| Products | Standard ICs | PCA |
PCA9510, PCA9511, PCA9512, PCA9513, and PCA9514 "A" versus non-A versions
Introduction
The "A" versions of the PCA9510, PCA9511, PCA9512, PCA9513, and PCA9514 have higher series resistance outputs than their non-A versions.
The benefit of the increased series resistance is improved signal integrity.
The drawback, however, is reduced drive current.
Both versions are offered for different applications.
Specifics
The original, non-A versions were designed with a low output resistance of approximately 5Ω.
The newer "A" versions have an approximate 70Ω series output resistance.
This means that any application using the high-drive capability of the non-A versions (lower offset, especially at 3mA) cannot migrate to the "A" versions.
In the original, non-A versions, under slow rise conditions—especially at low VCC, the NMOS pull-down can fail to shut-off.
This has the possibility of dragging the high level down and this occurs only when the rise time is too slow to fire the rising edge accelerator.
This condition no longer causes the above behavior due to functional improvements in the "A" versions.
FAQ
| Q | Which version is preferred: A or non-A? |
| A |
Customers can convert to the "A" versions or continue using the non-A versions.
Both will continue to be supported, but the "A" version is recommended for new applications.
The "A" versions are new products with different characteristics than the original non-A versions.
Customers are encouraged to consider and evaluate the "A" version during new designs or board respins to determine which version is more suitable but are not required to change to or to use the newer "A" versions.
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| Q | Are there any reasons to choose the "A" version over the non-A version if I don't need the higher drive? |
| A |
Yes, as described above, the new "A" versions have an improved design to avoid a potential problem at low VCC with slow rise time conditions.
Also, as shown in the detailed test results below, the new "A" versions have an improved propagation delay from high to low.
The original, non-A versions have different propagation delays for rising edges and falling edges that can cause some applications to see a false STOP condition.
The typical propagation delay for rising edges is 25ns, but is 380ns for falling edges in the non-A products.
In the first bit of the slave address, the master sends a falling edge on SCL followed by a rising edge on SDA in preparation to clock in a one.
What is perceived as skew between SDA and SCL is really the result of this difference in rising and falling edges.
These edges propagate differently though the non-A products due to the fact that they have different slopes (one rising, one falling) and not because they are on different paths.
In the figure below, the master generates a delay of 100ns between these edges.
The data sheet tells us that the falling edge will be delayed by 355ns more than the rising edge.
This results in a net delay of 255ns from the rising edge of SDA to the falling edge of SCL, and the slave may interpret this as a STOP.
In summary, the more closely matched timing of the rising and falling edges and other improvements in the "A" versions offer improved signal integrity when used under light load conditions.
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| Q | How do I determine if the "A" version will work in my non-A design? |
| A |
The "A" versions of the products will work without any modification to the circuit and can be freely substituted for the non-A versions if the higher drive/lower series resistance is not required.
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| Q | What is the availablity of the newer "A" versions? |
| A |
"A" versions of the PCA9510, PCA9511, PCA9512, PCA9513, and PCA9514 are being produced in SO-8 and TSSOP-8 (MSOP) packages with 4-week lead times.
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| Q | How do the design and production of the two versions compare? |
| A |
Both the "A" versions and non-A versions of the products were developed by the same designer.
Both versions are offered in the same 8-pin SO and TSSOP packages and use the same CMOS process and the same logistics flow.
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| Q | Is there any price difference? |
| A |
While we cannot control the final retail price (through distributors, etc.), we price the A and non-A versions the same.
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| Q | How can I get samples or more support if I still have questions? |
| A |
Samples can be requested through your local sales account manager or sales office.
Samples and answers to your additional questions can also be obtained by contacting us through the I2C Logic product and technical support email link.
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| Q | Are there alternate sources? |
| A |
Yes.
The Linear Technology LTC4300A-1IMS8 is an alternate source for the PCA9511ADP (TSSOP/MSOP-8 package).
The Linear Tech LTC4300A-2IMS8 is an alternate source for the PCA9512ADP (TSSOP/MSOP-8 package).
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Test Results
Following is a detailed comparison of signal integrity for the original
NXP PCA9511, the
NXP PCA9511A, and the Linear Technology LTC4300A-1 under light-load conditions.
The figure below shows the test setup.
VDD = Vt = 3.6V.
A 1MHz pulse is generated by a HFS9002 signal generator and is buffered by the I2C adapter board.
10KΩ pullup resistors are used.
The input/output signals are measured at either pins 3 or 6 and pins 2 or 7 by 6249 probes as shown.
Test Setup Schematic
In the traces below, the vertical scale is 1.0V per division.
The horizontal scale is 200ns per division.
The brown trace indicates the probe at pin 3/6 while the blue trace indicates the probe at pin 2/7.
PCA9511 Waveforms
PCA9511A Waveforms
LTC4300A-1 Waveforms
More Information
Support
- Contact Us for More Assistance
Links
- PCA9510(A), PCA9511(A), PCA9512(A), PCA9513(A), and PCA9514(A)
Device Highlight - I2C/SMBus Repeater/Hub/Extender Functions
- PCA Family
