MAXIM MAX3660

19-4223; Rev 0; 7/08
KIT
ATION
EVALU
E
L
B
A
AVAIL
Analog CATV Transimpedance Amplifier
The MAX3660 high-linearity analog RF transimpedance
amplifier (TIA) is intended for passive optical network
(PON) video receiver applications. With 66dBΩ maximum variable gain and integrated uptilt, the MAX3660
provides 23dBmV/channel ±1dB at 870MHz
(19dBmV/channel at 47MHz) for optical inputs between
+2dBm to -8dBm (at 4.2% OMI) using simple feed-forward automatic gain control (AGC). It can also be configured with feedback AGC for even greater dynamic
range. CNR is better than 48dB from 47MHz to 870MHz
(1.0A/W photodiode and -165dB/Hz RIN) at -8dBm with
4.2% OMI, or -6dBm with 3.3% OMI. CSO and CTB are
better than -61dBc and -65dBc, respectively. The device
supports extended frequency operation to > 1000MHz.
The very low true-TIA input impedance accommodates
a variety of photodiodes, eliminating the need for an
input matching network and improving yield.
Applications
FTTH Optical Network Termination (ONT)
Features
♦ Pin Compatible with MAX3654
♦ Operates to > 1000MHz
♦ 23dBmV/ch Output at 870MHz
♦ 4.5pA/Hz1/2 Amplifier EIN without Photodiode
♦ 58dBm OIP2
♦ 24dBm OIP3
♦ No Input Matching Required
♦ Single +5V Supply
♦ 650mW Dissipation
♦ -40°C to +85°C Operating Temperature Range
Ordering Information
PART
MAX3660ETE+
TEMP RANGE
PIN-PACKAGE
-40°C to +85°C
16 TQFN-EP*
+Denotes a lead-free/RoHS-compliant package.
*EP = Exposed pad.
Pin Configuration
VCC
OUT+
OUT-
VCC
TOP VIEW
12
11
10
9
TEST 13
GND 14
MAX3660
+
VCC
1
EP*
2
3
4
VCC
GND 16
IN-
GND 15
IN+
Typical Application Circuit appears at end of data sheet.
8
GND
7
HYST
6
MUTE
5
VAGC
THIN QFN-EP
(4mm × 4mm)
*THE EXPOSED PAD MUST BE CONNECTED TO GROUND.
________________________________________________________________ Maxim Integrated Products
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
1
MAX3660
General Description
MAX3660
Analog CATV Transimpedance Amplifier
ABSOLUTE MAXIMUM RATINGS
Supply Voltage Range, VCC........................................-0.3V to +5.5V
IN+, IN-, VAGC, MUTE,
HYST, TEST..................................(VEE - 0.4V) to (VCC + 0.4V)
Output Current (OUT+, OUT-) ............................................60mA
Maximum Voltage (OUT+, OUT-) ............................(VCC + 0.4V)
Continuous Power Dissipation (TA = +70°C)
16-Pin TQFN-EP (derate 16.9mW/°C above +70°C)..1349mW
Operating Temperature Range ...........................-40°C to +85°C
Storage Temperature Range .............................-55°C to +175°C
Lead Temperature (soldering, 10s) .................................+300°C
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 in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
DC ELECTRICAL CHARACTERISTICS
(VCC = +4.75V to +5.25V, TA = -40°C to +85°C. Typical values are at VCC = +5V, TA = +25°C, unless otherwise noted.) (Note 1)
PARAMETER
Supply Current
Gain Control Input Current
MUTE Input High
MUTE Input Low
MUTE Input Current
SYMBOL
CONDITIONS
MIN
ICC
I VAGC
VVAGC = 1.4V
VIH
TYP
MAX
UNITS
130
180
mA
-15
-200
μA
2.0
V
VIL
IIL, IIH
VMUTE = 0.5V, 2.0V
0.5
V
±30
μA
AC ELECTRICAL CHARACTERISTICS
(VCC = +4.75V to +5.25V, TA = -40°C to +85°C, output ZL = 75Ω, unless otherwise noted. Typical values are at VCC = +5V, TA =
+25°C, unless otherwise noted.)
