LT5527 データシートの表示（PDF） - Linear Technology
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LT5527 Datasheet PDF : 20 Pages
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LTC5590
Applications Information
Table 4. Performance Comparison with VCCIF = 3.3V and 5V
(RF = 900MHz, High Side LO, IF = 190MHz)
VCCIF
R2A
ICCIF
GC
P1dB IIP3
NF
(V)
(Ω) (mA) (dB) (dBm) (dBm) (dB)
3.3 Open 191
8.7
10.7 26.0
9.7
1k
191
7.5
11.4 26.0 9.75
5
Open 200
8.7
14.1 25.5
9.8
The IFBA pin (Pin 20) is available for reducing the DC
current consumption of the IF amplifier, at the expense of
IIP3. The nominal DC voltage at Pin 20 is 2.1V, and this pin
should be left open-circuited for optimum performance.
The internal bias circuit produces a 4mA reference for the
IF amplifier, which causes the amplifier to draw approxi-
mately 100mA. If resistor R1A is connected to Pin 20 as
shown in Figure 7, a portion of the reference current can
be shunted to ground, resulting in reduced IF amplifier
current. For example, R1A = 1k will shunt away 1.5mA
from Pin 20 and the IF amplifier current will be reduced
by 38% to approximately 62mA. Table 5 summarizes RF
performance versus IF amplifier current.
Table 5. Mixer Performance with Reduced IF Amplifier Current
RF = 900MHz, High Side LO, IF = 190MHz, VCC = VCCIF = 3.3V
ICCIF
GC
IIP3
P1dB
NF
R1
(mA)
(dB)
(dBm)
(dB)
(dB)
Open
95.5
8.7
26.0
10.7
9.7
4.7kΩ
86.5
8.7
25.6
10.6
9.7
2.2kΩ
78.3
8.6
25.0
10.6
9.6
1kΩ
68.6
8.5
24.1
10.5
9.6
RF = 1400MHz, Low Side LO, IF = 190MHz, VCC = VCCIF = 3.3V
ICCIF
GC
IIP3
P1dB
NF
R1
(mA)
(dB)
(dBm) (dBm)
(dB)
Open
95.5
8.4
27.3
11
9.7
4.7kΩ
86.4
8.5
26.8
10.9
9.6
2.2kΩ
78.2
8.5
26.2
10.9
9.6
1kΩ
68.5
8.4
25.1
10.8
9.6
Low Current Mode
Both mixer channels can be set to low current mode us-
ing the ISEL pin. This allows flexibility to select a reduced
current mode of operation when lower RF performance is
acceptable, reducing power consumption by 36%. Figure
12 shows a simplified schematic of the ISEL pin interface.
When ISEL is set low (<0.3V), both channels operate at
nominal DC current. When ISEL is set high (>2.5V), the DC
current in both channels is reduced, thus reducing power
consumption. The performance in low power mode and
normal power mode are compared in Table 6.
VCCA
19
LTC5590
ISEL
18
500Ω
BIAS A
VCCB
BIAS B
5590 F13
Figure 12. ISEL Interface Schematic
Table 6. Performance Comparison Between Different Power Modes
RF = 900MHz, High Side LO, IF = 190MHz, VCC = VCCIF = 3.3V
ICCIF
GC
IIP3
P1dB
NF
ISEL
(mA)
(dB)
(dBm) (dBm)
(dB)
Low
376
8.7
26.0
10.7
9.7
High
239
7.7
21.5
10.4
9.9
Enable Interface
Figure 13 shows a simplified schematic of the ENA pin
interface (ENB is identical). To enable channel A, the ENA
voltage must be greater than 2.5V. If the enable function
is not required, the enable pin can be connected directly
to VCC. The voltage at the enable pin should never exceed
the power supply voltage (VCC) by more than 0.3V. If this
VCCA
19
ENA
17
LTC5590
500Ω
ESD
CLAMP
5590 F13
Figure 13. ISEL Interface Schematic
5590p
17
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