RF2713
Pin
1
Function Description (Modulator Configuration)
Interface Schematic
When the RF2713 is configured as a Quadrature Modulator, each
mixer is driven by an independent baseband modulation channel (I and
Q). The mixers can be driven single-endedly (as shown in the modula-
tor application circuit) or differentially. When driving single-endedly, the
B Inputs (pins 2 and 4) should be connected to each other. This
ensures that the baseband signals will reach each mixer with the same
DC reference, yielding the best carrier suppression. Note that the input
impedance changes according to the drive mode (see the mixer equiv-
alent circuit on the previous page). The single-ended input impedance
(as shown in the modulator application circuit) is 1200Ω for each of the
two inputs. In the balanced configuration, the input impedance would
be 2400Ω for each of the two inputs.
I INPUT A
VCC
VCC
1260
Ω
1260
Ω
INPUT A
INPUT B
The mixers are Gilbert Cell designs with balanced inputs. The equiva-
lent schematic for one of the mixers is shown on the previous page.
The input impedance of each pin is determined by the 1200Ω resistor
to V in parallel with a transistor base. Note from the schematic that
CC
all four input pins have an internally set DC bias. For this reason, all
four inputs (pins 1 through 4) should be DC blocked. The capacitance
values of the blocking capacitors is determined by the baseband fre-
quency. When driving single-endedly, both the series (pins 1 and 3) and
shunt (pins 2 and 4) blocking capacitors should be low impedances, rel-
ative to the input impedance.
DC bias voltages may be supplied to the inputs pins, if required, in
order to increase the amount of carrier suppression. For example, the
DC levels on the reference inputs (pins 2 and 4) may be offset from
each other by adding different resistor values to ground. These resis-
tors should be larger than 2kΩ. Note from the mixer schematic that all
four input pins have an internally set DC bias. If DC bias is to be sup-
plied, the allowable ranges are limited. For 5V applications, the DC ref-
erence on both I pins or both Q pins must not go below 2.7V , and in
DC
no case should the DC voltage on any of the four pins go below 2.0V
DC
or above 5.5V . IF a DC reference is to be supplied, the source must
DC
also be capable of sinking current. If optimizing carrier suppression fur-
ther is not a concern, it is recommended that all four inputs (pins 1
through 4) be DC blocked.
Same as pin 1, except complementary input.
Same as pin 1, except Q Buffer Amplifier.
Same as pin 3, except complementary input.
See pin 1.
See pin 1.
See pin 1.
2
3
4
5
I INPUT B
Q INPUT A
Q INPUT B
BG OUT
Band Gap voltage reference output. This voltage output is held con-
stant over variations in supply voltage and operating temperature and
may be used as a reference for other external circuitry. This pin should
not be loaded such that the sourced current exceeds 1mA. This pin
should be bypassed with a large (0.1μF) capacitor.
Connecting pins 6 and 7 to each other accomplishes the summing
function of the upconverted I and Q channels. In addition, because
6
I IF OUT
IF OUT
these outputs are open collector type, they must be connected to V
CC
in order to properly bias the Gilbert Cell mixers. Maximum gain and out-
put power occur when the load on these two pins is ~1200Ω. In most
applications the impedance of the next stage will be lower and a reac-
tive impedance transforming match should be used if maximum gain
and output level are of concern. For applications where the gain is not
as critical, a 1200Ω resistor may be added in parallel with a choke
inductor. If neither gain nor output level is critical, the inductor may be
replaced with a resistor that sets the desired source impedance to drive
the next stage. If the next stage is an "open" at DC, the blocking capac-
itor may be eliminated.
7-52
Rev A5 061016
RFMD [ RF MICRO DEVICES ]
