SLVAE59A February   2019  – April 2022 DRV8242-Q1 , DRV8243-Q1 , DRV8244-Q1 , DRV8245-Q1 , DRV8343-Q1 , DRV8702-Q1 , DRV8702D-Q1 , DRV8703-Q1 , DRV8703D-Q1 , DRV8803 , DRV8804 , DRV8805 , DRV8806 , DRV8860 , DRV8873 , DRV8873-Q1 , DRV8874 , DRV8874-Q1 , DRV8876 , DRV8876-Q1 , DRV8935 , DRV8955

 

  1.   Trademarks
  2. 1Introduction
    1. 1.1 Types of Solenoids
  3. 2Solenoid Driving Typologies
    1. 2.1 Low-Side and High-Side Configuration
    2. 2.2 Half-Bridge and H-Bridge Driver Configurations
  4. 3Basics of Driving Solenoid Loads
    1. 3.1 Current Control
    2. 3.2 Fast Discharging Circuits
      1. 3.2.1 Freewheeling and Clamping
      2. 3.2.2 Passive Voltage Clamping
  5. 4DRV Motor Driver Features for Solenoid Driving
    1. 4.1 Current Sensing and Regulation Solutions
    2. 4.2 Independent Low-/High-Side Driving
    3. 4.3 Half-Bridge Driving
    4. 4.4 Integrated and Gate Driver H-Bridges
  6. 5Summary
  7. 6Revision History

2.2 Half-Bridge and H-Bridge Driver Configurations

The half-bridge driver uses two MOSFETs to control the current through a solenoid; one MOSFET to forward drive the solenoid and the other to recirculate current.

The H-bridge driver uses four MOSFETs, or two half-bridges joined by a load, to control current through a solenoid. With four MOSFETs, bidirectional current control is possible. This makes H-bridge drivers a good choice for single-coil and latching or dual-coil relays.

The H-bridge and half-bridge configurations can be seen in Figure 2-4 and Figure 2-5.

GUID-ED291D75-C923-4C3A-8544-0E1D630F4BA9-low.gif Figure 2-4 H-Bridge Drive and Recirculation Current Paths
GUID-494C6DA0-E60C-46CD-86C1-681CA835B2E7-low.gif Figure 2-5 Half-Bridge Drive and Recirculation Current Paths

While the half-bridge can only enable slow decay, the half-bridge integrates the freewheeling diode, which is typically an external component. This further reduces the solution size. There is also the benefit of flexibility between driving high- or low-side loads with the half-bridge.

The H-bridge driver can enable both slow and fast decay (coast) by recirculating current with either high- or low-side MOSFETs. Figure 2-6 shows how an H-Bridge can be utilized to drive a conventional solenoid valve with high-side recirculation.

GUID-52C776F2-8D44-4A72-918B-FA4BA4427FA8-low.gif Figure 2-6 H-Bridge Configuration Utilized to Drive a Solenoid Valve

An H-Bridge can also be used as an effective fast discharge circuit. Fast decay can be accomplished by turning off the MOSFETs and allowing current to flow through the body diodes. This results in an opposing voltage to the solenoid current equal to VM plus the forward voltage of the two body diodes. Figure 2-7 shows current flow for fast decay with H-Bridge.

GUID-FD726CF6-4B57-4E5A-9B9C-9618FCB01A4B-low.gif Figure 2-7 H-Bridge Fast Decay

If fast decay and improved system thermal performance are desirable, an H-Bridge configuration could be a good fit.