Data Sheet

3
APPLICATION EXCELLENCE
Upper-side Gate Drive Voltage Measurement
An upper-side device has an applied gate voltage floating above
ground. Any conventional HV differential probe with high tip
capacitance in parallel with C
GE
or C
GS
, and/or high impedance
and large loop inductance in series with the gate drive impedance
will at best load the gate drive signal and at worst cause circuit
malfunction. Measurement interference from the low-side device
switching can also interfere with proper upper-side gate voltage
measurement. The HVFO is optimized for the best upper-side gate
drive voltage measurements.
Floating Control or Sensor Signal Measurements
The HVFO measures only the low voltage sensor voltage across its high impedance input leads. Total load on the device
under test (DUT) is very small. Furthermore, the low lead loop inductance, >100dB CMRR, and low attenuation provide
superior signal delity, noise and rejection.
The HVFO (yellow trace) and a conventional HV differential probe
(magenta trace) capture an upper-side gate drive signal. The HVFO
exhibits a classic, textbook shape while the HV differential probe has
more loading and lower-side device high dV/dt signal interference.
In this upper-side gate drive measurement, the gate drive is captured
when current is sinking into the half-bridge phase in a cascaded
H-bridge. The Miller effect can be clearly observed.
HV Fiber-optically
Isolated Probe
Conventional HV
Differential Probe
The HVFO measures only the small signal voltage with high probe
input impedance; therefore, total DUT load is very small. Low tip
loop inductance and 140 dB CMRR provide superior signal delity,
noise and rejection.
The HV differential probe measures the full common mode + sensor
voltage. Therefore, the DUT load is ~100 times larger than with the
HVFO. This excessive load will impact the signal delity and may even
cause the circuit to malfunction.