max2511eeit Maxim Integrated Products, Inc., max2511eeit Datasheet - Page 10

• Manufacturer Part Number: max2511eeit
• Description: Max2511 Low-voltage If Transceiver With Limiter And Rssi
• Manufacturer: Maxim Integrated Products, Inc.

The following sections describe each of the blocks
shown in Figure 1.
The receiver consists of two basic blocks: the image-
reject downconverter mixer and the limiter/RSSI section.
The receiver inputs are the RXIN, RXIN pins, which
should be AC coupled and may require a matching net-
work, as shown in the Typical Operating Circuit. To
design a matching network for a particular application,
refer to the Applications Information section and the
receiver input impedance plots in the Typical Operating
Characteristics .
Low-Voltage IF Transceiver
with Limiter and RSSI
Figure 1. Functional Diagram
10
_______________Detailed Description
OSCOUT
______________________________________________________________________________________
TXOUT
TXOUT
TANK
TANK
RXIN
RXIN
RECEIVE IMAGE-REJECT MIXER
PA
VGA
LO PHASE
SHIFTER
0°
90°
TRANSMIT IMAGE-REJECT MIXER AND VGA/PA
90°
0°
Receiver
MIXOUT
VREF = V
GM
CC
IF BPF
/ 2
90°
0°
The downconverter is implemented using an image-
reject mixer consisting of an input buffer with dual out-
puts, each of which is fed to a double-balanced mixer.
The LO signal is generated by an on-chip oscillator and
an external tank circuit. The buffered oscillator signal
drives a quadrature phase generator that provides two
outputs with 90° of phase shift between them. This pair
of LO signals is fed to the two receive mixers. The
mixer’s outputs are then passed through a pair of
phase shifters, which provide 90° of phase shift across
their outputs. The resulting two signals are then
summed together. The final phase relationship is such
that the desired signal is reinforced, and the image sig-
nal is largely canceled. The downconverter mixer’s
LIMIN
VREF
CZ
CORRECTION
OFFSET
LIMITER
AND BIAS CONTROL
RSSI
VOLTAGE GAIN
MAX2511
CZ
GC
Image-Reject Mixer
BIAS
VGA
LIMOUT
LIMOUT
RSSI
RXEN
TXEN
TXIN
TXIN