1
MITSUBISHI 〈DIGITAL ASSP〉
M66515FP
LASER-DIODE DRIVER/CONTROLLER
VCC2
RO
NC
LD
GND2
PD
DATA
ENB
2RM
1RM
RS
GND1
RB
VB
Vref
Vr
CH
S/H
VCC1
TEST
MITSUBISHI 〈DIGITAL ASSP〉
M66515FP
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 spe-
cific 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 pos-
sible to realize an internal APC∗ system that requires no ex-
ternal 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)
BLOCK DIAGRAM
LASER CURRENT
ENABLE CONTROL
INPUT
Vr
S/H
V
ref
R
B
GND1
ENB
DATA
SAMPLE-HOLD
CONTROL INPUT
SWITCHING
DATA INPUT
5
17 19
14
2
13
6
8
1
4
3
11 12 15
DIFFRENTIAL AMP
C
H
7
GND2
16
V
CC2
20
V
CC1
RO
1RM 2RM
V
B
R
S
PD LD
9
MONITORING
LOAD INPUT
I
PD
I
B+
I
SW
I
SW
I
B
MONITORING
DIODE INPUT
LASER CURRENT
OUTPUT
LASER CURRENT
LOAD RESISTOR
REFERENCE
VOLTAGE OUTPUT
REFERENCE
VOLTAGE SOURCE
(1.2V typ)
CURRENT SWITCHING
CIRCUIT
SWITCHING CURRENT
SOURCE (I
SW
)
120mA max.
BIAS CURRENT
SOURCE (I
B
)
30mA max.
SAMPLE-HOLD
CIRCUIT
REFERENCE
VOLTAGE INPUT
HOLDING CAPACITANCE
LOAD INPUT/OUTPUT
OUTPUT T O SWITCHING
CURRENT SETTING
LOAD
BIAS CURRENT SETTING
VOLTAGE INPUT
OUTPUT T O BIAS
CURRENT SETTING LOAD
V
CC1
, GND1: For analog circuits in IC
V
CC2
, GND2: For digital circuits in IC
LASER CURRENT
LOAD OUTPUT
LASER CURRENT
OUTPUT
MONITORING DIODE
INPUT
SWITCHING DATA INPUT
LASER CURRENT
ENABLE INPUT
MONITORING LOAD
INPUT
OUTPUT TO SWITCHING
CURRENT SETTING LOAD
OUTPUT TO BIAS CURR-
ENT SETTING LOAD
BIAS CURRENT
SETTING VOLTAGE INPUT
REFERENCE VOLTAGE
OUTPUT
REFERENCE VOLTAGE INPUT
HOLDING CAPACITANCE
LOAD INPUT/OUTPUT
SAMPLE-HOLD CONTROL
INPUT
TEST PIN
1
2
3
4
5
6
7
8
9
10
20
18
16
14
12
11
19
17
15
13
→
→
←
←
←
←
←
←
←
→
←
→
→←
→
M66515FP
Outline 20P2N-A
NC: No Connection
2
MITSUBISHI 〈DIGITAL ASSP〉
M66515FP
LASER-DIODE DRIVER/CONTROLLER
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.
FUNCTIONS
The M66515 is a semiconductor laser-diode driver/controller.
Its functions are the driving and laser power control of a spe-
cific 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 moni-
toring photodiode (PD).
The functions to drive LD and to control laser power are car-
ried out by connecting an external capacitor to the C H 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 I B, which is the
bias current to LD independent of the state of the DATA input.
Pin
LD
PD
RS
RB
VB
DATA
1RM, 2RM
ENB
RO
S/H
CH
Vref
Vr
TEST
VCC1
VCC2
GND1
GND2
PIN DESCRIPTIONS 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
3
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 volt-
age of holding capacitor connected to the CH pin.
(1) ISW (switching current)
ISW [mA] = 12 ×
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)
IB [mA] = 10 ×
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 DAT A = “L,” the LD drive current is ISW + IB; if DAT A = “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 of f at the cur-
rent 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 or-
der 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 re-
sistor RO is:
RO(max.) [Ω] =
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 maxi-
mum.
6. Sample-Hold Circuit
(1) Circuit Operation Overview
The following is an overview of the operation of the sample-
hold circuit contained in the M66515.
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 C H
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), irre-
spective of the state of VM, Vr , and DATA input.
