DRV2700RGPT Integrated Circuits (ICs)

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1. Description

The DRV2700RGPT device is a single-chip piezo driver with an integrated 105-V boost switch, integrated power diode, and integrated fully-differential amplifier. This versatile device is capable of driving both high- voltage and low-voltage piezoelectric loads. The input signal can be either differential or single-ended and AC or DC coupled. The DRV2700 device supports four GPIO-controlled gains: 28.8 dB, 34.8 dB, 38.4 dB, and 40.7 dB. The boost voltage is set using two external resistors. The boost current-limit is programmable through the R(REXT) resistor. The boost converter architecture does not allow the demand on the supply current to exceed the limit set by the R(REXT) resistor which allows the user to optimize the DRV2700 circuit for a given inductor based on the desired performance requirements. Additionally, this boost converter is based on a hysteretic architecture to minimize switching losses and therefore increase efficiency. A typical startup time of 1.5 ms makes the DRV2700 device an ideal piezo driver for coming out of sleep quickly. Thermal overload protection prevents the device from damage when overdriven.

2. Features

    1. 100-V Boost or 1-kV Flyback Configuration

    2. ±100-V Piezo Driver in Boost + Amplifier Configuration

        – 4 GPIO-Adjustable Gains

        – Differential or Single-Ended Output

        – Low-Voltage Control

        – AC and DC Output Control

    3. 0 to 1-kV Piezo Driver in Flyback Configuration

        – Low-Voltage Control

        – AC and DC Output Control

    4. Integrated Boost or Flyback Converter

        – Adjustable Current-Limit

        – Integrated Power FET and Diode

    5. Fast Startup Time of 1.5 ms

    6. Wide Supply-Voltage Range of 3 to 5.5 V

    7. 4-mm × 4-mm × 0.9-mm VQFN package

    8. 1.8-V Compatible Digital Pins

    9. Thermal Protection

3. Applications

    1. Piezo Positioning Actuators

    2. Piezo Sounder Driver

    3. Piezo Inkjet Printer

    4. Piezo Transducers 

    5. Piezoelectric Micropumps

4. Pin configuration

5. Pin Description

6. Boost Converter and Control Loop

The DRV2700 device creates a boosted supply rail with an integrated DC-DC converter that can go up to 105 V. The switch-mode power supplies have a few different sources of losses. When boosting to very high voltages, the efficiency begins to degrade because of these losses. The DRV2700 device has a hysteretic boost design to minimize switching losses and therefore increase efficiency. A hysteretic controller is a self-oscillation circuit that regulates the output voltage by keeping the output voltage within a hysteresis window set by a reference voltage regulator and, in this case, the current-limit comparator. Hysteretic converters typically have a larger ripple as a trade off because of the minimized switching. This ripple may vary depending on the output capacitor and load. The power FET and power diode of the boost converter are both integrated within the device to provide the required switching while minimizing external components. Additionally, the boost voltage output (BST) can be easily fed into the high-voltage amplifier through the adjacent pin (PVDD) to help minimize routing inductance and resistance on the board.

7. High-Voltage Amplifier

When using the high-voltage amplifier in conjunction with the boost converter, the PVDD pin is located next to the BST pin to immediately feed the high voltage signal back into the device to power the amplifier. The DRV2700 device was designed as a differential amplifier. A major benefit of the fully differential amplifier is the improved common-mode rejection ratio (CMRR) over single-ended input amplifiers. The increased CMRR of the differential amplifier reduces sensitivity-to-ground offset that is related noise injection which is important in lownoise systems. The high-voltage amplifier can be used in a single-ended DC input configuration to provide a DC output on the OUT+ and OUT– pins. The amplifier is very linear across the full voltage range and by using a DAC (digital-toanalog converter) input, the output can be controlled with very good granularity. Precautions must be taken into thermal concerns of this amplifier because high frequencies, voltage, and capacitive load combinations can overheat the device. See the Piezo Load Selection section for a general guideline.

8. Fast Start-Up

The DRV2700 device features a fast startup time, which is beneficial for the device come out of shutdown very quickly. When the EN pin transitions from low to high, the boost supply is turned on, the input capacitor is precharged to VDD / 2, and the amplifier is enabled in a 1.5 ms (typical) total start-up time. When AC coupled with larger input capacitors, the input can require additional time to charge up to VDD / 2. Because the charging current on the input capacitors are not ensured to be exactly the same, a non-zero differential value can exist during startup. Although this differential output voltage (voltage pop) during startup is not specified, it should be fairly small and not exceed 2 V.

9. Adjustable Boost Voltage

The output voltage of the integrated boost conver Adjusted by a resistive feedback divider between Boost Output Voltage (BST) and Feedback Pin (FB). The boost voltage should be programmed to a value Greater than the maximum peak signal voltage the user would expect from the DRV2700 amplifier. reduce Boost voltage allows for better system efficiency and should therefore be used with lower amplitude signals application. The minimum required boost voltage should be used to save power and heat dissipation. The maximum allowable boost voltage is 105 V.

10. Internal Charge Pump

The DRV2700 device has an integrated charge pump to provide gate drive for internal nodes. The output of this charge pump is placed on the VPUMP pin. An X5R or X7R storage capacitor with a value of 0.1 µF and a voltage rating of 10 V or greater must be placed at this pin for proper operation. This pin and voltage should not be used as an external reference or driver.

11. Application Information

The DRV2700 is intended to drive piezo loads. This includes: capacitive loads, piezo sounders, piezo valves, piezo positioning actuators, piezo micropumps, piezo polymers and more.