TEXAS INSTRUMENTS DNET2511TA Technical data
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OUT+
OUT−
VCC
GND
Bandgap Voltage
Reference and
Bias Current
Generation
Offset
Cancellation
CML
Output
Buffer
+
−
+
−
IN
FILTER
RSSI
Voltage
Amplifier
Transimpedance
Amplifier
R
F
Disable
750
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FEATURES DESCRIPTION
• 2.5 GHz Bandwidth
• 4.0 k Ω Differential Transimpedance
• 10 pA/ √ Hz Typical Input Referred Noise
• 2 mA Maximum Input Current
• Offset Cancellation
• Received Signal Strength Indication
• Differential CML Data Outputs
• Single +3.3V Supply
• Bare-Die Option
APPLICATIONS
• SONET OC-48
• SDH STM-16
• APD Preamplifier-Receivers
• PIN Preamplifier-Receivers
ONET2511TA
2.5 GBPS TRANSIMPEDANCE AMPLIFIER WITH RSSI
SLLS622 – SEPTEMBER 2004
The ONET2511TA is a high-speed transimpedance
amplifier used in SDH/SONET systems with data
rates up to 2.5Gbps. It features a low input referred
noise, 2.5GHz bandwidth, 4.0k Ω transimpedance,
and a received signal strength indicator.
The ONET2511TA device is available in die form and
requires a single +3.3V supply. It is very power
efficient and dissipates less than 83 mW (typical). It is
characterized for operations from –40 ° C to 85 ° C.
AVAILABLE OPTIONS
T
A
–40 ° C to 85 ° C ONET2511TAY
DETAILED DESCRIPTION
DIE
BLOCKDIAGRAM
The ONET2511TA is a high performance 2.5 Gbps transimpedance amplifier that can be segmented into the
signal path, filter, and offset cancellation block.
The signal path consists of a transimpedance amplifier stage, a voltage amplifier, and an output buffer.
The filter circuit provides a filtered VCC for the photodiode.
The offset correction circuit uses an internal low pass filter to cancel the DC on the input and it provides a signal
to monitor the received signal strength.
A simplified block diagram of the ONET2511TA is shown in Figure 1 .
Figure 1. Simplified Block Diagram of the ONET2511TA
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas
Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2004, Texas Instruments Incorporated
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1,030µm
654µm
origin
0,0
x
y
PAD#1
ONET2511TA_B2003
1
2 3
4
5
67
8
9
10
ONET
2511TA
2 3
4
5
6
1
VCC
N.C.
FILTER
IN109
8
7
OUT+
OUT–
GND
RSSI
GND
VCC
ONET2511TA
2.5 GBPS TRANSIMPEDANCE AMPLIFIER WITH RSSI
SLLS622 – SEPTEMBER 2004
DETAILED DESCRIPTION (continued)
SIGNAL PATH
The first stage of the signal path is a transimpedance amplifier that takes the photodiode current and converts it
to a voltage signal. The second stage is a voltage amplifier that provides additional gain. The output of the
second stage feeds the output buffer and the offset cancellation circuitry. The third and final signal path stage of
the ONET2511TA is the output buffer. The output buffer provides CML outputs with an on-chip 50 Ω
back-termination to VCC.
FILTER CIRCUITRY
The filter pin provides a filtered VCC for the photodiode bias. The on-chip low pass filter for the photodiode VCC
is implemented using a filter resistor of 750 Ω and an internal capacitor. If additional filtering is required for the
application, an external capacitor should be connected to the FILTER pin.
OFFSET CANCELLATION AND RSSI
The offset cancellation circuitry performs low pass filtering of the output signal of the voltage amplifier. This
senses the DC offset at the input of the ONET2511TA. The circuitry subtracts current from the input to effectively
cancel the DC. The sensed current is mirrored and is used to generate the RSSI output through an external 10
k Ω resistor. To disable the offset correction loop, the FILTER pin should be tied to GND.
BOND PAD DESCRIPTION
The ONET2511TA is available as bare-die. The location of the bondpads is shown in Figure 2 . The circuit is
characterized for ambient temperatures between –40 ° C and 85 ° C. Table 1 shows the pad descriptions for the
ONET2511TA.
PAD SYMBOL TYPE DESCRIPTION
1 FILTER Analog Bias voltage for photodiode (connects to an internal 750- Ω resistor to VCC). To disable offset correction
2 RSSI Analog-Out Analog output voltage proportional to the input data amplitude. Indicates the strength of the received
3, 6 GND Supply Circuit ground.
2
Figure 2. Bond Pad Assignment of ONET2511TA
Table 1. Pad Description of the ONET2511TA
loop connect FILTER to GND.
signal (RSSI).
