28 V, 12 A, Low Iq, High Current
Synchronous Buck Converter
with +/- 1 A LDO and Buffered Reference
The NB685A provides a complete power supply
with the highest power density for DDR3,
DDR3L, LPDDR3, and DDR4 memory. It
integrates a high-frequency, synchronous,
rectified, step-down, switch-mode converter
(VDDQ) with a 1 A sink/source LDO (VTT) and
buffered low noise reference (VTTREF).
The NB685A operates at high efficiency over a
wide output current load range based on MPS
proprietary switching loss reduction technology
and internal low Ron power MOSFETs.
Adaptive constant-on-time (COT) control mode
provides fast transient response and eases loop
stabilization. The DC auto-tune loop provides
good load and line regulation.
The VTT LDO provides 1 A sink/source current
capability and requires only a 22 μF ceramic
capacitor. The VTTREF tracks VDDQ/2 with
excellent 1% accuracy.
Full protection features include OC limit, OVP,
UVP, over-temperature warning (OTW), and
The converter requires a minimum number of
external components and is available in a QFN
3mm x 3mm package.
Wide 4.5 V to 28 V Operating Input Range
Compatible for IMVP8
135 μA Low Quiescent Current
12 A Continous Output Current
13 A Peak Output Current
Selectable Ultrasonic Mode
Selectable 500 k/700 k Switching
Built-in +/- 1 A VTTLDO
1% Buffered VTTREF Output
Adaptive COT for Fast Transient
DC Auto-Tune Loop
Stable with POSCAP and Ceramic Output
Internal Soft Start
OCL, OVP, UVP, and Thermal Shutdown
Latch-Off Reset via EN or Power Cycle
QFN 3mm x 3mm Package
Distributed Power Systems
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registered trademarks of Monolithic Power Systems, Inc.
4.5 V-24 V
VIN OTW BST SW
22 μF x 1
EN 2 NB685A
(Needs external 3.3 V
1.35 V/10 A
22 μF x 3
0.675 V/1 A
NB685A Rev. 1.02
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