19-4223; Rev 0; 7/08
KIT
ATION
EVALU
BLE
AVAILA
Analog CATV Transimpedance Amplifier
General Description
The MAX3660 high-linearity analog RF transimpedance
amplifier (TIA) is intended for passive optical network
(PON) video receiver applications. With 66dBΩ maxi-
mum 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-for-
ward automatic gain control (AGC). It can also be config-
ured 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.
♦
Pin Compatible with MAX3654
♦
Operates to > 1000MHz
♦
23dBmV/ch Output at 870MHz
♦
4.5pA/Hz
1/2
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
Features
MAX3660
Ordering Information
PART
MAX3660ETE+
TEMP RANGE
-40°C to +85°C
PIN-PACKAGE
16 TQFN-EP*
Applications
FTTH Optical Network Termination (ONT)
+Denotes
a lead-free/RoHS-compliant package.
*EP
= Exposed pad.
Pin Configuration
OUT+
OUT-
10
TOP VIEW
V
CC
12
11
V
CC
9
TEST 13
8
7
GND
HYST
MUTE
VAGC
Typical Application Circuit appears at end of data sheet.
GND 14
GND 15
GND 16
MAX3660
EP*
6
5
+
1
V
CC
2
IN+
3
IN-
4
V
CC
THIN QFN-EP
(4mm
×
4mm)
*THE EXPOSED PAD MUST BE CONNECTED TO GROUND.
________________________________________________________________
Maxim Integrated Products
1
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.
Analog CATV Transimpedance Amplifier
MAX3660
ABSOLUTE MAXIMUM RATINGS
Supply Voltage Range, V
CC........................................
-0.3V to +5.5V
IN+, IN-, VAGC,
MUTE,
HYST, TEST..................................(V
EE
- 0.4V) to (V
CC
+ 0.4V)
Output Current (OUT+, OUT-) ............................................60mA
Maximum Voltage (OUT+, OUT-) ............................(V
CC
+ 0.4V)
Continuous Power Dissipation (T
A
= +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
(V
CC
= +4.75V to +5.25V, T
A
= -40°C to +85°C. Typical values are at V
CC
= +5V, T
A
= +25°C, unless otherwise noted.) (Note 1)
PARAMETER
Supply Current
Gain Control Input Current
MUTE
Input High
MUTE
Input Low
MUTE
Input Current
SYMBOL
I
CC
I
VAGC
V
IH
V
IL
I
IL
, I
IH
V
MUTE
= 0.5V, 2.0V
V
VAGC
= 1.4V
2.0
0.5
±30
CONDITIONS
MIN
TYP
130
-15
MAX
180
-200
UNITS
mA
μA
V
V
μA
AC ELECTRICAL CHARACTERISTICS
(V
CC
= +4.75V to +5.25V, T
A
= -40°C to +85°C, output Z
L
= 75Ω, unless otherwise noted. Typical values are at V
CC
= +5V, T
A
=
+25°C, unless otherwise noted.)
PARAMETER
Frequency Response Flatness
(Notes 2, 3, 4)
SYMBOL
CONDITIONS
47MHz to 870MHz
47MHz to 1000MHz
47MHz, V
VAGC
= 0V
47MHz, V
VAGC
= 0.175V (Note 2)
Transimpedance, Differential
ZT
47MHz, V
VAGC
= 0.5V (Note 2)
47MHz, V
VAGC
= 1.4V (Note 2)
47MHz, V
VAGC
= 1.6V
Gain Tilt
Gain Control Stability
Output Second-Order Intercept
Output Third-Order Intercept
OIP2
OIP3
Linear, 870MHz vs. 47MHz (Note 4)
0.175V V
VAGC
(Notes 2, 5)
1.4V, R
HYST
= open
V
VAGC
V
VAGC
1.4V
1.4V
3.8
63.5
54
45.5
66
66
56.5
48
46.5
4.5
±0.8
58
20
24
5.0
±2.0
dB
dB
dBm
dBm
67.5
58
49.5
dB
MIN
TYP
MAX
±0.9
±1.0
UNITS
dB
47MHz to 870MHz, 0.175V
(Note 6)
47MHz to 870MHz, 0.175V
(Note 6)
2
_______________________________________________________________________________________
Analog CATV Transimpedance Amplifier
AC ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= +4.75V to +5.25V, T
A
= -40°C to +85°C, output Z
L
= 75Ω, unless otherwise noted. Typical values are at V
CC
= +5V, T
A
=
+25°C, unless otherwise noted.)
PARAMETER
Equivalent Input Noise,
Including Photodiode
Gain Control Hysteresis
(Notes 1, 7)
Transimpedance, Mute
RF Output Return Loss
-S22
SYMBOL
EIN
CONDITIONS
47MHz to 870MHz, 0.175V
(Notes 2, 4)
R
HYST
= open
R
HYST
= GND
V
MUTE
0.8V, 47MHz
20
47MHz to 870MHz (Notes 4, 8)
V
VAGC
1.4V
MIN
TYP
5.5
±0.14
±0.75
20
MAX
7.3
UNITS
pA/Hz
1/2
dB
(optical)
dB
dB
MAX3660
Note 1:
DC parameters are tested at T
A
= +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 connect-
ing 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.
48dBΩ
TO 54dBΩ
V
CC
5Ω
1nH
0.5pF
0.5pF
5nH
0.3pF
TO TIA
5nH
0.3pF
60dBΩ
TO 66dBΩ
IN+/-
TIA
54dBΩ
TO 60dBΩ
OUT+/-
5Ω
1nH
0.5pF
MAX3660
MUTE
HYST
VAGC
Figure 1. Photodiode and Header Model
Figure 2. Functional Diagram
_______________________________________________________________________________________
3
Analog CATV Transimpedance Amplifier
MAX3660
Typical Operating Characteristics
(V
CC
= +5.0V, T
A
= +25°C, unless otherwise noted. CNR, CSO, and CTB are for the MAX3660 EV Kit at P
IN
= -8dBm, with channels
above 350MHz attenuated 6dB.)
