LG Electronics KS360 service manual Dcxo, Front End Module control

3. TECHNICAL BRIEF

3.24 DCXO

The transceiver contains a fully integrated 26MHz digitally controlled crystal oscillator (DCXO) with three outputs for the system clock, one output for the GSM baseband and two additional for other subsystems (GPS, Bluetooth, etc.). The only external part of the oscillator is the crystal itself. The overall pulling range of the DCXO consists of eight subranges. The subrange closest to the ‘0ppm’ at the middle AFC-value is selected during the calibration process in the mobile’s production and is used for the rest of the lifetime. The frequency tuning is performed along the selected subrange by programming the frequency control word (XO_TUNE) via the three wire bus (“3Wbus”).

3.25 Front End Module control

Implemented in the Transceiver are two outputs for direct control of front end modules with two logic input pins to select RX- and TX-mode as well as low- and high band operation.

RF

VC1

C622

33p

VC2

C627

33p

PAD600 PAD601

PAD602

R608 C631

05p

C633 L605

0.75p 12nH

1

			CN600
		MM8430-2600RB3
4	6			C632
IN GND2GND1	GND4GND3 OUT		2	22p
3	5

L604

NA

	16	10		9	12	14	15	18		19	20
	VC1		VC2	GND1		GND2	GND3	GND4	GND5	NC1 NC2
17 ANT										GSM1800 1900TX GSM850 900TX
GSM850RX1 GSM850RX2			GSM900RX1	GSM900RX2 GSM1800RX1		GSM1800RX2	GSM1900RX1	GSM1900RX2
1	2	3	4	5	6	7	8		11	13

U601 LMSP43NA-782

C634

0.5p

	VC1	VC2
	PIN 14	PIN 13
GSM850_EGSM TX	H	L
DCS_PCS TX	L	H
GSM850 RX	L	L
EGSM900 RX	L	L
DCS1800 RX	L	L
PCS1900 RX	L	L

							C641
C643	C644	C645	C646		C648	C649	DNI
				C647			C650
2.5p	2.5p	3.9p
			3.9p	3.3p	3.3p	5.6p	5.6p
	L607		L608	L609		L610
	22nH		18nH	5.1nH		5.6nH
	GSM850		GSM900	DCS1800		PCS1900

GSM850_RXP GSM850_RXN GSM900_RXP GSM900_RXN DCS1800_RXP DCS1800_RXN PCS1900_RXP PCS1900_RXN

Figure 27. FEM Circuit Diagram

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