PDu150 – Three Channel Ultra-Low Noise 150V Piezo Driver

The PDu150 is a complete miniaturized power supply and ultra-low noise driver for up to three 100V, 120V or 150V piezoelectric stack actuators. Output currents up to 100mA per channel are developed at frequencies up to 80 kHz with exceptionally low noise. The three channels can be connected in parallel to produce an output current of up to 300mA. The noise level of 26uV is typically an order of magnitude better than the best full-size instruments even though the output power is similar. With a peak-to-peak resolution exceeding one part-per-million or 20-bit, the PDu150 exceeds the most demanding requirements in semiconductor machinery, scanning probe microscopy, optics, vibration control, and nanopositioning.

The PDu150 is protected against short-circuit, average current overload, and excessive temperature. Passive cooling is available for low power applications or the integrated fan can be used for power dissipations above 5W. The PDu150 can be mounted with four M2.5 screws. The PCB mounting version (PDu150-PCB) is supplied with headers for direct mounting onto a host motherboard.

PDu150 Three Channel Ultra-low Noise 150V Piezo Driver Amplifier
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Specifications

Power Supply +24 V (+/-10%)
Output Voltage -30 V to +150 V
Peak Current 100 mA (300 mA single channel)
RMS Current 78 mA (235 mA single channel)
Power Bandwidth 80 kHz (150 Vp-p)
Signal Bandwidth 180 kHz
Slew Rate 38 V/us
Gain 20 V/V
Input Impedance 9.16 kOhm (Input), 3.3 kOhm (Offset)
Input Offset +/- 5 mV
Load Unlimited
Output Noise 26 uV RMS (1 uF load, 0.03 Hz to 1 MHz)
Protection Short circuit, over-current, and temperature
Quiescent Current 100 mA (10 mA in shutdown)
Connectors Screw terminals (AWG 20-30)
Dimensions 76 x 40 x 44 mm (L x W x H)
Environment -40C to 60C (-40F to 140F)
Weight 80 gram

Connection Diagram

PDu150 Connection
Pin Function
G Ground
EN Enable
OS Offset
R- -2V Reference
R+ +10V Reference

Operation

The amplifiers have differential inputs where the negative input can be connected to an external reference or the internal offset generator. A precision +10V and -2V reference voltage (R+ and R-) are provided to allow external potentiometers to generate the amplifier inputs. The amplifier outputs use a novel low-noise differential architecture that cannot be connected to ground, for example, to the ground lead of an earthed oscilloscope.

PDu150 Operation

PDu150 Block Diagram

Offset Voltage Configuration

The offset voltage can be set from either the internal potentiometer or by an external source by configuring the jumper LK1 to either “Internal” or “External”. When using the internal offset source, the offset voltage is set by connecting a multimeter across the output and varying the potentiometer until the desired offset is obtained.

In the external offset mode, the offset voltage is determined by the voltage applied to the OS pin. The offset voltage can be set to zero by grounding the OS pin, which is the standard configuration.

Single Channel Mode

The power bandwidth and output current can be tripled by connecting three amplifiers in parallel as shown below. A third configuration with two parallel channels and one single channel is also possible.

PDu150 SingleChannel

Single Channel Mode

Using the Reference Voltages

A precision +10V and -2V reference voltage (R+ and R-) is provided to allow an external potentiometer to generate the amplifier input, as shown below. Multiple potentiometers can be used for multiple channels. The 10uF capacitor reduces the noise bandwidth but is not strictly necessary. The capacitor should preferably be a film type but ceramic is acceptable in most applications.

PDu150 References2

Using the Reference Voltages

Output Current

The peak output current is 100mA per channel or 300mA for three channels in parallel. In addition, the maximum average current is 35mA per amplifier. The average current is useful for calculating the power dissipation and average supply current. For a sine wave, the average positive output current is equal to $$ I_{av} = \frac{ \sqrt{2} }{ \pi } I_{rms} = \frac{1}{\pi} I_{pk}. $$

Supply Current

The quiescent power for the amplifier is approximately 2 W or 85 mA. This can be reduced to <10 mA by pulling the Enable pin low with an open collector circuit. If the fan is used, the quiescent power is increased by 0.5W,

$$ I_s= \frac{200 \times \left( I_{av} + 0.010 \right)}{24} $$ where \(I_{av}\) is the total average output current. The maximum supply current is 0.9A at full power.

