Electronic Components Datasheet Search |
|
BA8274 Datasheet(PDF) 5 Page - Rohm |
|
BA8274 Datasheet(HTML) 5 Page - Rohm |
5 / 9 page BA8274 / F Audio ICs 5/8 Attached components 1. Selection of external components (1) Pull-up resistance calculation In practical system the pull-up resistance is determined by the rise time limit for I 2C systems. As an approximation this limit will be satisfied if the time constant (product of the net resistance and net capacitance) of the total system is set to 1 microsecond. The total time constant may either be set by considering each bus node individually (i.e., the I 2C nodes, and the buffered bus node) and choosing pull-up resistors to give time constants of 1 microsecond for each node; or by combining the capacitances into an equivalent capacitive loading on the buffered bus, and calculating the buffered bus pull-up resistor required by this equivalent capacitance. For each separate bus the pull-up resistor may be calculated as follows: R = 1 µsec Cdevice + Cwiring Where : Cdevice = Sum of device capacitances connected to each bus. Cwiring = Total wiring and stray capacitance on each bus. If these capacitances are not know then a good approximation is to assume that each device presents 10pF of load capacitance and 10pF of wiring capacitance. The capacitance figures for one or more individual I 2C bus nodes should be multiplied by a factor of about 10 times, and then added to the buffered bus capacitance. Calculation of a new buffered bus pull-up resistor will allow this single pull-up resistor to act for both the included I 2C bus nodes and the buffered bus. Thus it is possible to combine some or all of these separate pull-up resistors into a signal resistor on the buffered bus (the value of which is calculated from the sum of the scaled capacitances on the buffered bus.) If the buffer is to be permanently connected into the system then all the separate pull-up resistors should be combined. But if it is to be connected by adding it onto an existing system, then only those on the additional I 2C bus system can be combined onto to the buffered bus if the original system is required to be able to still operate on a stand-alone basis. A further restriction is that the maximum pull-up current, with the bus LOW, should not exceed the I 2C bus specification maximum of 3mA, or 30mA on buffered bus. The following formula applies: Where : Rp = Scaled parallel combination of all pull-up resistors. If this condition is met, the fall time specifications will also be met. 30mA > V CC -0.4 Rp |
Similar Part No. - BA8274 |
|
Similar Description - BA8274 |
|
|
Link URL |
Privacy Policy |
ALLDATASHEET.COM |
Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Datasheet Upload | Contact us | Privacy Policy | Link Exchange | Manufacturer List All Rights Reserved©Alldatasheet.com |
Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
Family Site : ic2ic.com |
icmetro.com |