Mitsubishi M61880FP Datasheet

DESCRIPTION

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 40mA and a maximum switching current of 100
mA,which is switching at a rate of 200Mbps.
Since the M61880FP 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

The M61880FP is a semiconductor laser-diode driver/

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M61880FP

Laser-diode driver / controller

PIN CONFIGURATION (TOP VIEW)

FEATURES

Built-in sample-hold circuit for internal APC function
Hold error voltage is less than 1% for 1µs(C=0.047µF)

High speed switching 200Mbps

Large driving current 100mA (max)

Capable of setting bias current (40mA max)

5V single power supply

APPLICATION

Semiconductor laser-diode applied equipment
Laser beam printer(LBP)
Plain Paper Copier(PPC)

BLOCK DIAGRAM

OUTPUT TO SWITCHING
CURRENT SETTING LOAD

OUTPUT TO BIAS CURRENT
SETTING LOAD

BIAS CURRENT SETTING
VOLTAGE INPUT

REFERENCE VOLTAGE
OUTPUT

REFERENCE VOLTAGE
INPUT

HOLDING CAPACITOR
LOAD INPUT/OUTPUT

SAMPLE-HOLD
CONTROL INPUT

1

RS

RB
VB

Vr

Vcc1

NC

2

3

4

5
6
7

8
9

10

GND1

Vref

CH

S / H

Outline 20P2N-A

20

Vcc2

RO

N C

LD

GND2

PD
DATA

ENB
2RM

1RM

LASER CURRENT
LOAD OUTPUT

LASER CURRENT
OUTPUT

MONITORING
DIODE INPUT

SWITCHING
DATA INPUT

LASER CURRENT
ENABLE INPUT

MONITORING
LOAD INPUT 2

MONITORING
LOAD INPUT 1

19

18

17

16

15

14

13

12

11

NC : No connection

Vcc2 RO N C GND2 PD 2RM 1RM

181920

IB

1 2 3

GND1

RS RB VB Vref Vr Vcc1 NC

LD

17

+

4

16

ISW

50K

1.5V

5 6

1

( / )

TTL/ECL

2.5V

Reference
voltage

11

DATA

15

7

ENB

1314

8 9

12

11

COMP

10

S/H

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is not used.

bias current to LD independent of the state of the DATA input.

M61880FP

Laser-diode driver / controller

FUNCTIONS

The M61880 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-

PIN DESCRIPTIONS

Pin Name
LD
PD

Rs

RB

Laser current output Connect to cathode on semiconductor laser diode.
Monitoring diode input
Switching current

Set load output
Bias current

Set load output

Connect to anode on monitoring photodiode.
Connect a load resistor between this pin and GND for the setting of current (lsw)

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.

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" and
DATA = "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, lsw,
which is controlled by the DATA input, and IB , which is the

Description

VB

DATA

1RM,2RM

ENB

RO
S/H

CH

Vref

Vr

Vcc1 Power supply pin 1

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

Bias current (IB) is set by applying a voltage at this pin. Leave this pin open if I

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.
( 2RM pin connects to GND in the IC.)

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 M61880

Connect a holding capacitor between this pin and GND. Inside the M61880

this pin connects to the output of the sample-hold circuit and the current source

this pin connects to the output of the sample-hold circuit and the current source

input for Isw.

input for Isw.

Internal reference voltage (1.5Vtyp.) output pin of M61880.

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 M61880 is to be used.

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

B

Vcc2
GND1

GND2

Power supply pin 2
GND pin 1
GND pin 2 GND for internal digital circuits.

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

2

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OPERATION

1.Laser Drive Currents Setting Method

Laser Drive Current=Isw(switching current)+IB(bias current)
at switching mode
(1)Isw(Switching Current)
First it is necessary to decide the center value(Isw0) of
maximum switching current Isw(max).Isw0 is depend on
Rs ( load for switching current setting) by the following
equation.
(a)

Isw0 [mA] = 30 X

(b) When switching current is center value( Isw0) , it is
necessary to set up Rm ( load resistor for monitor of
photodiode current ) as follows:
VM(voltage across resistor Rm) = Vr (reference voltage )
at this condition CH pin voltage =2.5V.
When CH pin voltage < 2.5V , Isw <Isw0
When CH pin voltage > 2.5V , Isw >Isw0
(CH pin voltage changes from 2V to 3V at APC mode)
(c) The usable range of ISW at APC mode
That is 20 ~180% of Isw0 accurately.

