Power Electronics

Buck Controller Reduces Output Cap Requirements

Intersil‘s family of four-phase synchronous PWM buck controllers, the ISL6312, ISL6312A and ISL6322, provide a complete, integrated precision voltage regulation system for Intel VR10/11(Intel Core 2 Duo and Intel Core 2 Extreme) and AMD AM2 5/6-bit microprocessors. This family features programmable VID (voltage identification) codes for Intel and AMD DAC tables.

These devices use Intersil’s proprietary active pulse positioning (APP) and adaptive phase alignment (APA) modulation schemes to achieve fast transient response with few output capacitors over competitive designs. APP and APA are pulse-width and positioning modulation techniques that speed up load-transient response and reduce the need for external bulk output capacitors required to supply stored energy to the CPU (central processing unit) during abrupt changes in line voltage and load current.

All three devices incorporate a unity gain differential amplifier for remote voltage sensing that compensates for differences between remote and local grounds. The ISL6312/12A/22 also integrate three MOSFET drivers and a PWM output for a fourth external MOSFET driver.

The ISL6312, ISL6312A and ISL6322 provide advanced control loop features to optimize transient response to load-apply and removal functions. These include highly accurate and fully differential continuous dc-resistance (DCR) current sensing for load line programming and channel current balance. These features also ensure individual channel current and average overcurrent protection (OCP). These devices incorporate key features developed by Intersil specifically for these applications, including active pulse positioning modulation, enabling rapid initial response to high di/dt load transients. The ISL6312/12A/22 also include adaptive phase alignment that enables the fastest possible load transient response with capacitor elimination when there is a severe load turn-on.

The ISL6312A incorporates an added IOUT pin to the basic ISL6312 architecture for output current measurement. The ISL6322 provides an I2C bus input for adjusting four basic regulator functions, such as the output voltage, overvoltage protection (OVP) level, operating frequency per phase, and MOSFET driver adaptive dead time control. This family also features overvoltage, undervoltage, and overcurrent protection. Additionally, the ISL6312/12A/22 include open circuit protection on the remote sensing inputs.

The ISL6312, ISL6312A, and ISL6322 are available now in 48-lead, 7-mm x 7-mm QFN packages. Pricing begins at $6.67 each and ranges to $7.42 each in 1000-piece quantities.

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