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shilchenbach
Level 2
Level 2
First solution authored First reply posted 10 sign-ins

Hello,

when a pad is configured as weak or medium driver, does in this case the maximum output current is lower compared to a strong configuration? The datasheet isn't very clear about this topic. For driving LEDs, the weak drive strength would fit, but a sufficient current is required. In a different document I found this schematic:

shilchenbach_0-1710945412992.png

"In Weak Driver Mode, only the weak transistor is activated while the other transistors remain off. This results in smooth transitions with low current peaks (and reduced susceptibility for noise) on the cost of increased transition times, i.e. slower edges, depending on the capacitive load, and low static current."

 

Thanks in advance,

Stephan

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1 Solution
shilchenbach
Level 2
Level 2
First solution authored First reply posted 10 sign-ins

Hello,

today I measured voltage and current on a A2 and A1+ pad with a 480 Ohm resistor. Here are my results:

A2 pad
Strong configuration: 3.2V / 6.5mA
Medium configuration: 2.8V / 5.8mA
Weak configuration: 1.9V / 3.8mA

A1+ pad
Strong configuration: 2.8V / 5.8mA
Medium configuration: 2.7V / 5.6mA
Weak configuration: 1.9V / 3.8mA

My results match to the assumption of my first post. The output power is related to the pad configuration. A weak configuration is not suitable for driving higher loads. For A1+ pads the strong configuration is equal to a medium configuration.

Best Regards,

Stephan

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8 Replies
Maragani
Moderator
Moderator
Moderator
25 solutions authored 10 likes received 100 replies posted

HI @shilchenbach 

Here is the additional data on drive mode from User Manual on XMC4700/4800

Maragani_0-1711001133886.png

Thanks & Regards
Sateesh M

 

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shilchenbach
Level 2
Level 2
First solution authored First reply posted 10 sign-ins

Hello Sateesh,

thank you for the excerpt from the TRM. I know this section. There is no information about the power rating in the different modes. Is the maximum output current in weak and medium configuration lower compared to a strong configuration?

Best Regards,

Stephan

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Maragani
Moderator
Moderator
Moderator
25 solutions authored 10 likes received 100 replies posted

hi @shilchenbach 
In the XMC4700/XMC4800 data sheet has the drive current details listed in different tables  [ 22, 23  and 24]. Based on the pad type the drive current will vary.
Below is the snippet of the table 22 of Pads Class_A1+, which contains the drive mode with drive current details.

Hope this clarifies the drive current vs drive strength in XMC devices. 

Maragani_0-1712236187634.png


Thanks & Regards
Sateesh M

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Hello Sateesh,

according to the data sheet an output pin can drive 5ms. The snippet above shows the test conditions for a voltage drop of 0.4V. According to this table, strong and medium pads are equal. Weak pads can drive about 25% of strong/medium pads. To avoid high output voltage drop, weak pins should not drive more than 0.5mA and strong/medium pads should not drive more then 2mA. Is this correct?

Best Regards,

Stephan

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Maragani
Moderator
Moderator
Moderator
25 solutions authored 10 likes received 100 replies posted

Hi @shilchenbach 
Yes the device can support 5mA of drive current. To limit the drive current ( sink or source )  you have to provide series resistors and you should not over load the pad maximum rated current as per the DC Electrical parameters.

The snippet above is explaining about the pads drive strength which is used in Communication mode, for example you have CLK pin in SPI mode. Which should give Sharp Edge or curved edge or normal edge is derived based on the  drive mode (Weak, medium or Strong )and the PAD class (A1, A1+ and A2). Based on the Pad class and Pad strength internally that particular pad will have pull-up and load capacitor is provided, which helps in Signal Rise and Fall time (Slew Rate of the GPIO).

Kindly refer device data sheet Electrical characteristics Table 21-24. (Here I am talking about XMC4700/4800)

Hope this clarifies to your query.


Thanks & Regards
Sateesh M

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Hello Sateesh,

do you commit then, a weak configuration can drive up to 5mA on any pad (A1, A1+, A2)? The same as a strong configuration?

Best Regards,

Stephan

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Maragani
Moderator
Moderator
Moderator
25 solutions authored 10 likes received 100 replies posted

hi @shilchenbach 

The data sheet of the XMC4700/4800 stated that the operating current of port pin is +/- 5mA.

For overload current , the max rating is reflecting the internal diode rating.
In case the voltage drop across the diode is more  than MCU supply  voltage then max current per port allowed is 20mA , this is not a continuous current that is supported by port.
It is an overload current that is supported by port internal protection diode  due to higher voltage( more then 3.3V) on pin in  comparison to the VDDP (3.3V).
Kindly check the below operating conditions of Port & Port Pins. 

Maragani_0-1713279197971.png

 

Thanks & Best Wishes
Sateesh M

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shilchenbach
Level 2
Level 2
First solution authored First reply posted 10 sign-ins

Hello,

today I measured voltage and current on a A2 and A1+ pad with a 480 Ohm resistor. Here are my results:

A2 pad
Strong configuration: 3.2V / 6.5mA
Medium configuration: 2.8V / 5.8mA
Weak configuration: 1.9V / 3.8mA

A1+ pad
Strong configuration: 2.8V / 5.8mA
Medium configuration: 2.7V / 5.6mA
Weak configuration: 1.9V / 3.8mA

My results match to the assumption of my first post. The output power is related to the pad configuration. A weak configuration is not suitable for driving higher loads. For A1+ pads the strong configuration is equal to a medium configuration.

Best Regards,

Stephan

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