ISDB-T Single-Segment Low-IF Tuners

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21

Layout Considerations

The EV kit serves as a guide for PC board layout. Keep

RF signal lines as short as possible to minimize losses

and radiation. Use controlled impedance on all high-

frequency traces. For proper operation of the TQFN

package, the exposed paddle must be soldered evenly

to the board’s ground plane. Use abundant vias

beneath the exposed paddle for maximum heat dissi-

pation. Use abundant ground vias between RF traces

to ground with a 100pF capacitor placed as close to

the pin as possible.

In addition, the ground returns for the VCO, VTUNE,

and charge pump require special layout consideration.

The VCOBYP capacitor (C37) and the VCCVCO bypass

capacitor (C19) ground returns must be routed back to

the GNDVCO pin and then connected to the overall

ground plane at that point (GNDVCO). All loop filter

component grounds (C27–C30) and the VCCCP

bypass capacitor (C17) ground must all be routed

together back to the GNDCP pin. GNDTUNE must also

be routed back to the GNDCP pin along with all other

grounds from the PLL loop filter. The GNDCP pin must

then be connected to the overall ground plane. Figure

4 shows a schematic drawing of the required layout

connections. Refer to the MAX2160 evaluation kit for a

recommended board layout.

Table 16. Typical Supply Current Fluctuations for Nondefault Register Settings

MODE

BIT CHANGE

TYPICAL

NOMINAL

Default register settings

46.5mA

—

QOFF = 1 (Q channel off)

—

-3.3mA

BBL[1:0] = 00 (lower linearity)

—

-2mA

BBL[1:0] = 01 (nominal linearity)

—

-1mA

BBL[1:0] = 11 (high linearity)

—

+1mA

MOD = 1 (7dB baseband gain step enabled)

—

+0.3mA

EPD = 1 (power detector enabled)

—

+1mA

EPB = 0 (charge-pump prebias disabled)

—

+5.1mA

Receive

XD[4:0] = 00000 (XTALOUT buffer disabled)

—

-40µA

Shutdown

SHDN = GND

1µA

—

Standby

STBY = 1

2.2mA

—

Power-Down

PWDN = 1

13.5µA

—

34

33

32

38

37

36

35

40

39

C17

C28

C27

C29

C30

R20

R21

R22

C19

C37

ROUTE GNDTUNE, C17, AND ALL

LOOP FILTER COMPONENT GROUNDS TO

GNDCP.

CONNECT GNDCP TO THE BOARD'S

GROUND PLANE.

ROUTE C19 AND C37 TO GNDVCO.

CONNECT GNDVCO TO THE BOARD'S

GROUND PLANE.

Figure 4. Ground Return Layout Connections for the VCO, Charge Pump, and VTUNE