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02129-DSH-001-D Mindspeed Technologies® August 2010Mindspeed Proprietary and Confidential

M021291/6/8 Gbps TIA with AGC and Rate Select

Applications• Fibre Channel Transceivers (2x,4x, 8x,10x)

• CPRI (1.2288 Gbps to 6.144 Gbps)

• Dual rate ROSA

• SFP/SFP+ Modules

The M02129 is a multi-rate TIA supporting data rates from 1 Gbps to 8.5 Gbps and having a wide input dynamic range to support different transmission distance requirements. Input overload of 3 mAPP and an input sensitivity of better than -19.5 dBm is useful for Fiber Channel and CPRI applications.

In order to satisfy such high sensitivity and good optical overload requirements, automatic gain control (AGC) is implemented in the M02129. The AGC monitors the output amplitude and automatically reduces the TIA gain when the photodiode current exceeds the AGC threshold, maintaining the output at a constant level.

Requiring no extra pins on the ROSA, rate select is controlled by the DC potential on the mon pad. Low rate is optimized for 1G/1.25 Gbps performance with a typical sensitivity lower than -22 dBm. A replica of the average photodiode current is available at the MON pad for photo-alignment and SFF-8472 Rx power monitoring.

Typical Applications Diagram

PINA

DOUT

DOUTB

VCC

PINK

1 nF

Monitor Output /Rate SelectRm

Typically AC-Coupled to Limiting Amplifier

Limiting AmplifierM02129

Features• Typical -19.5 dBm average sensitivity @ 8.5 Gbps (10 dB ER,

0.9A/W PD responsivity)

• Data rates to 8.5 Gbps

• Low rate mode for 1G/1.25 Gbps operation

• No filter (PINK) capacitor required

• AGC provides dynamic range of 23 dB

• 2.5 kΩ differential transimpedance

• 3 mAPP overload input current

• Photodiode current monitor

• Internal or external bias for photodiode

• Single +3.3V supply

02129-DSH-001-D Mindspeed Technologies®2

Mindspeed Proprietary and Confidential

Typical Eye Diagram (-15 dBm) Pad Configuration

Ordering InformationPart Number Package Operating Temperature

M02129 Waffle Pack –40 °C to 95 °C

M02129 Expanded whole wafer on a ring –40 °C to 95 °C

Revision HistoryRevision Level Date Description

D Released August 2010 Updated bare die layout.

C Preliminary May 2009 Updated specifications.

B Preliminary August 2008 Corrected Section 3.2.3 and Figure 4-1.

A Preliminary June 2008 Initial release.

MON

PINA

PINK

VCC AGC DOUT

GND

GND

12

3

4

5 6 7

1314

VCC DOUT NC

98 10

12 11

NC

Die size ≈ 1242 x 932µm



1.0 Product Specification

1.1 Description of Key Specifications

1.1.1 Input Referred NoiseIn the design of a Transimpedance Amplifier, the primary goal is to minimize the input referred noise of the amplifier. This achieves the best S/N ratio for optimum bit error rate performance of the incoming optical data stream. The noise performance of a TIA is a key specification for meeting the stringent optical sensitivity requirement. In general, the input referred noise calculations for a TIA are identical to those in other conventional amplifiers. The input referred noise can be determined from several methods. Traditionally at Mindspeed, TIA noise is obtained from dividing the output RMS voltage noise of the TIA by the transimpedance. The small signal transimpedance of the TIA can be calculated by applying a known p-p input current and then measuring the p-p differential output voltage. The equations used for IN (Input Referred Noise) and GTIA (Transimpedance) are shown below. The TIA output RMS noise can be measured conveniently by using a wide band oscilloscope (or by using a power meter and converting the noise power to noise voltage).

IN = (VoutRMS / GTIA)

GTIA = (VoutPP/ I_inputPP), where:

IN = Input referred noise in RMS

GTIA = TIA small signal transimpedance

I_inputPP= p-p input current

1.1.2 Optical Input SensitivityTIA input sensitivity can be calculated from the optical sensitivity equation directly based on the input referred noise, photodiode responsivity and transmitter extinction ratio information. Note that the Signal to Noise (S/N) must exceed 14.1 to achieve a system bit error rate (BER) of 1x10-12.

