Features
•Synchronous Buck Controller (VDDQ)
„ Ultra-High Efficiency
„ No Current-Sense Resistor (Lossless ILIMIT)
„ Quasi-PWM with 100ns Load-Step Response
„ 1.8V(DDRII) /1.5V(DDRIII) Fixed or 0.75V to 3.6V
Adjustable Output Range
„ 2V to 28V Battery Input Range
„ Programmable Switching Frequency
„ OVP & UVP of VDDQ Output
„ Drives Large Synchronous-Rectifier FETs
„ Power-Good Indicator
•2-A LDO (VTT), Buffered Reference (VTTREF)
„ Support DDR (1.25 VTT) , DDR II (0.9 VTT) and
DDRIII(0.75 VTT) Requirements
„ VLDOIN Voltage Range: 1.2V to 3.6V
„ Requires Only 20µF Ceramic VTT Output Capacitance
„ Supports High-Z in S3 and Soft-Off in S5
„ Integrated Divider Tracks 1/2 VDDQSNS for
Both VTT and VTTREF
„ Remote Sensing (VTTSNS)
„ ±20mV Accuracy for VTT and VTTREF
„ 10mA Buffered Reference (VTTREF)
„ Built-In Soft-Start to Reduce the VLDOIN Surging Current
„ Over Current Protection of VTT Output
„ Thermal Shutdown Protection

Applications
„ Notebook Computers
„ CPU Core Supply
„ Chipset/RAM Supply as Low as 0.75V
„ 1.8V and 2.5V I/O Supply

General Description
The G5616A is intended for DDR/SSTL-2,
DDRII/SSTL-18 and DDRIII memory systems. It integrates a synchronous buck PWM controller with a 2A
sink-source linear regulator and buffered reference.
The PWM controller uses constant on-time control
scheme to handle wide input/output voltage ratios with
ease and provides 100ns “instant-on” response to
load transients while maintaining a relatively constant
switching frequency. The G5616A achieves high efficiency at a reduced cost by eliminating the current-sense resistor found in traditional current-mode
PWMs. Efficiency is further enhanced by an ability to
drive very large synchronous rectifier MOSFETs. Single-stage buck conversion allows these devices to
directly step down high-voltage batteries for the highest possible efficiency.
The 2A sink/source tracking termination regulator is
specifically designed for low-cost/ low-external component count systems. The regulator contains a high
speed operational amplifier that provides fast load
transient response with only 20µF (2x10µF) of ceramic
output capacitance. The G5616A supports remote
sensing functions and all features required to power
the DDR /DDRII /DDRIII VTT bus termination according to the JEDEC specification. In addition, the
G5616A includes integrated sleep-state controls placing VTT in High-Z in S3 (suspend to RAM) and soft-off
for VTT and VTTREF in S5 (Shutdown).
The G5616A provides OVP, UVP, over current and
thermal shutdown protection functions and is available
in a 20-pin 3X3 TQFN package and 24-pin 4X4 TQFN
includes over voltage protection.