SN74GTL2003: SN74GTL2003PW

Santosh Gurral

Part Number: SN74GTL2003
Other Parts Discussed in Thread: TXU0104, SN74AXC8T245, , LSF0108

We are using this level translator on our board for SPI interface at 6MHz.

A-side(SREF) voltage is connected to 1.2V and B-side (DREF) voltage is connected to 1.8V. with this we are having an issue with the high-level voltages for signals on the B-side or only max up to 1V it is not reaching 1.8V why is this? and also the rising edges look so sloppy why is this happening? what is the fix for this?

Thanks

Santosh

over 2 years ago

0 Clemens Ladisch over 2 years ago

Guru 317390 points

The difference between the reference voltages should be at least 1.5 V (see footnote (1) in section 6.3).

This device has open-drain outputs; the rising edges are generated only by the pull-up resistors. Apparently, the capacitive load is too high.

Are the signals really bidirectional? If not, use a buffered translator like the TXU0104 or SN74AXC8T245.

0 Santosh Gurral over 2 years ago in reply to Clemens Ladisch

Prodigy 120 points

what is the maximum capacitive load SN74GTL2003 can drive?

I have connected this level translator to a Flash IC with a trace capacitance of 30pF and the memory device input capacitance is 6.5pF

0 Clemens Ladisch over 2 years ago in reply to Santosh Gurral

Guru 317390 points

This device is a passive switch and has no drive strength. The 1.2 V device must be able to sink the current through the pull-up resistors. To get faster rising edges, use smaller resistors, but this increases the V_OL of your 1.2 V device.

0 Santosh Gurral over 2 years ago in reply to Clemens Ladisch

Prodigy 120 points

"Supports 50 MHz up or down translation at ≦20 pF capacitive load"

i am confused with this statement form SN74GTL2003 datasheet. please help me understand what does this mean?

0 Clemens Ladisch over 2 years ago in reply to Santosh Gurral

Guru 317390 points

Your load is much larger than 20 pF. (That connector implies a cable.)

What kind of SPI are you using? For unidirectional signals, a buffered translator would work much better.

0 Santosh Gurral over 2 years ago in reply to Clemens Ladisch

Prodigy 120 points

Quad SPI. and already have SN74GTL2003 on our board we can not change it for now.

Please suggest what is this 20pF parameter defined for SN74GTL2003? what does this mean if the level translator is a passive switch and has no drive strength? why is this parameter defined?

0 Clemens Ladisch over 2 years ago in reply to Santosh Gurral

Guru 317390 points

Replace it with the LSF0108, which is pin-to-pin compatible and has better electrical characteristics.

The only way to affect the signals is to adjust the pull-up resistors.

For how this device works, see [FAQ] How do the LSF translators work?

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SN74GTL2003: SN74GTL2003PW