Product category:
Power Supply ICs and Controllers
News Release from: Intersil | Subject: ISL88550A
Edited by the Electronicstalk Editorial
Team on 21 November 2005
Power controller handles DDR memory
needs
A new synchronous step-down controller uses a constant-on-time PWM architecture with a programmable switching frequency of up to 600kHz.
Intersil has introduced a synchronous step-down controller that uses a constant-on-time PWM (pulsewidth modulation) architecture with a programmable switching frequency of up to 600kHz This control feature handles wide input/output voltage ratios with ease and provides 100ns "instant-on" response to load transients while maintaining high efficiency and a constant switching frequency, making it ideal for DDR memory applications in desktops, notebooks and graphics cards
This article was originally published on Electronicstalk on 8 Jan 2001 at 8.00am (UK)
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With up to 95% efficiency, Intersil's ISL88550A integrates a synchronous buck PWM controller, a sourcing and sinking LDO (low dropout) regulator, and a 10mA reference output buffer.
The PWM controller generates VDDQ (voltage for double datarate memory), the LDO regulator generates VTT (termination voltage supply) and the reference output buffer generates VTTR (termination voltage reference).
With the combined features, the ISL88550A provides a complete solution for DDR (double datarate) I and II memory power supplies.
It can also be used for other applications that require voltages down to 0.7V.
The ISL88550A drives two external N-channel MOSFETs to generate output voltages down to 0.7V from a 2 to 25V input with output currents up to 20A.
The LDO can sink or source up to 2.5A.
Both the LDO output and the 10mA reference buffer output can be designed to track the REFIN voltage through a built-in resistive divider.
The device also offers fully programmable UVP/OVP and skip mode options that are well suited to portable applications.
Skip mode allows for improved efficiency at lighter loads.
The VTT and VTTR outputs of the ISL88550A track within 1% of VREFIN/2.
The high bandwidth of this LDO regulator allows excellent transient response without the need for bulky capacitors, thereby reducing overall system cost and size.
Key features of the ISL8850A include constant-on-time PWM with 100ns load-step response, startup with prebiased output voltage, 1.8/2.5V fixed or 0.7 to 3.5V adjustable output, 200/300/450/600kHz switching frequencies, and programmable current limit with foldback capability.
Target applications for the device include DDR I and DDR II memory power supplies, desktop computers, notebooks (including ultraportable and web tablets), graphics cards, and game consoles.
The ISL88550A is available now in a 28-pin (5 x 5mm) thin QFN package.
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