RF212

Image-Reject Front End

2

Conexant

100780D

May 24, 2000

Proprietary Information and Specifications are Subject to Change

1

2

3

4

5

6

7

8

9

10

20

19

18

17

16

15

14

13

12

11

NC

GND

GND

LNA900IN

GAINSEL

LNA1800IN

GND

ENA

VCC

GND

STEPSEL

C067

IFOUT+

IFOUT-

GND

BANDSEL1

LOIN

LOGND

NC

VCC

VCC

Figure 3. RF212 Dual-Band Device Pin Configuration

−−−− 20-Pin

ETSSOP

Technical Description

Both RF212 devices form front ends of a dual-band or a tri-band

super-heterodyne receiver. The RF212 dual-band device is

optimized for an EGSM900/DCS1800 design, while the RF212

tri-band device is suitable for EGSM900, DCS1800, and PCS

1900. Each frequency band has its own separate front-end

receiver path. Each receiver path contains an LNA, an image-

reject filter, and a mixer. The IF and LO ports are common to all

frequency bands. The image rejection achievable by this front-

end design without any additional external components is 35 dB

minimum for an IF of 400 MHz. Both devices operate over a

supply voltage range of 2.7 V to 3.6 V.

The RF212 dual-band device has one band selection pin

(BANDSEL1 on pin 14). When BANDSEL1 is set to logic “0,” the

EGSM900 receiver path is active. The LO frequency needs to

be higher than the RF input frequency (i.e., a high side injection

is used). When BANDSEL1 is set to logic “1,” the DCS1800

receiver path is active. The LO frequency needs to be less than

the RF input frequency (i.e., a low-side injection is used). With a

400 MHz IF, this arrangement allows a single, wide-range

Voltage Controlled Oscillator (VCO) to be used for each band of

operation.

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2

3

4

5

6

7

8

9

10

20

19

18

17

16

15

14

13

12

11

NC

GND

GND

LNA900IN

GAINSEL

LNA1800IN

LNA1900IN

ENA

VCC

GND

STEPSEL

C122

IFOUT+

IFOUT-

BANDSEL2

BANDSEL1

LOIN

LOGND

NC

VCC

VCC

Figure 4. RF212 Tri-Band Device Pin Configuration – 20-Pin

ETSSOP

Similarly, the RF212 tri-band device has two band selection pins

(BANDSEL1 and BANDSEL2, pins 14 and 15, respectively). The

EGSM900 path uses the high side injection for the LO, while

DCS1800 and PCS1900 paths use the low side injection. Tables

1 and 2 provide the frequency band selection settings for the

dual and tri-band devices, respectively.

All the LNAs have switchable gain. The gain mode is selectable

using the GAINSEL signal (pin 7). Low gain mode is selected by

driving the GAINSEL signal to a logic “1”; high gain mode is

selected by driving the signal to a logic “0.” Depending on the

need of the handset design on the gain distribution, the gain

step between the high gain and low gain modes can be set to

either a 12 dB step or a 20 dB step. This gain step is selectable

with the STEPSEL signal (pin 18).

Electrical and Mechanical Specifications ________________

The RF212 signal pin assignments and functional pin

descriptions are found in Table 3 (dual-band) and Table 4 (tri-

band). The absolute maximum ratings of the RF212 are

provided in Table 5, the operating conditions are specified in

Table 6, and electrical specifications are provided in Table 7.

Figure 3 shows the diagram for a typical application circuit using

the RF212 front end. Figure 4 provides the package dimensions

for both of the 20-pin ETSSOP devices.

ESD Sensitivity

The RF212 is a static-sensitive electronic device. Do not operate

or store near strong electrostatic fields. Take proper ESD

precautions.