ETC UX2222

UX 2222
155Mbps to 2Gbps Laser Driver
General Description
Features
The UX2222 is a complete CMOS laser driver for
SFP/SFF applications from 155Mbps to 2Gbps.It
is fully compliant with the SFP MSA timing and
the SFF-8472 transmit diagnostic requirements.
The UX2222 consists of an automatic power
control (APC) feedback loop, a reference voltage
generator with temperature compensation and a
safety-logic
circuit.
The
UX2222
provides
complementary output currents. The APC feature
allows an optical transmitter to maintain constant
—
Single +3.3V Power Supply
—
Automatic Average Power Control (APC)
—
Modulation Compensation
—
Fully Compliant with SFP and SFF-8472 MSA
—
100mA Bias Current
—
85mA Modulation Current
—
Rise and Fall Times less than 250ps
—
Apply to FP、DFB、VCSEL Laser
Pin Configuration
average optical power by a monitor photodiode,
despite changes in laser threshold current over
temperature and lifetime. Optional temperature
compensation
extinction
compensates
ratio
change
with
Laser
Diode
temperature.
External resistors set the require laser current
level. The UX2222 also provides transmit-disable
control (TX_DISABLE), a single-point latched
transmit-failure monitor output (TX_FAULT),
photocurrent
monitoring,
and
bias-current
monitoring to indicate faults.
Figure 1. Pin Configuration QFN 24
Typical Application Circuit
Figure 2. Typical Application Circuit
2007 Preliminary Datasheet
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UX 2222
155Mbps to 2Gbps Laser Driver
Pin Description
Pin No.
Name
1
MODTC
2,5,14,17
VCC
+3.3V Power Supply Voltage
3
INP
Noninverted data input
4
INN
Inverted data input
6
TX_DISABLE
7
PC_MON
8
BC_MON
9
SHUTDOWN
10,12
GND
11
TX_FAULT
13
BIAS
Laser Bias-Current Output
15
OUTN
Inverted Data Output
16
OUTP
Data Output
18
MD
19
APCFILT1
Connect a capacitor(CAPC) between pin19(APCFILT1) and
pin20(APCFILT1) to set the time constant of the APC feedback
loop
20
APCFILT2
(See pin 19)
21
APCSET
A resistor connected from this pin to ground sets the desired
average optical power
22
MODSET
A resistor connected from this pin to Ground
23
RE
24
RTTH
2007 Preliminary Datasheet
Function
Connecting a resistor between this pin and ground sets the
temperature coefficient of IMOD when temperature is higher than
the threshold set by Rtth
Transmitter Disable, TTL. Laser output is disabled when DISABLE
is asserted high or left unconnected. The laser output is enabled
when this pin is asserted low
Photodiode-current Monitor Output. Current out of this pin
develops a ground referenced voltage across an external resistor
that is proportional to the monitor-diode current
Bias-current Monitor Output. Current out of this pin develops a
ground referenced voltage across an external resistor that is
proportional to the bias current
Shutdown Driver Output, Voltage output to control an external
transistor for optional shutdown circuitry
Ground
Open-Collector Transmit Fault indicator
Photodiode feedback input pin
Connecting a resistor between this pin and ground sets the
coefficient of IMOD by temperature. Leave open for zero-coupling
Threshold temperature compensation. A resistor at this pin
programs the temperature above which compensation is added to
the modulation current optional
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UX 2222
155Mbps to 2Gbps Laser Driver
Absolute Maximum Ratings
Symbol
VCC
TA
TSTG
Parameter
Rating
Units
4
V
Operating ambient
-40 to +85
°C
Storage temperature
-65 to +150
°C
Power Supply (VCC-GND)
DC Characteristics
Symbol
Parameter
IBIAS
Range of Programmable Laser Bias Current
Vin
Total Differential Input Signal
VMD
The dc Voltage of Input
Min.
Typ.
Max.
Units
100
mA
2400
mV
200
0.6 VCC
V
RBC_MON
IBIAS/IBC_MON
80
mA / mA
RPC_MON
IMD/IPC_MON
1
mA / mA
TTH
Threshold-Setting Range for Temperature
Compensate
-20
+80
°C
Re
IMOD Compensation-Setting Range by IBIAS
0
1.5
mA / mA
IMD
Monitor-Diode Input Current Range
20
2000
uA
VHI
TX_DISABLE Input High
2.0
VLO
TX_DISABLE Input Low
0.8
V
VOL
FAILOUT Output Low
0.4
V
Shutdown Output High
V
V
VCC-0.4
Shutdown Output Low
V
0.4
AC Characteristics
(RLOAD (at OUTP and OUTN) = 25Ω connected to VCC, Typical values are at VCC = +3.3V and TA = +25°C.) (Note 1)
Symbol
Parameter
Range of
IMOD
Programmable
Modulation Current
TR, TF
Modulation-Current
Rise and Fall Time
2007 Preliminary Datasheet
Conditions
Min.
Typ.
Minimum differential input
swing is 200mVp-p (Note 2)
Max.
Units
85
mA
250
ps
IBIAS = 20mA, IMOD = 40mA,
2.5ns unit interval; measured
150
from 20% to 80%
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UX 2222
155Mbps to 2Gbps Laser Driver
TPWD
Modulation-Current
IBIAS = 20mA, IMOD = 40mA,
Pulse-Width Distortion
5ns period
25
BIAS and Modulation
Turn-on Delay
ps
100
us
Max.
Units
Note 1: AC characteristics are guaranteed by design and characterization.
Note 2: An 200mVp-p differential is equivalent to complementary 10mVp-p signals on VINP and VINN.
Transmit diagnostic Characteristics
Symbol
Parameter
Time to initialize,
T_init
including reset of
TX_Fault
TX_Fault
TX_Fault Assert Time
Conditions
Min.
From power on or negation of
TX_Fault using TX_Disable
Time from fault to TX_Fault
on.
Typ.
21
ms
250
ns
45
us
350
ns
Time from falling edge of
T_on
TX_Disable Negate
TX_Disable to when the
Time
modulated optical output
rises above 90% of nominal
Time from rising edge of
T_off
TX_Disable Assert Time
TX_Disable to when the
optical output falls below
10% of nominal
T_reset
TX_Disable to reset
2007 Preliminary Datasheet
TX_Disable must be held
high to reset TX_fault
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us
4
UX 2210
155Mbps to 2Gbps Laser Diode Driver
Package Information
Figure 6. QFN24 Package
2006 Preliminary Datasheet
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