Summary of Regulator generates bus termination for DDR3
The LTC3617 is a high-efficiency synchronous buck regulator designed for DDR termination in DDR, DDR2, and DDR3 memory applications. It supports input voltages from 2.25V to 5.5V and delivers ±6A output current at low voltages down to 0.5V. Key features include programmable switching frequencies up to 4MHz, internal soft-start, power good status, and thermally enhanced packaging. The device integrates buffer amplifiers for VTTR generation and offers forced continuous mode to minimize noise and RF interference.
Parts used in the LTC3617 Project:
- LTC3617 Synchronous Buck Regulator
- Surface Mount Inductors
- External Clock Source (for synchronization)
- Output Capacitors
- Internal Resistor Divider
- Internal Amplifier
- Top Power Switch (35mohm RDS(ON))
- Bottom Power Switch (25mohm RDS(ON))
- 24-Pin 3mm × 5mm QFN Package
Description
The LTC3617 is a high efficiency monolithic synchronous buck regulator utilizing a current mode, constant frequency architecture. It operates from an input voltage range of 2.25V to 5.5V and provides a regulated output voltage equal to 0.5 • VDDQIN while sourcing and sinking up to 6A of load current. An internal amplifier provides a VTTR output voltage equal to 0.5 • VDDQIN with an output current capability of ±10mA.
The operating frequency is externally programmable up to 4MHz, allowing the use of small surface mount inductors. For switching-noise-sensitive applications, the LTC3617 can be synchronized to an external clock up to 4MHz.
Forced continuous mode operation in the LTC3617 reduces noise and RF interference. Adjustable external compensation allows the transient response to be optimized over a wide range of loads and output capacitors.
Applications
- DDR Termination
- Supports DDR, DDR2 and DDR3 Standards
- Tracking Supplies
Features
- ±6A Output Current
- 2.25V to 5.5V Input Voltage Range
- ±10mV Output Voltage Accuracy
- Optimized for Low Output Voltages Down to 0.5V
- High Efficiency
- Integrated Buffer for VTTR = VDDQIN • 0.5
- Shutdown Current: <1µA
- Adjustable Switching Frequency: Up to 4MHz
- Optional Internal Compensation
- Internal Soft-Start
- Power Good Status Output
- Input Overvoltage Protected
- Thermally Enhanced 24-Pin 3mm × 5mm QFN Package
Linear Technology has introduced a synchronous step-down switching regulator, capable of generating a bus termination voltage for DDR/DDR2/DDR3 and future standard memory applications requiring sourcing and sinking of current.
An internal resistor divider sets the VTT DDR termination supply and VTTR reference voltages equal to half the voltage applied to the input, with output current capability of ±6A (sinking/sourcing) at VTT and ±10mA at VTTR.
The outputs are capable of operation down to 0.5V.
The device operates from an input voltage range of 2.25V to 5.5V and allows switching frequencies as high as 4MHz, allowing for very small externals.
The internal synchronous top and bottom power switches have an RDS(ON) of only 35mohm and 25mohm respectively, enabling the LTC3617 to attain efficiencies as high as 93%.
This can eliminate the need for an external catch diode, said the supplier.
For more read: Regulator generates bus termination for DDR3
- What voltage range does the LTC3617 operate from?
The device operates from an input voltage range of 2.25V to 5.5V. - How much load current can the LTC3617 source and sink?
It sources and sinks up to 6A of load current. - Can the operating frequency be adjusted externally?
Yes, the operating frequency is externally programmable up to 4MHz. - Does the LTC3617 support DDR memory standards?
Yes, it supports DDR, DDR2, and DDR3 standards. - What is the maximum efficiency of this regulator?
The LTC3617 can attain efficiencies as high as 93%. - Is external compensation required for this project?
No, it features optional internal compensation. - How small can the output voltage go?
The outputs are capable of operation down to 0.5V. - What package type is used for the LTC3617?
It uses a thermally enhanced 24-pin 3mm × 5mm QFN package.