Sensitivity = 10log {((S/N x IN x (ER + 1)) / (2 x ρ x (ER – 1))) x 1000} dBm

Where:

Sensitivity = Input sensitivity expressed in average power

S/N = 14.1(for 10-12 BER)

IN = Input Referred Noise in RMS

ER = Extinction Ratio = 10 (typically)

ρ = Photodiode Responsivity = 0.9 (typically)

Product Specification



1.2 Absolute Maximum RatingsThese 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.

1.3 Recommended Operating Conditions

Table 1-1. Absolute Maximum Ratings

Symbol Parameter Rating Units

VCC Power supply (VCC-GND) -0.4 to +4 V

TSTG Storage temperature -65 to +150 °C

IIN_AVG PINA Input current (average) 5.0 mA

IIN_PP PINA Input current (peak to peak) 8 mAPP

VPINA, VDout, VDoutB,VAGC

Maximum input voltage at PINA, Dout, DoutB and AGC -0.4 to 1.65 V

VPINK, VMON Maximum input voltage at PINK and MON -0.4V to Vcc +0.4V V

IPINK Maximum average current sourced out of PINK 10 mA

IDout, IDoutB Maximum average current sourced out of Dout and DoutB 10 mA

Table 1-2. Recommended Operating Conditions

Parameter Rating Units

VCC Power supply (VCC - GND) 3.3 ± 10% V

CPD Max. Photodiode capacitance (Vr = 1.75V when using PINK), for 8.5 Gbps data rate

0.25 pF

TA Operating ambient temperature -40 to +95 °C

RLOAD Recommended differential output loading 100 Ω (1)

NOTES:1. 100Ω is the load presented by the input of a Mindspeed post amp.




1.4 DC CharacteristicsVCC = +3.3V ±10%, TA = -40 °C to +95 °C, TJ = -40 °C to +110 °C, typical specifications are for VCC = 3.3V, TA = 25 °C, unless otherwise noted.

1.5 AC CharacteristicsTVCC = +3.3V ±10%, CIN = 0.25 pF, LIN = 0.5 nH, TA = -40 °C to +95 °C, TJ = -40 °C to +110 °C, typical specifications are for VCC = 3.3V, TA = 25 °C, 8.5 Gbps data rate unless otherwise noted.

Table 1-3. DC Characteristics

Symbol Parameter Min Typ Max Units

ICC Supply current (no loads) — 37 — mA

VB Photodiode bias voltage (PINK - PINA) 1.6 1.75 2 V

VCM Common mode output voltage — 2.5 — V

V_RateSEL

Mon Pad voltage for High Rate (> 1.25 Gbps) operation 0 — 1.0V

Mon Pad voltage for Low Rate (≤ 1.25 Gbps) operation 1.6 — 2.0 (1)

ROUT Output resistance - Differentially 80 100 120 Ω

NOTES:1. 2.0 V is the maximum value to allow MON pad to source current as defined by SFF-8472 Average Power Monitoring.

Table 1-4. AC Characteristics

Parameter Conditions Minimum Typical Maximum Units

Small signal bandwidth -3dB electrical (below AGC turn-on, linear gain region)

— 7.8 — GHz

Small signal transimpedance Differential Output (below AGC turn-on, linear gain region)

2000 2500 — Ω

Overload Input Current (1) 2 3 — mAPP

Maximum input saturation (2) +4 — — dBm

Maximum differential output swing Iin range: 150 μAPP – 2.0 mAPP 150 200 — mVPP

Input Referred Noise (RMS) (3) High rate (unfiltered) — 1200 —

nALow rate (unfiltered) — 600 —

Duty Cycle Distortion p-p (DCD) Iin range: 20 μAPP – 2.0 mAPP — 5 10 ps

Deterministic Jitter p-p (DJ) Iin range: 20 μAPP – 2.0 mAPP(Includes DCD)

— 8 19 ps

AGC settling time To reach 1% of AGC final value within six time constants

1 — — μs

Low frequency cut-off -3 dB electrical — 27 60 kHz

Photodiode current monitor offset No input current — 2 μA




Photodiode current monitor accuracy (4) Iin range: 10 μAAVG –2.0 mAAVG after offset removed, VMON = 0 – 2V

— — 1 dB

Photodiode current monitor gain ratio VMON = 0 to 2V — 1:1 — -

Power supply rejection ratio DC to 1 MHz — 30 — dB

Optical input sensitivity 8.5 Gbps (5) — -19.5 —

dBm6.144 Gbps (5) — -20 —

1.25 Gbps (5) — -22 —

NOTES:1. Overload is the largest p-p input current that the M02129 accepts while meeting specifications.

