![]() They do not store directly personal information, but are based on uniquely identifying your browser and internet device. They may be used by Analog Devices to build a profile of your interests and show you relevant content on our site. Targeting Cookies: These cookies may be set through our site by Analog Devices and our service providers. If you do not allow these cookies we will not know when you have visited our site, and will not be able to monitor its performance. All information these cookies collect is aggregated and therefore anonymous. They help us to know which pages are the most and least popular and see how visitors move around the site. Performance Cookies: These cookies allow us to count visits and traffic sources so we can measure and improve the performance of our site. If you do not allow these cookies then some or all of these services may not function properly. They may be set by us or by third party providers whose services we have added to our pages. Functional Cookies: These cookies enable the website to provide enhanced functionality and personalization. These cookies do not store any personally identifiable information. You can set your browser to block or alert you about these cookies, but some parts of the site will not then work. They are usually only set in response to actions made by you which amount to a request for services, such as setting your privacy preferences, logging in or filling in forms. Strictly Necessary Cookies: (Always Active) These cookies are necessary for the website to function and cannot be switched off in our systems. After we finish updating our website, you will be able to set your cookie preferences. AuthorĪnalog Devices is in the process of updating our website. fileadmin/ftp/I 2C_bus_specification_1995.pdf If a distance larger than 8 meters is necessary, or if there is more than 40 pF of total capacitance connected to side one, the maximum operating frequency can be reduced to allow a longer rise time and a larger bus capacitance. Side two could connect a four way ribbon cable (up to 8 meters in length) that transfers isolated data to additional I 2C devices connected to the bus. For a cabling application, an ADUM1250 could connect one section of the I 2C bus with 40 pF of total bus capacitance to side one. Normally, this type of ribbon cable is approximately 50 pF per meter. The higher drive strength of side two (30 mA) allows for a lower pull-up resistor value than side one’s 3 mA drive strength permits.įour-way ribbon cable can be used to extend an I 2C bus. The primary reason for the different load capacitance values of each side of the ADUM1250 is due to their drive strengths. The data sheet values account for design margin, ESD protection, and 400 pF is a standard for an I 2C bus. These are theoretical maximum capacitance values the suggested load capacitance values in the ADUM1250 data sheet are 40 pF for side one and 400 pF for side two. ![]() Using the data sheet recommended pull-up resistor values for 5 V operating conditions for side one and side two of an I 2C compliant hot swappable digital isolator ( ADUM1250), we can calculate that the maximum cable capacitance for side one is 88 pF and for side two is 780 pF. This equation is derived by solving the voltage of a charging capacitor for V C = 0.3 × V DD and V C = 0.7 × V DD. In this case, rise time ( t R) is the time it takes a signal to rise from 0.3 ×V DD to 0.7 ×V DD. With a fixed value of the pull-up resistor ( R P), a linear relationship between rise time ( t R) and total bus capacitance ( C B) is described by Equation 1. ![]() If 1 MHz operating frequency is not necessary, fast mode (400 kHz maximum operating frequency) can be used, which permits a rise time up to 300 ns. ![]() The fast-mode plus (1 MHz maximum operating frequency) specification declares a maximum rise time for a data or clock signal to be 120 ns. The I 2C bus specifications restrict the rise time of a signal for different operating frequencies. Two basic I 2C devices connected to an I 2C bus.
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