AD8310ARMZ-REEL7 Analog Devices Inc, AD8310ARMZ-REEL7 Datasheet - Page 18

• Manufacturer Part Number: AD8310ARMZ-REEL7
• Description: IC,Log/Antilog Amplifier,SINGLE,BIPOLAR,TSSOP,8PIN,PLASTIC
• Manufacturer: Analog Devices Inc
• Type: Logarithmic Amplifierr

Specifications of AD8310ARMZ-REEL7

• Applications: Receiver Signal Strength Indication (RSSI)
• Mounting Type: Surface Mount
• Package / Case: 8-MSOP, Micro8™, 8-uMAX, 8-uSOP,
• Number Of Channels: 1
• Number Of Elements: 6
• Power Supply Requirement: Single
• Input Resistance: 0.0012@5VMohm
• Single Supply Voltage (typ): 3/5V
• Dual Supply Voltage (typ): Not RequiredV
• Power Dissipation: 200mW
• Rail/rail I/o Type: Rail to Rail Input
• Single Supply Voltage (min): 2.7V
• Single Supply Voltage (max): 5.5V
• Dual Supply Voltage (min): Not RequiredV
• Dual Supply Voltage (max): Not RequiredV
• Operating Temp Range: -40C to 85C
• Operating Temperature Classification: Industrial
• Mounting: Surface Mount
• Pin Count: 8
• Package Type: MSOP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

AD8310
OUTPUT FILTERING
For applications in which maximum video bandwidth and,
consequently, fast rise time are desired, it is essential that the
BFIN pin be left unconnected and free of any stray capacitance.
The nominal output video bandwidth of 25 MHz can be reduced
by connecting a ground-referenced capacitor (C
pin, as shown in Figure 35. This is generally done to reduce out-
put ripple (at twice the input frequency for a symmetric input
waveform such as sinusoidal signals).
C
The video bandwidth should typically be set at a frequency
equal to about one-tenth the minimum input frequency. This
ensures that the output ripple of the demodulated log output,
which is at twice the input frequency, is well filtered.
In many log amp applications, it might be necessary to lower
the corner frequency of the postdemodulation filtering to
achieve low output ripple while maintaining a rapid response
time to changes in signal level. An example of a 4-pole active
filter is shown in the
FILT
is selected using the following equation:
C
Figure 35. Lowering the Postdemodulation Video Bandwidth
FILT
C
FILT
=
(
= 1/(2π × 3kΩ × VIDEO BANDWIDTH) – 2.1pF
2μA/dB
2
π
×
3kΩ
3
AD8307
k
Ω
×
VideoBandw
AD8310
1
data sheet.
+4
V
BFIN
OUT
idth
)
C
−
FILT
2
FILT
1 .
) to the BFIN
pF
(11)
Rev. F | Page 18 of 24
LOWERING THE HIGH-PASS CORNER FREQUENCY
OF THE OFFSET COMPENSATION LOOP
In normal operation using an ac-coupled input signal, the
OFLT pin should be left unconnected. Input-referred dc offsets
of about 1.5 mV in the signal path are nulled via an internal
offset control loop. This loop has a high-pass −3 dB corner at
about 2 MHz. In low frequency ac-coupled applications, it is
necessary to lower this corner frequency to prevent input
signals from being misinterpreted as offsets. An external
capacitor on OFLT lowers the high-pass corner to arbitrarily
low frequencies (Figure 36). For example, by using a 1 μF
capacitor, the 3 dB corner is reduced to 60 Hz.
The corner frequency is set by the following equation:
where C
f
CORNER
OFLT
Figure 36. Lowering the High-Pass Corner Frequency
is the capacitor connected to OFLT.
=
(
2
π
of the Offset Control Loop
×
AD8310
2625
1
×
OFLT
C
OFLT
C
(SEE TEXT)
OFLT
)
(12)