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The ISL6237 dual step-down, switch-mode power-supply (SMPS) controller generates logic-supply voltages in battery-powered systems. The ISL6237 includes two pulse-width modulation (PWM) controllers, 5V/3.3V and 1.5V/1.05V. The output of SMPS1 can also be adjusted from 0.7V to 5.5V. The SMPS2 output can be adjusted from 0.5V to 2.5V by setting REFIN2 voltage. This device features a linear regulator providing 3.3V/5V, or adjustable from 0.7V to 4.5V output via LDOREFIN. The linear regulator provides up to 100mA output current with automatic linear-regulator bootstrapping to the BYP input. When in switchover, the LDO output can source up to 200mA. The ISL6237 includes on-board power-up sequencing, power-good (POK_) outputs, digital soft-start, and internal soft-stop output discharge that prevents negative voltages on shutdown.

Constant on-time PWM control scheme operates without sense resistors and provides 100ns response to load transients while maintaining a relatively constant switching frequency. The unique ultrasonic pulse-skipping mode maintains the switching frequency above 25kHz, which eliminates noise in audio applications. Other features include pulse skipping, which maximizes efficiency in light-load applications, and fixed-frequency PWM mode, which reduces RF interference in sensitive applications.

Key Features

• Wide Input Voltage Range 5.5V to 25V
• Dual Fixed 1.05V/3.3V and 1.5V/5.0V Outputs or Adjustable 0.7V to 5.5V (SMPS1) and 0.5V to 2.5V (SMPS2), ±1.5% Accuracy
• 1.7ms Digital Soft-Start and Independent Shutdown
• Fixed 3.3V/5.0V, or Adjustable Output 0.7V to 4.5V, ±1.5% (LDO): 200mA
• 2.0V Reference Voltage
• Constant ON-TIME Control with 100ns Load-Step Response
• Selectable Switching Frequency
• rDS(ON) Current Sensing
• Programmable Current Limit with Foldback Capability
• Selectable PWM, Skip or Ultrasonic Mode
• BOOT Voltage Monitor with Automatic Refresh
• Independent POK1 and POK2 Comparators
• Soft-Start with Pre-Biased Output and Soft-Stop
• Independent ENABLE
• High Efficiency - Up to 97%
• Very High Light Load Efficiency (Skip Mode)
• 5mW Quiescent Power Dissipation
• Thermal Shutdown
• Extremely Low Components Count
• Pb-Free (RoHS Compliant)

Applications

• Notebook and Sub-Notebook Computers
• PDAs and Mobile Communication Devices
• 3-Cell and 4-Cell Li+ Battery-Powered Devices
• DDR1, DDR2, and DDR3 Power Supplies
• Graphic Cards
• Game Consoles
• Telecommunication