Reference voltage input
Potential difference on resistor RM
V
r
V
M
Comparator
−
+
Control
circuit
S/H
Sample-hold
control input
ENB
SW1
SW2
C
H
T
r1
Externat capacitor
Constant current
source for charging
Constant current
source for discharging
Output
Conceptual Diagram : Sample-Hold circuit
VC [V]
RS [kΩ]
VB [V]
RB [kΩ]
Vcc(min.) –2.5 [V]
ISW(max.) [A]
4
MITSUBISHI 〈DIGITAL ASSP〉
M66515FP
LASER-DIODE DRIVER/CONTROLLER
Output
Fixed to “L”
High impedance state (hold)
Constant current sourcing (sample)
Constant current sinking (sample)
Input
ENB
H
L
L
S/H
×
H
L
VM, Vr
×
×
VM < Vr
VM > Vr
FUNCTION T ABLE Switch condition
SW1
OFF
OFF
ON
OFF
SW2
OFF
OFF
OFF
ON
Tr1
ON
OFF
OFF
OFF
×: 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).
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 in-
ternal 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 × 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)
APC Timing Chart
∆I
LD
Power supply
ENB input
S/H input
Sample
Hold
DATA input
Laser drive current
Hold
Sample
Sample
Hold
5
MITSUBISHI 〈DIGITAL ASSP〉
M66515FP
LASER-DIODE DRIVER/CONTROLLER
Min.
4.75
–20
Typ.
5.0 Max.
5.25
120
30
70
Unit
V
mA
mA
°C
Parameter
Supply voltage
Switing current
Bias current
Operating ambient temperature
RECOMMENDED OPERATIONAL CONDITIONS (Ta = –20 ~ 70°C unless otherwise noted)
Ratings
–0.5 ~ +7.0
–0.3 ~ VCC
–0.3 ~ +7.0
–0.3 ~ +7.0
150
45
1200
–65 ~ 150
Parameter
Supply voltage
Input voltage
Output voltage
Switching current
Bias current
Power dissipation
Storage temperature
Symbol
VCC
VI
VO
ISW
IB
Pd
Tstg
Unit
V
V
V
mA
mA
mW
°C
ABSOLUTE MAXIMUM RATINGS (Ta = –20 ~ 70°C unless otherwise noted)
Conditions
Measured being mounted
Ta = 25°C
CH, Vr
DATE, ENB, S/H
RO
Symbol
VCC
ISW
IB
Topr
Limits
Max.
0.8
2.0
VCC
0.6
20
–0.2
±1
–2.0
2.0
±5
50
50
75
74
Test
circuit
“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
Switching current (Note)
Bias current (Note)
Load charging current
Load discharging current
Test conditions
IO = –10µA
Ta =
–
20 ~ 25°C
Ta = 20 ~ 70°C
ENB = 0.8V, I
OH
= –2mA
ENB = 0.8V, I
OL
= 2mA
VI = 2.7V
VI = 0.4V
VI = 0 ~ VCC
CH = 3.0V, RS = 300
Ω
, VLD = 2V
Ta = 20 ~ 70°C
V
B
= 1.2V, R
B
= 360
Ω
, V
LD
= 2V
ENB = 0.8V, V
O
= 0.6 ~ 4.0V
ENB = 0.8V, V
O
= 0.6 ~ 4.0V
V
O
= 0 ~ V
CC
, Hold condition
ENB = 0.8V, DAT A = 2.0V
ENB = 2.0V, DAT A = 0.8V
VCC = 5.25V,
ENB = 0V,
C
H
= 3.0V, VB = 1.2V,
R
S
= 300
Ω
, R
B
= 360
Ω
,
RO = LD = 5.0V
Min.
2.0
0.4
2.5
V
CC
– 1.8
4.0
–0.66
0.66
Limits
Symbol
VIH
VIL
Vr
Vref
VLD
VI
VOH
VOL
II
ISW
IB
Icg
Idg
Ioz
IOFF
ICC
ELECTRICAL CHARACTERISTICS (Ta = –20 ~ 70°C, VCC = 5V±5% unless otherwise noted)
Unit
V
V
V
V
mV/°C
V
V
V
V
µA
mA
µA
mA
mA/°C
mA
mA
mA
µA
µA
mA
Typ.∗
DATA, ENB, S/H
DATA, ENB, S/H
Vr
Vref
Temprature
coefficient
LD
CH
CH
CH
DATA, ENB
CH
LD
LD
CH
CH
CH
LD
Parameter
Temprature coefficient
DATA = 0V
DAT A = 4.5V
1.2
–0.9
–0.9
V
CC
– 1.4
120
0.11
30
0.03
0.01
54
52
1
1
1
2
2
3
3
3
2
4
∗ 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.
