[TTL - TTL ]
[TTL - CMOS {74xxT} ]
[TTL - CMOS {74xx}] [CMOS {74xx} - TTL]
[TTL - CMOS {4xxx}] [CMOS {4xxx} - TTL]
[TTL - ECL] [ECL - TTL] [ECL - CMOS]
[PECL to TTL] [PECL to LVDS] [LVPECL to LVDS]
[TTL - Low Voltage {74LVxx}]
[EIA422 to EIA232]
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Note: except for glue logic IC devices, TTL based devices do not really exist in any other device. All devices [other then glue logic ICs] produced use CMOS devices, and their I/O pins switch at CMOS levels. However, CMOS devices can be made to switch at TTL, even as they use CMOS devices. See this page for a listing of Glue Logic IC manufacturers.

TTL to TTL Logic

Any of these 5 volt TTL devices {listed on the left} will drive any of the 5 volt TTL devices listed on the right. No translation is needed.
Of course Fan-Out requirements still have to be observed. Fan-Out varies with each different logic family. Fan-Out defines the number of devices an IC can drive.

74xx, 74Lxx 74LSxx, 74ALSxx 74ASxx, 74Fxx

74xx, 74Lxx 74LSxx, 74ALSxx 74ASxx, 74Fxx

{Back to Logic Family Voltage Translation Index}

TTL to CMOS {74xxT} Logic

Any of these 5 volt TTL devices {listed on the left} will drive any of the 5 volt CMOS devices listed on the right. No translation is needed.
The { T } in the CMOS part number indicates the input switches at TTL levels [the output still switches at CMOS levels]. Chart comparing 5 volt TTL, CMOS Switching Levels

74xx, 74Lxx 74LSxx, 74ALSxx 74ASxx, 74Fxx

74HCTxx, 74AHCTxx 74ACTxx, 74FCTxx 74FACTxx, 74ACTQxx

{Logic Family Voltage Translation Index}

TTL to CMOS {74xx} Logic

Any of these 5 volt TTL devices {listed on the left} will drive any of the 5 volt CMOS devices listed on the right. A level switching Pull-Up resistor is required.
A value of between 1K and 2K will work well, the true value depends on the Fan-Out of the TTL gate.
The larger the Fan-Out (the more devices it's driving), the higher the resistor value. Fan-Out varies with each different logic family.

74xx, 74Lxx 74LSxx, 74ALSxx 74ASxx, 74Fxx

74Cxx, 74HCxx 74AHCxx, 74ACxx 74ACQxx

The TTL gate will output between 2.4v [V_OH min.] and 3.3v [V_OH max.] for a high level (depending on the logic family).
The CMOS gate requires a minimum of 3.7 volts to register a high. The Pull-Up resistor increases
the output voltage from the TTL driver. The resistor allows the TTL chip to deive a CMOS chip.

A 74ACTxx series device could be used, instead of the pull-up resistors. The 'T' CMOS part accepts TTL levels at the input while keeping the output at CMOS levels, and the internal device is still all CMOS [so the current consumption is still very low]. Refer to the TTL to CMOS {74xxT} Logic example.

{Logic Family Voltage Translation Index}

CMOS {74xx} to TTL Logic

Any of these 5 volt CMOS devices {listed on the left} will drive any of the 5 volt TTL devices listed on the right. No translation is needed.
Of course Fan-Out requirements still have to be observed. A 74xx CMOS device will always drive a TTL device, the V_OL is lower and the V_OH is higher.

74Cxx, 74HCxx 74HCTxxx, 74AHCxx 74AHCTxx, 74ACxx 74ACTxx, 74ACQxx 74ACQTxx, 74FCTxx 74FACTxx

74xx, 74Lxx 74LSxx, 74ALSxx 74ASxx, 74Fxx

{Logic Family Voltage Translation Index}

TTL to CMOS {4xxx} Logic

This really depends on the Vcc of the CMOS device, which could be up to +15 volts.
So this Translation is not addressed here. Common power supply voltages for 4000 series logic include 12 volts, 5 volts, or any voltage in between.

CMOS {4xxx} to TTL Logic

This really depends on the Vcc of the CMOS device, which could be up to +15 volts.
So this Translation is not addressed here.

{Logic Family Voltage Translation Index}

TTL to ECL Logic

A (10124) TTL to ECL translator is used to switch between the two logic families. Only the 10K family is shown,
the same is true for the 100K ECL family.
ECL Termination resistors (not shown) are required between the 10124 and the ECL device. Standard ECL design practices.

