HV7351 Ultrasound Tx Beamformer Evaluation Board User’s Guide
DS50002375A-page 18
2015 Microchip Technology Inc.
2.3
EVALUATING THE HV7351 ULTRASOUND TX BEAMFORMER EVALUATION
BOARD
The best way to evaluate the HV7351 Ultrasound Tx Beamformer Evaluation Board is
to explore the circuit and measure the voltages and currents with a Digital Voltage
Meter (DVM) while probing the board with an oscilloscope.
2.4
NORMAL OPERATION
The HV7351 Ultrasound Tx Beamformer Evaluation Board should be powered up with
multiple lab DC power supplies that feature current-limiting functions.
To meet the typical loading condition when using the high-impedance probe of an
oscilloscope, the on-board dummy load (330 pF||2.5 k
) should be connected to the
high-voltage pulser output through the solder jumper. To evaluate different loading
conditions, the values of the RC may be changed within the current and power limits of
the device.
In order to drive the user’s piezoelectric transducers with a cable, the output load
impedance should be properly matched to avoid cable and transducer reflections.
A 70 to 75 k
coaxial cable is recommended. The coaxial cable end should be
soldered to the TX1 - TX8 and GND directly with very short leads. If the user’s load is
being used, the on-board dummy load should be disconnected by cutting the small
shorting copper trace in between the 0k
resistors (R8, R12, R29, R30, R10, R37, R52
and R53) and the eight resistor pads. They are shorted by factory default.
All on-board test points are designed to work with the high-impedance probe of an
oscilloscope. Some probes may have limited input voltage range. When using the
probe on these high-voltage test points, make sure that the V
PP
/V
NN
voltages do not
exceed the probe limit. When using the high-impedance oscilloscope probe on the
on-board test points, it is important to have short ground leads to the circuit board
ground plane.
WARNING
Carefully double-check the voltage of every supply rail, current-limit value and
polarity individually to avoid board damage.
Take extreme care while connecting the supplies to the board since
connecting them incorrectly to the wrong pins could result in permanent
damage to the entire board.