Preliminary Information - REV _D May 2001
Preliminary Information
MC2042-4
LED/Laser Driver
Data Sheet
Features
Description
Applications
Pin Descriptions
Measurement Tables
Information provided in this Data Sheet is ADVANCED and is subject to change without notice.
Mindspeed™ Technologies, Inc, Proprietary and Confidential
Preliminary Information - REV _D Page 2 of 13
MC2042-4
LED/Laser Driver
Preliminary Information
Information provided in this Data Sheet is ADVANCED and is subject to change without notice.
Mindspeed™ Technologies, Proprietary and Confidential
T
ABLE
O
F
C
ONTENTS
Features ..................................................................................................................................3
Applications............................................................................................................................3
Connections............................................................................................................................3
General Description ...............................................................................................................3
Ordering Informati on..... ................. ........................... .......................... ...................... .............3
Top Level Diagram.................................................................................................................3
Pin Descriptions.............................................. .............................................. .........................4
Absolute Maximum Ratings...................... ........................... .......................... .......................5
DC Electrical Characteristics.................... ................. ................. ...................... ................. ...5
AC Electrical Characteristics.................... ................. ................. ...................... ................. ...5
Signal Path Descrip tion...................... ............................... ................................ ....................6
Current Switch.............................................................................................................................................................6
LED Drive and Temperature Compensation...............................................................................................................6
Pre-emphasis or ‘peaking’...........................................................................................................................................6
LED clamping, Laser driving.......................................................................................................................................6
LED drive Pulse Width Adjust (PWA)..........................................................................................................................6/7
Temperature Compensation Contour Plots.................................................................................................................7
Typical Performance Curves (diagrams)...............................................................................................................8
Typical Performance Curves (diagrams)...............................................................................................................9
Functional Block Diagram.....................................................................................................10
Typical Applications Circuit..................................................................................................10
Bare Die Pad Co-ordinates...................................................................................................11
Disclaimer...............................................................................................................................12
World Wide Sales Offices.............................................. ............................... .........................13
Preliminary Information - REV _D Page 3 of 13
MC2042-4
LED/Laser Driver
Preliminary Information
Information provided in this Data Sheet is ADVANCED and is subject to change without notice.
Mindspeed™ Technologies, Proprietary and Confidential
F
EATURES
Data rates to >300 Mbps, depending on LED
Single chip solution, available as die or in
TSSOP20.or QSOP16 Fabricated in deep sub-
micron CMOS for lowest cost & power consumption
and long term reliability.
Programmable outp ut c urren t from 5 mA to 100 mA.
RC programmable pre-emphasis or ‘peaking’ circuit
giving drive current rise and fall times <500 ps
Resistor programmable compensation for
temperature dependence of LED output power.
PECL input with optional Pulse Width Adjust.
V
REF
voltage generator and output pin.
Supports most LED types (e.g. 660 to 1300 nm)
Single +5 V to +3.3 V operation.
A
PPLICATIONS
FDDI
Fast Ethernet
Fibre Channel
OC3/STM1
C
ONNECTIONS
G
ENERAL
D
ESCRIPTION
The MC2042-4 is a full custom CMOS IC designed for
high-speed LED drive in low-cost optical fibre based
transmissi on sy ste ms . Dependi ng on the LED used , data
rates to >300Mbps can be achieved.
The LED drive current is set by a resistor. To improve
LED ‘on’ time, a pre-emphasis circuit is included, which
may be set via a simple RC network.
To minimise the effects of temperature on LED output
power, LED drive temperature compensation can be set
by resistor over a 500 - 10,000 ppm/°C range.
Differential positive-ECL (PECL) data on the input pins
can be shaped, if desired, by the differential voltage on
the Pulse Width Adjust (PWA) pins. This adjustment is
continuous over a ±500 ps range. In addition, the V
REF
output pin allows single-ended input to the MC2042 and
provides compatibility with industry-standard FO
modules.
