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RF137

Transceiver For GSM Applications

Conexant Systems 

Transceiver

RF137

Table 3. RF137 Electrical Specifications (4 of 4)

(TA = 25 °C, Vcc = 3.0 V, except where specified)

Parameter

Symbol

Test Condition

Min Typical Max

Transceiver

Enable and control VIH

VIH

Enable and control VIL

VIL

Enable and control IIH

IIH

Vcc–0.4

0.4

20

60

Enable and control IIL

Total supply current:

Rx mode

Tx mode

Synthesizer mode

Sleep mode @Vcc = 3.0V

Power supply range

Operating temperature range

IIL

–10

–1

0

ICC

RXENA = SXENA = high

48

TXENA = SXENA = high

60

SXENA = high

27

RXENA = SXENA =

TXENA = low

0.04

0.2

VCC (Note 5)

VCCB

2.7

3.75

3.94

2.7

3.75

3.94

TA

–30

+25

+85

Note 1: For 1Vp-p, 100 kHz differential signals across Iin and Qin.

Note 2: For 1 MHz loop bandwidth and external VCO with phase noise of –165 dBc/Hz @ 20 MHz offset from a carrier frequency of 900 MHz.

Note 3: “NX spurs” denotes the order of the fLO harmonic that can mix with a harmonic of fIF and result in a product at zero frequency.

Note 4: Using varactors with similar characteristics as Loral part KV1925.

Note 5: V CC must not be less than VCCB – 0.4 V if separate supply voltages are used for V CC and VCCB.

Units

V

V

µA

µA

mA

mA

mA

mA

V

V

°C

The buffer amplifier following the image reject mixer has an

output impedance of 330 Ω for direct connection to the external

ceramic filter.

The second IF amplifier converts the single-ended output from

the ceramic filter to a differential signal which may be input to a

bandpass sigma-delta A/D converter. The input impedance of

the amplifier is a nominal 330 Ω, which matches the external

ceramic filter. The nominal gain of the amplifier is 18 dB, but is

reduced to 6 dB when bit S8 = 0 (Rx Gain Sel2) and CO = 1.

Transmit Section. The transmit section consists of the following

functional blocks:

• A baseband to IF quadrature modulator with an output

amplifier.

• A translation loop circuit consisting of a phase and

frequency detector, a charge pump, a TxRF input buffer, an

LO input buffer, a mixer, and a low pass filter.

The I/Q-to-IF modulator takes in differential I and Q baseband

signals. The baseband signals are initially low pass filtered and

then input to a pair of double balanced mixers. Pins 13 and 14

(TXMO+ and TXMO–, respectively), the modulator output, and

Pins 6 and 7 (TXIF+ and TXIF–, respectively), the IF input, allow

for any additional filtering required before the signals enter the

translation loop.

The translation loop circuit of the RF137, together with a VCO

and an external loop filter, forms a Phase-Locked Loop (PLL).

The inherent bandpass filtering that occurs in the PLL eliminates

the need for a duplexer or a Surface Acoustic Wave (SAW) filter

that is usually required to suppress transmission noise. The

overall efficiency is increased as a result of the elimination of

high loss, post-PA bandpass filters. This results in increased

handset talk time.

The VCO output of the translation loop is at the transmit RF

frequency. A portion of the VCO output must be fed back to Pin

47 (TXRFIN+) of the device and mixed with a buffered LO signal

to create an IF signal. The IF output from the mixer is input to

the phase and frequency detector where the IF output from the

mixer is compared with the modulated IF input to the device.

When CO = 1, the S6 bit on the three-wire bus allows for a high

side/low side injection setting.

Synthesizer Section (Sx). The synthesizer section consists of

the following functional blocks:

• Frequency synthesizers

• On-chip oscillator with external resonant circuit

• Three-wire bus control circuit

100777C

Conexant - Proprietary

Data Subject to Change

7

October 11, 2000

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