If 90 days has elapsed since applying for EAD renewal, you can go to the local BCIS office and get an interim EAD.
But legally, you are not supposed to work if dont have EAD. It's not the question of Employer noticing or not. You may want to go on vacation for that period or openly talk to your employer.
Read the following:
Sec. 274a.14 Termination of employment authorization.
(a) Automatic termination of employment authorization.
(1) Employment authorization granted under Sec. 274a.12(c) of this chapter shall automatically terminate upon the occurrence of one of the following events:
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(i) The expiration date specified by the Service on the employment authorization document is reached;
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(ii) Exclusion or deportation proceedings are instituted (however, this shall not preclude the authorization of employment pursuant to Sec. 274a.12(c) of this part where appropriate); or
(iii) The alien is granted voluntary departure.
(2) Termination of employment authorization pursuant to this paragraph does not require the service of a notice of intent to revoke; employment authorization terminates upon the occurrence of any event enumerated in paragraph (a)(1) of this section. However, automatic revocation under this section does not preclude reapplication for employment authorization under Sec. 274a.12(c) of this part.