Crist=F3v=E3o Dalla Costa wrote:

> How do other chip families compare wrt input protection? Avr, arm...?

Atmel AVR... generally their abs max specs seem to be input voltage -0.5V t=
o =

Vcc+0.5V. AT90CAN32/64/128 data sheet has "injection current" spec in absol=
ute =

maximum ratings of +/-5.0mA, with notes to say max current per port of +/-3=
0mA =

and "functional corruption may occur". Corrupt when? Above 5mA or below?

Texas Instruments... MSP430x22x2 abs max specs:
Voltage applied to any pin -0.3 V to VCC+0.3 V
Diode current at any device terminal =B12 mA

Freescale MC9S08GT16A abs max specs:
Digital input voltage VIn -0.3 to VDD + 0.3 V
Instantaneous maximum current Single pin limit (applies to all port pins) I=
D =B1 25 mA
With this note: "Input must be current limited to the value specified. To d=
etermine =

the value of the required current-limiting resistor, calculate resistance v=
alues for =

positive (VDD) and negative (VSS) clamp voltages, then use the larger of th=
e two =

resistance values." .. and this under DC charactersistcs:

DC Injection Current, Single pin limit
VIN > VDD Max 2mA
VIN < VSS Max -0.2mA
Total MCU limit, includes sum of all stressed pins
VIN > VDD Max 25mA
VIN < VSS Max -5mA

Holtek HT48F70E abs max specs:
Input Voltage VSS-0.3V to VDD+0.3V

Philips LPC2101 abs max specs:
Input Voltage -0.5V to VDD+0.5V

Mitsubishi M16C abs max specs:
Input Voltage -0.3 to Vcc+0.3

Analog Devices ADuC824 abs max specs:
Input Voltage -0.3 to Vcc+0.3
Analog Input current 30mA

Cypress PSoC CG6462AM abs max specs:
DC Input Voltage Vss - 0.5 - Vdd + 0.5 V
Maximum Current into any Port Pin -25 - +50 mA

ST ST6220C abs max specs:
Input voltage on any pin VSS-0.3 to VDD+0.3
Output voltage on any pin VSS-0.3 to VDD+0.3
Injected current on RESET pin =B15mA
Injected current on any other pin =B15mA
With notes on injection currents: When the current limitation is not possib=
le, the VIN =

absolute maximum rating must be respected, otherwise refer to IINJ(PIN) =

specification. A positive injection is induced by VIN>VDD while a negative =
injection =

is induced by VIN<VSS. Negative injection disturbs the analog performance o=
f the =

device. In particular, it induces leakage currents throughout the device in=
cluding the =

analog inputs. To avoid undesirable effects on the analog functions, care m=
ust be =

taken: - Analog input pins must have a negative injection less than 1mA (as=
suming =

that the impedance of the analog voltage is lower than the specified limits=
).
- Pure digital pins must have a negative injection less than 1mA. In additi=
on, it is =

recommended to inject the current as far as possible from the analog input =
pins.

ST STR71x ARM abs max specs:
Input voltage Vss-0.3V to Vdd+0.3V
Injected current on any other pin +/-5mA
Total injected current (sum of all I/O and control pins) +/-25mA

Allowable injected current (normal operating) on any I/O pin +/-4mA

-- =

Brent Brown, Electronic Design Solutions
16 English Street, St Andrews,
Hamilton 3200, New Zealand
Ph: +64 7 849 0069
Fax: +64 7 849 0071
Cell: 027 433 4069
eMail:  brent.brown@clear.net.nz



-- =

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