PDu100 Micro Piezo Driver

The PDu100 is the industry’s smallest and lightest driver for piezoelectric actuators. The PDu100 can drive two-wire piezoelectric actuators and benders up to +/-100 V. The PDu100 can also drive three-wire piezoelectric benders and stack actuators up to +100 V. Applications include battery powered robotics, piezoelectric motors, and ultra low-power positioning and manipulation systems.

The PDu100 is protected against short circuit, current overload, and excessive temperature. A shutdown pin is also provided that reduces the supply current to 1 mA when pulled low. The output voltage range and gain of the PDu100 is customizable to meet the requirements of OEM applications.

PDu100 Micro Piezo Driver
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Compatible Actuators

Stack Actuators up to 100V
Plates and Tubes Up to +/-100V
Two Wire Benders Up to +/-100V
Three Wire Benders 0 to 100V with 100V bias

Specifications

Power Supply 3 V to 5.5 V
Max Unipolar Output +100 V
Max Bipolar Output >+/-100 V
RMS Output Current 33 mA
Average DC Current 15 mA
Power Bandwidth 3.2 kHz
Peak Output Current 100 mA
Signal Bandwidth 60 kHz (unloaded)
Dimensions 11.8 x 12.9 mm (0.46 x 0.51 in)
Weight 560 mg (0.018 oz)
Gain 27.5 V/V
Input Voltage 0.5 Vs +/- 1.8V
Input Offset +/-100 mV
Load Capacitance Unlimited
Overload Protection Thermal and current
Noise 70mV RMS (10uF Load)
Environment -40 to 70 C (-40 to 158 F)
Quiescent Current 25 mA (1 mA in Shutdown)

Connection Diagram

pdu100 connection diagram

Operation

The system block diagram is illustrated in Figure 2. A boost converter generates a high-voltage rail to supply a pair of complementary amplifiers. A single output can be used to drive a unipolar load up to +100 V or both amplifiers can be used to produce +/-100 V.

The input is selectable between a unipolar signal biased at half the supply voltage or a bipolar signal. The amplifier gain is 27.5 so a 3.6 Vp-p input will produce a 100 Vp-p output. Both amplifier channels are biased at half the output range (50 V).

pdu100 operation 339w

The overall system gain is determined by the output configuration. The possible combinations are listed below.

 

Output Type Gain Input Range Output Range
Unipolar 27.5 0.5 Vs +/- 1.8V 100 V
Bipolar 55 0.5 Vs +/- 1.8V +/-100 V

System gain and voltage range

 

Both outputs are biased at approximately half the HV bus voltage, e.g. 50 V. The output voltage equations are listed below.

 

Output Type Output Equation
Unipolar \( 27.5 \times \left(V_{in}-\frac{V_S}{2} \right) + 50 \)
Bipolar \( 55 \times \left(V_{in}-\frac{V_S}{2} \right) \)

System gain and voltage range

 

The gain and output voltage ranges can be customized by contacting info@piezodrive.com.

Example Applications

Some typical application circuits are shown below. The optional output resistance \( R_O \) is used to reduce noise as described in “Noise”. For general purpose applications, the recommended value for \( R_O \) is 270 Ohms.

pdu100 examples a 296w
pdu100 examples b 338w

Power Bandwidth

Calculate Power Bandwidth

The output slew-rate of the PDu100 is 1 V/us. Therefore, the maximum frequency sine-wave is
$$ f_{max}=\frac{1 \times 10^6}{\pi V_{L(p-p)}} .$$ The power bandwidth for each voltage range is listed below

Voltage Range Power Bandwidth
60 V 5.3 kHz
70 V 4.5 kHz
90 V 3.5 kHz
100 V 3.2 kHz

Unloaded power bandwidth

With a capacitive load, the power bandwidth is limited by the maximum output current. For a sine wave
$$ f_{pwr}=\frac{I_{av}}{V_{L(p-p)} \pi C_L } .$$ The average DC current is the average current flowing in either the positive or negative direction. For a sine wave, the average DC current is related to the RMS current by
$$I_{av}=\frac{\sqrt{2}}{\pi} I_{rms}.$$ The power bandwidth for a range of load capacitances and output voltages is listed below.

Load (uF) 60 V 100 V +/-100 V
0.01 5300 3200 2300
0.03 2600 1500 790
0.1 790 470 230
0.3 260 150 79
1 79 47 23
3 26 15 8.0
10 8.0 4.8 2.4
30 2.7 1.6 0.7

Power bandwidth versus voltage range and capacitance (in Hz)

In the following figure, the maximum peak-to-peak voltage is plotted against frequency for a range of capacitive loads.

pdu100 pbw 334w

Noise

The output voltage of the PDu100 contains switching noise from the boost converter and random noise from the high-voltage amplifier. The amount of noise seen by the load capacitance is determined by the size of the output resistance and signal bandwidth. If there is no output resistance, a value of 100 Ohms can be used to calculate the bandwidth and predict noise.

To determine the output resistance required for a particular noise level, the required bandwidth should be selected from Figure 9 below. The correct resistance can then be calculated from
$$ R_O = \frac{1}{2 \pi f_{bw} C_L }$$

pdu100b noise 380w

The noise measurements are performed with a static input voltage. When current is drawn from the output, the ripple will increase due to action from the boost converter.

Signal Bandwidth

The unloaded small signal bandwidth of the PDu100 is approximately 60 kHz. With a capacitive load, the signal bandwidth is determined by the output resistance, that is
$$ f_{bw} = \frac{1}{2 \pi R_0 C_L} .$$

Supply Current

The supply current \( I_S \) is related to the load current \( I_L \) through the following power balance equation
$$ I_S = I_L \frac{105}{ V_S \times 0.7} ,$$ where \( V_S \) is the supply voltage. With a capacitive load and sinusoidal voltage, the peak and average output current is
$$ I_{L(pk)} = \pi f C_L V_{L(p-p)} ,$$ $$ I_{L(av)} = 2 f C_L V_{L(p-p)} ,$$ where \( V_L \) is the peak to peak voltage across the load capacitance. The average supply current can be written $$ I_{S(av)} = 2 f C_L V_{L(p-p)} \frac{105}{V_S \times 0.7} .$$

Power Dissipation

With a capacitive load, power dissipation is the product of supply voltage and the average current, that is
$$ P_D = V_S \times I_{S(av)} $$ When operating at full power bandwidth, the worst-case power dissipation is approximately 2.5 W. The thermal impedance of the PDu100 from junction to ambient is 45 K/W . Therefore, the maximum temperature rise is approximately 90 degrees C above ambient.

When continuous power dissipation above 1 W is required, the PDu100 is designed to be mounted onto a thermal sink using a thermally conductive double-sided adhesive such as 3M 8940 or Bergquist BOND-PLY 100.

Enable / Shutdown

The Enable pin can be pulled low to disable the amplifier and reduce the quiescent current to 1 mA. It can be driven by a logic output or an open collector output. The recovery time after a shut-down is 2 ms.

Overload Protection

The PDu100 is protected against over-current and thermal overload. If the temperature exceeds 150 degrees C, the amplifier will be disabled until the temperature reduces.

Dimensions

pdu100 dims 302w

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