O
RDERING
I
NFORMATION
T
OP
L
EVEL
D
IAGRAM
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
Microcosm
MC2042-4
Datecode
GND
V
DD2
GND
I
OUT
I
OUT
I
OUT
PEAK
V
DD2
QSOP16
PWA-
V
DD1
PWA+
D
IN
D
IN
V
REF
RT
SET2
RT
SET
6.5X4.4mm TSSOP Package
4.3X3.9mm QSOP Package
1
2
3
4
5
6
7
8
9
10
20
19
18
17
16
15
14
13
12
11
Microcosm
MC2042-4
Datecode
PWA-
NC
D
IN
D
IN
V
REF
RE
SET2
RT
SET
V
DD1
PWA-
NC GND
V
DD2
GND
I
OUT
I
OUT
I
OUT
PEAK
V
DD2
NC
NC
TSSOP20
Fig.1
Part Pin-Package
MC2042-4DIE Waffle pack
MC2042-4DIEW Expanded Whole Wafer on a ring
MC2042-4Q16 QSOP16
MC2042-4T20 TSSOP20
Inp ut D a ta Pu lse S h a pin g Current Switch and Peaking
Control
VREF Generator Programmable
Current Sink
GND GND2 RTSET RTSET2
IOUT PEAK
VDD2
VDD1
DIN
PWA
IOUT
PWA
DIN
VREF
Fig. 2
MC2042-4
Preliminary Information - REV _D Page 4 of 13
LED/Laser Driver
Preliminary Information
Information provided in this Data Sheet is ADVANCED and is subject to change without notice.
Mindspeed™ Technologies, Proprietary and Confidential
P
IN
D
ESCRIPTIONS
TSSOP20
PIN QSOP16
PIN NAME Description
1 - NC Not connected
2 1 PWA Inverse pulse width adjust input.
32PWA
Differential pulse width adjust input. Allows continious adjustment of input data pulse
width
43
D
IN+
Differential data input
54
D
IN-
Inverse differential data input
65
V
REF
Reference output. Can be used with single-ended data input
76
RT
SET2
Temperature compensation adjustment pin. Allows temperature dependance of LED
light output to be reduced or removed
87
RT
SET
Sets nominal LED drive current
98
V
DD1
Power pin, connect to most positive supply
10 - NC Not connected
11 - NC Not connected
12, 13 9, 10 V
DD2
LED shorting pin, connect to most positive supply. Speeds LED switch off
14 11 PEAK Connection for pre-emphasis or peaking circuit
15, 16 12, 13 I
OUT
Driver output. Connect LED between this pin and V
DD
17 14 I
OUT
Logical inverse of pin 8. Connect resistor of approximately the same value as LED (at
the programmed drive current level) between this pin and V
DD
18, 19 15,16 GND Ground pin. Connect to the most negative supply
20 - NC Not connected
Preliminary Information - REV _D Page 5 of 13
MC2042-4
LED/Laser Driver
Preliminary Information
Information provided in this Data Sheet is ADVANCED and is subject to change without notice.
Mindspeed™ Technologies, Proprietary and Confidential
A
BSOLUTE
M
AXIMUM
R
ATINGS
These are the absolute maximum ratings at or beyond which the IC can be expected to fail or be damaged. Reliable
operation at these extremes for any length of time is not implied.
