Level converter for HF

[Stefan Oedenkoven]

Hi ng,

i'm currently building a serial controller between a 5V and a 3.3V
microcontroller. Maybe someone of you can tell me, if there exists any
common electronic component which can convert digital signals at ~ 1MHz with
high level varying from 3.0 to 5.0 Volt and should output a signal with high
level at 3.3Volt . (low level is always 0V)

first i tried to build a simple voltage divider with two resistors, which
was only acceptable with stable 0V Low /5V High input... the other problem
is a fixed input capacitor at the 3.3V device of 50pF which - in combination
with my voltage divider - passed only low frequencies.

thanks in advance,
Stefan

 

[TimPerry]

Hi ng,

i'm currently building a serial controller between a 5V and a 3.3V
microcontroller. Maybe someone of you can tell me, if there exists any
common electronic component which can convert digital signals at ~ 1MHz with
high level varying from 3.0 to 5.0 Volt and should output a signal with high
level at 3.3Volt . (low level is always 0V)

first i tried to build a simple voltage divider with two resistors, which
was only acceptable with stable 0V Low /5V High input... the other problem
is a fixed input capacitor at the 3.3V device of 50pF which - in combination
with my voltage divider - passed only low frequencies.

thanks in advance,
Stefan

i believe you are looking for a circuit called a clamper that is then
followed by a clipper.

if i understand the question correctly you have a square wave (or pulses)
that are 2 V peak to peak that is floating 3 volts above ground and you wish
to turn it into 3.3 volt pulses referenced to ground.

there are probably several way to accomplish this. one way would to be use
an op-amp. use a capacitor to block the DC component and set the amp gain so
that the output saturates (goes all the way up to the supply voltage) this
helps square up the waveform. then a resister on the output and a 3.3 volt
zener diode to ground. the zener will limit (clip) the waveform.

 

[Stefan Oedenkoven]

i believe you are looking for a circuit called a clamper that is then

followed by a clipper.

if i understand the question correctly you have a square wave (or pulses)
that are 2 V peak to peak that is floating 3 volts above ground and you wish
to turn it into 3.3 volt pulses referenced to ground.

not exactly... the output is from a fpga, which has a fixed high level once
it is programmed. But if i reprogramm it, the high level on the same port
may be higher or lower (from 3 volts to 5 volts).
The low level is alway 0 volts.

FPGA => Microprocessor
0v 5v 0v 5v => 0v 3.3v 0v 3.3v
reprogramm:
0v 3v 0v 3v => 0v 3.3v 0v 3.3v
reprogramm:
0v 4v 0v 4v => 0v 3.3v 0v 3.3v