MAX2832 datasheet(23/33 Pages) MAXIM

23 / 33 page

2.4GHz to 2.5GHz 802.11g/b RF Transceiver, PA,

and Rx/Tx/Antenna Diversity Switch

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Transmitter

The transmitter integrates baseband lowpass filters,

direct-upconversion mixers, a VGA, a PA driver, and a lin-

ear RF PA with a power detector. A logic-high on the

RXTX input (pin 48) and a logic-high on the SHDN input

(pin 12) enable the transmitter. The PA outputs are routed

to ANT2, regardless of the state at ANTSEL.

Transmitter I/Q Baseband Inputs

The differential analog inputs of the transmitter baseband

amplifier I/Q inputs (TXBBI+, TXBBI-, TXBBQ+, TXBBQ-)

have a differential impedance of 20k

Ω || 1pF. The inputs

require an input common-mode voltage of 0.9V to 1.3V,

which is provided by the DC-coupled I and Q DAC out-

puts of the accompanying baseband IC.

Transmitter Baseband Lowpass Filtering

The transmitter integrates lowpass filters that can be

tuned to -3dB corner frequencies of 8MHz (11b),

11MHz (11g), 16.5MHz (turbo 1 mode), and 22.5MHz

(turbo 2 mode) through programming bits D1:D0 in

(A3:A0 = 0111). The -3dB corner frequency is tightly

controlled on-chip and does not require user adjust-

ment. Additionally, provisions are made to fine tune the

-3dB corner frequency through bits D5:D3 in the Filter

Programming register (A3:A0 = 0111). See Tables 9

and 10.

Transmitter Variable-Gain Amplifier

The variable-gain amplifier of the transmitter provides

31dB of gain control range programmable in 0.5dB

steps over the top 8dB of the gain control range and in

1dB steps below that. The transmitter gain can be pro-

grammed serially through the SPI interface by setting

bits D5:D0 in Register 12 (A3:A0 = 1100) or in parallel

through the digital logic gain-control pins B6:B1 (pins

3, 6, 8, 11, 14, 23, and 34, respectively). Set bit D10 =

0 in Register 9 (A3:A0 = 1001) to enable parallel pro-

gramming, and set bit D10 = 1 to enable programming

through the 3-wire serial interface. See Table 11 for the

transmitter VGA gain-control settings.

Table 11. Transmitter VGA Gain-Control

Settings

NO.

D5:D0 OR

B6:B1

OUTPUT SIGNAL POWER

111111

Max

111110

Max - 0.5dB

111101

Max - 1.0dB

110001

Max - 7dB

110000

Max - 7.5dB

101111

Max - 8dB

101110

Max - 8dB

101101

Max - 9dB

101100

Max - 9dB

000101

Max - 29dB

000100

Max - 29dB

000011

Max - 30dB

000010

Max - 30dB

000001

Max - 31dB

000000

Max - 31dB

Table 9. Transmitter LPF Coarse -3dB

Corner Frequency Settings in Register

(A3:A0 = 1000)

BITS (D1:D0)

-3dB CORNER

FREQUENCY (MHz)

MODE

11b

11g

16.5

Turbo 1

22.5

Turbo 2

Table 10. Transmitter LPF Fine -3dB

Corner Frequency Adjustment in

BITS (D5:D3)

% ADJUSTMENT RELATIVE TO

COARSE SETTING

000

001

010

100

011

105

100

110 (11g)

101

115

101–111

Not used

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