GAIN (ZT) vs. FREQUENCY
(V
VAGC
= 0.10V, 0.175V, 0.25V, 0.35V, 0.7V,
1.05V, 1.4V, 1.6V; T
A
= -40°C, +25°C, +85°C)
MAX3660 toc01
GAIN (ZT) vs. VAGC
(T
A
= -40°C, +25°C, +85°C)
MAX3660 toc02
DEVIATION FROM LINEAR TILT vs. FREQUENCY
(V
VAGC
= 0 TO 1.6V; T
A
= -40°C, +25°C, +85°C)
0.8
0.6
DEVIATION (dB)
0.4
0.2
0
-0.2
-0.4
-0.6
T
A
= +85°C
T
A
= +25°C
T
A
= -40°C
MAX3660 toc03
80
75
70
GAIN (ZT) (dBΩ)
65
60
55
50
45
40
0
V
VAGC
= 1.6V
V
VAGC
= 0.1V
75
70
65
GAIN (ZT) (dBΩ)
60
55
50
45
40
F = 47MHz
F = 875MHz
1.0
-0.8
-1.0
0.1
1
VAGC (V)
10
0
200
400
600
800
1000
FREQUENCY (MHz)
200 400 600 800 1000 1200 1400 1600
FREQUENCY (MHz)
DEVIATION FROM IDEAL GAIN vs. VAGC
(FREQUENCY = 47MHz, T
A
= -40°C, +25°C, +85°C)
MAX3660 toc04
OIP2, OIP3 vs. VAGC
MAX3660 toc05
EQUIVALENT INPUT NOISE
vs. FREQUENCY
6.8
6.6
NOISE (pA/H
1/2
)
6.4
6.2
6.0
5.8
5.6
5.4
5.2
T
A
= -40°C
T
A
= +85°C
T
A
= +25°C
MAX3660 toc06
1.0
0.8
DEVIATION FROM GAIN (dB)
0.6
0.4
0.2
0
-0.2
-0.4
-0.6
-0.8
-1.0
0
0.4
0.8
VAGC (V)
1.2
T
A
= +85°C
T
A
= -40°C
T
A
= +25°C
80
70
OIP2
OIP2, OIP3 (dBm)
60
50
40
OIP3
30
20
7.0
5.0
0
0.5
1.0
VAGC (V)
1.5
2.0
0
100 200 300 400 500 600 700 800 900
FREQUENCY (MHz)
1.6
CNR vs. FREQUENCY
(110 CHANNELS, OMI = 4.2%/2.1%)
P
IN
= +2dBm
55
CNR (dB)
P
IN
= -2dBm
P
IN
= +2dBm
CSO, CTB (dBc)
MAX3660 toc07
CSO, CTB vs. FREQUENCY
(110 CHANNELS, P
IN
= +2dBm, OMI = 4.2%/2.1%)
MAX3660 toc08
S22
NORMALIZED TO 75Ω
MAX3660 toc09
60
-50
-55
-60
CSO
0
-5
-10
S22 (dB)
DUT AND BALUN
CS
-65
-70
CTB
-75
CTB
-15
-20
DUT ONLY
-25
-30
-35
50
P
IN
= -2dBm
P
IN
= -6dBm
45
P
IN
= -8dBm
P
IN
= -6dBm
-80
0
40
P
IN
= -8dBm
0 100 200 300 400 500 600 700 800 900 1000
FREQUENCY (MHz)
200
400
600
800
1000
0
200
400
600
800
1000
FREQUENCY (MHz)
FREQUENCY (MHz)
4
_______________________________________________________________________________________
Analog CATV Transimpedance Amplifier
Pin Description
PIN
1, 4, 9, 12
2
3
5
6
7
8, 14, 15, 16
10
11
13
—
NAME
V
CC
IN+
IN-
VAGC
MUTE
HYST
GND
OUT-
OUT+
TEST
EP
+5.0V Supply
Positive Analog Input. Connect to photodiode cathode.
Negative Analog Input. Connect to photodiode anode.
AGC Control Input. See the Gain (ZT) vs. Frequency graph.
Active-Low Mute Control Input. V
MUTE
< 0.8V to disable output.
AGC Hysteresis Control Input. A resistor from HYST to GND controls the hysteresis level.
Supply Ground
Negative RF Output
Positive RF Output
Reserved for test. Connect to GND for normal operation.
Exposed Pad. The exposed pad must be soldered to the circuit board ground for proper thermal
and electrical performance.
FUNCTION
MAX3660
Detailed Description
The MAX3660 variable gain TIA has differential AC-
coupled photocurrent inputs and 75Ω differential RF
output. When used with a low-cost operational amplifi-
er, 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 AC-
coupled to the anode and cathode of the analog photo-
diode in a PON triplexer. The maximum input current to
achieve rated linearity is 1.675mA
P-P
.
Very low TIA input impedance provides excellent fre-
quency response with no (internal or external) compen-
sation 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. volt-
age characteristic in the range 0.175V
≤
V
VAGC
≤
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 inter-
face. 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 (V
VAGC
= 350mV
and V
VAGC
= 700mV), there can be a small (approxi-
mately 50ns) deviation in the output, causing an inter-
ruption to the CATV signal. Hysteresis is provided for
the VAGC input to prevent the output signal from dither-
ing when the average optical input level is very close to
one of these two switching points. The amount of hys-
teresis can be controlled by the value of R
HYST
, and is
minimum (0.14dB) when R
HYST
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
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