(2) IB(Bias Current)
Bias current (IB) is set by RB (resistor for the setting of
bias current) and VB (voltage for the setting of bias current).

IB [A] = 1 X

1.2V ≤ VB ≤ Vcc-2.7V
IB(max.)=40mA

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 M61880'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.

Vref(1.5V) [V]
Rs [kΩ]

VB [V]
RB [Ω]

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M61880FP

Laser-diode driver / controller

4.Internal Reset Function

The M61880 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.
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 :

RO(max.) [Ω] =

where Isw(max.) is the maximum of Isw. If, for example,

Vcc(min.)= 4.75V and Isw(max.)= 100mA, RO(max.)=22Ω.

Accordingly, if the resistance of RS is selected so as to gain

maximum Isw of 100mA, RO should be 22Ω 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 M61880.

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. This operation occurs

when the S/H input is "L" and DATA= "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.

Vcc(min.) -2.5 [V]
Isw(max.) [mA]

2Isw0

Isw0

0

1.0

3.0

4.0

2.5

2.0

CH pin voltage VCH (V)

200%

100%

0%

( / )

Constant

Comparator

current source
for charging

Vr

Vm

SW1

Control

S / H

ENB

circuit

SW2

Constant
current source
for discharging

Conceptual Diagram: sample-hold circuit

11

3

Output

CH

External
capacitor

Tr1

FUNCTION TABLE

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M61880FP

Laser-diode driver / controller

Input

ENB S/H Vm,Vr

H

L

X : 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.

DATA

X

HL

L

X
X
H

L

X
X

X
Vm < Vr
Vm > Vr

Switch condition

SW1 SW2
OFF

OFF OFF
OFF

ON

OFF

OFF

OFF
OFF

ON

Vcc

ENB input

sample

S / H input

hold

Tr1

ON
OFF
OFF
OFF
OFF

sample

Output

Fixed to "L"
High impedance state (hold)

High impedance state (hold)
Constant current sourcing (sample)

Constant current sinking (sample)

Note that in the example it is assumed that the leak current
occurring at the CH pin under hold condition flows into
the M61880 (in the positive direction).

sample

hold

hold

DATA input

∆I LD

Laser drive current

An example of APC Timing Chart

7.Vcc and GND Pins

Pins related to the power supply function are Vcc1, Vcc2,
GND1, and GND2. The role of these pins in terms of the in­ternal circuits are as follows.
Vcc1, GND1: connected to analog circuits
Vcc2, GND2: 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 GND1.
(3) Allocate by-pass capacitors near Vcc2 and GND2.

Notes on the Wiring for Peripheral Components

Lay out peripheral components necessary for the M61880 to
operate in closest possible proximity to the M61880.

Calculation Method for Power Dissipation

The approximate power dissipation, P, of the M61880FP 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) = 100mA, power dissipation at times of turning laser
on and off will be as follows.
(1) Laser ON (DATA = "L" and Icc = 55mA)
PON = 55 x 5.25 + 0 + 100 x 2.5 = 538.8(mW)
(2) Laser OFF (DATA = "H" and Icc = 55mA)
POFF = 55 x 5.25 +0+100 x 2.5 = 538.8(mW)

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M61880FP

Laser-diode driver / controller

ABSOLUTE MAXIMUM RATINGS (Ta = -20 ~ 70°C unless otherwise noted)

Symbol
Vcc

VI
VO

Isw
IB

Pd

Tstg

Note: For operation above 25°C, derating of 9.8mW/°C is necessary.

Supply voltage

Input voltage

Output voltage
Switching current
Bias current

Power dissipation
Storage temperature

Parameter

CH, Vr

DATA, ENB, S/H
RO

RECOMMENDED OPERATIONAL CONDITIONS (Ta = -20 ~ 70°C unless otherwise noted)

Symbol Parameter

Vcc

Isw

IB

Topr

Note: Isw + IB ≤ 100mA

Supply voltage
Switching current
Bias current
Operating ambient temperature

4.75

ELECTRICAL CHARACTERISTICS (Ta = -20 ~ 70°C, Vcc = 5V±5% unless otherwise noted)

Symbol

VIH
VIL

Vr

Vref

VLD

VI
VOH
VOL

II

Isw

IB

Icg
Idg

Ioz

LOFF

Icc

"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

Bias current (Note)
Load charging current
Load discharge current

Output current under off
condition

Output current under off
condition

Supply current

Parameter

DATA,ENB,S/H
DATA,ENB,S/H

Vr
Vref

Temperature
coefficient

LD
CH
CH
CH

DATA,ENB
LD

LD
CH
CH

CH

LD

Conditions

Measured being mounted
Ta = 25°C(Note)

Limits
Typ.

