LTC6360CDD#PBF Linear Technology, LTC6360CDD#PBF Datasheet - Page 15
LTC6360CDD#PBF
Manufacturer Part Number
LTC6360CDD#PBF
Description
Manufacturer
Linear Technology
Datasheet
1.LTC6360CDDPBF.pdf
(24 pages)
Specifications of LTC6360CDD#PBF
Lead Free Status / Rohs Status
Supplier Unconfirmed
Available stocks
Company
Part Number
Manufacturer
Quantity
Price
applicaTions inForMaTion
The amount that the loop gain and subsequent bandwidth
will be reduced is equal to this zero-pole ratio. For example,
for 20dB of loop gain reduction (one decade bandwidth
reduction), R
Figure 8 shows the open loop gain without compensation
and with a 10Ω/330pF RC compensation network. The
pole-zero can be seen to reduce the open loop gain above
10MHz, stabilizing the amplifier for unity gain applications.
The following is a guideline for designing the RC filter to
ensure stability with a circuit gain less than five:
1. In order to sufficiently reduce the gain prior to the
2. The zero should be located below to the unity gain
unity loop gain crossover point, f
should be greater than 5/NG, where NG is the circuit
noise gain. For example, based on Equation 5, a unity
gain configuration allows a maximum R
11.25Ω.
crossover frequency, f
troduced, f
where f
without the RC network. Thus, the following condition
should be met:
where f
Figure 8. Open Loop Gain and Phase with and without
Output Compensation
f
f
C
Z
< f
= f
C(AMP)
C(AMP)
C(AMP)
C(AMP)
140
100
–20
80
60
40
20
0
FILT
10
C
will occur at a lower frequency given by:
GAIN
is the unity gain-bandwidth of the amplifier
100
/(f
/(f
should be made equal to 5Ω.
is approximately 1GHz.
Z
Z
/ f
1k
/ f
PHASE
UNCOMPENSATED
P
P
FREQUENCY (Hz)
10k 100k 1M 10M 100M
• NG)
• NG)
C
. Once the RC network is in-
10 /330pF
COMPENSATED
UNCOMPENSATED
10 /330pF
COMPENSATED
C
, the zero-pole ratio
6360 F08
1G
FILT
180
90
45
0
–45
–90
–135
–180
value of
(7)
(6)
3. Select R
The layout of the filter RC network is critical to the stability
of the part and care should be taken to minimize parasitic
inductance in this path.
Table 1 lists suggested RC filter values for some common
circuit gains. Note that longer filter time constants can be
implemented by increasing the C
shown in Table 1 without degrading stability. For large C
values, it may be necessary to use multiple high quality
surface mount capacitors to reduce ESR and maintain a
high self resonant frequency.
Table 1. Component Values for Various Circuit Gains
DNI – Do Not Install
Interfacing the LTC6360 to A/D Converters
When driving an ADC, a single-pole RC filter between
the output of the LTC6360 and the input of the ADC can
improve system performance. The sampling process
of ADCs creates a charge transient at the ADC input
This sets a lower limit on CL of:
Note that for large zero-pole ratios, additional margin
may be needed. In this case, setting f
a phase margin of at best 45°. In practice, the ampli-
fier’s higher order poles will further reduce the phase
margin below 45°. Therefore, f
than f
margin in the case of large pole-zero ratios case can
be estimated as tan
Likewise for small zero-pole ratios, the pole will not
have contributed a full 90° of lagging phase prior to the
zero contributing leading phase. The requirement for
f
while meeting the two constraints listed above.
Noise Gain (NG)
Z
being lower than f
C
FILT
C
20
10
1
2
5
in order to ensure adequate phase margin. Phase
FILT
> (f
Z
and C
/ f
P
FILT
• NG)/(2πR
R
2k
2k
2k
2k
–1
0
F
C
to yield the desired filter bandwidth
(f
can be relaxed in these cases.
C
/f
0.2pF
Z
DNI
2pF
DNI
DNI
C
).
FILT
F
FILT
Z
f
should be made lower
C(AMP)
value beyond what is
500
222
DNI
181
R
2k
G
Z
LTC6360
equal to f
)
R
DNI
DNI
DNI
25
10
FILT
15
C
330pF
150pF
C
yields
DNI
DNI
DNI
FILT
FILT
6360f
(8)