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DDR bus termination regulator
Providing well-regulated power for memory bus termination circuits, the single-chip NE57810, NE57811 and NE57814 DDR regulators have a very fast linear design, eliminating the need for external inductors or power FETs. Also, lower load and line decoupling capacitances are required, improving performance over alternative switching or linear regulator designs.
Dramatically reducing component count, board space and overall system cost, these advanced devices also decrease design complexity compared to previous solutions. Handling current up to ±3.5 A, they are compatible with today's 2.5 V memories and also support next generation 1.8 V systems.
Key features
- Fast transient response time
- DDR-I and DDR-II operation
- Thermally robust packaging
- Over-current and Over-temperature protection
- Automatically generates half supply voltage for termination power
- External reference out
- Enhanced efficiency mode for notebooks (NE57814)
- External Reference in (NE57810, NE57814)
- Reduced power mode (NE57811) and very low power standby mode (NE57814)
Key applications
- Desktop computers
- Servers and workstations
- Laptop computers
- Networking routers and switches
- Game machines
- Set-top boxes
- Digital VCRs and PVRs
- Computer graphics display adaptors
- Embedded systems
Information resources
NE57810/NE57811/NE57814 Advanced DDR Bus Termination Regulator leaflet
Simplified system diagrams
Product overview
The NE5781x family is designed to provide power for termination of a Double Date Rate (DDR) SDRAM memory bus. The NXP devices significantly reduce parts count, board space, layout complexity and overall system cost as well as offering improved reliability when compared to competing solutions.
The NE5781x DDR termination regulators maintain an output voltage (DDR reference bus voltage) that is one-half that of the DDR SDRAM supply voltage. It is capable of providing up to ±3.5A for sustained periods. Over-current limiting protects the NE5781x devices from inrush currents at startup, and over-temperature shutdown protects the devices in extreme temperature situations. The NE57810 and NE57814 have an external reference input that (optionally) serves two functions. First, it can be used to trim the output voltage (VTT) for improved memory noise immunity in certain special circumstances. Secondly, it can be used to set VTT to the required output voltage (usually 1.25V) when the input voltage (VDD) is other than the memory supply voltage source. This feature is useful for powering the NE57810 or NE57814 from 3.3V from the computer power supply. The NE5781x family all support DDR-I (2.5V) DDR SDRAM systems as well as DDR-II (1.8V) systems.
All the NE5781x family parts supply an output voltage reference for use by other memory components in establishing 1/0 threshold levels.
The NE57811 and NE57814 also offer reduced power modes. The NE57814 can be set into a very low current (800 µA) 'standby' mode by use of the STANDBY input. This makes the device very attractive for notebook computer applications where low power standby is critical. The NE57811 has a lower-power mode. Activated by the SHUTDOWN signal, it tri-states the final output section and reduces quiescent current by about 25%.
The NE57814 has another feature that is extremely desirable for notebook computer applications - 'enhanced efficiency' mode. This mode is enabled by powering the final output section of the device at lower voltage than the memory supply voltage, essentially using the device as a Low Dropout Regulator (LDO). The final output section supply (VD) may be as low as 0.25V higher than the desired output voltage (VTT). Lower voltage drop across the high transistor in the output stage results in lower power consumption overall and less power dissipation in the device.
All members of the NE5781x family have been designed with the goal of reducing the overall number of external components needed in the system solution. The result is lower system cost, reduced board space and reduced layout complexity. Compared to switching regulator designs, the NE5781x family requires no external switching FETs, no external diodes, no external inductors, and substantially fewer input and output capacitors. Compared to other linear designs (discrete or integrated) the fast response of the NE5871x family greatly reduces the number of input and output capacitors required. The NE5781x family is stable with less than 100µF of output capacitance, 1/8 or less capacitance than competing solutions require.
The SPAK-5 (NE57810, NE57811) and HSO8 (NE57814) packages are thermally robust for flexibility of thermal design and high reliability. The SPAK-5 package has a thermal coefficient of about 17°C/W while the HSO8 package has a thermal coefficient of about 39°C/W. This permits the NXP devices to be used in normal applications with minimal attention to cooling as well as higher device reliability and longer device lifetime in the field. Note that competing linear solutions use packages with thermal coefficients as high as 130°C/W, requiring strict attention to cooling and substantially lowering reliability in the field.
All these benefits - lower parts count, reduced board space, reduced complexity, reduced system cost, useful operating modes, and thermal robustness - make the NE57810, NE57811, and NE57814 the industry's best values for DDR SDRAM termination power.