VCC – Supply Voltage range. The device operation is defined only in this voltage range.
VREF – Reference voltage. Used to define the switching threshold of differential input devices.
VIH – High level input voltage. A minimum voltage required to detect the input voltage as logic high (in positive logic). VIHmin – can be considered for worst case analysis
Note 1: Unlike CMOS (which has very high impedance due to gate insulation resistance), bipolar transistors inputs will draw small amount of current through the input terminals when logic high voltage (VIH) is applied across the input. Higher the VIH , more the current that will be drawn by the Bipolar input
It is very important to maintain input voltage levels in valid range (>VIHmin for logic high and <VILmax for logic Zero) especially for CMOS. If not, the device may draw huge currents and may switch states randomly, generates high noise currents and power and ground surge currents or in worst case permanent device damage may occur
VIL – Low level input voltage, Voltage below this range at the input will be treated as logic zero (in Positive logic). For Most Bipolar devices, when a low voltage is applied at the input, certain amount of current will be sourced out. Lower the input voltage across the input, higher the sourced out current.
Note 3: In general, a device with VIH of 2.4 and VIL of 0.8 has a TTL compatible input. The devices whose input levels are scaled (0.7 VDD and 03 VDD) will have CMOS inputs
IOH – High Level Output Current, the current into an output with input conditions applied, establishes a high level at the output. CMOS devices will have limited current driving capability while output of logic high is produced. If the load connected to the CMOS output pin (LED) sinks more current, then the output voltage level starts to fall down since MOSFETs will be seen as low impedance resistors when turned on (Increasing current increases internal ohmic voltage loss). Hence the datasheet will say the maximum IOH that the device can source while still maintaining output voltage higher than the specified VOH minimum.
IOL – Low level output current, the current into an output with input conditions, establishes a low level at the output. CMOS devices will have limited current driving capability while output of logic low is produced. If the load connected to the CMOS output pin pull-up of very low value, then the output voltage level starts to rise since MOSFETs will be seen as low impedance resistors when turned on (Increasing current increases internal ohmic voltage loss). Hence the datasheet will say the maximum IOL that the device can sink while still maintaining output voltage lower than the specified VOL maximum.
The current out of the port is mentioned as negative value and current into the port is mentioned as positive value.
VOL – Low level output voltage, The voltage level at an output terminal with input conditions applied that, establishes a low level at the output.
VOH – High level output voltage, The voltage level at an output terminal with input conditions applied that, establishes a high level at the output.
IIH, IIL are input currents when logic high and low is applied to the input port respectively. For CMOS, the current will be a few µA.
VREF – Reference voltage. Used to define the switching threshold of differential input devices.
VIH – High level input voltage. A minimum voltage required to detect the input voltage as logic high (in positive logic). VIHmin – can be considered for worst case analysis
Note 1: Unlike CMOS (which has very high impedance due to gate insulation resistance), bipolar transistors inputs will draw small amount of current through the input terminals when logic high voltage (VIH) is applied across the input. Higher the VIH , more the current that will be drawn by the Bipolar input
It is very important to maintain input voltage levels in valid range (>VIHmin for logic high and <VILmax for logic Zero) especially for CMOS. If not, the device may draw huge currents and may switch states randomly, generates high noise currents and power and ground surge currents or in worst case permanent device damage may occur
VIL – Low level input voltage, Voltage below this range at the input will be treated as logic zero (in Positive logic). For Most Bipolar devices, when a low voltage is applied at the input, certain amount of current will be sourced out. Lower the input voltage across the input, higher the sourced out current.
Note 3: In general, a device with VIH of 2.4 and VIL of 0.8 has a TTL compatible input. The devices whose input levels are scaled (0.7 VDD and 03 VDD) will have CMOS inputs
IOH – High Level Output Current, the current into an output with input conditions applied, establishes a high level at the output. CMOS devices will have limited current driving capability while output of logic high is produced. If the load connected to the CMOS output pin (LED) sinks more current, then the output voltage level starts to fall down since MOSFETs will be seen as low impedance resistors when turned on (Increasing current increases internal ohmic voltage loss). Hence the datasheet will say the maximum IOH that the device can source while still maintaining output voltage higher than the specified VOH minimum.
IOL – Low level output current, the current into an output with input conditions, establishes a low level at the output. CMOS devices will have limited current driving capability while output of logic low is produced. If the load connected to the CMOS output pin pull-up of very low value, then the output voltage level starts to rise since MOSFETs will be seen as low impedance resistors when turned on (Increasing current increases internal ohmic voltage loss). Hence the datasheet will say the maximum IOL that the device can sink while still maintaining output voltage lower than the specified VOL maximum.
The current out of the port is mentioned as negative value and current into the port is mentioned as positive value.
VOL – Low level output voltage, The voltage level at an output terminal with input conditions applied that, establishes a low level at the output.
VOH – High level output voltage, The voltage level at an output terminal with input conditions applied that, establishes a high level at the output.
IIH, IIL are input currents when logic high and low is applied to the input port respectively. For CMOS, the current will be a few µA.
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