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LM5116: Voltage output by HO and LO pins to MOSFET gates

Part Number: LM5116

I am using the buck controller, LM5116MHX/NOPB (found here https://www.digikey.com/en/products/detail/texas-instruments/LM5116MHX-NOPB/1871901). In the datatsheet(https://www.ti.com/lit/ds/symlink/lm5116.pdf?ts=1615589704827) near the bottom of page 7 it lists the output voltage for the HO and LO pins which drive the gates of the high and low MOSFETs respectively. I am confused by the values given. For the LO gate driver, the high-state output voltage is only 0.25 V and for the HO gate driver the high-state output is only 0.45V. These seem very small and significantly less than most N-MOSFET's gate-source threshold voltage.

I was led to think these values are incorrect as on page 22 of the same documentation an example is given where specific components are selected. They documentation selects an N-MOSFET from Vishay Siliconix with part number Si7850DP. This particular MOSFET has a Vgsth between 1-3V, which is significantly greater than the above mentioned output voltage for the HO and LO pins.

Are these the correct values for the voltage output by the HO and LO pins to the MOSFET gates or is the actual value higher? If these are not the correct values, could you let me know what voltage is output by the HO and LO pins?

Thanks,

Eric

  • Hello Eric 

    VOHL is defined as V(VCC)-V(LO) (Please see the test condition). For example, if V(VCC)=7V and VOHL is 0.25V, then the LO-GND voltage will be 6.75V (7-0.25=6.75)

    VOHH is defined as V(HB)-V(HO) (Please see the test condition). For example, if V(HB)-V(SW)=7V and VOHL is 0.45V, then the HO-SW voltage will be 6.55V (7-0.45=6.55)

    - Eric Lee ( Applications Engineering)