315MHz/433MHz Low-Noise

Amplifier for Automotive RKE

6

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RF Input Coupling Capacitor

Input IP3 vs. Enable Time

The value of the coupling capacitor affects input IP3

and turn-on time. A larger coupling capacitor results in

higher input IP3 at the expense of longer turn-on time.

See Table 3 for the typical amount of trade-off.

Integrated Output Matching

Network and DC-Block

The MAX2634 integrates the output matching network

and DC-block, eliminating the need for external match-

ing components while providing a broadband match.

See the

Functional Diagram/Typical Operating Circuit

for component values.

Shutdown

The MAX2634 features a shutdown pin to disable the

entire chip. Apply a logic-high to the SHDN pin to place

the part in the active mode, and a logic-low to place the

part in the shutdown mode.

Power-Supply Bypassing

gain/linearity performance. See the

Functional

Diagram/Typical Operating Circuit for bypassing

capacitor values.

Layout Information

A properly designed PCB is essential to any RF/

microwave circuit. Use controlled-impedance lines on

all high-frequency inputs and outputs. Bypass with

decoupling capacitors located close to the device’s

additional decoupling capacitors. These additional

capacitors can be located farther away from the device

package. Proper grounding of the GND pins is essen-

tial. If the PCB uses a topside RF ground, connect it

directly to all GND pins. For a board where the ground

plane is not on the component layer, the best technique

is to connect the GND pins to the board with a plated

through-hole located close to the package.

FREQUENCY

(MHz)

FMIN

(dB)

|

|

ANGLE

Ω)

308

0.64

0.50

27.0

9.78

315

0.65

0.49

27.7

9.78

418

0.78

0.44

37.4

9.87

434

0.80

0.44

38.9

9.88

INPUT DC-BLOCKING

CAPACITOR,

C1 (nF)

ENABLE

TIME

(µs)

INPUT IP3 AT

315MHz

(dBm)

1

6

-19

3.3

20

-14

22

130

-12

100

600

-11

1000

6000

-11

Table 2. MAX2634 Typical Noise

Parameters

Table 3. RF Input Coupling Capacitor

Input IP3 vs. Enable Time

Chip Information

PROCESS: SiGe BiCMOS