VDD

NIN n

PIN n

VPP

VPF

VDN

Input

Buffer

VNN

HVGND

AGND

Level

Shifter

VLL

EN

OTP

Temp

Sensor

Buffer

Buffer

Level

Shifter

Down

Vout n

MOD

VSUB

VNF

Active

Damper

Level

Shifter

Up

Regulates

LM96551

www.ti.com

SNAS511B – OCTOBER 2011 – REVISED MAY 2013

DC Characteristics

Unless otherwise stated, the following conditions apply.

VLL = +3.3V, VDD =

Symbol

Parameter

Conditions

Min

Typ

Max

Unit

Low Input “LO” threshold

1

V

High Input “HI” threshold

2.3

V

input current

1

µA

Overview

The LM96551 pulser provides an 8-channel transmit side solution for medical ultrasound applications suitable for

integration into multi-channel (128/256 channel) systems. Its flexible, integrated ±50V pulser architecture enables

low-power designs targeting portable systems. A complete system can be designed using Texas Instrument’s

companion LM965XX chipset.

Figure 3. Block Diagram of High-Voltage Pulser Channel

A functional block diagram of the LM96551 is shown in Figure 3. It has an input buffer at its CMOS logic

interface, which is powered by VLL (2.5 to 5.0V). When EN=HI, driving a channel’s inputs (PIN n or NIN n) HI will

pulled to either the positive or negative supplies, VPP or VNN by power MOSFETs.

When PIN and NIN are both LO, Vout is actively clamped to GNDHI at 0V. This clamping reduces harmonic

distortions compared to competing architectures that use bleeding resistors for implementing the return to zero of

the output. The user must avoid the condition in which PIN and NIN are both HI simultaneously, as this

will damage the output stage!

The impedance of the output stage can be controlled via the Mode-pin. When the Mode = HI as shown, only one

output transistor pair drives the output resulting in a peak current of 600 mA at VPP = -VNN = 50V. When

Mode=LO, a peak-current of 2A is achievable resulting in faster transients at the output. However, faster output

transients can lead to significant overshoot of the output signal. This can be avoided using the lower drive current

option.

Copyright © 2011–2013, Texas Instruments Incorporated

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