Datasheet LT6600-5 (Analog Devices) - 10

LT6600-5
APPLICATIONS INFORMATION
2.5V 45 90 INTEGRATED NOISE, GAIN = 1X 0.1μF 40 INTEGRATED NOISE, GAIN = 4X 80 SPECTRUM NOISE DENSITY, GAIN = 1X COILCRAFT ANALYZER 35 NOISE DENSITY, GAIN = 4X 70 R 3 ) INTEGRA V IN TTWB-1010 IN 1 INPUT Hz – 25Ω 1:1 /√ 30 60 7 + 4 LT6600-5 (nV TED NOISE (μ Y 25 50 2 50Ω 25Ω 8 – 20 40 + 5 0.1μF R 6 IN 15 30 V) 66005 F07 NOISE DENSIT 10 20 –2.5V 5 10 0 0
Figure 7
0.01 0.1 10 100 FREQUENCY (MHz) 66005 G08 Example: With the IC removed and the 25Ω resistors
Figure 8
grounded, measure the total integrated noise (eS) of the spectrum analyzer from 10kHz to 5MHz. With the IC in- Conversely, if each output is measured individually and the serted, the signal source (VIN) disconnected, and the input noise power added together, the resulting calculated noise resistors grounded, measure the total integrated noise level will be higher than the true differential noise. out of the fi lter (eO). With the signal source connected, set the frequency to 1MHz and adjust the amplitude until
Power Dissipation
VIN measures 100mVP-P. Measure the output amplitude, The LT6600-5 amplifi ers combine high speed with large- VOUT, and compute the passband gain A = VOUT/VIN. Now signal currents in a small package. There is a need to compute the input referred integrated noise (eIN) as: ensure that the dies’s junction temperature does not exceed 150°C. The LT6600-5 package has Pin 6 fused (e )2 – (e )2 e = O S to the lead frame to enhance thermal conduction when IN A connecting to a ground plane or a large metal trace. Metal trace and plated through-holes can be used to spread the Table 1 lists the typical input referred integrated noise for heat generated by the device to the backside of the PC various values of RIN. board. For example, on a 3/32" FR-4 board with 2oz cop- Figure 8 is plot of the noise spectral density as a function per, a total of 660 square millimeters connected to Pin 6 of frequency for an LT6600-5 with R of the LT6600-5 (330 square millimeters on each side of IN = 806Ω and 200Ω using the fi xture of Figure 7 (the instrument noise has the PC board) will result in a thermal resistance, θJA, of been subtracted from the results). about 85°C/W. Without extra metal trace connected to the V– pin to provide a heat sink, the thermal resistance will
Table 1. Noise Performance
be around 105°C/W. Table 2 can be used as a guide when
INPUT REFERRED
considering thermal resistance.
PASSBAND INTEGRATED NOISE INPUT REFERRED GAIN (V/V) RIN 10kHz TO 10MHz NOISE dBm/Hz Table 2. LT6600-5 SO-8 Package Thermal Resistance
4 200Ω 24μVRMS –149
COPPER AREA
2 402Ω 38μVRMS –145
TOPSIDE BACKSIDE BOARD AREA THERMAL RESISTANCE
1 806Ω 69μVRMS –140
(mm2) (mm2) (mm2) (JUNCTION-TO-AMBIENT)
The noise at each output is comprised of a differential 1100 1100 2500 65°C/W component and a common mode component. Using a 330 330 2500 85°C/W transformer or combiner to convert the differential outputs 35 35 2500 95°C/W to single-ended signal rejects the common mode noise and 35 0 2500 100°C/W gives a true measure of the S/N achievable in the system. 0 0 2500 105°C/W 66005fb 10