High Leakage Current in SN74LVC1G240 for +3V3 Logic

Ditish Maharjan

Other Parts Discussed in Thread: SN74LVC1G240, SN74AVC2T45, SN74LVC2T45, SN74AHCT1G125, SN74LV1T125, SN74AVC2T244

I am using SN74LVC1G240 as inverting buffer for SDI. Transmission Logic is at +5V and Receive Logic is at +3V3. When i Transmit some data through SDI the current consumption increased by values of around 5-15 mA. And when i tried receiving some data there was no unusual change in current. Apparently, SN74LVC1G240 when the LOGIC LEVEL at EN, TX are below the Supply Voltage VCC(+5V) it caused the device to consume more current. So, if the SDI_TX_EN and SDI_TX lines are at +5V logic then there is no current leakage.

What i want to know is, SN74LVC1G240 is a buffer / level Shifter , so why was there a current leakage because of difference in logic level of +3V3 at TX_EN, TX and +5V at VCC?

over 8 years ago

0 Clemens Ladisch over 8 years ago

Guru 316600 points

The '240 is not a level shifter. Where did you get that description from?

There is increased current consumption when an input is not at VCC or GND but somewhere between. To convert the voltages of the input signal from 3.3 V to 5 V, add buffers with TTL-compatible inputs (SN74AHCT1G125, SN74LV1T125), or an actual level translator (SN74AVC2T244, SN74AVC2T45, SN74LVC2T45).