[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.
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 |
|
74xx, 74Lxx |
{Back to Logic Family Voltage Translation Index}
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 |
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74HCTxx, 74AHCTxx 74ACTxx, 74FCTxx 74FACTxx, 74ACTQxx |
{Logic Family Voltage Translation Index}
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 |
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74Cxx, 74HCxx 74AHCxx, 74ACxx 74ACQxx |
The TTL gate will output between 2.4v [VOH min.] and 3.3v
[VOH 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}
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 VOL is lower and the VOH is higher.
|
74Cxx, 74HCxx 74HCTxxx, 74AHCxx 74AHCTxx, 74ACxx 74ACTxx, 74ACQxx 74ACQTxx, 74FCTxx 74FACTxx |
|
74xx, 74Lxx 74LSxx, 74ALSxx 74ASxx, 74Fxx |
{Logic Family Voltage Translation Index}
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.
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}
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}
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 |
If the device is CMOS then you require the same pull-up listed above (TTL to CMOS). A resistor between 1K and 2K ohms.
{Logic Family Voltage Translation Index}
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 |
A (10351) TTL to PECL 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.
If the device is CMOS then you require the same pull-up listed above (TTL
to CMOS). Between 1K and 2K ohms.
{Logic Family Voltage Translation Index}
|
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}
|
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:
VA = VCC – 2v = VCC x [(R2 +
R3)/R1 + R2 +R3)]
RAC = R1 // (R2 + (R3 // 50) = 50 Ohms
RDC = 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}
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 |
Pull-up resistors could be used instead of the TTL - CMOS translator listed above. The resistor should be between 1K and 2K ohms.
{Logic Family Voltage Translation Index}
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 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 refer to that page.
See this page for a listing of Glue Logic manufacturers.
{Back to Logic Family Voltage Translation Index}
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