DAN-101 EXAR | Alldatasheet
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EXAR Corporation, 48720 Kato Road, Fremont, CA 94538 • (510) 668-7000 • FAX (510) 668-7017 Visit Exar Web Site at www.exar.com DA TA COMMUNICA TIONS APPLICA TION NOTE DAN-101 Replacing SCN68681 with XR68C681 DUART
Description
This application note describes the major difference between the Exar XR68C681 and the Philips SCN68681. Items noted herein must be carefully considered whenever replacing with the XR68C681 device. Check your design to see if it applies.
1.0 Software
The XR68C681 is software compatible to the Philips SCN68681. All registers are compatible and there is no software change requirement.
2.0 Hardware
2.1 The XR68C681 is pin-to-pin compatible to the SCN68681 in the following packages:
XR68C681CJ = SCN68681C1A44 ; commercial temperature XR68C681J = SCN68681E1A44 ; industrial temperature XR68C681CP = SCN68681C1N40 ; commercial temperature XR68C681P = SCN68681E1N40 ; industrial temperature XR68C681N = SCN68681E1F40 ; ceramic package and industrial temperature
2.2 The XR68C681 is fabricated in low power CMOS process and the SCN68681 is made in NMOS
process. The XR68C681 consumes 10 times less power than SCN68681. Icc XR68C681 SCN68681 Typical 6mA n.a Maximum 15mA 150-175mA 2.3 The oscillator circuit on X1 and X2 pins is different and depending upon application environment it may or may not be compatible, refer to figure 1 on the next page. Figure 1 shows 3 applications that will need to be considered in the review process. The oscillator circuit and connection for SCN68681 is exhibited in the second column and the circuit for XR68C681 is shown under the third column. As it is illustrated, the internal inverter for the oscillator circuit is reversed. Hence, the XR68C681 is compatible under application #1 and should work fine. However, application #2 and #3 must be carefully reviewed by the designer. EXAR Corporation, 48720 Kato Road, Fremont, CA 94538 • (510) 668-7000 • FAX (510) 668-7017 May 1999
EXAR Corporation, 48720 Kato Road, Fremont, CA 94538 • (510) 668-7000 • FAX (510) 668-7017 Visit Exar Web Site at www.exar.com DA TA COMMUNICA TIONS APPLICA TION NOTE DAN-101 SCN68681 XR68C681, SCC68692, XR68C92, XR68C192, 2) OSCILLATOR OUTPUT CLOCK FEEDS OTHER PERIPHERAL(S) 3) EXTERNAL CLOCK INPUT X1 X2 X1 X2 Ext. Clock Ext. Clock 1) OSCILLATOR ALONE X1 X2X1 X2
APPLICATIONS
Osc. Clock to Peripherals X1 X2 Osc. Clock to Peripherals Figure 1. Oscillator Circuit Applications
EXAR Corporation, 48720 Kato Road, Fremont, CA 94538 • (510) 668-7000 • FAX (510) 668-7017 Visit Exar Web Site at www.exar.com DA TA COMMUNICA TIONS APPLICA TION NOTE DAN-101 NOTICE EXAR Corporation reserves the right to make changes to the products contained in this publication in order to im-prove design, performance or reliability. EXAR Corporation assumes no responsibility for the use of any circuits de-scribed herein, conveys no license under any patent or other right, and makes no representation that the circuits are free of patent infringement. Charts and schedules contained here in are only for illustration purposes and may vary depending upon a user’s specific application. While the information in this publicatio has been carefully checked; no responsibility, however, is assumed for inaccuracies. EXAR Corporation does not recommend the use of any of its products in life support applications where the failure or malfunction of the product can reasonably be expected to cause failure of the life support system or to significantly affect its safety or effectiveness. Products are not authorized for use in such applications unless EXAR Corporation receives, in writing, assurances to its satisfaction that: (a) the risk of injury or damage has been minimized; (b) the user assumes all such risks; (c) potential liability of EXAR Corporation is adequately protected under the circum-stances. Copyright 1999 EXAR Corporation. Reproduction, in part or whole, without the prior written consent of EXAR Corporation is prohibited.