LT5558 데이터 시트보기 (PDF) - Linear Technology
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LT5558 Datasheet PDF : 16 Pages
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LT5558
PIN FUNCTIONS
LO (Pin 3): LO Input. The LO input is an AC-coupled single-
ended input with approximately 50Ω input impedance at
RF frequencies. Externally applied DC voltage should be
within the range –0.5V to (VCC + 0.5V) in order to avoid
turning on ESD protection diodes.
BBPQ, BBMQ (Pins 7, 5): Baseband Inputs for the
Q-channel. The differential input impedance is 3kΩ. These
pins are internally biased at about 2.1V. Applied common
mode voltage must stay below 2.5V.
VCC (Pins 8, 13): Power Supply. Pins 8 and 13 are con-
nected to each other internally. It is recommended to use
0.1μF capacitors for decoupling to ground on each of
these pins.
RF (Pin 11): RF Output. The RF output is an AC-coupled
single-ended output with approximately 50Ω output im-
pedance at RF frequencies. Externally applied DC voltage
should be within the range –0.5V to (VCC + 0.5V) in order
to avoid turning on ESD protection diodes.
BBPI, BBMI (Pins 14, 16): Baseband Inputs for the
I-channel. The differential input impedance is 3kΩ. These
pins are internally biased at about 2.1V. Applied common
mode voltage must stay below 2.5V.
BLOCK DIAGRAM
VCC
BBPI 14
V-I
BBMI 16
8
13
LT5558
0°
90°
BBPQ 7
V-I
BBMQ 5
2469
GND
BALUN
11 RF
1 EN
3 10 12 15 17
LO
GND
5558 BD
APPLICATIONS INFORMATION
The LT5558 consists of I and Q input differential voltage-
to-current converters, I and Q up-conversion mixers, an
RF output signal combiner/balun, an LO quadrature phase
generator and LO buffers.
External I and Q baseband signals are applied to the dif-
ferential baseband input pins, BBPI, BBMI, and BBPQ,
BBMQ. These voltage signals are converted to currents and
translated to RF frequency by means of double-balanced
up-converting mixers. The mixer outputs are combined
in an RF output balun, which also transforms the output
impedance to 50Ω. The center frequency of the resulting
RF signal is equal to the LO signal frequency. The LO in-
put drives a phase shifter which splits the LO signal into
in-phase and quadrature LO signals. These LO signals
8
are then applied to on-chip buffers which drive the up-
conversion mixers. Both the LO input and RF output are
single-ended, 50Ω-matched and AC coupled.
Baseband Interface
The baseband inputs (BBPI, BBMI), (BBPQ, BBMQ) pres-
ent a differential input impedance of about 3kΩ. At each
of the four baseband inputs, a low-pass filter using 200Ω
and 1.8pF to ground is incorporated (see Figure 1), which
limits the baseband –1dB bandwidth to approximately
250MHz. The common-mode voltage is about 2.1V and
is slightly temperature dependent. At TA = -40°C, the
common-mode voltage is about 2.28V and at TA = 85°C
it is about 2.01V.
5558fa
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