DC E
LECTRICAL
C
HARACTERISTICS
AC E
LECTRICAL
C
HARACTERISTICS
Symbol Parameter Rating Units
P
TOT
Total power dissipation (TSSOP20) 255 mW
V
CC
Power supply (V
CC
-GND) 7V
T
J
Junction temperature 150 °C
T
A
Operating ambient -40 to +85 °C
T
STG
Storage temperature -65 to +50 °C
Symbol Parameter Min Typ Max Units
V
IN_H
PECL high input level V
CC
-1.0 -V
CC
V
V
IN_L
PECL low input level V
CC
-2.0 -V
CC
-1.8 V
V
REF
Voltage reference V
CC
-1.6 V
CC
-1.4 V
CC
-1.03
I
LED’
ON LED drive current 5 - 120 mV
I
LED’
OFF LED off current - - 50 µA
I
COMP
LED drive current temperature compensation range 0.05 - 1 %/°C
VLEDH LED headroom voltage - - V
DD
-2.0 V
Symbol Parameter Min Typ Max Units
F
C
Maximum data rate 300 - - Mbps
T
PWA
Input data pulse width adjust range -500 - 500 ps
LED t
R
LED drive rise time - 0.7 1 ns
LED t
F
LED drive fall time - 0.7 1 ns
I
PEAK
Peaking current (as % of LED drive current) 0 - 50 %
PEAK t
R
Peaking current rise time - - 1 ns
PEAK t
F
Peaking current fall time - - 1 ns
PEAK t
D
Peaking current decay time - C1X(R4+5) - S
I
DD
Supply current - I
LED
+10 I
LED
+20 mA
Preliminary Information - REV _D Page 6 of 13
MC2042-4
LED/Laser Driver
Preliminary Information
Information provided in this Data Sheet is ADVANCED and is subject to change without notice.
Mindspeed™ Technologies, Proprietary and Confidential
S
IGNAL
P
ATH
D
ESCRIPTION
Current Switch
Differential Positive-ECL (PECL) data on the data input
pins controls the LED current switch. The LED current
flows either through the LED or via the dummy load so
that V
DD
noise is minimised. To reduce LED ‘turn-off’
time, the LED is momentarily short-circuited, via V
DD2
,
before the current is switched to the dummy load.
LED Drive and Temperature
Compensation
The two resistors R1 and R2 set the LED drive current
and temperature compensation. The simplified
application diagram (Fig. 6) shows R1 connected
between RT
SET
and GND, and R2 between RT
SET
and
the RT
SET2
pin.
The current flowing out of the RT
SET
pin determines the
LED drive current.
The temperature independent component of the LED
drive current is set mainly by R1. The temperature
dependent c omp onent is set main ly by R2. Howeve r, R1
and R2 are not independent.
The RT
SET2
pin connects to an internal diode on the IC,
which exhibits standard diode behaviour with
temperature. As temperature rises, the voltage on the
diode drops, the current flowing th rough R2 increases and
the LED drive current increases.
Given the various interdependencies of the drive current,
R1, R2, and temperature compensation, the relationships
have been plotted as contour plots (see Temperature
Compensation Contour Plots). Please contact
Mindspeed™ if other combinations are required.
The LED ‘on’ current is controlled to ±5 %.
Pre-emphasis or ‘peaking ’
To improve LED ‘turn on’ time an optional pre-emphasis
function is included on the MC2042-4. If this is not
required, then the PEAK pin should be left floating.
Two external components (R4, C1) are required to
implement peaking. As shown in Fig. 6.
When the LED is turned on, the vo ltage on PEAK is pull ed
LOW very rapidly. This voltage transient is coupled
through R4 and C1 and exerts a transient current on the
LED.
When the LED is turned off, the voltage on PEAK is pulled
HIGH rapidly. This voltage transient is coupled through
R4 and C1 and exerts a transient current in the opposite
direction on the LED. .
The transient current amplitude and RC decay are given
approximately by:
Peak current (Amps): 4/(R4 + 5)
Decay (seconds): C1 x (R4 + 5)
The above approximations assume an ideal LED model
with 0 Ohms resistance. Real LEDs will slightly alter the
peaking effect. Typical values for R4 and C1 are:
R4 = 50 Ohms
C1 = 20 pF
LED clamping, Laser driving
Since most LEDs exhibit a longer ‘turn off’ time than ‘turn
on’ time, a clamping function is included on the MC2042
in order to reduce the ‘turn off’ time. Clamping is effected
via the two V
DD2
connections.
The disadvantage of clamping is that the LED’s internal
capacitanc e has to b e fully charge d again before th e LED
starts to emit li ght. This delay ed ‘turn on’ effec t bec om es
noticeable when the nominal LED drive current is low.
Use of th e peaking circuit hel ps solve this pr oblem. Thus,
the combination of peaking and clamping results in very
fast ‘turn on’ and ‘turn off’ times for the LED.
