Product category: Power Supply ICs and Controllers
News Release from: Intersil | Subject: ISL6227
Edited by the Electronicstalk Editorial Team on 20 April 2004
PWM chip provides
flexible notebook power control
The ISL6227 is a dual PWM controller IC designed to power DDR memory, graphics, chipsets and other systems in notebook PCs
Its wide input voltage range capability allows for voltage conversion directly from an AC/DC adapter, from the Li-ion battery pack or from system 5 or 3.3V 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 article was originally published on Electronicstalk on 20 April 2004 at 8.00am (UK)
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"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 convertor if constant-frequency continuous-conduction operation is desired for all load levels.
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Efficiency is further enhanced by using the lower mosfet's on-resistance 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 minimised through the use of a channel-to-channel PWM phase shift of 0, 90 or 180 degrees and is determined by the input voltage and the status of the DDR pin.
The ISL6227 can control two independent output voltages adjustable from 0.9 to 5.5V.
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 signal is asserted for each channel after the soft-start sequence has completed and the output voltage is within the power-good window.
In the DDR mode, CH1 generates the only power-good signal.
Built-in overvoltage protection prevents the output from going above 115% of the set point by holding the lower mosfet on and the upper mosfet off.
When the output voltage re-enters regulation, power-good 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% of its set point value.
Adjustable overcurrent protection monitors the voltage drop across the on-resistance of the lower mosfet.
If more precise current sensing is required, an external current sense resistor can be used.
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