Mitsubishi M66516FP Datasheet

MITSUBISHI 〈DIGITAL ASSP〉

DESCRIPTION

The M66516 is a semiconductor laser-diode driver/controller. Its functions are the driving and laser power control of a specific type (Mitsubishi’s R type laser) of semiconductor laser diode, in which the cathode of a semiconductor laser diode is connected in stem structure to the anode of a monitoring photodiode. The IC has a laser drive current output pin of source type and is capable of driving a laser diode on a maximum bias current of 30mA and a maximum switching current of 120 mA, which is switched at a rate of 20Mbits/sec. Since the M66516 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 APC function

• High speed switching (20Mbps)

• Large drive current (150mA max.)

• Capable of setting bias current (30mA max.)

• 5V single power supply

M66516FP

LASER-DIODE DRIVER/CONTROLLER

PIN CONFIGURATION (TOP VIEW)

SWITCHING CURRENT

SETTING INPUT 1

OUTPUT TO SWITCHING

CURRENT SETTING LOAD

SWITCHING CURRENT

SETTING INPUT 2

OUTPUT TO SWITCHING

CURRENT SETTING LOAD

LASER CURRENT

ENABLE INPUT

OUTPUT TO BIAS

CURRENT SETTING LOAD

MONITORING LOAD

MONITORING ANALOG

COMPARATOR OUTPUT

INPUTS

OUTPUT

MONITORING

VCC1

→

VL1

1RC

←

VL2 2RC ENB 3RC

GND1

 

1RM



2RM

→

←

→

←

8 9

→

←

Outline 24P2N-B

24 23 22 21

M66516FP

20 19 18 17 16 15 14 13

M66516FP

OUTPUT TO LASER

→

CURRENT LOAD LASER CURRENT

→

OUTPUT

MONITORING DIODE

←

INPUT

GND2

REFERENCE VOLTAGE

Vref

→

OUTPUT REFERENCE VOLTAGE

←

INPUT SWITCHING DATA

DATA

←

INPUT DUTY CONTROL

INPUT

VCC2

CONNECTION PIN FOR

CSH

SAMPLE-HOLD CAPACITOR SAMPLE-HOLD

S/H

←

CONTROL INPUT

NC: No Connection

APPLICATION

Semiconductor laser-diode applied equipment

BLOCK DIAGRAM



SWITCHING CURRENT SETTING INPUTS



 

1RC



2RC



3RC

GND

MONITORING

COMPARATOR OUTPUT

COMPARATOR

3 5







 

DIFFERENTIAL



AMP

ANALOG OUTPUT

MONITORING

1112

LINEAR AMP

SAMPLE-HOLD

CIRCUIT

REFERENCE

VOLTAGE OUTPUT

ref

CURRENT

SWITCHING

CIRCUIT

REFERENCE

VOLTAGE

SOURCE

SWITCHING

CURRENT

SOURCE

BIAS CURRENT

SOURCE

2RM PD LD

1RM

MONITORING LOAD INPTUT

S/H



SAMPLE-HOLD

CONTROL INPUT

CONNECTION

PIN FOR

DIODE INTPUT

MONITORING

SAMPLE-HOLD

CAPACITOR

21 23

OUTPUT TO

LASER

CURRENT LOAD

DUTY CONTROL

INPUT

DATA

SWITCHING

DATA INPUT

ENB

LASER CURRENT

ENABLE INPUT

PIN DESCRIPTIONS

Pin LD PD

VL1

1RC

VL2

2RC

3RC DA T A 1RM, 2RM

ENB

S/H

CSH

Vref

VCC1 VCC2 GND1 GND2

Laser current output Monitoring diode input

Switching current setting input 1

Output to switching current setting load 1

Switching current setting input 2

Output to switching current setting load 2

Output to bias current setting load

Switching data input Monitoring load input

Monitoring analog output

Monitoring comparator output

Laser current enable input

Laser current load output

Duty control input Sample-hold control

input Connection pin for

sample-hold capacitor Reference voltage

output

Reference voltage input

Name

MITSUBISHI 〈DIGITAL ASSP〉

M66516FP

LASER-DIODE DRIVER/CONTROLLER

Description Connect to anode on semiconductor laser diode. Connect to cathode on monitoring photodiode.

