MAX1718 General Description
The MAX1718 step-down controller is intended for core CPU DC-DC converters in notebook computers. It fea- tures a dynamically adjustable output, ultra-fast transient response, high DC accuracy, and high efficiency need- ed 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 corre- sponding 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 tran- sitions.
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 bat- tery) at a higher switching frequency allows the mini- mum possible physical size.
The MAX1718 is available in a 28-pin QSOP package.
MAX1718 Maximum Ratings
V+ to GND............................................................-0.3V to +30V
VCC, VDD to GND ..................................................-0.3V to +6V
D0D4, ZMODE, VGATE, OVP, SUS, to GND .........-0.3V to +6V
SKP/SDN to GND .................................................-0.3V to +16V
ILIM, CC, REF, POS, NEG, S1, S0,
TON, TIME to GND....................................-0.3V to (VCC + 0.3V)
DL to GND................................................-0.3V to (VDD + 0.3V)
BST to GND..........................................................-0.3V to +36V
DH to LX ..................................................-0.3V to (BST + 0.3V)
LX to BST...............................................................-6V to +0.3V
REF Short Circuit to GND.........................................Continuous
Continuous Power Dissipation
28-Pin QSOP (derate 10.8mW/°C above +70°C)........860mW
Operating Temperature Range ....................-40°C to +85°C
Junction Temperature..................................................+150°C
Storage Temperature..................................-65°C to +150°C
Lead Temperature (soldering, 10s) ...........................+300°C
MAX1718 Features
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
MAX1718 Typical Application
IMVP-II™ Notebook Computers
2-Cell to 4-Cell Li+ Battery to CPU Core Supply
Converters
5V to CPU Core Supply Converters
MAX1718 Connection Diagram
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