PARAMETER
SYMBOL
Frequency Response Flatness
(Notes 2, 3, 4)
CONDITIONS
MIN
47MHz to 1000MHz
±1.0
47MHz, VVAGC = 0.175V (Note 2)
ZT
66
47MHz, VVAGC = 0.5V (Note 2)
54
56.5
58
47MHz, VVAGC = 1.4V (Note 2)
45.5
48
49.5
47MHz, VVAGC = 1.6V
Linear, 870MHz vs. 47MHz (Note 4)
Gain Control Stability
0.175V VVAGC 1.4V, RHYST = open
(Notes 2, 5)
Output Second-Order Intercept
OIP2
47MHz to 870MHz, 0.175V VVAGC 1.4V
(Note 6)
Output Third-Order Intercept
OIP3
47MHz to 870MHz, 0.175V VVAGC 1.4V
(Note 6)
UNITS
dB
66
63.5
Gain Tilt
2
MAX
±0.9
47MHz, VVAGC = 0V
Transimpedance, Differential
TYP
47MHz to 870MHz
67.5
dB
46.5
3.8
20
4.5
5.0
dB
±0.8
±2.0
dB
58
dBm
24
dBm
_______________________________________________________________________________________
Analog CATV Transimpedance Amplifier
(VCC = +4.75V to +5.25V, TA = -40°C to +85°C, output ZL = 75Ω, unless otherwise noted. Typical values are at VCC = +5V, TA =
+25°C, unless otherwise noted.)
PARAMETER
Equivalent Input Noise,
Including Photodiode
SYMBOL
CONDITIONS
EIN
47MHz to 870MHz, 0.175V VVAGC 1.4V
(Notes 2, 4)
Gain Control Hysteresis
(Notes 1, 7)
MIN
TYP
MAX
UNITS
5.5
7.3
pA/Hz1/2
RHYST = open
±0.14
RHYST = GND
±0.75
VMUTE 0.8V, 47MHz
Transimpedance, Mute
RF Output Return Loss
-S22
dB
(optical)
20
47MHz to 870MHz (Notes 4, 8)
dB
20
dB
Note 1: DC parameters are tested at TA = +25°C and +85°C.
Note 2: Guaranteed by design and characterization.
Note 3: Frequency response flatness is the maximum difference between the frequency response at any point and a line connecting the end points of 47MHz and 870MHz.
Note 4: Measured using the MAX3660 EV kit circuit in Figure 4 with an Excelight SXT5241-Q/GPA triplexer (8mm photodiode lead
length).
Note 5: Gain control stability is the maximum variation in transimpedance (over process, voltage, and temperature) for any valid
VAGC voltage.
Note 6: OIP2 and OIP3 values are tested with tones at 800MHz and 850MHz.
Note 7: Hysteresis is referred to optical gain, equivalent to two times electrical gain (dB).
Note 8: Not including balun.
VCC
48dBΩ
TO 54dBΩ
5Ω
1nH
0.5pF
5nH
0.3pF
0.5pF
5Ω
IN+/-
54dBΩ
TO 60dBΩ
TIA
OUT+/-
TO TIA
1nH
0.5pF
5nH
60dBΩ
TO 66dBΩ
0.3pF
MAX3660
MUTE
Figure 1. Photodiode and Header Model
HYST
VAGC
Figure 2. Functional Diagram
_______________________________________________________________________________________
3
MAX3660
AC ELECTRICAL CHARACTERISTICS (continued)
Typical Operating Characteristics
(VCC = +5.0V, TA = +25°C, unless otherwise noted. CNR, CSO, and CTB are for the MAX3660 EV Kit at PIN = -8dBm, with channels
above 350MHz attenuated 6dB.)