2. The device may be damaged beyond this optical input signal level.

3. Input Referred Noise is derived by calculation as (RMS output noise) / (Gain at 100 MHz).

4. Includes variation over supply and temperature.

5. Measured by using 10 -12 BER. Transmitter extinction ratio is 10 dB and responsivity of photo diode is 0.9 A/W.

Table 1-4. AC Characteristics

Parameter Conditions Minimum Typical Maximum Units



2.0 Pad Definitions

Table 2-1. Pad Descriptions

Die Pad # Name Function

1 AGC Monitor or force AGC voltage.

2 VCC Power pin. Connect to most positive supply.

3 PINK Common PIN input. Connect to photo diode cathode.(1)

4 PINA Active PIN input. Connect to photo diode anode.

5 VCC Power pin. Connect to most positive supply.

6 MON Analog current source output. Current output matches to average photodiode current when PINK is used to bias the photodiode cathode. If externally biasing the photodiode cathode, the Imon feature will not be usable in this case. MON pad can also be used for rate selection. See Section 3.2.3 for detailed information.

7 DOUT Differential data output (goes low as light increases).

8, 13 NC No Connect. Leave floating.

9,10,11,12 GND Ground pin. Connect to the most negative supply(2).

14 DOUT Differential data output (goes high as light increases).

NA Backside Backside. Connect to the lowest potential, usually ground.

NOTES:1. Alternatively the photodiode cathode may be connected to a decoupled positive supply, e.g. VCC.

2. All ground pads are common on the die. Only one ground pad needs to be connected to the TO-Can ground. However, connecting more than one ground pad to the TO-Can ground, particularly those across the die from each other can improve performance in noisy environments.



3.0 Functional Description

3.1 OverviewThe M02129 is a multi-rate TIA with a wide input dynamic range to support different transmission distance requirements. Input overload of 3.0 mAPP is provided to support short-haul Fiber Optic systems. In order to satisfy such high sensitivity and good optical overload requirements, automatic gain control circuit (AGC) is implemented in the M02129. The AGC monitors the output amplitude and automatically reduces the TIA gain when the photodiode current exceeds the AGC threshold, maintaining the output at a constant level.

A replica of the average photodiode current is available at the MON pad for photo-alignment and SFF-8472 Rx power monitoring. A low pass filter can be engaged by pulling the MON pad above 1.6V, for 1.25 Gbps operation.

Figure 3-1. M02129 Block Diagram

DCRestore

PhaseSplitter

AGC

DOUT

DOUT

AGC

TIA

MON/Rate Select

DC Servo

Level shift

OutputPINA

PINK

Voltage Reg

Functional Description



3.2 General Description

3.2.1 TIA (Transimpedance Amplifier)The transimpedance amplifier consists of a high gain single-ended amplifier (TIA) with a feedback resistor. The feedback creates a virtual low impedance at the input and nearly all of the input current passes through the feedback resistor defining the voltage at the output. Advanced design techniques are employed to maintain the stability of this stage across all input conditions.

An on-chip low dropout linear regulator has been incorporated into the design to give excellent noise rejection up to several MHz.

The circuit is designed for PIN photodiodes in the “grounded cathode” configuration, with the anode connected to the input of the TIA and the cathode connected to AC ground, such as the provided PINK terminal. Reverse DC bias is applied to reduce the photodiode capacitance. PIN photodiodes and Avalanche photodiodes may also be connected externally to a voltage higher than VCC. Care should be taken to correctly sequence the power supply to the externally biased photodiode so that the bias voltage does not appear when the TIA is powered down. Doing so may cause damage to the input of the TIA, as the photodiode bias can become capacitively coupled to the PIN input, and cause damage.

3.2.2 Output StageThe signal from the TIA enters a phase splitter followed by a DC-shift stage and a pair of voltage follower outputs. These are designed to drive a differential (100Ω) load. They are stable for driving capacitive loads such as interstage filters. Each output has its own GND pad; it is recommended but not required that all four GND pads on the chip should be connected. Since the M02129 exhibits rapid roll-off (3 pole), no external filtering is necessary.

3.2.3 Monitor O/P and Rate Select Between 1G and 8G OperationsThe monitor is a high impedance output which sources an average photodiode current for alignment or power monitoring use. This output is mirrored off the PINK current source, and PINK must be used to enable IMON usage. If PINK is not used as in the case of externally biased PIN or APD detectors, then photo current must be monitored via that external bias supply and the MON pin tied to high or low depending on the input data rate.

This output is compatible with the DDMI Receive Power Specification (SFP-8472). An interfacing example is shown below where the M02129 is connected to the M0217x driver General Purpose I/O (GPIO) and Rx Power monitoring A/D. Ensure that the voltage on VMON is in the range of 0 to 2.0V. Refer to Table 3-1 and Figure 3-2.

For non-217X implementations, assume that the MON output would go into a resistor that is measured with a voltage ADC. That being the case, a voltage drop (diode or other) would need to be switched in and out to create the necessary voltage at the MON pin for both rate settings.

