LT6604CUFF-10#PBF Linear Technology, LT6604CUFF-10#PBF Datasheet - Page 12

• Manufacturer Part Number: LT6604CUFF-10#PBF
• Description: IC AMP DIFF LN DUAL 34-QFN
• Manufacturer: Linear Technology

Specifications of LT6604CUFF-10#PBF

• Amplifier Type: Differential
• Number Of Circuits: 2
• Output Type: Differential
• Current - Input Bias: 40µA
• Voltage - Input Offset: 8000µV
• Current - Supply: 36mA
• Voltage - Supply, Single/dual (±): 3 V ~ 11 V, ±1.5 V ~ 5.5 V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 34-QFN
• No. Of Amplifiers: 2
• Input Offset Voltage: 35mV
• Bandwidth: 10MHz
• Supply Voltage Range: 3V To 11V
• Supply Current: 36mA
• Amplifier Case Style: QFN
• No. Of Pins: 34
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Output / Channel: -
• -3db Bandwidth: -
• Slew Rate: -
• Gain Bandwidth Product: -

LT6604-10
APPLICATIONS INFORMATION
The LT6604-10 was designed to process a variety of
input signals including signals centered on the mid-sup-
ply voltage and signals that swing between ground and
a positive voltage in a single supply system (Figure 1).
The range of allowable input common mode voltage (the
average of V
the power supply level and gain setting (see the Electrical
Characteristics section).
Common Mode DC Currents
In applications like Figures 1 and 3 where the LT6604-10
not only provides lowpass fi ltering but also level shifts the
common mode voltage of the input signal, DC currents
will be generated through the DC path between input and
output terminals. Minimize these currents to decrease
power dissipation and distortion. Consider the application
in Figure 3. V
the 1st differential amplifi er inside the LT6604-10 channel
(see the Block Diagram section) at 2.5V. Since the input
common mode voltage is near 0V, there will be approxi-
mately a total of 2.5V drop across the series combination
of the internal 402Ω feedback resistor and the external
100Ω input resistor. The resulting 5mA common mode
DC current in each input path, must be absorbed by the
sources V
output voltage of the 2nd differential amplifi er inside
the LT6604-10 channel, and therefore sets the common
mode output voltage of the fi lter. Since, in the example of
Figure 3, V
2.5mA (1.25mA per side) of DC current will fl ow in the
resistors coupling the 1st differential amplifi er output stage
to the fi lter output. Thus, a total of 12.5mA per channel is
used to translate the common mode voltages.
12
IN
OCM
+
MID
IN
and V
+
differs from V
sets the output common mode voltage of
and V
IN
–
IN
. V
–
in Figure 1) is determined by
OCM
MID
sets the common mode
by 0.5V, an additional
A simple modifi cation to Figure 3 will reduce the DC com-
mon mode currents by 36%. If V
the common mode output voltage of both op amp stages
will be 2V and the resulting DC current will be 8mA per
channel. Of course, by AC coupling the inputs of Figure 3,
the common mode DC current can be reduced to 2.5mA
per channel.
Noise
The noise performance of the LT6604-10 channel can be
evaluated with the circuit of Figure 6. Given the low noise
output of the LT6604-10 and the 6dB attenuation of the
transformer coupling network, it will be necessary to mea-
sure the noise fl oor of the spectrum analyzer and subtract
the instrument noise from the fi lter noise measurement.
Example: With the IC removed and the 25Ω resistors
grounded, Figure 6, measure the total integrated noise (e
of the spectrum analyzer from 10kHz to 10MHz. With the
IC inserted, the signal source (V
input resistors grounded, measure the total integrated noise
out of the fi lter (e
set the frequency to 1MHz and adjust the amplitude until
V
V
compute the input referred integrated noise (e
Table 1 lists the typical input referred integrated noise for
various values of R
Table 1. Noise Performance
PASSBAND
IN
OUT
e
GAIN
measures 100mV
IN
, and compute the passband gain A = V
4
2
1
=
(e
O
)
100Ω
200Ω
402Ω
2
R
A
– (e
IN
O
IN
). With the signal source connected,
S
.
P-P
)
2
INTEGRATED NOISE
INPUT REFERRED
10kHz TO 10MHz
. Measure the output amplitude,
24μV
34μV
56μV
RMS
RMS
RMS
IN
) disconnected, and the
MID
is shorted to V
INPUT REFERRED
NOISE dBm/Hz
OUT
–149
–146
–142
IN
/V
) as:
IN
. Now
660410fb
OCM
S
)