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

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. Prices start at $1.60 (1000-up, FOB USA). Samples and evaluation kits are available upon request.