* Sees Q1 rev $158 mln-$163 mln vs est. $172.1 mln
* Q4 rev $192.2 mln vs est. $190.7 mln
* Q4 adj profit $0.78/ADS vs est. $0.71/ADS
* Shares fall 12 pct
Feb 29 (Reuters) - Shanghai-based cellphone chip designer Spreadtrum Communications Inc forecast first-quarter revenue below analysts' expectations on lower 3G handset demand at China's largest telecom carrier China Mobile .
Spreadtrum shares fell as much as 12 percent to $15.87 in morning trade on the Nasdaq on Wednesday.
The company supplies chips to major original equipment manufacturers and local Chinese handset makers, which in turn supply handsets to China Mobile.
Last week, competitor Marvell Technologies said it was witnessing a weak Chinese business and expects its mobile and wireless chip sales to dip in line with seasonality.
China Mobile's handset division recently underwent a management change, resulting in a slowdown in the procurement of cellphones using China's home-grown proprietary 3G technology TD-SCDMA, Spreadtrum's Chief Executive Leo Li said on a conference call.
"Seasonally, the first quarter is lower for 2.5G. This year it is particularly low also for TD-SCDMA," Li said.
Chips meant for phones based on the local 3G technology accounted for more than a third of the company's revenue in the fourth quarter.
Li said he does not expect the management changes at China Mobile hurt the company's results any further.
However, its first-quarter revenue estimate of $158 million to $163 million was below the $172.1 million analysts were expecting on average, according to Thomson Reuters I/B/E/S.
Spreadtrum's competitors for the Chinese 3G market also include T3G Technology Co and Taiwan's MediaTek Inc.
For the October-December quarter, the company earned $35.2 million, or 66 cents per ADS, compared with $30 million, or 56 cents per ADS, a year ago.
The company's stock has fallen more than 40 percent in value since hitting a year high in November.