VVAGC = 0.1V
70
0.6
60
55
DEVIATION (dB)
65
F = 875MHz
60
55
50
50
0.2
TA = +25°C
0
-0.2
-0.4
F = 47MHz
45
VVAGC = 1.6V
TA = +85°C
-0.8
40
40
0
-1.0
0.1
200 400 600 800 1000 1200 1400 1600
10
1
0
200
400
600
800
FREQUENCY (MHz)
VAGC (V)
FREQUENCY (MHz)
DEVIATION FROM IDEAL GAIN vs. VAGC
(FREQUENCY = 47MHz, TA = -40°C, +25°C, +85°C)
OIP2, OIP3 vs. VAGC
EQUIVALENT INPUT NOISE
vs. FREQUENCY
70
TA = +25°C
6.6
0
-0.2
TA = +85°C
60
NOISE (pA/H1/2)
0.2
-0.4
6.8
OIP2
OIP2, OIP3 (dBm)
0.4
7.0
50
40
5.8
TA = -40°C
5.0
20
0.4
0.8
1.2
1.6
0
0.5
1.0
1.5
0
2.0
100 200 300 400 500 600 700 800 900
VAGC (V)
VAGC (V)
FREQUENCY (MHz)
CNR vs. FREQUENCY
(110 CHANNELS, OMI = 4.2%/2.1%)
CSO, CTB vs. FREQUENCY
(110 CHANNELS, PIN = +2dBm, OMI = 4.2%/2.1%)
S22
NORMALIZED TO 75Ω
PIN = -6dBm
-10
-60
CS
S22 (dB)
PIN = -2dBm
-65
DUT AND BALUN
-15
-20
DUT ONLY
CTB
-70
PIN = -8dBm
-25
CTB
-75
PIN = -8dBm
-5
PIN = +2dBm
PIN = -2dBm
MAX3660 toc09
CSO
-55
0
MAX3660 toc08
PIN = +2dBm
50
-50
MAX3660 toc07
60
CSO, CTB (dBc)
0
40
TA = +25°C
6.0
5.2
-1.0
45
6.2
5.4
30
-0.8
55
TA = +85°C
6.4
5.6
OIP3
-0.6
1000
MAX3660 toc06
TA = -40°C
0.6
80
MAX3660 toc05
0.8
MAX3660 toc04
1.0
-30
PIN = -6dBm
0 100 200 300 400 500 600 700 800 900 1000
FREQUENCY (MHz)
4
TA = -40°C
0.4
-0.6
45
DEVIATION FROM GAIN (dB)
0.8
65
GAIN (ZT) (dBΩ)
GAIN (ZT) (dBΩ)
70
1.0
MAX3660 toc02
75
75
MAX3660 toc01
80
DEVIATION FROM LINEAR TILT vs. FREQUENCY
(VVAGC = 0 TO 1.6V; TA = -40°C, +25°C, +85°C)
GAIN (ZT) vs. VAGC
(TA = -40°C, +25°C, +85°C)
MAX3660 toc03
GAIN (ZT) vs. FREQUENCY
(VVAGC = 0.10V, 0.175V, 0.25V, 0.35V, 0.7V,
1.05V, 1.4V, 1.6V; TA = -40°C, +25°C, +85°C)
CNR (dB)
MAX3660
Analog CATV Transimpedance Amplifier
-35
-80
0
200
400
600
FREQUENCY (MHz)
800
1000
0
200
400
600
FREQUENCY (MHz)
_______________________________________________________________________________________
800
1000
Analog CATV Transimpedance Amplifier
PIN
NAME
1, 4, 9, 12
VCC
FUNCTION
2
IN+
Positive Analog Input. Connect to photodiode cathode.
3
IN-
Negative Analog Input. Connect to photodiode anode.
5
VAGC
AGC Control Input. See the Gain (ZT) vs. Frequency graph.
6
MUTE
Active-Low Mute Control Input. VMUTE < 0.8V to disable output.
