High-Efficiency, 36V, Dual Synchronous Buck Converters (3.5A/2A) for Automotive Applications

The MAX20457 offers two automotive-grade synchronous buck converters with fixed frequency of either 2.1MHz or 400kHz. The two high-voltage synchronous step-down converters operate 180 degrees out of phase. The IC operates with an input voltage supply from 3.5V to 36V and can operate in dropout conditions by running at 95% duty cycle. It is intended for applications with mid- to high-power requirements that operate at a wide input voltage range such as during automotive cold-crank or engine stop-start conditions.

High switching frequency up to 2.1MHz allows small external components, reduced output ripple, and guarantees no AM band interference. The switching frequency is fixed at 400kHz or 2.1MHz. FSYNC input programmability enables three modes for optimized performance: forced fixed-frequency operation, skip mode with ultra-low quiescent current, and phase-locked synchronization to an external clock. The spread spectrum option minimizes EMI interference.

The IC features power-OK indicators and undervoltage lockout for the buck converters. Protection features include cycle-by-cycle current limit and thermal shutdown. The MAX20457 is specified for operation over the -40°C to +125°C automotive temperature range.

Applications

* Automotive Start-Stop System * Instrument Cluster * Navigation and Radio Head Units * Telematics Applications

* Meets Stringent OEM Module Power Consumption and Performance Specifications

* 10µA Supply Current with 5V Buck On

* 8µA Supply Current with 3.3V Buck On

* 10µA Supply Current with Both Bucks On

* Enables Crank-Ready Designs

* Wide Input Supply Range from 3.5V to 36V

* EMI Reduction Features Reduce Interference with Sensitive Radio Bands without Sacrificing Wide Input-Voltage Range

* 20ns (typ) Minimum On-Time Guarantees Skip-Free Operation for 3.3V Output at 2.1MHz

* Spread-Spectrum Option

* Phase-Locked Loop (PLL) Frequency Synchronization

* Integration and Thermally Enhanced Packages Save Board Space and Cost

* Two 2.1MHz Current-Mode Converters with Forced Fixed Frequency and Skip Modes

* Thermally Enhanced 5mm x 5mm, 28-Pin TQFN-EP Package

* Protection Features Improve System Reliability

* Supply Undervoltage Lockout

* Overtemperature and Short-Circuit Protection