Output current under off
condition
Supply current
Output current under off
condition
6
MITSUBISHI 〈DIGITAL ASSP〉
M66515FP
LASER-DIODE DRIVER/CONTROLLER
Test condition
ILD (L) = 0mA
ILD (H) = 60mA (Note 1)
ILD (L) = 55mA
ILD (H) = 65mA (Note 1)
IPD (L) = 0mA
IPD (H) = 2mA
RM = 1kΩ(Note 2)
|∆IPD| = 0.2mA
RM = 1kΩ(Note 2)
I
PD
= 0mA, 2mA,
(Note 3)
RM = 1kΩ,Vr = 1.2V
ILD (H) = 60mA (Note 4)
ILD (H) = 60mA (Note 4)
Limits
Min. Typ.
40 Max.
7
2
15
8
8
5
2
Parameter
Operating frequency
Circuit response time 1
Circuit response time 2
Circuit response time 3
Circuit ON time
Circuit OFF time
Symbol
fop
tRP1
tRP2
tRP3
tON
tOFF
Unit
Mbps
µs
µs
µs
µs
µs
SWITCHING CHARACTERISTICS (Ta = 25°C, VCC = 5V)
Test pin
Input
CH voltage
PD current
S/H voltage
ENB voltage
ENB voltage
Output
LD current
CH voltage
CH voltage
LD current
LD current
Oscilloscope (Output) Oscilloscope (Input)
Current probe
3kΩ
18Ω
50Ω
RM
I
PD
V
CC
C
H
R
S
1RM
2RM
RO
LD
S/H
DATA
ENB
GND
t
r
=t
f
=6
ns
P.G.
PD
V
r
1.2V
18Ω
Other pins are opened
Oscilloscope
(Output)
Oscilloscope (Input)
Current probe
Other pins are opened
300Ω
18Ω
RM
PD LD
ILD
VCC
CH
RS
1RM
2RM
RO
LD
S/H
DATA
ENB
GND
PD
50Ω
tr=tf=6ns
P.G.
C
H
voltage
LD current
V
IL
I
LD(H)
I
LD(L)
90%
50%
10%
t
RP1
t
RP1
50%V
IH
PD current
C
H
voltage
t
RP2
50%
t
RP2
50%
1.2V 1.2V
V
OL
I
PD(H)
I
PD(L)
V
OH
I
PD0∗
∆I
PD
∆I
PD
: I
PD
gained at the moment C
H
output is inverted.
∗
TIMING CHARTS TIMING CHARTS
NOTE1: TEST CIRCUIT NOTE2: TEST CIRCUIT
7
MITSUBISHI 〈DIGITAL ASSP〉
M66515FP
LASER-DIODE DRIVER/CONTROLLER
Oscilloscope (Output)
Oscilloscope (Input)
3kΩ
18Ω
50Ω
RM
I
PD
V
CC
C
H
R
S
1RM
2RM
RO
LD
S/H
DATA
ENB
GND
t
r
=t
f
=6
ns
P.G.
PD
V
r
1.2V
18Ω
Other pins are opened
S/H voltage
t
RP3
1.5V
0V
V
OL
V
OH
C
H
voltage 3.0V
0.4V
3V
High impedance
ENB voltage
LD current
I
LD(H)
I
LD(L)
90%
10%
t
ON
t
OFF
0V
3V
1.5V 1.5V
TIMING CHARTS TIMING CHARTS
Vr
S/H
V
ref
R
B
GND1
ENB
DATA
Sample-hold
signal
Data stream
517 19
14
2
13
6
8
1
4
3
11 12 15
Differential
amp
C
H
7
GND2
16
V
CC2
20
V
CC1
RO
1RM 2RM
V
B
R
S
PD LD
9
I
PD
I
B+
I
SW
I
SW
I
B
Reference
volttage source
(1.2V typ)
Switching current
source (I
SW
)
120mA max.
Bias current
source
(I
B
)
30mA max.
Sample-hold
circuit
RM 18Ω
Current switching
circuit
300Ω
1MΩ
1µF
470Ω
Control signal
APPLICATION EXAMPLE
NOTE3: TEST CIRCUIT NOTE4: TEST CIRCUIT
Oscilloscope (Output)
Oscilloscope (Input)
Current probe
300Ω
18Ω
50Ω
RM
PD LD
I
LD
V
CC
C
H
R
S
1RM
2RM
RO
LD
S/H
DATA
ENB
GND t
r
=t
f
=6
ns
P.G.
PD
Other pins are opened
