HV748DB1 Datasheet, PDF (1/9 Pages) Supertex, Inc – HV748 ±75V 1.25A Ultrasound Pulser Demo Board

HV748DB1
HV748 ±75V 1.25A Ultrasound Pulser Demo Board
Introduction
The HV748 is a monolithic 4-channel, high speed, high
voltage, ultrasound transmitter pulser. This integrated, high
performance circuit is in a single 7x7mm, 48-lead QFN
package.
The HV748 can deliver up to ±1.25A source and sink
current to a capacitive transducer. It is designed for
medical ultrasound imaging and ultrasound material NDT
applications. It can also be used as a high voltage driver
for other piezoelectric or capacitive MEMS transducers, or
for ATE systems and pulse signal generators as a signal
source.
HV748’s circuitry consists of controller logic circuits, level
translators, gate driving buffers and a high current and high
voltage MOSFET output stage. The output stages of each
channel are designed to provide peak output currents over
±1.8A for pulsing, when MC0=1 and MC1=1, with up to ±75V
swings. When in mode 1, all the output stages drop the peak
current to ±410mA for low-voltage CW mode operation to
save power. Two floating 9VDC power supplies, referenced
to V_PP and V_NN, supply the P- and N-type power FET gate
drivers. This pulser waveform’s frequency upper limit is
20 MHz depending on the load capacitance. One HV748
can also be used as four damping circuits to generate fast
return-to-zero waveforms by working with another HV748
as four pulsing circuits. It also has built-in under-voltage and
over-temperature protection functions.
Designing a Pulser with HV748
This demo board data sheet describes how to use the
HV748DB1 to generate the basic high voltage pulse
waveform as an ultrasound transmitting pulser.
The HV748 circuit uses the DC coupling method in all
level translators. There are no external coupling capacitors
needed. The V_PP and V_NN rail voltages can be changed
rather quickly, compared to a high voltage capacitor gate
coupled driving pulser. This direct coupling topology of the
gate drivers not only saves two high voltage capacitors per
channel, but also makes the PCB layout easier.
The input stage of the HV748 has high-speed level
translators that are able to operate with logic signals of
1.2V to 5.0V and are optimized at 2.5V to 3.3V. In this demo
board, the control logic signals are connected to a high-
speed ribbon cable connector. The control signal logic-high
voltage should be the same as the V voltage of the demo
CC
board, and the logic-low should be reference to GND.
The HV748DB1 output waveforms can be displayed by using
an oscilloscope probe directly connected to the test point
TX1~4 and GND. The soldering jumper can select whether
or not to connect the on-board equivalent-load, a 330pF,
200V capacitor, parallel with a 2.5kΩ, 1.0W resistor. Also, a
coaxial cable can be used to connect the user’s transducer
to easily drive and evaluate the HV748 transmitter pulser.
Application Circuit
+2.5V +9V
+75V V_PP-9V 0V to +75V
V_CC
OTP
EN
MC0
MC1
Logic ^PIN1
Control _NIN1
GREF
V_LL
V_DD
V_SUB V_PF
V_PP
Level
Translator
P-Driver
HV748
Level
Translator
N-Driver
RGND
TXP1
TXN1
1 of 4 Channels Shown
V_SS
GND
V_NF
V_NN
RGND
V_NN + 9V 0V to -75V
HV_OUT1
GND