Min.

5.0 5.25

Test conditions

Io = ±10µA
Ta = -20 ~ 25°C
Ta = 25 ~ 70°C

ENB= "L" ,IoL= (-0.6mA)

ENB= "L" ,IoH= (0.6mA)
VI = 2.7V
VI = 0.4V

CH=3.5V,Rs=1.2kΩ,VLD=3V
VB=1.5V,RB=70Ω,VLD=3V

ENB= "L" ,Vo=( 0.6 ~ Vcc-1.6V)

ENB= "L" ,Vo=( 0.6 ~ Vcc-1.6V)

Vo=2.0 ~ 3.0V, Hold condition
ENB= "L" ,DATA= "H" ,Isw=50mA

ENB= "H" ,DATA= "L" ,Isw=50mA

Vcc=5.25V,ENB=0V,

CH=3.5V,VB=1.4V

Isw=75mA,IB=25mA

RO=LD=5.0v

Max.

100

40
70-20

Unit

V
mA
mA

°C

DATA=0V

DATA=4.5V

Ratings

-0.3 ~ +5.5

-0.3 ~ +Vcc

-0.3 ~ +Vcc

-0.3 ~ +Vcc
120

50

980

-60 ~ +150

Min. Typ. Max.

2.0

0.35

1.4

2.5

2.7 3.0

Vcc-1.6

-0.2

0.66

-0.5

Unit

V
V

V

mA
mA

mW

°C

Limits

1.5

0.1

-0.1

75
20

-1.0

43 63

43

1.0

0.8

2.0

1.6

Vcc

0.6
20

-0.66

+0.5

50

50

63

Unit

V
V

V
V

mV/°C

V
V
V
V

µA

mA

mA

mA
mA

mA
µA
µA

µA

mA

*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.

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SWITCHING CHARACTERISTICS (Ta=25°C,Vcc=5V)

M61880FP

Laser-diode driver / controller

Symbol

fop

tRP1

tRP2

tON
tOFF

NOTE1:TEST CIRCUIT

oscilloscope
(Input)

P. G.

0.047µF

50Ω

840Ω

RM

Parameter

Operating frequency

Circuit response time1

Circuit response time2

Circuit ON time
Circuit OFF time

20Ω

Vcc

CH

Vr

RS

1RM
2RM

RO

P D

L D

S / H

DATA

ENB

GND

Other pins are open

ENB voltage

ENB voltage

ILD

Current probe

Test pin

Input

Vr voltage

Vr voltage

L DP D

oscilloscope

( Output )

Output

LD current

LD current

LD current
LD current

NOTE2:TEST CIRCUIT

0.047µF

Test condition

ILD=50mA, Rs=840Ω,
CH=0.047µF
APC adjustment;
RM=adjustment(CH=2.5V)
Vr=1.5V± 0.5% (Note1)

ILD=50mA, Rs=840Ω,
CH=0.047µF
APC adjustment;
RM=adjustment(CH=2.5V)
Vr=1.5V± 2.5% (Note1)

ILD(H)=50mA (Note2)
ILD(H)=50mA (Note2)

20Ω

Vcc

1.5V

840Ω

RM

CH

Vr

RS

1RM
2RM

GND

RO

P D

L D

S / H

DATA

ENB

Other pins are open

Min.

Limits

Typ.

100

1

3

ILD

50Ω

Unit

Max.

Mbps

µS

µS

350

µS

5

µS

LDPD

oscilloscope

( Output )

Current probe

oscilloscope

( Input )

P.G.

t r=t f= 6ns

TIMING CHARTS

1.5V

Vr voltage

LD current

0%

TRP1(TRP2)

10%

TRP1(TRP2)

90%

1.5V± change value

ILD(H)

ILD(L)

6

( / )

TIMING CHARTS

ENB
voltage

LD
current

11

1.5V

TON

90 %

1.5 V

TOFF

10 %

3 V

0 V

ILD (H)

ILD (L)

APPLICATION EXAMPLE

LD driver M61880FP

1920

RO

10Ω

300pF

36Ω

N C

18

5V

Vcc2

digital

5V

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M61880FP

Laser-diode driver / controller

Vcc

Control signal

Data stream

LD

+

GND2

digital

PD

TTL/ECL

DATA

14151617

2RM 1RM

ENB

111213

1

RS

1.5KΩ

IB

2 3

GND1
analog

RB
150Ω

VB

ISW

50K

4

Vref Vr

2.5V

Reference
voltage

1.5V

5 6

0.047µF

7

8

S/H

S/H signal

COMP

9 10

Vcc1
analog

5V

NC

7

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The circuit of setting center
value (Isw0)of maximum
switching current(2X Isw0)

