The MAX17000 pulse-width modulation (PWM) con-
troller provides a complete power solution for notebook
DDR, DDR2, and DDR3 memory. It comprises a step-
down controller, a source-sink LDO regulator, and a ref-
erence buffer to generate the required VDDQ, VTT, and
VTTR rails.
The VDDQ rail is supplied by a step-down converter
using Maxim’s proprietary Quick-PWM? controller. The
high-efficiency, constant-on-time PWM controller han-
dles wide input/output voltage ratios (low duty-cycle
applications) with ease and provides 100ns response
to load transients while maintaining a relatively constant
switching frequency. The Quick-PWM architecture cir-
cumvents the poor load-transient timing problems of
fixed-frequency current-mode PWMs while also avoid-
ing the problems caused by widely varying switching
frequencies in conventional constant-on-time and con-
stant-off-time PWM schemes. The controller senses the
current to achieve an accurate valley current-limit pro-
tection. It is also built in with overvoltage, undervoltage,
and thermal protections. The MAX17000 can be set to
run in three different modes: power-efficient SKIP
mode, low-noise forced-PWM mode, and standby
mode to support memory in notebook computer stand-
by operation. The switching frequency is programma-
ble from 200kHz to 600kHz to allow small components
and high efficiency. The VDDQ output voltage can be
set to a preset 1.8V or 1.5V, or be adjusted from 1.0V to
2.5V by an external resistor-divider. This output has 1%
accuracy over line-and-load operating range.
The MAX17000 includes a ±2A source-sink LDO regu-
lator for the memory termination VTT rail. This VTT regu-
lator has a ±5mV deadband that either sources or
sinks, ideal for the fast-changing load burst present in
memory termination applications. This feature also
reduces output capacitance requirements.
The VTTR reference buffer sources and sinks ±3mA,
providing the reference voltage needed by the memory
controller and devices on the memory bus.
The MAX17000 is available in a 24-pin, 4mm x 4mm,
Thin QFN package.