RF2948B Ver la hoja de datos (PDF) - RF Micro Devices

Número de pieza

componentes Descripción

Fabricante

RF2948B

2.4GHz SPREAD-SPECTRUM TRANSCEIVER

RF Micro Devices 

RF2948B

Pin

1

Function

PD

Description

This pin is used to power up or down the transmit and receive base-

band sections. A logic high powers up the quad demod mixers, TX and

RX GmC LPF’s, baseband VGA amps, data amps, and IF LO buffer

amp/ phase splitter. A logic low powers down the entire IC for sleep

mode. Also, see State Decode Table.

Interface Schematic

VCC

Pins

3, 4, 5

10 kΩ

ESD

To

Logic

2

RX EN

Enable pin for the receiver 15dB gain IF amp and the RX VGA amp. See pin 1.

Powers up all receiver functions when PD is high, turns off the receiver

IF circuits when low. Also, see State Decode Table.

When this pin is a logic “high”, the device is in receive mode. When this

3

4

5

6

7

RX IF BIAS

VCC1

RX IF IN

TX IF IN

VCC9

pin is a logic “low”, the device is in transmit mode.

Shunt resistor of 23.7±1% to ground. Biases IF AMPS.

Power supply for RX VGA amplifier, IC logic and RX references.

S IF input for receiver section. Must have DC-blocking cap. The capacitor

value should be appropriate for the IF frequency. For half-duplex opera-

N tion, connect RX IF IN and TX IF IN signals together after the DC block-

ing caps, then run a transmission line from the output of the IF SAW.

AC coupling capacitor must be less than 150pF to prevent delay in

G switching RX to TX/TX to RX.

I Input for the TX IF signal after SAW filter. External DC-blocking cap

required. For half-duplex operation, connect RX IF IN and TX IF IN sig-

S nals together after the DC-blocking caps, then run a transmission line

from the output of the IF SAW. AC coupling capacitor must be less than

E 150pF to prevent delay in switching RX to TX/TX to RX.

See pin 6.

IF

SAW

Filter

D Power supply for the TX 15dB gain amp and TX VGA.

50 Ω µstrip

DC

Block Pin 7

Pin 8

8

TX VGC

9

IF LO

10

VCC8

11

VCC6

12

PA OUT

NOT

Gain control setting for the transmit VGA. Positive slope.

IF LO input. Must have DC-blocking cap. The capacitor value should be

appropriate for the IF frequency. LO frequency=2xIF. Quad

W mod/demod phase accuracy requires low harmonic content from IF LO,

so it is recommended to use an n=3 LPF between the IF VCO and IF

E LO. This is a high impedance input and the recommended matching

approach is to simply add a 100Ω shunt resistor at this input to con-

N strain the mismatch.

Power supply for IF LO buffer and quadrature phase network.

R Power supply for transmitter bias generator.

This is the output transistor of the power amp stage. It is an open col-

Olector output. The output match is formed by an inductor to VCC, which

Fsupplies DC and a series cap.

Recommended Matching

Network for IF LO

IF VCO

C2

150 pF

100 Ω

IF LO

Pin 9

VCC

CBYP

L

22 nF

C

Power

Amp

Output

PA OUT

From

TX RF

Image Filter

PA IN

14 mA

Bias

Rev A6 040930

11-243

Share Link: