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LG Electronics U250 service manual LO generation and distribution circuits, Off-chip RF Components

Models: U250

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3. TECHNICAL BRIEF

3.4 LO generation and distribution circuits

The integrated LO generation and distribution circuits are driven by internal VCOs to support various modes to yield highly flexible quadrature LO outputs that drive all GSM and UMTS band upconverters and downconverters; with the help of these LO generation and distribution circuits, zero-IF architecture is employed in all GSM and UMTS band receivers and transmitters to translate the signal directly from RF to baseband and from baseband to RF.

Two fully functional fractional-N synthesizers, including VCOs and loop filters, are integrated within the RTR6275 IC. The first synthesizer (PLL1) creates the transceiver LOs that support the UMTS 2100/1900/1800 transmitter, and all four GSM band receivers and transmitters including: GSM 850, GSM 900, GSM 1800, and GSM 1900. The second synthesizer (PLL2) provides the LO for the UMTS 2100/1900/1800 receiver. An external TCXO input signal is required to provide the synthesizer frequency reference to which the PLL is phase and frequency locked. The RTR6275 IC integrates most of PLL loop filter components on-chip except two off-chip loop filter series capacitors, and significantly reduces off-chip component requirement. With the integrated fractional-N PLL synthesizers, the RTR6275 has the advantages of more flexible loop bandwidth control, fast lock time, and low-integrated phase error

3.5 Off-chip RF Components

3.5.1 WCDMA PAM (U103: WS2512-TR1G)

The UMTS PA output power is monitored by l power detector circuits(U100 : RTR6275) . This detector voltage can be used for transmitter calibration and monitor to meet RF system

WCDMA

Rev.D

L404

1.8nH

4

FL104

1

 

 

 

PGND

RX

 

 

 

3

2

 

 

C162

ANT

TX

 

 

 

 

 

 

3.3p

 

ACMD-7602

 

 

 

 

 

 

 

 

0.5p

L125

50OHM OUT

51R119 41

+VPWR

 

 

 

 

 

C155

C158

 

 

 

 

 

4.7u

15p

 

 

 

 

L123

 

Rev_1.0

 

 

 

 

1nH

 

 

2

 

 

C164

C165

 

 

IN

 

 

 

 

 

 

0.5p

1p

 

20dB

COUP

 

 

 

 

 

 

U102

 

 

 

 

3

 

 

 

 

 

CP0402A1950DNTR

 

 

 

 

 

R120

PWR_DET

 

 

 

 

R121

R122

 

 

 

 

130

47

130

 

 

 

 

 

 

 

7dB

 

WS2512_TR1G

U103

 

 

 

10

VCC2

VCC1

1

 

 

9

GND4

RFIN

2

 

8

RFOUT

GND1

3

 

 

7

GND3

VCONT

4

 

 

6

GND2

 

 

 

11

 

5

 

 

 

BGND

VREF

 

 

 

 

 

 

 

 

 

 

 

 

Rev_1.0

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

C154

 

 

 

 

 

 

 

 

 

 

 

+VPWR

 

 

 

 

 

1.5p

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

FL102

 

 

 

C159

 

 

 

 

 

 

 

 

 

 

 

 

4

5

EFCH1950TDF1

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

L122

 

 

 

C157

 

O1 G3

1

 

 

 

 

15p

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

IN

 

 

 

 

 

 

 

 

 

 

NA

 

 

 

10nH

 

G2

G1

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

3

2

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

PA_R0

 

 

TR100

 

 

KRX102U

 

5

1

 

 

2

PA_ON

 

 

 

 

Rev.B

4

3

VREG_TCXO_2.85V

 

 

C192

C170

100p

0.1u

[Figure 1.5] WCDMA PAM, Duplexer, Coupler

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LG Electronics U250 LO generation and distribution circuits, Off-chip RF Components, Wcdma PAM U103 WS2512-TR1G
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