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ONET2511TA
2.5 GBPS TRANSIMPEDANCE AMPLIFIER WITH RSSI
SLLS622 – SEPTEMBER 2004
DETAILED DESCRIPTION (continued)
Table 1. Pad Description of the ONET2511TA (continued)
PAD SYMBOL TYPE DESCRIPTION
4 OUT- Analog-Out Inverted data output. On-chip 50- Ω back-terminated to VCC.
5 OUT+ Analog-Out Non-inverted data output. On-chip 50- Ω back-terminated to VCC.
7, 8 VCC Supply 3.3-V ± 10% supply voltage
9 IN Analog-In Data input to TIA. Connect to anode of PIN or APD diode.
10 NC Not connected
ABSOLUTE MAXIMUM RATINGS
over operating free-air temperature range (unless otherwise noted)
V
CC
V
V
OUT+
V
FILTER
I
IN
I
FILTER
Supply voltage
Voltage of OUT+ and Out-
OUT-
V
Voltage of FILTER and RSSI
RSSI
Current into IN -4 to 4 mA
Current into FILTER -8 to 8 mA
ESD ESD rating at all pins except IN
ESD rating at IN
T
Jmax
T
STG
T
A
Maximum junction temperature 150 ° C
Storage temperature -65 to 85 ° C
Operating free-air tempature -40 to 85 ° C
(1) Stresses beyond those listed under "absolute maximum ratings" may cause permanent damage to the device. These are stress ratings
only, and functional operation of the device at these or any other conditions beyond those indicated under "recommended operating
conditions" is not implied. Exposure to absolute–maximum–rated conditions for extended periods may affect device reliability.
(2) All voltage values are with respect to network ground terminal.
(3) For optimum high-frequency performance, the input pin has reduced ESD protection.
(2)
(2)
(2)
(3)
(3)
(1)
-0.3 to 4.0 V
VCC– 1.5 to V
+0.5 V
CC
-0.3 to 4.0 V
2 kV (HBM)
1 kV (HBM)
UNIT
RECOMMENDED OPERATING CONDITIONS
over operating free-air temperature range (unless otherwise noted)
PARAMETER TEST CONDITIONS MIN NOM MAX UNIT
V
CC
T
A
Supply voltage 3 3.3 3.6 V
Operating free-air temperature -40 85 ° C
DC ELECTRICAL CHARACTERISTICS
over operating free-air temperature range, V
PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
V
CC
I
CC
V
IB
I
IN-OVL
R
OUT
R
FILTER
Supply voltage 3 3.3 3.6 V
Supply current 25 35 mA
Input bias voltage 0.66 0.83 1.1 V
DC input overload current 2 mA
Ouput resistance (OUT+, OUT-) Single-ended to V
Photodiode filter resistance (FILTER) 750 Ω
= 3.3 V, TA= 25 ° C (unless otherwise noted)
CC
CC
50 Ω
3
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ONET2511TA
2.5 GBPS TRANSIMPEDANCE AMPLIFIER WITH RSSI
SLLS622 – SEPTEMBER 2004
AC ELECTRICAL CHARACTERISTICS
over operating free-air temperature range, V
PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
I
IN-OVL
A
RSSI
Z
21
f
H-3dB
f
L-3dB
f
H-3dB-RSSI
I
N-IN
DJ Deterministic jitter IIN= 10 µA (K28.5 pattern) 21 ps
V
OD(MAX)
PSRR Power supply rejection ratio f < 2 MHz 55 dB
AC input overload current 2 mA
Input linear range 0.95 < linearity < 1.05 40 µA
RSSI gain 10-k Ω load 2000 V/A
Small-signal transimpedance Differential output 3000 4000 5000 Ω
Small-signal bandwidth C
Low-frequency -3dB bandwidth -3 dB, IIN< 20 µA DC 7 kHz
RSSI bandwidth 4 kHz
Input refered RMS noise 470 640 nA
Input refered noise density 10 pA/ √ Hz
Differential output voltage, maximum IIN= 1 mA
= 3.3 V, TA= 25 ° C (unless otherwise noted)
CC
EXTERNAL
= 0.85 pF
(1)
2.5 GHz
IIN= 100 µA (K28.5 pattern) 25 ps
IIN= 2 mA (K28.5 pattern) 16 ps
p-p
200 320 400 mV
p-p
p-p
RMS
p-p
p-p
p-p
p-p
(1) C
EXTERNAL
bondpad.
= is the total capacitance comprising of the photodiode capacitance, board capacitance, and pad capacitance at the IN
4
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