Voltage input to set output current (IL1) of current source 1.

Connect load resistor between this pin and GND for IL1 setting.

Voltage input to set output current (IL2) of current source 2.

Connect a load resistor between this pin and GND for IL2 setting. Connect a load resistor between this pin and GND for setting IB (bias current). Leave this

pin open if IB is not used. If this pin is “L,” a current of IL1 + IL2 + IB flows through laser diode; if “H,” current IB flows. Connect a load resistor between pins 1RM and 2RM for conversion of current generated by

monitoring photodiode into changes in voltage. If DATA = “L” the potential difference generated on monitoring load resistor from photodiode

monitoring current is output as a voltage referenced to GND. If DATA = “H” the output at this pin is fixed at “H” saturation level.

The potential difference generated on monitoring load resistor from photodiode monitoring current is compared with the voltage on pin Vr. The result of the comparison is output in TTL level. This pin acts as comparator output pin only when S/H = “H” and DATA = “L.” In other states, this output pin is fixed to “H.”

If this pin is “H,” all current supply circuits are turned off.

Connect a laser current load resistor between this pin and Vcc. Connect a capacitor between this pin and GND for duty correction of light intensity

switching waveforms. If duty correction is not required, leave this pin open. In internal APC mode, if this pin is “L,” sampling (APC) occurs, if “H,” holding (switching). In

external APC mode, connect this pin to Vcc. Connect a capacitor for sample-hold function between this pin and GND.

Internal reference voltage (1.2V typ.) output pin of M66516

A reference voltage is applied to this pin to operate the comparator and the sample-hold circuit. Connect this pin to the Vref pin if the internal reference voltage of the M66516 is used.

Power supply for internal analog circuits. Connect to a positive power source (+5V). Power supply for internal digital circuits. Connect to a positive power source (+5V). GND for internal analog circuits. GND for internal digital circuits.

MITSUBISHI 〈DIGITAL ASSP〉

M66516FP

LASER-DIODE DRIVER/CONTROLLER

OPERATION

1.Settings for Laser Drive Currents The M66516 has built-in current sources for switching, IL1 and IL2, and a bias current source, IB. Each output current can be controlled independently. Approximate equations used for determining the current output from each of these current sources are as follows. (1) IL1 IL1 is determined by the voltage on the VL1 pin and the resistor (RC 1) connected between the 1RC pin and GND. The following equation is used for approximation.

IL1 [mA] = 12 ×

(2) I

VL1 [V]

RC1 [kΩ]

IL2 is determined by the voltage on the VL2 pin and the resistor (RC 2) connected between the 2RC pin and GND. The following equation is used for approximation.

IL2 [mA] = 12 ×

(3) I

VL2 [V]

RC2 [kΩ]

IB is determined by the internal reference voltage (Vref) and the resistor (RC 3) connected between the 3RC pin and GND. The following equation is used for approximation.

Buffer amp

2RM

1RM

−

Differential amp

− +

−

Comparator

B [mA] = 10 ×

Vref [V]

RC3 [kΩ]

2.Laser Drive Current Switching Operation If DA TA = “L,” laser drive current is I I

L1 + IL2 + IB; if DA TA = “H,”

3.Laser Power Monitoring Operation At the MO and CO pins, the M66516 outputs data obtained by the monitoring photodiode (PD) contained in laser, in the sequence explained below. (1) A current equal to the PD current generated from laser light flows through the resistor (RM) inserted between 1RM and 2RM. Thence a potential difference (V

M) occurring on

RM is converted by the internal differential amp. to a level from GND.

M is output at the MO pin as an analog signal through a

(2) V buffer amp. At the same time, the comparator compares V with the voltage applied to the Vr pin, then the result of the comparison is output at the CO pin in TTL level.

M < Vr , CO output = “L”; and if V M > Vr, CO output = “H.”

If V As the condition of the above operation, both the MO and CO output circuits should be in monitoring operation. See the table below.

Monitor Function Table

Input Output

S/H

L H H

DATA

L H L H

MO output

Analog output

“H” saturation

Analog output

“H” saturation

CO output Fixed to “H” Fixed to “H”

Comparator output

Fixed to “H”

A Schematic Diagram of Monitor Circuits

+ 7 hidden pages