MAX2308EGI Maxim Integrated Products, MAX2308EGI Datasheet - Page 9

• Manufacturer Part Number: MAX2308EGI
• Description: Modulator / Demodulator CDMA IF VGAs and I-Q Demodulators with V
• Manufacturer: Maxim Integrated Products

Specifications of MAX2308EGI

• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Figure 1. MAX2306 Typical Operating Circuit
The LO signal for downconversion is provided by a
voltage-controlled oscillator (VCO) consisting of an on-
chip differential oscillator, and an off-chip high-Q reso-
nant network. Figure 4 shows a simplified schematic of
the VCO oscillator. Multiband operation is supported by
the MAX2306 with dual VCOs. VCO_H and VCO_L are
selectable with the MODE pin or the VCO_SEL (VS)
control bit. They oscillate at twice the desired LO fre-
quency. For applications requiring an external LO, the
VCOs can be bypassed with the VCO_BYP (VB) control
bit.
Buffers, and Quadrature Generation
Voltage-Controlled Oscillator,
_______________________________________________________________________________________
0.068µF
2.4kΩ
10kΩ
10kΩ
10kΩ
10kΩ
I
CDMA IF VGAs and I/Q Demodulators
V
CC
33pF
33pF
33pF
33pF
0.01µF
2pF
2pF
47pF
0.01µF
47pF
33nH
33nH
10kΩ
with VCO and Synthesizer
BYP
CP_OUT
GND
TANKL+
TANKL-
TANKH+
MODE
V
GND
REF
SHDN
IOUT+
IOUT-
TANKH-
CC
MAX2306
The MAX2309 buffers the output of the VCO and pro-
vides this signal at the LOOUT pin. This signal is
enabled by the BUFEN (BE) control bit or by the
BUFEN control pin. The frequency of this signal is
selected by the BUF_DIV (BD) control bit, and can be
either the VCO frequency or half the VCO frequency.
Quadrature downconversion is realized by providing in-
phase (I) and quadrature-phase (Q) components of the
LO signal to the LO ports of the demodulator described
above. The quadrature LO signals are generated by
dividing the VCO output frequency using two latches.
CDMA+
CDMA-
QOUT+
QOUT-
LOCK
DATA
FM+
VGC
BYP
BYP
FM-
CLK
V
EN
CC
V
CC
0.01µF
0.01µF
0.1µF
680Ω
10kΩ
47kΩ
3-WIRE
47pF
V
CC
V
FM
CDMA
CC
DAC
Q
9