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Dual PWM controller converts directly from AC/DC adaptor, reduces real estate, BoM

Milpitas, CA, April 19, 2004 — Intersil Corporation announced the release of the ISL6227, a new dual PWM controller IC designed to power DDR memory, graphics, chip sets and other systems in notebook PCs. Its wide input voltage range capability allows for voltage conversion directly from an AC/DC adaptor, from the Li-ion battery pack or from system 5 V or 3.3 V buses. The ISL6227 is a pin-compatible performance upgrade for the ISL6225.

“The ISL6227 is an advanced and highly integrated dual PWM controller that reduces board space, bill-of-materials and manufacturing costs to meet notebook power needs as compared to most legacy solutions,” said Dean Henderson, Director of Intersil's Notebook Power Products. “This new controller delivers high performance for notebook system power requirements including the powering of DDR1 and DDR2 memory. It provides on-chip tracking, a buffered reference output and current sink and source capability for DDR memory termination.”

The ISL6227 dual PWM controller delivers highly efficient and precise voltage regulation. Automatic mode transition of constant-frequency synchronous rectification at heavy load, and hysteretic (HYS) diode-emulation at light load, assure high efficiency over a wide range of conditions. The HYS mode of operation can be disabled separately on each PWM converter if constant-frequency continuous-conduction operation is desired for all load levels. Efficiency is further enhanced by using the lower MOSFET's RDS(ON) as the current sense element.

Voltage feed-forward ramp modulation, current-mode control, and internal feedback compensation provide fast response to input voltage and load transients. Input current ripple is minimized through the use of a channel-to-channel PWM phase shift of 0, 90, or 180 degrees and is determined by theVin pin voltage and the status of the DDR pin.

The ISL6227 can control two independent output voltages adjustable from 0.9 V to 5.5 V. By activating the DDR pin, the ISL6227 is transformed into a complete DDR memory power supply solution. In DDR mode, the channel 2 (CH2) output voltage (VTT) tracks at half the channel 1 (CH1) output voltage (VDDQ). The CH2 output can both source and sink current, an essential power supply feature for DDR memory. The reference voltage (VREF) required by DDR memory is generated as well.

In dual power supply applications, the ISL6227 monitors the output voltage of both CH1 and CH2. An independent power good (PGOOD) signal is asserted for each channel after the soft-start sequence has completed and the output voltage is within the PGOOD window. In the DDR mode, CH1 generates the only PGOOD signal.

Built-in over-voltage protection prevents the output from going above 115 percent of the set point by holding the lower MOSFET on and the upper MOSFET off. When the output voltage re-enters regulation, PGOOD goes HIGH and normal operation automatically resumes. After the soft-start sequence has completed, undervoltage protection latches the offending channel off if the output drops below 75 percent of its set point value. Adjustable over-current protection monitors the voltage drop across the RDS(ON) of the lower MOSFET. If more precise current-sensing is required, an external current sense resistor can be used.

ISL6227 Technical Summary
– Provides two precise voltage outputs in the 0.9 to 5.5 V range
– Cost-saving high-performance solution for DDR memory, graphics, chip sets and system
– Accepts input from AC/DC adaptors/chargers, 5 to 24 V battery or from 3.3/5 V buses
– Complete DDR1 and DDR2 memory power solution
— VTT tracks VDDQ/2 without additional external tracking circuitry
— Buffered reference voltage output
— Current source and sink for VTT
– Synchronous-buck mode for heavy loads and hysteretic mode for light loads
— Hysteretic diode emulation mode can be disabled
– Choice of loss-less RDS(ON) current sensing or external current-sense resistor
– Excellent dynamic response with voltage feed-forward and current mode control accommodating wide range LC filter selections
– Power good indicator for each channel
– Over-voltage, under-voltage and over-current protection for each channel
– 28-lead SSOP package ” Pb-free version available
– Pin-compatible performance upgrade for the ISL6225

The ISL6227CA is available now. The suggested resale price for quantities of 100 to 999 units is $2.37 on tape and reel in the 28-lead SSOP package.

For more information about Intersil visit www.intersil.com.

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