IR2112 High and Low Side Driver IC

Key Features

• High-Side and Low-Side Drive: Contains two independent drivers, one for the high-side switch and one for the low-side switch.
• Output Voltage Range: Can drive a high-side N-channel MOSFET with a supply voltage of up to V_B + 0.3 V.
• Gate Drive Voltage: Capable of driving gate voltages up to +10 V to +20 V (typically +10 V recommended).
• Bootstrap Operation: Utilizes a bootstrap capacitor for high-side gate driving, which allows the driver to function with a lower supply voltage.
• Isolation: Features provide a level of electrical isolation between the high-side and low-side circuits.
• Desaturation Protection: Built-in protection against accidental over-current conditions in IGBTs.
• Typical Operating Frequency: Suitable for applications running at switching frequencies up to 500 kHz.

Pin Configuration

The IR2112 comes in a DIP-16 or similar package with the following pin configuration (refer to the specific datasheet for exact pin arrangement):

Copy       +--------------+
    1  | VCC        LO|  8
    2  | VS         COM|  7
    3  | HS         HO |  6
    4  | VB         HS |  5
   +--------------+

Pin Description

1. VCC: Supply voltage for the low-side driver.
2. COM: Common ground reference for the lower side (low-side driver).
3. LO: Output for the low-side gate driver.
4. VS: Source terminal of the high-side MOSFET. It connects directly to the high-side source.
5. VB: Supply voltage for the high-side driver. Usually connected to a bootstrap capacitor.
6. HO: Output for the high-side gate driver.
7. HS: High-side source pin; connects to the load.
8. nFAULT: Depending on the specific version, this pin may serve a specific fault detection signal.

Operating Principles

The IR2112 operates by controlling the gate voltage of two transistors (typically MOSFETs) to create a switching cycle. The following describes the key operating modes:

1. Low-Side Driving: The LO output directly drives the gate of the low-side MOSFET, allowing current to flow from the source to the load when activated.
2. High-Side Driving: The HO output drives the gate of the high-side MOSFET. This output is bootstrapped to a higher voltage, allowing it to turn on the high-side MOSFET, even when it needs to operate above the load voltage.
3. Bootstrap Capacitor: A capacitor is connected between the VB and VS terminals which charges when the low-side switch is on. It allows the driver to generate sufficient gate voltage for the high-side switch.

Typical Application Circuit

Here’s an example of connecting the IR2112 to control a half-bridge configuration with two N-channel MOSFETs:

Copy             +---------------------+
             |                     |
         V_B |                   D |
             |   +-------+ +---+  |
             +---| VB   HO| HS |  |
            +    +-------+ +---+  |
    +-------+    |          GND   |
    |    Load+---| LO       COM   |
    |       |    +-------+ +---+  |
   +|       |            |       +|
   |         |     MOSFET3   MOSFET4 |
   +---------+---------------+

Basic Operation

1. To turn on the low-side MOSFET (MOSFET3), the internal circuit sets the LO high and HO low.
2. To turn on the high-side MOSFET (MOSFET4), the HO output is driven high, and the bootstrap capacitor provides the necessary high-level voltage.
3. The driver allows for seamless switching between MOSFETs, making it ideal for inverter applications and driving synchronous rectifier circuits.

Protection Features

• Under-Voltage Lockout: Prevents operation when supply voltages are below a set threshold.
• Short Circuit Protection: Provides circuit protection during over-load conditions.
• Thermal Shutdown: Protects against overheating by shutting down the driver under excessive temperatures.

Considerations

1. Gate Resistor: A gate resistor (typically around 10-100 ohms) should be used to control the switching speed and limit the gate current.
2. Bootstrap Capacitor: Choose an appropriate capacitor size based on the load and the frequency of operation. Typically, values around 0.1 µF to 1 µF are used.
3. High and Low-Side Switching: The IR2112 can create an H-Bridge configuration by using four devices with the IR2112 controlling two switches at any one time, allowing control of AC loads.