7
HYST
AGC Hysteresis Control Input. A resistor from HYST to GND controls the hysteresis level.
8, 14, 15, 16
GND
Supply Ground
10
OUT-
Negative RF Output
11
OUT+
Positive RF Output
13
TEST
Reserved for test. Connect to GND for normal operation.
—
EP
+5.0V Supply
Exposed Pad. The exposed pad must be soldered to the circuit board ground for proper thermal
and electrical performance.
Detailed Description
The MAX3660 variable gain TIA has differential ACcoupled photocurrent inputs and 75Ω differential RF
output. When used with a low-cost operational amplifier, photodiode assembly, bias network, and balun, the
MAX3660 provides a complete high-performance
BPON/GPON video receiver with a simple and effective
feed-forward AGC. It can also be used with feedback
AGC.
Low-Noise Variable-Gain Amplifier
The low-noise differential input is designed to be ACcoupled to the anode and cathode of the analog photodiode in a PON triplexer. The maximum input current to
achieve rated linearity is 1.675mAP-P.
Very low TIA input impedance provides excellent frequency response with no (internal or external) compensation between photodiode and amplifier, thus
simplifying design, manufacturing, and photodiode
selection.
VAGC and Hysteresis Control
The overall transimpedance is controlled using the VAGC
input pin. See the Typical Operating Characteristics for
descriptions of the transimpedance, OIP2 (CSO), and
OIP3 (CTB) performance for VAGC voltages between 0
and 1.8V.
The MAX3660 has a very flat and stable gain vs. voltage characteristic in the range 0.175V ≤ VVAGC ≤ 1.4V,
enabling a simple feed-forward AGC based on average
optical power level as measured by the photodiode DC
current (see Figure 4 for the EV kit schematic).
Feedback AGC can be used to achieve a wider
dynamic range, in which case the VAGC voltage would
be controlled by an external power detector, such as
the MAX2014, typically through a microcontroller interface. In this case, the maximum voltage at VAGC
should be kept below approximately 1.65V to maintain
adequate linearity levels for typical GPON applications.
The forward signal path is implemented with three
switched variable gain stages, each covering one-third
of the total dynamic range. When the voltage input at
VAGC crosses the points on the Gain (ZT) vs. VAGC
curve where a new stage is selected (VVAGC = 350mV
and VVAGC = 700mV), there can be a small (approximately 50ns) deviation in the output, causing an interruption to the CATV signal. Hysteresis is provided for
the VAGC input to prevent the output signal from dithering when the average optical input level is very close to
one of these two switching points. The amount of hysteresis can be controlled by the value of RHYST, and is
minimum (0.14dB) when RHYST is open.
RF Output and Cable Tilt Compensation
The MAX3660 includes integrated cable compensation
(uptilt). With a photodiode assembly similar to that
described in Figure 1, the output at 870MHz is 4dB
higher compared to the output at 47MHz. About half of
the uptilt is due to the combination of photodiode
capacitance and the inductance of the triplexer leads,
and half is internal to the MAX3660.
_______________________________________________________________________________________
5
MAX3660
Pin Description
MAX3660
Analog CATV Transimpedance Amplifier
RF Output and Input Stage
The differential outputs should be connected to a
balun transformer to produce a single-ended 75Ω output. If the MAX3660 is used to drive a single-ended
postamplifier, the use of a balun is recommended
(refer to Maxim Reference Design HFRD-22.4) to
achieve adequate linearity and noise performance.
With a typical low-cost balun, output return loss (-S22)
is better than 15dB up to 550MHz and is limited by the
balun performance.
When MUTE is logic-low, the transimpedance is less
than 20dBΩ.
Applications Information
Photodiode/TIA Interface
The MAX3660 is designed to provide a 23dBmV/channel output at 870MHz with excellent CSO, CTB, and
CNR, and its frequency response extends well beyond
1000MHz.
