What is the max current sink/source per pin ? I want to supply 24LC16B EEPROM
Vcc with one MSP430F135 pin.
24LC16B Operating current = 3mA , 5mA
Does supply P4.4 pins EEPROM Vcc?
Current sink/source for direct LED driver
Started by ●July 7, 2006
Reply by ●July 9, 20062006-07-09
microman wrote:
> What is the max current sink/source per pin ? I want to supply 24LC16B
> EEPROM
> Vcc with one MSP430F135 pin.
> 24LC16B Operating current = 3mA , 5mA
The problem is not the max current per pin but the voltage "droop" when
the EEPROM is programming a cell. You could get around this a little bit
by connecting a large value capacitor to the pin but then that would
also introduce a few other problems that come to mind. Isn't it easier
to use a p-ch/pnp or even a pico-gate in an sot-23 pack to drive it?
BTW, the 24LC16B specs 3ma write current but this is at 5.5V! The
internal high-voltage generator certainly works more efficiently at the
higher voltage which is probably why they quote that figure but you will
find that the lower the voltage you supply then the more current it will
require. The poor MSP I/O lines will droop to an unacceptable level if
this is the case.
*Peter*
> What is the max current sink/source per pin ? I want to supply 24LC16B
> EEPROM
> Vcc with one MSP430F135 pin.
> 24LC16B Operating current = 3mA , 5mA
The problem is not the max current per pin but the voltage "droop" when
the EEPROM is programming a cell. You could get around this a little bit
by connecting a large value capacitor to the pin but then that would
also introduce a few other problems that come to mind. Isn't it easier
to use a p-ch/pnp or even a pico-gate in an sot-23 pack to drive it?
BTW, the 24LC16B specs 3ma write current but this is at 5.5V! The
internal high-voltage generator certainly works more efficiently at the
higher voltage which is probably why they quote that figure but you will
find that the lower the voltage you supply then the more current it will
require. The poor MSP I/O lines will droop to an unacceptable level if
this is the case.
*Peter*
Reply by ●July 9, 20062006-07-09
On Fri, 7 Jul 2006 01:58:14 -0700 (PDT), you wrote:
>
>What is the max current sink/source per pin ? I want to supply 24LC16B EEPROM
>Vcc with one MSP430F135 pin.
>24LC16B Operating current = 3mA , 5mA
>
>Does supply P4.4 pins EEPROM Vcc?
According to the '135 datasheet (SLAS272F 2004 version pg 28) for a supply voltage
of 3V, and an output high, a port pin will be about 2.7V@5mA. I would consider this
sailing a bit close to the wind, and would endeavour to use a separate FET switch,
such as a Fairchild FDG312P to turn the power on or off to the eeprom, if it was necessary.
The 100nF supply capacitor would also comprise a non-linear load at turn-on to the port pin,
in addition to the load presented by the eeprom. These two factors *might* damage the port pin
due to excessive current. Also, Microchip doesn't supply graphs in the 'LC16B datasheet to
allow the user to determine the current usage during byte or block writes at different supply
voltages. I guess you'd have to determine that yourself.
By the way. You don't need the 100pf capacitors on the SCL and SDA lines.
>
>What is the max current sink/source per pin ? I want to supply 24LC16B EEPROM
>Vcc with one MSP430F135 pin.
>24LC16B Operating current = 3mA , 5mA
>
>Does supply P4.4 pins EEPROM Vcc?
According to the '135 datasheet (SLAS272F 2004 version pg 28) for a supply voltage
of 3V, and an output high, a port pin will be about 2.7V@5mA. I would consider this
sailing a bit close to the wind, and would endeavour to use a separate FET switch,
such as a Fairchild FDG312P to turn the power on or off to the eeprom, if it was necessary.
The 100nF supply capacitor would also comprise a non-linear load at turn-on to the port pin,
in addition to the load presented by the eeprom. These two factors *might* damage the port pin
due to excessive current. Also, Microchip doesn't supply graphs in the 'LC16B datasheet to
allow the user to determine the current usage during byte or block writes at different supply
voltages. I guess you'd have to determine that yourself.
By the way. You don't need the 100pf capacitors on the SCL and SDA lines.
Reply by ●July 10, 20062006-07-10
