11-244
RF2948B
Rev A6 040930
Pin
Function
Description
Interface Schematic
13
PA IN
Input to the power amplifier stage. This is a 50
Ω input. Requires DC-
blocking/tuning cap.
See pin 12.
14
VCC5
Supply for the RF LO buffer, RF upconverter and amplifier.
15
RF LO
Single-ended LO input for the transmit upconverter. External matching
to 50
Ω and a DC-block are required.
See pin 14.
16
RF OUT
Upconverted Transmit signal. This 50
Ω output is intended to drive an
RF filter to suppress the undesired sideband, harmonics, and other out-
of-band mixer products.
See pin 14.
17
IF1 OUT-
The inverting open collector output of the quadrature modulator. This
pin needs to be externally biased and DC isolated from other parts of
the circuit. This output can drive a Balun with IF1 OUT+, to convert to
unbalanced to drive a SAW filter. The Balun can be either broadband
(transformer) or narrowband (discrete LC matching). Alternatively, just
IF1 OUT+ can be used to drive a SAW single-ended with an RF choke
(high Z at IF) from VCC to IF1 OUT-.
18
IF1 OUT+
The non-inverting open collector output of the quadrature modulator.
This pin needs to be externally biased and DC isolated from other parts
of the circuit. This output can drive a Balun with IF1 OUT-, to convert to
unbalanced to drive a SAW filter. The Balun can be either broadband
(transformer) or narrowband (discrete LC matching). Alternatively, just
IF1 OUT+ can be used to drive a SAW single-ended with an RF choke
(high Z at IF) from VCC to IF1 OUT+.
See pin 17.
19
TXI BP
This is the in-phase modulator bypass pin. A 10nF capacitor to ground
is recommended.
20
TXI DATA
I input to the baseband 5 pole Bessel LPF for the transmit modulator.
21
TXQ BP
This is the quadrature phase modulator bypass pin. A 10nF capacitor
to ground is recommended.
22
TXQ DATA
Q input to the baseband 5 pole Bessel LPF for the transmit modulator.
23
VCC4
Power supply for quadrature modulator.
24
I OUT
Baseband analog signal output for in-phase channel.
700mVP-P linear output.
25
Q OUT
Baseband analog signal output for quadrature channel.
700mVP-P linear output.
26
VREF1 BUF Buffered version of the VREF1 output. See pin 31.
Sink/Source current <1mA.
27
DCFB I
DC feedback capacitor for in-phase channel. Requires capacitor to
ground. (22nF recommended)
28
DCFB Q
DC feedback capacitor for quadrature channel. Requires decoupling
capacitor to ground. (22nF recommended)
29
BW CTRL
This pin requires a resistor to ground to set the baseband LPF band-
width of the receiver and transmit GmC filter amps.
30
VCC2
Supply for the I and Q baseband and GmC filters. This pin should be
bypassed with a 10nF capacitor.
C
BLOCK
22 pF
To TX RF
Image Filter
12 mA
From
TX VGA
V
CC
C
BYP
22 nF
V
CC
C
BYP
22 nF
RF LO
From
RF VCO
VB
VCC5
RF OUT
IF1 OUT+
IF1 OUT-
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