LT6604CUFF-5#PBF Linear Technology, LT6604CUFF-5#PBF Datasheet - Page 10

• Manufacturer Part Number: LT6604CUFF-5#PBF
• Description: IC AMP DIFF LN DUAL 34-QFN
• Manufacturer: Linear Technology

Specifications of LT6604CUFF-5#PBF

• Amplifier Type: Differential
• Number Of Circuits: 2
• Output Type: Differential
• Current - Input Bias: 30µA
• Voltage - Input Offset: 8000µV
• Current - Supply: 30mA
• 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: 5MHz
• Supply Voltage Range: 3V To 11V
• Supply Current: 30mA
• 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: -

APPLICATIONS INFORMATION
LT6604-5
Use Figure 4 to determine the interface between the
LT6604-5 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 = 806Ω, the gain equation reduces to A
= R1(Ω). The voltage at the pins of the DAC is determined
by R1, R2, the voltage on V
Consider Figure 4 with R1 = 49.9Ω and R2 = 750Ω. The
voltage at V
DAC pins is given by:
Evaluating the LT6604-5
The low impedance levels and high frequency operation
of the LT6604-5 require some attention to the matching
networks between the LT6604-5 and other devices. The
previous examples assume an ideal (0Ω) source impedance
and a large (1k) load resistance. Among practical examples
where impedance must be considered is the evaluation of
the LT6604-5 with a network analyzer.
Figure 5 is a laboratory setup that can be used to character-
ize the LT6604-5 using single-ended instruments with 50Ω
source impedance and 50Ω input impedance. For a unity
10
CURRENT
66045 F04
OUTPUT
A =
V
DAC
DAC
806 • R1
R1+ R2
= V
I
I
= 51mV +I
IN
IN
R1
R1
–
+
MID
MID
0.01μF
, for V
Ω
•
R1+ R2 + 806
IN
R2
R2
S
46.8Ω
= 3.3V, is 1.65V. The voltage at the
R1
34
4
6
2
Figure 4
MID
1/2
LT6604-5
–
+
25
3.3V
7
and the DAC output current.
+
–
0.1μF
+I
27
29
OUT
IN
V
OUT
/I
R1+ R2
I
R1• R2
IN
IN
+
+
V
V
– V
– I
. To compute the
OUT
OUT
IN
OUT
–
+
–
–
=
806 • R1
R1 + R2
gain confi guration the LT6604-5 requires an 806Ω source
resistance yet the network analyzer output is calibrated
for a 50Ω load resistance. The 1:1 transformer, 51.1Ω
and 787Ω resistors satisfy the two constraints above.
The transformer converts the single-ended source into a
differential stimulus. Similarly, the output of the LT6604-5
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 LT6604-5 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 LT6604-5 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
This is illustrated in Figure 6; the LT6604-5 channel 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 supply rails, the input/output behavior
of the IC shown in Figure 6 is relatively independent of
the power supply voltage.
ANALYZER
NETWORK
SOURCE
50Ω
P-P
51.1Ω
and it becomes noticeable above 3.5V
TTWB-1010
COILCRAFT
1:1
787Ω
787Ω
34
4
6
2
Figure 5
1/2
LT6604-5
+
–
25
–2.5V
7
2.5V
+
–
0.1μF
0.1μF
27
29
402Ω
402Ω
COILCRAFT
TTWB-16A
4:1
ANALYZER
NETWORK
INPUT
66045fa
66045 F05
50Ω
P-P
.