1.8A Step-Down Converter Allows Applications Processors to Run at Maximum Clock Speed in Handheld Applications

(Product News, 6 Nov 2009)

Maxim Integrated Products introduces the MAX8649, a 1.8A, synchronous, fixed-frequency, DC-DC step-down converter in a tiny, 4mm2 wafer-level package (WLP). This device delivers extremely tight output-voltage accuracy by integrating a highly precise bandgap reference and by minimizing offset errors in the feedback circuit. Fully differential remote sense ensures precise regulation at the load by eliminating the resistive losses associated with PCB trace impedance. The MAX8649 achieves an initial accuracy of ±0.5% at 1.27V and a total accuracy of better than ±2% over load, line, and temperature. This superior accuracy allows applications processors to run at maximum clock speed, thus making the MAX8649 ideal for high-performance portable handsets. Additionally, this device operates from an input supply as low as 2.5V to support the latest generation of deep-discharge battery chemistries.

This highly flexible step-down converter features an I2C interface that allows programming of the output voltage between 750mV and 1.38V in 10mV steps. The MAX8649 can operate either in fixed-frequency (3.25MHz) PWM mode or in power-save mode. It can also be configured to operate from the internal oscillator, or it can be synchronized to an external system clock for simplifying EMI reduction.

In power-save mode, the MAX8649 employs a proprietary hysteretic PWM control scheme that reduces the effective switching frequency. The end result is a dramatic increase in light-load efficiency (80% at 10mA), as compared to that in fixed-frequency PWM mode (21% at 10mA).

To simplify programming, the MAX8649 provides two logic controls to facilitate selection between four predefined power-management states. For each state, the user can individually program the output voltage, mode of operation (PWM or power save), and external clock synchronization (on/off).

Other features include output overvoltage and overcurrent protection, thermal shutdown, soft-start, and an ultra-low, 1microamp (max) shutdown current. The MAX8649 is offered in a tiny, 2.0mm x 2.0mm x 0.65mm, 16-bump WLP, and is fully specified over the -40 degrees Celsius to +85 degrees Celsius extended temperature range.