ADL5902-EVALZ AD [Analog Devices], ADL5902-EVALZ Datasheet - Page 21

• Manufacturer Part Number: ADL5902-EVALZ
• Description: 50 MHz to 9 GHz 65 dB TruPwr Detector
• Manufacturer: AD [Analog Devices]

In Figure 47, C
ally determined to be the minimum capacitance that ensures
good rms compliance when the ADL5902 is driven by a 1 C
W-CDMA signal (TM1-64). This test was carried out by
starting out with a large capacitance value on the CLPF pin (for
example, 10 µF). The value of V
power level (for example, −10 dBm). The value of C
progressively reduced (this can be done with press-down
capacitors) until the value of V
original value (this indicates that the accuracy of the rms
computation is degrading and that C
Figure 48
between off and −10 dBm) with C
resistor is placed in series with the VOUT pin, and the
capacitance from this resistor to ground (C
varied up to 1 µF.
Figure 48. Residual Ripple, Rise and Fall Times Using an RC Low-Pass Filter
300
250
200
150
100
50
0
1
shows the resulting rise and fall times (signal is pulsed
LPF
is equal to 10 nF. This value was experiment-
at VOUT, P
10
C
INLO
IN
FILTER
INHI
NC
NC
NC
= 0 dBm at 2.14 GHz
OUT
OUT
14
15
16
13
RESIDUAL RIPPLE (V p-p)
10% TO 90% RISE TIME (µs)
90% TO 10% FALL TIME (µs)
(nF)
2
LPF
started to deviate from its
ADL5902
was noted for a fixed input
(NEGATIVE SLOPE)
BIAS AND POWER-
LINEAR-IN-dB VGA
LPF
equal to 10 nF. A 2 kΩ
DOWN CONTROL
100
TADJ/PWDN
is getting too small).
FILTER
1
Figure 47. Optimizing Setting Time and Residual Ripple
in Figure 47) is
VPOS
3
LPF
VREF
VREF
1k
2.3V
was then
11
1M
100k
10k
1k
100
10
1
POS
X
X
10
Rev. 0 | Page 21 of 28
2
2
VTGT
12
I
I
DET
TGT
TEMPERATURE
SENSOR
9
COMM
G = 5
26pF
For large values of C
compared to Figure 46. This comes at the expense of a moderate
increase in rise time.
As C
the fall time is now dominated by the 10 nF C
present throughout the measurement.
Table 6 shows recommended minimum values of C
popular modulation schemes, using just a single filter capacitor
at the CLPF pin. Using lower capacitor values results in rms
measurement errors. Output response time (10% to 90%) is also
shown. If the output noise shown in Table 6 is unacceptably
high, it can be reduced by
•
•
•
4
FILTER
Increasing C
Adding an RC filter at VOUT, as shown in Figure 47
Implementing an averaging algorithm after the ADL5902’s
output voltage has been digitized by an ADC
COMM
8
7
6
5
is reduced, the fall time flattens out. This is because
VSET
VOUT
TEMP
CLPF
R
FILTER
C9
10nF
(SEE TABLE 6 AND
FIGURE 46.)
2kΩ
LPF
FILTER
C
(SEE FIGURE 48.)
FILTER
, the fall time is dramatically reduced
VOUT
LPF
which is
ADL5902
LPF
for