Note 10 - Stock-Based Compensation Plans (Tables)

12 Months Ended

Jan. 02, 2021

Notes Tables

Share-based Payment Arrangement, Expensed and Capitalized, Amount [Table Text Block]

	Year Ended
	January 2,		December 28,		December 29,
(In thousands)	2021		2019		2018
Cost of revenue	$	3,179	$	1,422	$	940
Research and development		10,124		5,640		4,357
Selling, general, and administrative		27,069		11,837		8,349
Total stock-based compensation	$	40,372	$	18,899	$	13,646

Schedule of Share-based Payment Award, Stock Options and Employee Stock Purchase Plan, Valuation Assumptions [Table Text Block]

	Year Ended
	January 2, 2021	December 28, 2019	December 29, 2018
Employee and Director Stock Options *
Expected volatility	n/a	n/a	39.87% to 41.11%
Risk-free interest rate	n/a	n/a	2.29% to 2.78%
Expected term (years)	n/a	n/a	4.08 to 4.25
Employee Stock Purchase Plan
Weighted average expected volatility	48.2%	31.6%	36.4%
Weighted average risk-free interest rate	0.89%	2.51%	1.61%
Expected term (in months)	6	6	6

Share-based Payment Arrangement, Option, Activity [Table Text Block]

(Shares and aggregate intrinsic value in thousands)	Shares			Weighted average exercise price		Weighted average remaining contractual term (years)		Aggregate Intrinsic Value
Balance, December 28, 2019		3,332		$	6.16
Granted		—			—
Exercised		(1,057	)		5.70
Forfeited or expired		(75	)		5.69
Balance, January 2, 2021		2,200		$	6.39
Vested and expected to vest at January 2, 2021		2,200		$	6.39		3.86	$	86,739
Exercisable, January 2, 2021		1,589		$	6.40		3.66	$	62,661

Schedule of Nonvested Restricted Stock Units Activity [Table Text Block]

(Shares in thousands)	Shares			Weighted average grant date fair value
Balance, December 28, 2019		3,611		$	11.50
Granted		984			26.48
Vested		(1,424	)		10.72
Forfeited or expired		(173	)		12.03
Balance, January 2, 2021		2,998		$	16.76

Schedule of Share-based Payment Award, Restricted Stock Units, Valuation Assumptions [Table Text Block]

	Year Ended
	January 2, 2021	December 28, 2019	December 29, 2018
Executive RSUs with a market condition or performance condition
Weighted average expected volatility	42.38%	40.15% to 41.10%	41.06% to 41.74%
Weighted average risk-free interest rate	1.40%	1.66% to 2.55%	2.71% to 2.87%
Expected term (years)	3.00	3.00	3.00 to 3.16

Share-based Payment Arrangement, Performance Shares, Outstanding Activity [Table Text Block]

(Shares in thousands)	Shares			Weighted average grant date fair value
Balance, December 28, 2019		1,163		$	14.49
Granted		349			32.23
Effect of vesting multiplier		472			—
Vested		(963	)		15.63
Canceled		—			—
Balance, January 2, 2021		1,021		$	20.42