The high impedance O/P source replicates the average photodiode current for monitoring purposes. The MON pad can be also used to select between 1G and 8G operation. When the 1G mode is selected, the TIA output is filtered to reduce the bandwidth to 1G levels and hence improve sensitivity. The device is in low rate mode for Vmon

Table 3-1. Selection of Rm for Maximum Input Current

IIN Max (mA) Optical Power (dBm) Rm (Ω)

2 +3 500

1 0 1000

0.5 -3 2000

Functional Description



greater than 1.6V and in high rate mode for Vmon less than 1V. The input current monitoring feature can still be used under the 1G and 8G operations.

Figure 3-2. Implementation with M0217x

RMON

AD_R

xP

GP

IO

1.3V

M02129

MON

M0217x

+

-BW_Sel

(high=8G)

8G Operation:- RMON value selected to limit full-scale voltage to < 1V- GPIO is set low- AD_RxP in voltage mode

1G Operation:- GPIO is set to an input (high-Z)- AD_RxP is in current mode (input voltage ~1.6V)



4.0 Applications Information

4.1 Recommended Pin Diode Connections

Figure 4-1. Suggested PIN Diode Connection Methods

NOTE:The monitor output is not usable if PINK does not bias the PD.Selection of Rm depends on the maximum input current as detailed in Table 3-1.

Alternative Circuit: External PD/APD Bias

(optional ) 1 nF

500 Ω

470 pF

PDC_Bias

PDC

TIA Bond Pad

TO Can Lead

PINA

DOUT

DOUTB

VCC

PINK

M02129

MONGND

Recommended Circuit

TIA Bond Pad

TO Can Lead

PINA

DOUT

DOUTB

VCC

PINK

(optional )1 nF

M02129

Rmon (optional. For IMON to VMON

MON

VCC

GND

Applications Information



4.2 TO-Can Layout

4.3 Treatment of PINKPINK does not require capacitor bypassing regardless of whether or not it is used to bias the photo diode.

Figure 4-2. Typical Layout Diagram with Photodiode Mounted on Metallized Shim or TO-Can Base (5 pin TO-Can)

NOTES:Typical application inside of a 5 lead TO-Can. It is only necessary to bond one VCC pad and one GND pad. However, bonding both GND pads is encouraged for improved performance in noisy environments.

The backside must be connected to the lowest potential, usually ground, with conductive epoxy or a similar die attach material. If a monitor output is not required then a 4 lead TO-Can may be used.

VCC

DOUTB

MON

DOUT

Shim/Substrate




4.4 T0-Can Assembly Recommendations

Figure 4-3. TO-Can Assembly Diagram

M02129

Ceramic ShimSubmount

TO Can Leads

PIN Diode

TO-CAN Header

Ceramic ShimSubmount

TO Can Leads

TO-CAN Header

NOT Recommended Example

Recommended Example

Metal Shim

@4 or 5

M02129PIN Diode

@4 or 5

This bond is too long and unreliable

This bond is unreliable




4.4.1 AssemblyThe M02129 is designed to work with a wirebond inductance of 0.5 nH ± 0.25 nH. Many existing TO-Can configurations will not allow wirebond lengths that short, since the PIN diode submount and the TIA die are more than 1 mm away in the vertical direction, due to the need to have the PIN diode in the correct focal plane. This can be remedied by raising up the TIA die with a conductive metal shim or a substrate. This will effectively reduce the bond wire length. Refer to Figure 4-3 on the following page for details.

Mindspeed recommends ball bonding with a 1 mil (25.4 µm) gold wire. It therefore requires more care in setting of the bonding parameters. For the same reason PINA has limited ESD protection.

In addition, please refer to the Mindspeed Product Bulletin (document number 0201X-PBD-001). Care must be taken when selecting chip capacitors, since they must have good low ESR characteristics up to 1.0 GHz. It is also important that the termination materials of the capacitor be compatible with the attach method used.

For example, Tin/Lead (Pb/Sn) solder finish capacitors are incompatible with silver-filled epoxies. Palladium/Silver (Pd/Ag) terminations are compatible with silver filled epoxies. Solder can be used only if the substrate thick-film inks are compatible with Pb/Sn solders.

4.4.2 Recommended Assembly ProceduresFor ESD protection the following steps are recommended for TO-Can assembly:

a. Ensure good humidity control in the environment (to help minimize ESD).b. Consider using additional ionization of the air (also helps minimize ESD).c. As a minimum, it is best to ensure that the body of the TO-can header or the ground lead of the header is

grounded through the wire-bonding fixture for the following steps. The wire bonder itself should also be grounded.

