1 Description
The STHV800 is an octal, monolithic, high-voltage and high-speed pulse generator. It is
designed for medical ultrasound applications, but can be used for other piezoelectric,
capacitive or MEMS transducers.
The device integrates a controller logic interface circuit (compatible with both 1.8 V and 3.3
V input signals), level translators, MOSFET gate drivers, noise blocking diodes, and high
power P-channel and N-channel MOSFETs as the output stage for each channel. These
MOSFETs are capable of providing more than 2 A of peak output current. Each channel
has a dedicated bridge in order to reduce power dissipation and jitter during continuous
wave mode (peak current is limited to 0.3 A). This CW bridge has dedicated power supplies
(HV_CW) which are fully independent on the main HV supplies.
These HV_CW supplies can be shorted to the HV supplies. The fundamental structure of
each channel also consists of active clamping to ground circuitry, anti-leakage and anti-
memory block, a thermal sensor to protect the device and an integrated TR-switch (just 8 Ω
as equivalent resistor ) to connect the HV output to its LV output, guaranteeing strong
decoupling during the transmission phase.
The eight independent T/R switches can be used in both a dedicated RX chain per channel
or in a multiplexing configuration.
The clamp circuit has a current capability up to 2 A and works directly on the output pin,
carrying this node exactly to zero. This feature allows minimized injection change during
the transition from clamp to RX state.
In addition, the STHV800 includes self-biasing circuitry which allows very low power
consumption during the RX phase (down to 200 µW global power dissipation) and thermal
shutdown block sensing by an external dedicated pin (THSD).
One of the main benefits of this device is that it requires very few external components:
only decoupling capacitors on the HV and LV supplies, and a resistor to pull up the THSD
pin (moreover, this resistor can be shared by many devices).
Each channel is driven independently by only 2 digital bits, which in CW mode become one
bit. An external clock can be used with the STHV800 to synchronize all the input signals.
This feature, however, is optional: if the CK pin is tied to ground the device works in
asynchronous mode.
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