ISL88550A Synchronous Step Down Controller with Sourcing and Sinking LDO Regulator

VIN (min) (V)	2
VIN (max) (V)	25
VOUT (min) (V)	0.7
VOUT (max) (V)	3.5
IOUT (max) (A)	15

ISL88550A integrates a synchronous buck PWM controller to generate VDDQ, a sourcing and sinking LDO linear regulator to generate VTT, and a 10mA reference output buffer to generate VTTR. The buck controller drives two external N-Channel MOSFETs to generate output voltages down to 0.7V from a 2V to 25V input with output currents up to 15A. The LDO can source up to 2.5A and sink up to -2.0A continuously. Both the LDO output and the 10mA reference buffer output can be made to track the REFIN voltage via a built-in resistive divider. These features make the ISL88550A ideally suited for DDR memory applications in desktops, notebooks and graphics cards.

The PWM controller in the ISL88550A uses constant-on-time PWM architecture with a programmable switching frequency of up to 600kHz. This control scheme handles wide input/output voltage ratios with ease and provides 100ns "instant-on" response to load transients while maintaining high efficiency and a relatively constant switching frequency. The ISL88550A offers full programmable UVP/OVP and skip mode options ideal in portable applications. Skip mode allows for improved efficiency at lighter loads.

The VTT and VTTR outputs track to VREFIN/2. The high bandwidth of this LDO regulator allows excellent transient response without the need for bulk capacitors, thus reducing the cost and size.

The buck controller and LDO regulators are provided with independent current limits. Adjustable loss-less fold-back current limit for the buck regulator is achieved by monitoring the drain-to-source voltage drop of the low side synchronous MOSFET. Once overcurrent is removed, the regulator is allowed to enter soft-start again. This helps minimize power dissipation during short-circuit condition. Additionally, overvoltage and undervoltage protection mechanisms are built in. The ISL88550A allow flexible sequencing and standby power management using SHDNA#, and STBY# inputs.

ISL88550A 特点

Pb-Free (RoHS Compliant) Buck Controller
Constant-On PWM with 100ns Load-Step Response
Start-up with Pre-biased Output Voltage
Up to 95% Efficiency
2V to 25V Input Voltage Range
2.5V Fixed or 0.7V to 3.5V Adjustable Output
200kHz/300kHz/450kHz/600kHz Switching Frequencies
Programmable Current Limit with Foldback Capability
1.7ms Digital Soft-Start and Independent Shutdown
Overvoltage/Undervoltage Protection Option
Power-Good Window Comparator LDO Section
Fully Integrated VTT and VTTR Capability
VTT has +2.5A/-2.0A Sourcing/Sinking Capability
Start-Up with Pre-Biased Output Voltage
VTT and VTTR Outputs Track VREFIN/2
VTT and VTTR 1% of VREFIN/2
Low All-Ceramic Output Capacitor Designs
1.0V to 2.8V Input REFIN Range
Analog Soft-Start Option and Independent Shutdown
Power-Good Window Comparator

ISL88550A 应用

DDR, DDR II and DDR III Memory Power Supplies
Desktop Computers
Notebooks and Desknotes
Graphics Cards
Game Consoles
Networking and RAID

ISL88550A 芯片订购指南

芯片型号	产品状态	温度范围	封装尺寸图	潮湿敏感度等级MSL	美元价格US $
ISL88550AEVAL1Z	量产		评估板	N/A	价格录入中
ISL88550AIRZ	量产	工业级	28 Ld TQFN	2	2.86
ISL88550AIRZ-T	量产	工业级	28 Ld TQFN T+R	2	2.86
ISL88550AEVAL1	停产		评估板	N/A	N/A