The RF output has 4dB ±1dB of uptilt and ±0.9dB of
flatness (47MHz to 870MHz) when used with a photodiode and assembly having characteristics similar to
those shown in Figure 1, which is consistent with a typical low-cost FTTH triplexer connected by 5mm leads to
matched vias. The MAX3660’s very low input impedance (approximately 10Ω) also provides tolerance to
variations in photodiode and assembly electrical characteristics.
It is particularly important to provide electrical symmetry in the anode and cathode connections, including
the triplexer/ROSA lead routing and PCB mounting configuration. Consult the EV kit and Maxim reference
designs for examples of good layout techniques. With
typical optical transmitter characteristics, the MAX3660
achieves CSO and CTB better than -65dBc and
achieves CNR (including amplifier noise, photodiode
shot noise, and transmitter RIN) of 48dB (at -6dBm or
greater with OMI = 3.3%, or at -8dBm or greater with
OMI = 4.2%) between 47MHz and 870MHz. Refer to
the MAX3660 EV kit data sheet for a description of the
setup used for CSO, CTB, and CNR typical operating
characteristics measurements.
To achieve optimum CNR performance, the AGC should
be configured so that the MAX3660’s gain is greatest
(VVAGC ≤ 0.175V) at the lowest intended optical input
level, typically -6dBm or -8dBm. To maintain CTB and
CSO performance, care should also be exercised when
designing the AGC so that the maximum operating
VAGC level is limited to approximately 1.6V. Operating
6
with input signal levels greater than 1.6mAP-P can result
in a reduction in linearity due to clipping.
Photodiode Bias Network
A combination of resistors and inductors, such as
shown in Figure 3, provides DC bias to the photodiode. The series connection of two inductors and one
resistor is intended to mitigate effects of inductor selfresonance.
The DC voltage drop across the lower resistor provides
an effective means to measure average optical power
for use as a signal strength indicator and/or feed-forward AGC.
The value of the resistors can be adjusted to vary the
feed-forward gain. Depending on the specific photodiode characteristics and desired frequency response,
between 5V and 12V should normally be used for VPD.
VPD
0.1μF
10μH
1.8kΩ BEAD
1kΩ
0.001μF
TIA IN+
0.001μF
1kΩ
1.8kΩ BEAD
10μH
Figure 3. Photodiode Bias Network
_______________________________________________________________________________________
TIA IN-
VMON
Analog CATV Transimpedance Amplifier
Uptilt
The integrated uptilt results in equal input levels producing an output voltage that is 4dB greater at 870MHz
compared to 47MHz, eliminating the loss normally
associated with an external passive tilt network. The
amount of uptilt can be varied by adjusting the triplexer
lead length, or by adding small inductors in series with
the anode and cathode, to compensate for photodiodes/triplexers that differ significantly from Figure 1.
⎡ 175mV ⎤
ZT(dBΩ) = 66dBΩ + 20 log ⎢
⎥ , ( 0..175V ≤ V VAGC ≤ 1.4V )
⎢⎣ V VAGC (mV ) ⎥⎦
The gain at 870MHz is 4dB greater (70dBΩ at VVAGC =
0.175V) because of the uptilt, although the amount of
uptilt can be modified as described above.
Between 0 and 0.175V the gain is constant, and above
1.5V it falls off relatively quickly. Operation above
VVAGC = 1.6V should be avoided to obtain adequate
linearity performance.
The high-impedance VAGC input should be driven by a
source (op amp, DAC, etc.) capable of sinking up to
200µA.
Feed-Forward AGC
With a feed-forward circuit like that of the EV kit, the
MAX3660 provides a constant (±1dB) output of
19dBmV/channel at 47MHz and 23dBmV/channel at
870MHz, for optical input levels ranging between
-8dBm and +2dBm at OMI = 4.2%.
Feedback AGC
The VAGC voltage can also be controlled from a power
detector, such as the MAX2014 or MAX9933, for feedback AGC.
