PB-FREE DUAL SWITCHER W/DRR OPTION, 30V

The ISL6227 dual PWM controller delivers high efficiencyprecision voltage regulation from two synchronous buck DC/DCconverters. It was designed especially to provide powerregulation for DDR memory, chipsets, graphics and othersystem electronics in Notebook PCs. The ISL6227’s wideinput voltage range capability allows for voltage conversiondirectly from AC/DC adaptor or Li-Ion battery pack.Automatic mode transition of constant-frequency synchronousrectification at heavy load, and hysteretic (HYS)diode-emulation at light load, assure high efficiency over a widerange of conditions. The HYS mode of operation can bedisabled separately on each PWM converter ifconstant-frequency continuous-conduction operation is desiredfor all load levels. Efficiency is further enhanced by using thelower MOSFET rDS(ON) as the current sense element.Voltage-feed-forward ramp modulation, current modecontrol, and internal feedback compensation provide fastresponse to input voltage and load transients. Input currentripple is minimized by channel-to-channel PWM phase shiftof 0°, 90° or 180° (determined by input voltage and status ofthe DDR pin). The ISL6227 can control two independent output voltagesadjustable from 0.9V to 5.5V, or by activating the DDR pin,transform into a complete DDR memory power supplysolution. In DDR mode, CH2 output voltage VTT tracks CH1output voltage VDDQ. CH2 output can both source and sinkcurrent, an essential power supply feature for DDR memory.The reference voltage VREF required by DDR memory isgenerated as well. In dual power supply applications the ISL6227 monitors theoutput voltage of both CH1 and CH2. An independent PGOOD(power good) signal is asserted for each channel after thesoft-start sequence has completed, and the output voltage iswithin PGOOD window. In DDR mode CH1 generates the onlyPGOOD signal. Built-in overvoltage protection prevents the output from goingabove 115% of the set point by holding the lower MOSFET onand the upper MOSFET off. When the output voltage re-entersregulation, PGOOD will go HIGH and normal operationautomatically resumes. Once the soft-start sequence hascompleted, undervoltage protection latches the offendingchannel off if the output drops below 75% of its set point value.Adjustable overcurrent protection (OCP) monitors the voltage. drop across the rDS(ON) of the lower MOSFET. If more precisecurrent-sensing is required, an external current sense resistormay be used.

• Provides Regulated Output Voltage in the Range 0.9V to 5.5V
• Operates From an Input Battery Voltage Range of 5V to 28V or From 3.3V/5V System Rail
• Complete DDR1 and DDR2 Memory Power Solution with VTT Tracking VDDQ/2 and a VDDQ/2 Buffered Reference Output
• Flexible PWM or HYS Plus PWM Mode Selection with HYS Diode Emulation at Light Loads for Higher System Efficiency
• rDS(ON) Current Sensing
• Excellent Dynamic Response With Voltage Feed-Forward and Current Mode Control Accommodating Wide Range LC Filter Selections
• Undervoltage Lock-Out on VCC Pin
• Power-Good, Overcurrent, Overvoltage, Undervoltage Protection for Both Channels
• Synchronized 300kHz PWM Operation in PWM Mode
• Pb-Free Available (RoHS compliant)