# PDu100 Micro Piezo Driver

The PDu100 is an extremely small and lightweight 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.

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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 | 0 to 70 C (-32 to 158 F) |

Quiescent Current | 25 mA (1 mA in Shutdown) |

### 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).

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 [email protected]

### 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.

### Power Bandwidth

The power bandwidth is the maximum frequency periodic signal that can be reproduced without distortion. The power bandwidth calculator determines the maximum operating frequency and required power for a given load capacitance. The calculator includes the effects of current limit, slew-rate, and signal bandwidth.

The calculator does not include the time-constant of the peak current limit, and therefore may become inaccurate when the power bandwidth is below 50 Hz.

### 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

$$ R_O = \frac{1}{2 \pi f_{bw} C_L }$$

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.