The MAX1718 step-down controller is intended for core
CPU DC-DC converters in notebook computers. It features
a dynamically adjustable output, ultra-fast transient
response, high DC accuracy, and high efficiency needed
for leading-edge CPU core power supplies. Maxim's
proprietary Quick-PWM™ quick-response, constant-on-time
PWM control scheme handles wide input/output
voltage ratios with ease and provides 100ns "instant-on"
response to load transients while maintaining a relatively
constant switching frequency.
The output voltage can be dynamically adjusted through
the 5-bit digital-to-analog converter (DAC) over a 0.6V to
1.75V range. The MAX1718 has an internal multiplexer
that accepts three unique 5-bit VID DAC codes corresponding
to Performance, Battery, and Suspend modes.
Precision slew-rate control† provides "just-in-time" arrival
at the new DAC setting, minimizing surge currents to
and from the battery.
The internal DAC of the MAX1718B is synchronized to
the slew-rate clock for improved operation under
aggressive power management of newer chipsets and
operating systems that can make incomplete mode transitions.
A pair of complementary offset control inputs allows
easy compensation for IR drops in PC board traces or
creation of a voltage-positioned power supply. Voltage-positioning
modifies the load-transient response to
reduce output capacitor requirements and total system
power dissipation.
Single-stage buck conversion allows these devices to
directly step down high-voltage batteries for the highest
possible efficiency. Alternatively, two-stage conversion
(stepping down the 5V system supply instead of the battery)
at a higher switching frequency allows the minimum
possible physical size.
The MAX1718 is available in a 28-pin QSOP package.
Key Features
Applications/Uses
Quick-PWM Architecture
±1% VOUT Accuracy Over Line and Load
5-Bit On-Board DAC with Input Muxes
Precision-Adjustable VOUT Slew Control
0.6V to 1.75V Output Adjust Range
Precision Offset Control
Supports Voltage-Positioned Applications
2V to 28V Battery Input Range
Requires a Separate 5V Bias Supply
200/300/550/1000kHz Switching Frequency
Over/Undervoltage Protection
Drives Large Synchronous-Rectifier FETs
700µA (typ) ICC Supply Current
2µA (typ) Shutdown Supply Current
2V ±1% Reference Output
VGATE Blanking During Transition
Small 28-Pin QSOP Package
2-Cell to 4-Cell Li+ Battery to CPU Core Supply Converters
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