Explanation for setting Laser switching current

Vcc

1:1

D1

1.5V

Vcc

2XISWO

+

AMP1

–

RS

2XISWO

ISW2

ISW

2.5V

I1

V1

M61880FP

Laser-diode driver / controller

ISW1

ISW2

Q1 Q2

∆Vd

2KΩ

D2

I2

V2

Id

VB

CH

LD

CURRENT SW

1:1

Fig.1 Equivalent circuits of setting switching current

1. The circuit of setting center value(Isw0) of
maximum switching current

The setting center value(Isw0) of maximum switching
current, 2 X Isw0,set up Rs ( load for switching current
setting). Isw0 (the value that is initialized) is

Isw0[mA]=30 x

2. The circuit of setting switching current

When ∆V is a difference voltage of between
CHpin and 2.5V,Id is

Id =

So I1 and I2 is as follows

I1=250µA-Id

(

I2=250µA+Id

Vref(1.5V)[V]

∆V

2KΩ

RS[kΩ]

(1)

(2)

(3)

250µA

2XISWO

250µA

The circuit of setting switching current

So Isw2 is

Isw2=2 • Isw0 x

Isw is as follows

Isw=2 • Isw0-Isw2 (7)

Next the relation between Isw and ∆V would be introduced .

Isw is able to solve with (6), (7),(3) and (2)equation.

Isw=2 • Isw0( )

Isw=Isw0(1+ )

Isw=Isw0(1+ )

I1+I2

I2

I1+I2

Id

250µA

∆V/2KΩ

250µA

I1

(6)

(8)
(9)

(10)

D1,D2,Q1 and Q2 construct a Gilbert circuit.
The relation of I1,I2,Isw1, Isw2 and Isw0 is

I1I2Isw2

=

Isw1

Isw1+Isw2=2 • Isw0

(4)

(5)

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TYPICAL CHARACTERISTICS

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M61880FP

Laser-diode driver / controller

THERMAL DERATING

1200
1000

800
600
400
200

0

AMBIENT TEMPERATURE Ta (°C)

25 75 125

VB PIN INPUT VOLTAGE •
BIAS OUTPUT CURRENT

60

50
40

30
20
10

0

Vcc=5V,Ta=25°C
RB=51Ω

1.5 2.5 3.5

INPUT VOLTAGE VB (V)

Reference Voltage -Ambient Temperature

Vcc=5V

1.54

1.52

1.50

1.48

1.46

1.44

100500-25

0

AMBIENT TEMPERATURE Ta (°C)

25 75 125

100500-25

VB PIN INPUT VOLTAGE-CURRENT

100.0

90.0

80.0

70.0

60.0

50.0

40.0

30.0

20.0

10.0

3.02.01.00.5

0

0

INPUT VOLTAGE VB (V)

Vcc=5V,Ta=25°C

1.0

2.0

BIAS CURRENT SET RESISTOR­ BIAS OUTPUT CURRENT

60
50
40

30
20

10

0

0 100

RESISTOR FOR BIAS CURRENT SET RB(Ω)

Vcc=5V,Ta=25°C

VB=1.5V

200

300 400

( 9 /11)

SWITCHING CURRENT SET RESISTOR­ SWITCHING OUTPUT CURRENT

120

100

80
60

40
20

0

0 1

RESISTOR FOR SWITCHING CURRENT SET Rs(KΩ)

Vcc=5V,Ta=25°C

VCH=2.5V

2

3 4

CHpin VOLTAGE - SWITCHING CURRENT

120

100

Vcc=5V,Ta=25°C

80

60

40

20

0

1 1.5 2 2.5 3 3.5

Rs=820Ω

CHpin VOLTAGE Vch(V)

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M61880FP

Laser-diode driver / controller

APC COMPARATOR
INPUT VOLTAGE-OFFSET VOLTAGE

10.0

9.0

8.0

7.0

6.0

5.0

4.0

3.
0

2.0

1.0
0

0

2RMpin INPUT VOLTAGE Vm (V)

Vcc=5V,Ta=25°C

1.0

2.0

( 10/11)

PACKAGE OUTLINE

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M61880FP

Laser-diode driver / controller

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