Interface Threshold Voltage Levels

Interface Devices Voltage Threshold Levels

Comparison of Input and Output [I/O] logic switching levels for:
CMOS [5V], PECL [5V], RS422/485, RS232, LVDS, BTL, GTL logic families.

The graph above provides a comparison between the Input and Output [I/O] logic switching levels for a few different Interface bus types.
The output logic levels above are defined by the Terms section below. For a review of Noise Margin numbers and a short description of many
of the IC logic families , refer to the Logic Family Selection page. A graph for Low Voltage [LV] devices resides on the LV Logic Threshold page.
An additional chart of Standard Logic Voltage levels is provided on the Logic Threshold Voltage Levels page

Terms -
V_CC: The voltage applied to the power pin(s). In most cases the voltage the device needs to operate at.
V_IH: [Voltage Input High] The minimum positive voltage applied to the input which will be accepted by the device as a logic high.
V_IL: [Voltage Input Low] The maximum positive voltage applied to the input which will be accepted by the device as a logic low.
V_OL: [Voltage Output Low] The maximum positive voltage from an output which the device considers will be accepted as the maximum positive low level.
V_OH: [Voltage Output High] The maximum positive voltage from an output which the device considers will be accepted as the minimum positive high level.
V_T: [Threshold Voltage] The voltage applied to a device which is "transition-Operated", which cause the device to switch. May also be listed as a '+' or '-' value.

Description of TTL, ECL and CMOS Glue Logic Families

Device Families: TTL (74xx) True TTL 74L Low power 74S Schottky 74H High speed 74LS Low power - Schottky 74AS Advanced - Schottky 74ALS Advanced - Low power - Schottky 74F(AST) Fast - (Advanced - Schottky) 74C CMOS...................check Vcc levels 74HC (U) High speed - CMOS (Unbuffered output) 74HCT High speed - CMOS - TTL inputs 74AHC Advanced - High speed - CMOS 74AHCT Advanced - High speed - CMOS - TTL inputs 74FCT (-A) Fast - CMOS - TTL inputs (speed variations) 74FCT (-T, -AT) Fast - CMOS - TTL inputs (speed variations) 74AC Advanced - CMOS 74ACT Advanced - CMOS - TTL inputs 74FACT AC, ACT (Q) series 74ACQ Advanced - CMOS - Quiet outputs 74ACTQ Advanced - CMOS - TTL inputs - Quiet outputs Bus Driver Families 74ABT Advanced - BiCMOS - Technology 74ABTE ABT - Enhanced Transceiver Logic 74ABTH Advanced - BiCMOS - Technology - bus Hold 74BCT BiCMOS - TTL inputs 74BTL Backplane - Transceiver - Logic 74GTL Gunning - Transceiver - Logic 74GTLP GTL Plus Low Voltage Families 74ALB Advanced - Low Voltage - BiCMOS 74LV (U) Low - Voltage (Unbuffered output) 74LVC (R) (U) LV - CMOS (damping Resistor)(Unbuffered output) 74LVCH Low - Voltage - CMOS - bus Hold 74ALVC Advanced - Low - Voltage - CMOS 74LVT (R) (U) LV - TTL (damping Resistor(Unbuffered output) 74LVTZ Low - Voltage - TTL - High Impedance power-up 74ALVC (R) ALV - CMOS (bus Hold) (damping Resistor) 74ALVCH Advanced - Low - Voltage - CMOS - bus Hold 74LCX LV - CMOS (operates with 3v & 5v supplies) 74VCX LV - CMOS (operates with 1.8v & 3.6v supplies 4000 True CMOS (non-TTL levels) ECL Device Families: MEC I 8nS* MEC II 2nS* MEC III (16XX) 1nS* .......* = Rise & Fall Times 101xx 100 series 10K ECL, 3.5nS* 102xx 200 series 10K ECL, 2.5nS* 108xx 800 series 10K ECL, voltage compensated, 3.5nS* 10Hxxx 10K - High speed, voltage compensated, 1.8nS* 10Exxx 10K - ECLinPS, voltage compensated, 800pS* 100xxx 100K, temperature compensated 100Hxxx 100K - High speed, temperature compensated 100Exxx 100K - ECLinPS, temp, voltage comp., 800pS*

**Related pages on this site:**
Logic Family Slew Rate.	.Description of Company Prefixes.	.Glue Logic Speed x Power Chart.	.How to Termination Traces.	.Digital Logic Pitfalls.

Back to the Logic Design Page

Engineering Design Key words: Glue Logic Families, CMOS, TTL, ECL, Speed, IC, Integrated Circuits, Propagation delay, Logic Types, logic switching levels, Output voltage, Low-Voltage, Threshold Voltage, 74xx, 74AC00, 74HC, 74AHC00, Description, Digital Logic, Definition for Logic family, Logic Terms, TTL: Transistor Transistor Logic, ECL: Emitter Coupled Logic, CMOS: Complementary Metal-Oxide Semiconductor, BICMOS: Bipolar Complementary Metal Oxide Semiconductor, Signalling levels.


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