MAX2121
Complete Direct-Conversion L-Band Tuner
9
PIN NAME FUNCTION
8 BYPVCO
Internal VCO Bias Bypass. Bypass to GND with a 100nF capacitor connected as close as possible to
the pin. Do not share capacitor ground vias with other ground connections.
9 TUNEVCO
High-Impedance VCO Tune Input. Connect the PLL loop filter output directly to this pin with as short of
a connection as possible.
10 GNDTUNE Ground for TUNEVCO. Connect to the PCB ground plane.
11 GNDSYN Ground for Synthesizer. Connect to the PCB ground plane.
12 CPOUT
Charge-Pump Output. Connect this output to the PLL loop filter input with the shortest
connection possible.
13 V
CC_SYN
DC Power Supply for Synthesizer Circuits. Connect to a +3.3V low-noise supply. Bypass to GND with
a 1nF capacitor connected as close as possible to the pin. Do not share capacitor ground vias with
other ground connections.
14 XTAL
Crystal-Oscillator Interface. Use with an external parallel-resonance-mode crystal through a series
1nF capacitor. See the Typical Application Circuit.
15 REFOUT Crystal-Oscillator Buffer Output. A DC-blocking capacitor must be used when driving external circuitry.
16 V
CC_DIG
DC Power Supply for Digital Logic Circuits. Connect to a +3.3V low-noise supply. Bypass to GND with
a 1nF capacitor connected as close as possible to the pin. Do not share capacitor ground vias with
other ground connections.
17 QOUT+
18 QOUT-
Quadrature Baseband Differential Output. AC-couple with 47nF capacitors to the demodulator input.
19 IOUT+
20 IOUT-
In-Phase Baseband Differential Output. AC-couple with 47nF capacitors to the demodulator input.
21 IDC+
22 IDC-
I-Channel Baseband DC Offset Correction. Connect a 47nF ceramic chip capacitor from IDC- to IDC+.
23 QDC+
24 QDC-
Q-Channel Baseband DC Offset Correction. Connect a 47nF ceramic chip capacitor from QDC- to QDC+.
25 V
CC_BB
DC Power Supply for Baseband Circuits. Connect to a +3.3V low-noise supply. Bypass to GND with
a 1nF capacitor connected as close as possible to the pin. Do not share capacitor ground vias with
other ground connections.
26 SDA 2-Wire Serial-Data Interface. Requires 1k pullup resistor to V
CC
.
27 SCL 2-Wire Serial-Clock Interface. Requires 1k pullup resistor to V
CC
.
28 ADDR Address. Must be connected to either ground (logic 0) or supply (logic 1).
— EP Exposed Pad. Solder evenly to the board’s ground plane for proper operation.
Pin Description (continued)
