HV748DB1
HV748 鹵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 鹵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鈥檚 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
鹵1.8A for pulsing, when MC0=1 and MC1=1, with up to 鹵75V
swings. When in mode 1, all the output stages drop the peak
current to 鹵410mA for low-voltage CW mode operation to
save power. Two 鏗俹ating 9VDC power supplies, referenced
to V
PP
and V
NN
, supply the P- and N-type power FET gate
drivers. This pulser waveform鈥檚 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
CC
voltage of the demo
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 2.5k惟, 1.0W resistor. Also, a
coaxial cable can be used to connect the user鈥檚 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
Control
PIN1
NIN1
GREF
V
LL
V
DD
V
SUB
V
PF
V
PP
RGND
Level
Translator
P-Driver
TXP1
HV
OUT
1
HV748
Level
Translator
TXN1
N-Driver
GND
1 of 4 Channels Shown
V
SS
GND
V
NF
V
NN
RGND
V
NN
+ 9V
0V to -75V
1
2
3
4
5
6
7
8
9