When driving Las ers, it will often be hel pful to disa ble thi s
clamping. This can be achieved by leaving the V
DD2
connections floating. V
DD1
must still be connected.
LED drive Pulse Width Adjust (PWA)
The input puls e width can be adj usted prior to applicati on
to the LED switch. The differential voltage on the PWA
(Pulse Width Adjust) pins shapes the input pulse linearly
over a nominal -500 to +500 ps range, according to the
formula:
Delta PW (ps) = K x V
PWA
Preliminary Information - REV _D Page 7 of 13
MC2042-4
LED/Laser Driver
Preliminary Information
Information provided in this Data Sheet is ADVANCED and is subject to change without notice.
Mindspeed™ Technologies, Proprietary and Confidential
Where:
K = 500 ± 100
and
V
PWA
= (V
PWA
+) - (V
PWA
-)
The maximum range for V
PWA
is ±1V. The input
impedance is 3.6 k
Ω
. V
PWA
+ and V
PWA
- will settle at a
nominal voltage equal to (0.6 * V
DD)
if left floating. It is
recommended that adjustment be implemented by pull
down resistors on PWA+ or PWA-. However, it is
common for one or other pin to be tied to ground as a
zero-cost, ‘gross’ adjustment.
If pulse width adjustment is not requi red PWA+ and PWA-
should be tied to ground.
Temperature Compens ation Contour
Plots.
On the following page there are two contour graphs at
junction temperatures of 50°C and 125°C showing R1
from 2k2 to 330 kΩ along the y-axis and R2 from 220 Ω
to 82 kΩ alon g the x-axis . The lab els on the contours are
the led currents (I
LED
).
Choose the contours that represent the required I
LED
at
the two different die temperatures, superimpose the two
graphs. Where the two contours cross gives the R1/R2
value.
NOTE: the contour graphs are based on MC2042-4
junction temperatures (Tj), at 50° and 125°C. The user
must take into acc ount the power di ss ipation and thermal
resistance to arrive at the die temperature.
The following table shows an example at V
CC
= 3.3 V
Looking at the intersection of the relevant curves on
pages 8/9:
log
10
(R1) = 4.18 R1 = 15 k
Ω
log
10
(R2) = 3.33 R2 = 2.2 k
Ω
There are two further contour plots at junction
temperatures of 75°C and 100°C. These can be used in
a similar manner to choose values of R1 and R2.
Ambient 25 85 °C
I
LED
70 100 mA
V
LED
1.5 1.5 V
P
STATIC
50 50 mW
P
DYNAMIC
(V
CC
-
V
LED
)x(70)=245
R
T
100 100 °C/watt
T
J
TA+24.5+5=54.5 85+35+5=125 °C
Preliminary Information - REV _D Page 8 of 13
MC2042-4
LED/Laser Driver
Preliminary Information
Information provided in this Data Sheet is ADVANCED and is subject to change without notice.
Mindspeed™ Technologies, Proprietary and Confidential
T
YPICAL
P
ERFORMANCE
C
URVES
log 10 R2
log 10 R1
Fig. 3
Preliminary Information - REV _D Page 9 of 13
MC2042-4
LED/Laser Driver
Preliminary Information
Information provided in this Data Sheet is ADVANCED and is subject to change without notice.
Mindspeed™ Technologies, Proprietary and Confidential
T
YPICAL
P
ERFORMANCE
C
URVES
Fig. 4
Preliminary Information - REV _D Page 10 of 13
MC2042-4
LED/Laser Driver
Preliminary Information
Information provided in this Data Sheet is ADVANCED and is subject to change without notice.
