the key is to remember that zero ('0') equates to the 'O' in Output. This is the same scheme for most microcontrollers The pin to an output when a zero is written and to an input when a '1' is The data sheet, usually, I did not look in this case, also specifies aĭe-rating parameter (or graph) so that if used within a hot enclosure (or anyĮnvironment) you have to reduce the maximum current consumed! MCP23017 Non interruptįor controlling I/O direction of each pin, register IODIR (A/B) lets you set Maximum temperature allowed, and measure the chip temperature at its surface. You should look at the data sheet for the The fact that the MCP23017 gets hot is not a problem if you keep the maximum Output current for the chip within the 150mA limit otherwise the chip gets hot You must always to keep the maximum overall Obviously reducing the number of outputs in use will allow increasingĬurrent up to a maximum of 25mA per pin but then you could drive only 6 pins atįull current! (150mA/25mA=6). Reduce the current by increasing the current limiting resistors for each Look at the overall output current from the chip by calculating the currentįrom each pin and then adding up these results. TIP: If your MCP23017 is getting hot, then So the MCP23017 I2C address range is 32 decimal to 37 decimal or 0x20 to The four left most bits are fixed a 0100 (specified by a consortium whoĭoles out address ranges to manufacturers). Otherwise they will get random values from electrical noise and the chip will These hardware inputs as 0V or (high) volts and not leave them floating The above corresponds to a hardware address for the three lines A0, A1, A2Ĭorresponding to the input pin values at the IC. Addresses available are specified in the I2C controlīyte and each device is selected by the I2C sequence below: The 23017 has three input pins to allow you to set a different address forĮach attached MCP23017. The "Current Max into Vdd" is the sum of all sourcing currents. The "Current Max out of Vss" is the sum of all sinking currents.
Source current is the flowing (to an external circuit) when a pin is taken Sink current is the current flowing (from an external circuit) when a pin is The overall sink current is 150mA Vss and overall source current is and relates to the fact that there must be aĪsymmetrical architecture in the chip that can accept only the specifiedĬurrent. Supply Current (idle): 1mA Operational Current Max out of Vss 150mA Operational Current Max into Vdd 125mA Output current per pin 25mA Standby Current 01uA Operating temperature
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