Income Taxes - Components of Deferred Tax Assets and Liabilities (Details) (USD $) In Thousands, unless otherwise specified	Jan. 25, 2015	Jan. 26, 2014
Components of Deferred Tax Assets and Liabilities [Abstract]
Total current deferred tax liabilities	$ 1,444	$ 930
Net deferred tax liabilities	(1,337)	(1,262)
Current Deferred Tax Asset [Member]
Components of Deferred Tax Assets and Liabilities [Abstract]
Deferred revenue	3,052	2,773
Inventory reserve	3,156	3,032
Payroll and related accruals	2,306	2,133
Bad debt reserve	927	416
Accrued service fees	608	591
Other deferred assets	1,191	1,562
Valuation allowance	(8,637)	(7,321)
Total current deferred tax asset	2,603	3,186
Noncurrent Deferred Tax Asset [Member]
Components of Deferred Tax Assets and Liabilities [Abstract]
Payroll and related accruals	7,148	6,268
Other deferred assets	5,054	3,567
Research and development charges	1,323	2,109
Research credit carryforward	40,819	39,350
NOL carryforward	29,144	31,165
Stock-based compensation	6,176	5,732
Valuation allowance	(66,899)	(53,931)
Total non-current deferred tax asset	22,765	34,260
Current Deferred Tax Liability [Member]
Components of Deferred Tax Assets and Liabilities [Abstract]
Inventory reserve - foreign	(826)	(430)
Payroll and related accruals	(256)	(223)
Other deferred tax liabilities	(373)	(517)
Total current deferred tax liabilities	(1,455)	(1,170)
Noncurrent Deferred Tax Liability [Member]
Components of Deferred Tax Assets and Liabilities [Abstract]
Other deferred tax liabilities	1,377	1,377
Purchase accounting deferred tax liabilities	(20,917)	(32,466)
Depreciation and amortization	(2,956)	(3,695)
Total non-current deferred tax liabilities	$ (25,250)	$ (37,538)