It is important to note that the Gain (ZT) vs. VAGC characteristic includes hysteresis at the two points where
the input stage switches gain (350mV and 700mV),
which can cause problems such as limit-cycle oscillation with continuous analog feedback implementations.
The feedback circuit should be designed to avoid oscillation or dithering.
Equivalent Input Noise
The typical equivalent input referred noise (EIN) of the
MAX3660 with a photodiode connected at the input is
5.5pA/Hz1/2, yielding 48dB or better CNR under normal
BPON/GPON conditions. Without a photodiode connected, the typical EIN is 4.5pA/Hz1/2.
RF Output
The RF output should be connected to the MAX3660
using AC-coupling capacitors and a balun transformer
to achieve the desired noise and linearity performance.
Without the capacitors, shorting OUT+ and OUTtogether, or shorting OUT+ or OUT- to ground, can
draw sufficient current to damage the output stage.
EV Kit Circuit
The MAX3660 EV kit circuit shown in Figure 4 was used
to collect the data in the Typical Operating
Characteristics figures. When connected to a photodiode-equipped triplexer, the EV kit circuit provides a
complete receiver, including photodiode bias, feed-forward AGC, and output transformer.
Jumper JU1 controls the MUTE input, JU3 sets the
amount of hysteresis, and JU2 controls the input of the
op amp driving the VAGC input. Install JU2 to enable
feed-forward VAGC, or alternatively, the gain can be
controlled by TP6 with JU2 removed.
_______________________________________________________________________________________
7
MAX3660
Gain vs. VAGC Voltage
The overall transimpedance at 47MHz is related to the
voltage at VAGC by the relation:
MAX3660
Analog CATV Transimpedance Amplifier
VPD
VPD
TP13
C3
0.1μF
VPD
VCC
TP1
L2
10μH
TP2
C14
33μF
TP5
GND
L1
1.8kΩ BEAD
C7
0.1μF
15
16
VCC
14
GND
GND
1
R1
1kΩ
13
GND
VCC
TEST
VCC
VCC
C4
0.001μF
IN+
3
C8
0.1μF
R21
1kΩ
OUT+
U1
C2
0.001μF
U5
C8
0.1μF
12
C1
0.001μF
2
11
IN-
OUT-
10
EP
VCC
4
VCC
VCC
VCC
MUTE
6
HYST
7
U8
CX2038
C5
0.001μF
MAX3660
VAGC
5
L5
1.8kΩ BEAD
C9
0.1μF
9
GND
8
R3
100kΩ
TP3
L6
10μH
R5
100kΩ
R22
OPEN
TP4
JP3
C11
1μF
C6
1μF
U2
R4
100kΩ
R9
20kΩ
JP1
JP2
TP6
C10
1μF
R6
1kΩ
R7
OPEN
R8
1kΩ
VCC
Figure 4. MAX3660 EV Kit Schematic
8
C13
33μF
VCC
_______________________________________________________________________________________
J2
Analog CATV Transimpedance Amplifier
VPD
0.1μF
10μH
+5V
1.8kΩ BEAD
VCC
1kΩ
TEST
MAX3660
0.001μF
0.001μF
-8dBm TO +2dBm,
-6dBm TO +2dBm
IN+
OUT+
IN-
OUT-
CX2038
75Ω
0.001μF
0.001μF
1kΩ
HYST
1.8kΩ BEAD
RHYST
MUTE
VAGC
GND
EP
+5V
100kΩ
1μF
10μH
100kΩ
Package Information
Chip Information
PROCESS: SiGe BiPOLAR
SUBSTRATE: SOI
For the latest package outline information and land patterns, go
to www.maxim-ic.com/packages.
PACKAGE TYPE
PACKAGE CODE
DOCUMENT NO.
16 TQFN-EP
T1644+3
21-0139
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 _____________________ 9
© 2008 Maxim Integrated Products
is a registered trademark of Maxim Integrated Products, Inc.
MAX3660
Typical Application Circuit