74xx, 74Lxx 74LSxx, 74ALSxx 74ASxx, 74Fxx 74Cxx, 74HCxx 74HCTxxx, 74AHCxx 74AHCTxx, 74ACxx 74ACTxx, 74ACQxx 74ACQTxx, 74FCTxx 74FACTxx

10xxx, 10Kxx 10Hxx, 10Exxx 10EPxx, 10ELxx

{Logic Family Translation Index}

ECL to TTL Logic

A (10125) ECL to TTL translator is used to switch between the two logic families. Only the 10K family is shown,
the same is true for the 100K ECL family.
ECL Termination resistors (not shown) are required between the ECL and the 10125 device. Standard ECL design practices.

10xxx, 10Hxx 10Exxx, 10EPxx 10ELxx

74xx, 74Lxx 74LSxx, 74ALSxx 74ASxx, 74Fxx 74HCTxxx, 74AHCTxx 74ACTxx, 74ACQTxx 74FCTxx, 74FACTxx

{Logic Family Voltage Translation Index}

PECL to TTL / TTL to PECL Logic

In this case PECL= Positive ECL
A (10350) PECL to TTL translator is used to switch between the two logic families. Only the 10K family is shown, the same
is true for the 100K ECL family. PECL switches to +3.2v for a low, and +4.1v for a high.

10xxx, 10Hxx 10Exxx, 10EPxx 10ELxx		74xx, 74Lxx 74LSxx, 74ALSxx 74ASxx, 74Fxx 74HCTxxx, 74AHCTxx 74ACTxx, 74ACQTxx 74FCTxx, 74FACTxx
74Cxx, 74HCxx 74HCTxxx, 74AHCxx 74AHCTxx, 74ACxx 74ACTxx, 74ACQxx 74ACQTxx, 74FCTxx 74FACTxx		10xxx, 10Hxx 10Exxx, 10EPxx 10ELxx

{Logic Family Voltage Translation Index}

PECL to LVDS

Both LVPECL and LVDS are differential voltage standards, but they use different transceivers and switch at different levels. The voltage levels have to be translated. For detailed EIA644 [LVDS] design information see the LVDS description page

{Back to Logic Family Voltage Translation Index}

LVPECL to LVDS

The graphic above only shows one end of the differential pair. The resistors need to be added to both pairs. Equations for calculating the resistors in the figure above:
V_A = V_CC – 2v = V_CC x [(R2 + R3)/R1 + R2 +R3)]
R_AC = R1 // (R2 + (R3 // 50) = 50 Ohms
R_DC = R1 // (R2 + R3) ~ 50 Ohms
Gain = (R3 // 50) / (R2 + (R3 // 50) > 0.17
3.3v / 275 ohms = 12mA or 6.8mW, so a 1/16 watt resistor will do.

Both LVPECL and LVDS are differential devices, but they switch at different levels. The voltage levels have to be translated. This circuit just shifts the voltage. LVPECL is PECL that switches at 3.3 volts instead of 5 volts. For detailed EIA644 [LVDS] bus description, see this LVDS description page

{Back to Logic Family Voltage Translation Index}

ECL to CMOS Logic

A (10125) ECL to TTL translator is used to switch between the two logic families. Only the 10K family is shown,
the same is true for the 100K ECL family.
ECL Termination resistors (not shown) are required between the ECL and the 10125 device. Standard ECL design practices.
In addition, a TTL to CMOS translator is required

10xxx, 10Hxx 10Exxx, 10EPxx 10ELxx

74xx, 74Lxx 74LSxx, 74ALSxx 74ASxx, 74Fxx 74Cxx, 74HCxx 74HCTxxx, 74AHCxx 74AHCTxx, 74ACxx 74ACTxx, 74ACQxx 74ACQTxx, 74FCTxx 74FACTxx

{Logic Family Voltage Translation Index}

Low Voltage {74LVxx} 3.3volt Logic

A (74LVC4245) Bidirectional 3.3v to 5volt transceiver is used to switch between the two logic families.
Bus "B" is the TTL +5volts side, Bus "A" is the +3.3volt side.

74LVxx, 74LVCxx 74LVTxx, 74LVTZxx 74LVCHxx, 74ALVCxx 74LCxx

74xx, 74Lxx 74LSxx, 74ALSxx 74ASxx, 74Fxx 74HCTxxx, 74AHCTxx 74ACTxx, 74ACQTxx 74FCTxx, 74FACTxx

{Logic Family Voltage Translation Index}

EIA422 to EIA232

EIA422 is a differential [two wire] bus, while RS232 is single wire. EIA422 sends data out as its 'true; and 'complement' value over two wires.
For a detailed RS422 interface bus description and information see the RS422 Bus page
For detailed RS232 bus design information see the RS232 Bus page

See this page for a listing of Glue Logic manufacturers.

{Back to Logic Family Voltage Translation Index}

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