LT6600IS8-15#PBF Linear Technology, LT6600IS8-15#PBF Datasheet - Page 8

• Manufacturer Part Number: LT6600IS8-15#PBF
• Description: IC AMP DIFF LP FLTR 15MHZ 8-SOIC
• Manufacturer: Linear Technology

Specifications of LT6600IS8-15#PBF

• Amplifier Type: Differential
• Number Of Circuits: 1
• Output Type: Differential
• Current - Input Bias: 35µA
• Voltage - Input Offset: 10000µV
• Current - Supply: 38mA
• Voltage - Supply, Single/dual (±): 3 V ~ 11 V, ±1.5 V ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Output / Channel: -
• -3db Bandwidth: -
• Slew Rate: -
• Gain Bandwidth Product: -

APPLICATIONS INFORMATION
LT6600-15
In Figure 3 the LT6600-15 is providing 12dB of gain. The
gain resistor has an optional 62pF in parallel to improve
the passband fl atness near 15MHz. The common mode
output voltage is set to 2V.
Use Figure 4 to determine the interface between the
LT6600-15 and a current output DAC. The gain, or “tran-
simpedance,” is defi ned as A = V
transimpedance, use the following equation:
By setting R1 + R2 = 536Ω, the gain equation reduces
to A = R1(Ω).
The voltage at the pins of the DAC is determined by R1,
R2, the voltage on Pin 7 and the DAC output current.
Consider Figure 4 with R1 = 49.9Ω and R2 = 487Ω. The
voltage at Pin 7 is 1.65V. The voltage at the DAC pins is
given by:
I
49.8Ω.
Evaluating the LT6600-15
The low impedance levels and high frequency operation
of the LT6600-15 require some attention to the matching
networks between the LT6600-15 and other devices. The
previous examples assume an ideal (0Ω) source impedance
and a large (1kΩ) load resistance. Among practical ex-
8
IN
A =
V
is I
DAC
IN
(
CURRENT
536 • R1
R1+ R2
+
OUTPUT
= V
= 77mV + I
DAC
or I
PIN7
IN
I
I
IN
IN
–
R1
R1
)
–
+
. The transimpedance in this example is
•
( )
Ω
R1+ R2 + 536
0.011μF
IN
• 45.3Ω
R1
Figure 4
R2
R2
1
7
2
8
+
–
LT6600-15
+ I
OUT
3.3V
6
3
IN
+
–
660015 F04
0.1μF
/I
•
4
5
IN
R1+ R2
R1• R2
. To compute the
V
V
OUT
OUT
+
–
amples where impedance must be considered is the evalu-
ation of the LT6600-15 with a network analyzer. Figure 5
is a laboratory setup that can be used to characterize the
LT6600-15 using single-ended instruments with 50Ω
source impedance and 50Ω input impedance. For a unity
gain confi guration the LT6600-15 requires a 536Ω source
resistance yet the network analyzer output is calibrated
for a 50Ω load resistance. The 1:1 transformer, 52.3Ω
and 523Ω resistors satisfy the two constraints above.
The transformer converts the single-ended source into a
differential stimulus. Similarly, the output of the LT6600-15
will have lower distortion with larger load resistance yet
the analyzer input is typically 50Ω. The 4:1 turns (16:1
impedance) transformer and the two 402Ω resistors of
Figure 5, present the output of the LT6600-15 with a 1600Ω
differential load, or the equivalent of 800Ω to ground at
each output. The impedance seen by the network analyzer
input is still 50Ω, reducing refl ections in the cabling be-
tween the transformer and analyzer input.
Differential and Common Mode Voltage Ranges
The differential amplifi ers inside the LT6600-15 contain
circuitry to limit the maximum peak-to-peak differential
voltage through the fi lter. This limiting function prevents
excessive power dissipation in the internal circuitry and
provides output short-circuit protection. The limiting
function begins to take effect at output signal levels above
2V
illustrated in Figure 6; the LT6600-15 was confi gured with
unity passband gain and the input of the fi lter was driven
with a 1MHz signal. Because this voltage limiting takes
place well before the output stage of the fi lter reaches the
NETWORK
ANALYZER
SOURCE
P-P
50Ω
and it becomes noticeable above 3.5V
52.3Ω
COILCRAFT
TTWB-1010
1:1
523Ω
523Ω
Figure 5
1
7
2
8
LT6600-15
+
–
–2.5V
3
6
2.5V
+
–
0.1μF
0.1μF
4
5
402Ω
402Ω
COILCRAFT
TTWB-16A
4:1
P-P
. This is
NETWORK
ANALYZER
INPUT
660015fb
660015 F05
50Ω