1. Wire bond the ground pad(s) of the die first.2. Then wire bond the VCC pad to the TO-Can lead.3. Then wire bond any other pads going to the TO-Can leads (such as DOUT, DOUT and possibly MON)4. Next wire bond any capacitors inside the TO-Can.5. Inside the TO-can, wire bond PINK.6. The final step is to wire bond PINA.




4.5 TIA Use with Externally Biased DetectorsIn some applications, Mindspeed TIAs are used with detectors biased at a voltage greater than available from TIA PIN cathode supply. This works well if some basic cautions are observed. When turned off, the input to the TIA exhibits the following I/V characteristic:

In the positive direction the impedance of the input is relatively high.

Figure 4-4. TIA Use with Externally Biased Detectors, Powered Off

PINA Unbiased

-300

-250

-200

-150

-100

-50

0

50

100

-800 -600 -400 -200 0 200 400 600 800 1000 1200

mV

µA




After the TIA is turned on, the DC servo and AGC circuits attempt to null any input currents (up to the absolute maximum stated in Table 1-1) as shown by the I/V curve in Figure 4-5.

It can be seen that any negative voltage below 200 mV is nulled and that any positive going voltage above the PINA standing voltage is nulled by the DC servo. The DC servo upper bandwidth varies from part to part, but is typically at least 27 kHz.

When externally biasing a detector such as an APD where the supply voltage of the APD exceeds that for PINA Table 1-1, care should be taken to power up the TIA first and to keep the TIA powered up until after the power supply voltage of the APD is removed. Failure to do this with the TIA unpowered may result in damage to the input FET gate at PINA. In some cases the damage may be very subtle, in that nearly normal operation may be experienced with the damage causing slight reductions in bandwidth and corresponding reductions in input sensitivity.

Figure 4-5. TIA Use with Externally Biased Detectors, Powered On

PINA biased

-1000

-800

-600

-400

-200

0

200

400

600

800

1000

-300 -200 -100 0 100 200 300 400 500 600 700

mV

µA



5.0 Die Specification

Figure 5-1. Bare Die Layout

MON

PINA

PINK

VCC AGC DOUT

GND

GND

12

3

4

5 6 7

1314

VCC DOUT NC

98 10

12 11

NC

Pad Number Pad X Y Pad

Number Pad X Y

1 AGC -126 338 8 (3) NC 178 -338

2 (1) VCC -278 338 9 (1, 2) GND 325 -338

3 PINK -493 124 10 (1, 2) GND 426 -338

4 PINA -493 -124 11(1, 2) GND 426 338

5 VCC -278 -338 12(1, 2) GND 325 338

6 MON -126 -338 13(3) NC 178 338

7 DOUT 26 -338 14 DOUT 26 338

NOTES:1. It is only necessary to bond one VCC pad and one GND pad.

However, bonding more GND pads is encouraged for improved performance in noisy environments.

2. Each location is an acceptable bonding location.

3. Leave floating.

Process technology: Silicon-Germanium, Silicon Nitride passivationDie thickness: 300 µmPad metallization: AluminumDie size: 1242 µm x 932 µmPad openings: 72 µm sq. Pad Centers in µm referenced to center of deviceConnect backside bias to ground

www.mindspeed.com

General Information:Telephone: (949) 579-3000Headquarters - Newport Beach4000 MacArthur Blvd., East TowerNewport Beach, CA 92660

© 2010 Mindspeed Technologies®, Inc. All rights 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. Except as provided in Mindspeed’s Terms and Conditions of Sale for such products or in any separate agreement related to this document, Mindspeed assumes no liability whatsoever. 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 and 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.

THESE MATERIALS ARE PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESS OR IMPLIED, RELATING TO SALE AND/OR USE OF MINDSPEED PRODUCTS INCLUDING LIABILITY OR WARRANTIES RELATING TO FITNESS FOR A PARTICULAR PURPOSE, CONSEQUENTIAL OR INCIDENTAL DAMAGES, MERCHANTABILITY, OR INFRINGEMENT OF ANY PATENT, COPYRIGHT OR OTHER INTELLECTUAL PROPERTY RIGHT. MINDSPEED FURTHER DOES NOT WARRANT THE ACCURACY OR COMPLETENESS OF THE INFORMATION, TEXT, GRAPHICS OR OTHER ITEMS CONTAINED WITHIN THESE MATERIALS. MINDSPEED SHALL NOT BE LIABLE FOR ANY SPECIAL, INDIRECT, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, INCLUDING WITHOUT LIMITATION, LOST REVENUES OR LOST PROFITS, WHICH MAY RESULT FROM THE USE OF THESE MATERIALS.

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