Mindspeed™ Technologies, Proprietary and Confidential
F
UNCTIONAL
B
LOCK
D
IAGRAM
T
YPICAL
A
PPLICATIONS
C
IRCUIT
Input Data Pulse S haping Current Switch and Peaking
Control
V
REF
Generator Programmable
Current Sink
GND GND2 RT
SET
RT
SET2
I
OUT
PEAK
V
DD2
V
DD1
D
IN
PWA
I
OUT
PWA
D
IN
V
REF
Fig. 5
In pu t Data Puls e Sha pin g C urrent Sw itch and P eaking
Control
V
REF
Generator Programmable
C urrent Sink
GND GND2 RT
SET
RT
SET2
I
OUT
PEAK
V
DD2
V
DD1
D
IN
PWA
I
OUT
PWA
D
IN
R4 C1
R1 R2
LED
Dummy
LED Load
V
CC
V
REF
Fig. 6
Preliminary Information - REV _D Page 11 of 13
MC2042-4
LED/Laser Driver
Preliminary Information
Information provided in this Data Sheet is ADVANCED and is subject to change without notice.
Mind speed™ Technologies, Proprietary and Confide n tial
B
ARE
D
IE
P
AD
C
O
-
ORDINATES
Pad Description X Y
1V
REF
-73 394.5
2RT
SET2
-219 394.5
3RT
SET
-397 214.7
4V
DD1
-397 68.7
5V
DD2
-397 -77.3
6V
DD2
-397 -223.3
7 PEAK -219 -394.5
8I
OUT
-73 -394.5
9I
OUT
73 -394.5
10 I
OUT
219 -394.5
11 GND 397 -223.3
12 GND 397 -77.3
13 PWA- 397 68.7
14 PWA+ 397 214.7
15 D
IN
219 394.5
16 D
IN
73 394.5
MC2042-4
Preliminary Information - REV _D Page 12 of 13
LED/Laser Driver
Preliminary Information
Information provided in this Data Sheet is ADVANCED and is subject to change without notice.
Mindsp eed™ Technologies, Proprietary and Confidential
D
ISCLAIMER
© 2001 Mindspeed Technologies™, as a wholly owned subsidiary and the Internet infrastructure business of Conexant
Systems, All Rights are Reserved.
Information in this document is provided in connection with Mindspeed Technologies. "Mindspeed" products. These
materials are provided by Mindspeed as a service to its customers and may be used for informational purposes only.
Mindspeed assumes no responsibility for errors or omissions in these materials. Mindspeed may make changes to
specifications and product descriptions at any time, without notice. Mindspeed makes no commitment to update the
information contained herein. Mindspeed shall have no responsibility whatsoever for conflicts or incompatibilities arising
from future changes to its specifications and product descriptions.
No license, express or implied, by estoppel or otherwise, to any intellectual property rights is granted by this document.
Except as provided in Mindspeed Terms and Conditions of Sale for such products, Mindspeed assumes no liability
whatsoever.
THESE MATERIALS ARE PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESS OR IMPLIED,
RELATING TO SALE AND/OR USE OF CONEXANT PRODUCTS INCLUDING LIABILITY OR WARRANTIES RELATING
TO FITNESS FOR A PARTICULAR PURPOSE, MERCHANTABILITY, OR INFRINGEMENT OF ANY PATE NT,
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completeness of the information, text, graphics or other items contained within these materials. Mindspeed shall not be
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Mindspee d produ cts are not intended for use in medi cal , life sav ing o r l ife s usta ini ng applicatio ns. Mindspee d cus tom ers
using or selling Mindspeed products for use in such applications do so at their own risk and agree to fully indemnify
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The following are trademarks of Mindspeed Technologies,. the symbol M1, Mindspeed™, and "Build It First™" Product
names or services listed in this publication are for identification purposes only, and may be trademarks of third parties.
Third-party brands and names are the property of their respective owners.
Reader Response: Mindspeed Technologies, strives to produce quality documentation and welcomes your feedback.
Please sen d comments and suggestions to mailto:tech. pubs@mindspeed.com . For technical questions, or to talk to a field
applications engineer contact your local Mindspeed™ sales office listed below. For literature send email request to
literature@mindspeed.com.
Preliminary Information - REV _D Page 13 of 13
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Inform ation provided in this Data Sheet is ADVANCED and is subject to change without notice.
Mindspeed™ Technologies, Proprietary and Confidential
