SA620 Ver la hoja de datos (PDF) - Philips Electronics
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SA620 Datasheet PDF : 11 Pages
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Philips Semiconductors RF Communications Products
Low voltage LNA, mixer and VCO — 1GHz
Product specification
SA620
LNA ENABLE
C23
C22
LNA IN
C1
100pF
1µF
4.7nH
535 mils
C2
1.8pF
0.44µF/(VCC–1)
L1
56nH
R6
R = 9k x (VCC – 1)
VCC
C21
C20
0.1µF
w = 15 mils
100pF
L = 260 mils
C3
0.1µF
C4
10µF
C5
3.9pF
L2
2.7nH
1 LNA ENABLE
2 LNA GND
3 LNA IN
4 LNA GND
5 LNA GND
6 OSC GND
7 MIXER PD
8 OSC PD
9 OSC1
10 OSC2
SA620
Vcc 20
LNA GND 19
LNA OUT 18
LNA BIAS 17
MIXER IN 16
MIXER GND 15
MIXER BYPASS 14
MIXER OUT 13
OSC GND 12
VCO OUT 11
VCC
GND
C6
100pF
L3
2.7nH
D1
C7
3.3pF
V_CONTROL
(0 to VCC)
SMV 1204 - 099
Alpha Industries
R1
R2
10kΩ
10kΩ
C8
0.1µF
VCO OUT
(50Ω)
C9
100pF
4.7nH
535 mils
C10
100pF
R3
22Ω
VCC
4.7nH
C19
535 mils
LNA OUT
100pF
w = 15 mils
L = 260 mils
C18
2.2pF
C17 MIXER IN
C16
5.6pF
100pF
w = 15 mils
L = 160 mils
4.7nH
535 mils
C13
12pF
C14
1-5pF
L4
150nH
VCC
C15
0.1µF
MIXER OUT
(1kΩ, 83MHz)
C11
1000pF
R4
1kΩ
C12
10pF
MIXER OUT
(50Ω, 83MHz)
R5
51Ω
Figure 1. A Complete LNA, Mixer and VCO
CIRCUIT TECHNOLOGY
LNA
Impedance Match: Intrinsic return loss at the
input and output ports is 7dB and 9dB,
respectively. With no external matching, the
associated LNA gain is ≈10dB and the noise
figure is ≈1.4dB. However, the return loss
can be improved at 900MHz using suggested
L/C elements (Figure NO TAG) as the LNA is
unconditionally stable.
Noise Match: The LNA achieves 1.6dB
noise figure at 900MHz when S11 = -10dB.
Further improvements in S11 will slightly
increase the NF and S21.
Thru-Mode: A series switch can be activated
to feed RF signals from LNA input to output
with an attenuator (S21 = –7.5dB). As a
result, the power handling is greatly improved
and current consumption is decreased by
3.2mA as well. However, if this mode is not
required, C23 and R6 can be deleted.
Temperature Compensation: The LNA has
a built-in temperature compensation scheme
to reduce the gain drift to 0.003dB/°C from
–40°C to +85°C.
Supply Voltage Compensation: Unique
circuitry provides gain stabilization over wide
supply voltage range. The gain changes no
more than 0.5dB when VCC increases from
3V to 5V.
Mixer
Input Match: The mixer is configured for
maximum gain and best noise figure. The
user needs to supply L/C elements to
achieve this performance.
Mixer Bypass: To optimize the IP3 of the
mixer input, one must adjust the value of C14
for the given board layout. The value
typically lies between 1 and 5pF. Once a
value if selected, a fixed capacitor can be
used. Further improvements in mixer IP3 can
be achieved by inserting a resistive loss at
the mixer input, at the expense of system
gain and noise figure.
Tracking Bandpass Filter: At the LO input
port of the mixer there is a second-order
bandpass filter (approx. 50MHz bandwidth)
which will track the VCO center frequency.
The result is the elimination of low frequency
noise injected into the mixer LO port without
the need for an external LO filter.
Power Down: The mixer can be disabled by
connecting Pin 7 to ground. If a Schottky
diode is connected between Pin 1 (cathode)
and Pin 7 (anode), the LNA disable signal will
control both LNA and mixer simultaneously
When the mixer is disabled, 3mA is saved.
Test Port: Resistor R5 can be substituted
with an external test port of 50Ω input
impedance. Since R5 and MIXER OUT have
the same output power, the result is a direct
power gain measurement.
VCO
Automatic Leveling Loop: An on-chip
detector and loop amplifier will adjust VCO
bias current to regulate the VCO amplitude
regardless of the Q-factor (>10) of the
resonator and varactor diode. However, the
real current reduction will not occur until the
VCO frequency falls below 500MHz. For a
typical resonator the steady-state current is
3mA at 800MHz.
Buffered VCO Output: The VCO OUT (Pin
11) signal can drive an external prescaler
directly (see also the Philips SA7025 low
voltage, fractional-N synthesizer). The
extracted signal levels need to be limited to
–16dBm or less to maintain mixer IIP3.
Phase Noise: If close-in phase noise is not
critical, or if an external synthesizer is used,
C4 (Pin 8) can be decreased to a lower
value.
Power-Down: The VCO can be disabled by
connecting Pin 8 to ground. If a Schottky
diode is connected between Pin 1 (cathode)
and Pin 8 (anode), the LNA disable signal will
control both LNA and VCO simultaneously.
When the VCO is disabled, 3mA is saved.
December 15, 1993
5
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