Mitsubishi M66515FP Datasheet
MITSUBISHI 〈DIGITAL ASSP〉
MITSUBISHI 〈DIGITAL ASSP〉
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 pos-
∗
sible 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
M66515FP
LASER-DIODE DRIVER/CONTROLLER
LASER-DIODE DRIVER/CONTROLLER
PIN CONFIGURATION (TOP VIEW)
OUTPUT TO SWITCHING
CURRENT SETTING LOAD
OUTPUT TO BIAS CURR-
ENT SETTING LOAD
BIAS CURRENT
SETTING VOLTAGE INPUT
REFERENCE VOLTAGE
REFERENCE VOLTAGE INPUT
HOLDING CAPACITANCE
SAMPLE-HOLD CONTROL
OUTPUT
LOAD INPUT/OUTPUT
TEST PIN
INPUT
RS
←
Vref
S/H
VCC1
1
2
RB
←
3
VB
→
4
←
5
Vr
→
6
CH
→←
7
→
8
9
10
GND1
TEST
Outline 20P2N-A
20
19
18
M66515FP
17
16
15
14
13
12
11
M66515FP
VCC2
LASER CURRENT
→
RO
LOAD OUTPUT
NC
LASER CURRENT
→
LD
OUTPUT
GND2
MONITORING DIODE
←
PD
INPUT
←
SWITCHING DATA INPUT
DATA
LASER CURRENT
←
ENB
ENABLE INPUT
←
2RM
MONITORING LOAD
INPUT
←
1RM
NC: No Connection
APPLICATION
Semiconductor laser-diode applied equipment
BLOCK DIAGRAM
MONITORING
LOAD INPUT
1RM 2RM
11 12
DIFFRENTIAL AMP
REFERENCE
VOLTAGE INPUT
SAMPLE-HOLD
CONTROL INPUT
HOLDING CAPACITANCE
LOAD INPUT/OUTPUT
OUTPUT TO SWITCHING
CURRENT SETTING
LOAD
BIAS CURRENT SETTING
VOLTAGE INPUT
OUTPUT TO BIAS
CURRENT SETTING LOAD
Vr
S/H
C
R
V
R
6
8
H
7
S
1
B
4
B
3
SAMPLE-HOLD
CIRCUIT
MONITORING
DIODE INPUT
PD LD
15
PD
I
V
CC1
, GND1: For analog circuits in IC
CC2
, GND2: For digital circuits in IC
V
LASER CURRENT
OUTPUT
REFERENCE
VOLTAGE OUTPUT
17 19
REFERENCE
VOLTAGE SOURCE
(1.2V typ)
+
I
B
I
SW
I
B
BIAS CURRENT
SOURCE (I
B
)
30mA max.
LASER CURRENT
LOAD RESISTOR
V
ref
RO
5
CURRENT SWITCHING
CIRCUIT
I
SW
SWITCHING CURRENT
SW
SOURCE (I
)
120mA max.
DATA
14
SWITCHING
DATA INPUT
V
CC1
9
V
CC2
20
GND1
2
GND2
16
ENB
13
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 C
applying a reference voltage to the V
r pin.
H pin and
The PD current generated by LD illumination flows through
the resistor connected between 1RM and 2RM, thereby gen-
PIN DESCRIPTIONS
Pin
LD
PD
RS
RB
VB
DA T A
1RM, 2RM
ENB
RO
S/H
CH
Vref
Vr
TEST
VCC1
VCC2
GND1
GND2
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
Name
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.
erating a potential difference (VM). VM is compared with the
voltage applied to the V
sourced through the C
charged. If V
M > Vr, a constant current sinks through the CH
r pin. If VM < Vr, a constant current is
H pin so that the external capacitor is
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 C
at high impedance state (hold), irrespective of the state of V
r, and DATA input.
V
The LD drive current is made up of the switching current, I
which is controlled by the DATA input, and I
H pin is maintained
M,
SW,
B, which is the
bias current to LD independent of the state of the DA TA input.
Description
2
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 V
age of holding capacitor connected to the C
SW (switching current)
(1) I
ISW [mA] = 12 ×
provided that 0 ≤ V
where R
the R
(2) I
S is the resistance of the resistor connected between
S pin and GND.
B (bias current)
IB [mA] = 10 ×
provided that 0 ≤ V
where R
the R
B is the resistance of the resistor connected between
B pin and GND.
VC [V]
R
S [kΩ]
C ≤ VCC – 1.8V and ISW (max.) =120mA
VB [V]
B [kΩ]
R
B ≤ Vcc – 2.7V and IB (max.) = 30mA
C is the volt-
H pin.
2. Switching Operation
If DATA = “L,” the LD drive current is I
I
B.
SW + IB; if DA TA = “H,”
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 C
der to discharge the capacitor connected to the C
H pin is compulsorily fixed to “L” in or-
H 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 I
(min.) = 4.75V and ISW(max.) =120mA, RO(max.) =18.8Ω.
Vcc
Accordingly, if the resistance of R
maximum I
Vcc(min.) –2.5 [V]
SW(max.) [A]
I
SW(max.) is the maximum of ISW. If, for example,
S is selected so as to gain
SW 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 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 (V
voltage applied to the Vr pin. If V
sourced through the C
charged. If V
M > Vr, a constant current sinks through the CH
H pin so that the external capacitor is
M). VM is compared with the
M < Vr, a constant current is
pin to discharge the external capacitor.This operation occurs
when the S/H input is “L” (sample). When the S/H input is “H,”
H pin is maintained at high impedance state (hold), irre-
the C
spective of the state of V
M, Vr, and DATA input.
Reference voltage input
Potential difference on resistor RM
Sample-hold
control input
Constant current
source for charging
Constant current
source for discharging
r
V
V
M
Comparator
−
+
S/H
ENB
Control
circuit
Conceptual Diagram : Sample-Hold circuit
SW1
SW2
Output
T
r1
H
C
Externat capacitor
3
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