opened
TIMING CHARTS
S/H voltage 1.5V 0V t RP3 3.0V CH voltage High impedance 0.4V VOH 3V
TIMING CHARTS
ENB voltage 1.5V t ON 90% LD current 10% 1.5V 0V t OFF ILD(H) 3V
VOL
ILD(L)
APPLICATION EXAMPLE
RM 1RM 11 2RM 12 5 Vref PD 15 17 LD IB + ISW
18 Data stream 19 RO
IPD Sample-hold signal Vr S/H 1F 470 RB 1M 300 VB RS CH 6 8 7 3 Differential amp
Reference volttage source (1.2V typ)
IB Sample-hold circuit Bias current source (IB) 30mA max.
Current switching circuit
14
DATA
9 VCC1 ISW 20 VCC2 2 GND1 16 GND2 Switching current source (ISW) 120mA max. 13 ENB
4 1
Control signal
7

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