Power Bandwidth

Power Bandwidth Calculator

Power Bandwidth (Three Channels in Parallel)

The nominal slew-rate of the PDu150 is 38 V/us. Therefore, the maximum frequency sine-wave is

$$ f_{max}= \frac{38 \times 10^6}{\pi~V_{L(p-p)}} $$ With a capacitive load, the power bandwidth is limited by the output current. The maximum frequency sine wave is

$$ f_{pwr} = \frac{I_{pk}}{\pi V_{L(p-p)}~C_L} $$ where \(I_{pk}\) is the peak current limit, \(V_{L(p-p)}\) is the peak-to-peak output voltage, and \(C_L\) is the effective load capacitance. The power bandwidth for a range of load capacitance values is listed below. Note that when all channels are connected in parallel, the output current and power bandwidth are tripled.

The maximum peak-to-peak voltage is plotted below.

PDu150 PowerBandwidth

Maximum Frequency Sine Wave versus Load Capacitance
(per Channel)

Load Voltage Range
Cap 50 100V 150V
10 nF 64 kHz 32 kHz 21 kHz
30 nF 21 kHz 11 kHz 7.1 kHz
100 nF 6.4 kHz 3.2 kHz 2.1 kHz
300 nF 2.1 kHz 1.1 kHz 710 Hz
1 uF 640 Hz 320 Hz 210 Hz
3 uF 210 Hz 110 Hz 71 Hz
10 uF 64 Hz 32 Hz 21 Hz
30 uF 21 Hz 11 Hz 7 Hz

Power Bandwidth versus Load Capacitance
(per Channel)

Small Signal Bandwidth

PDu150 SignalBandwidth

Small Signal Frequency Response

Load Capacitance Bandwidth
No Load 180 kHz
10 nF 105 kHz
30 nF 40 kHz
100 nF 11 kHz
300 nF 3.8 kHz
1 uF 1.0 kHz
3 uF 320 Hz
10 uF 62 Hz
30 uF 24 Hz

Small Signal Bandwidth versus Load Capacitance (-3dB)

Noise

The output noise contains a low frequency component (0.03 Hz to 10 Hz) that is independent of the load capacitance; and a high frequency component (10 Hz to 1 MHz) that is inversely related to the load capacitance.

Note that many manufacturers quote only the AC noise measured by a multimeter (20 Hz to 100 kHz) which is usually a gross underestimate.

The noise is measured with an SR560 low-noise amplifier (Gain = 1000), oscilloscope, and Agilent 34461A Voltmeter. The low-frequency noise is plotted below. The RMS value is 15 uV with a peak-to-peak voltage of 100 uV.

The high frequency noise (10 Hz to 1 MHz) is listed in the table on the right versus load capacitance. The total noise from 0.03 Hz to 1 MHz can be found by square summing the RMS values, that is $$ \sigma = \sqrt{ \sigma_{LF}^2 + \sigma_{HF}^2 } $$

PDu150 LFNoise

Low Frequency Noise from 0.03 Hz to 10 Hz.

Load Capacitance HF Noise RMS Total Noise RMS
10 nF 450 uV 450 uV
30 nF 170 uV 171 uV
100 nF 60 uV 62 uV
300 nF 34 uV 37 uV
1 uF 21 uV 26 uV
3 uF 16 uV 23 uV
10 uF 16 uV 22 uV
30 uF 18 uV 23 uV

High Frequency Noise (10 Hz to 1 MHz)
and Total Noise (0.03 Hz to 1 MHz)

Overload Protection / Shutdown

The PDu150 is protected against short-circuit and average current overload.
The amplifier can be shutdown manually by pulling the Enable pin low with an open-collector, or open-drain circuit. The Enable pin normally floats at 5V and should not be driven directly.

Heat Dissipation

The heat dissipation is approximately $$ P_d = 200 \times \left( I_{av} + 0.010 \right) $$

For example, with a sinusoidal output, the power is $$ P_d = 200 \times \left( V_{L(p-p)} C_L f + 0.010 \right) $$

For low-current applications that dissipate less than 5W, the heatsink fan may be removed. If the power dissipation is above 5W, forced air or the included fan is required.

Safety

This device produces hazardous potentials and should be used by suitably qualified personnel. Do not operate the device when there are exposed conductors. Parts of the circuit may store charge so precautions must also be taken when the device is not powered.

Dimensions

The mounting posts accept M2.5 screws. For the PCB mounting version (PDu150-PCB), a schematic and footprint library is available for Altium Designer, contact info@piezodrive.com to receive the file.

Dimensions (mm)

PDu150 Dimensions