19-1758; Rev 0; 8/00
High-Speed, Adjustable, Synchronous Step-Down
Controllers with Integrated Voltage Positioning
General Description
Features
The MAX1716/MAX1854/MAX1855 step-down con-
trollers are intended for core CPU DC-DC converters in
notebook computers. They feature a dynamically
adjustable output (5-bit DAC), 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 relative-
ly constant switching frequency.
o High-Efficiency Voltage Positioning
o Quick-PWM Architecture
o ±±1 V
Line-Regulation Accuracy
OUT
o Adjustable Output Range (5-Bit DAC)
MAX±7±6: 0.925V to ±.6V
MAX±854: 0.925V to 2.0V
MAX±855: 0.600V to ±.75V
o 2V to 28V Input Range
o 200/300/400/550kHz Switching Frequency
o Output Undervoltage Protection
The MAX1716/MAX1854/MAX1855 are designed
specifically for CPU core applications requiring a volt-
age-positioned supply. The voltage-positioning input
(VPS), combined with a high DC accuracy control loop,
is used to implement a power supply that modifies its
output set point in response to the load current. This
arrangement decreases full-load power dissipation and
reduces the required number of output capacitors.
o Overvoltage Protection (MAX±7±6/MAX±855)
o Drive Large Synchronous-Rectifier MOSFETs
o ±.7ms Digital Soft-Start
o 700µA I
Supply Current
CC
The 28V input range of the MAX1716/MAX1854/MAX1855
enables single-stage buck conversion from high-volt-
age batteries for the maximum possible efficiency.
Alternatively, the devices’ high-frequency capability
combined with two-stage conversion (stepping down
the +5V system supply instead of the battery) allows
the smallest possible physical size. The output voltage
can be dynamically adjusted through the 5-bit digital-
to-analog converter (DAC) inputs.
o ±µA Shutdown Supply Current
o 2V ±±1 Reference Output
o V
Transition-Complete Indicator
GATE
o Small 24-Pin QSOP Package
Typical Operating Circuit
The MAX1716/MAX1854/MAX1855 are available in a
24-pin QSOP package. For applications requiring
SpeedStep™ power control (see the MAX1717).
BATTERY
2V TO 28V
+5V INPUT
________________________Applications
V
V
DD
V+
CC
SHDN
ILIM
REF
Notebook Computers
BST
DH
Docking Stations
OUTPUT
CPU Core Supply
MAX1716
MAX1854
MAX1855
CC
LX
DL
Single-Stage (BATT to V
) Converters
CORE
SKIP
Two-Stage (+5V to V
) Converters
CORE
GND
TON
CS
VPS
Ordering Information
D0
D1
D2
D3
D4
PART
TEMP. RANGE
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
24 QSOP
PGND
DAC
INPUTS
MAX±7±6EEG
MAX±854EEG
MAX±855EEG
24 QSOP
FB
VGATE
24 QSOP
Quick-PWM is a trademark of Maxim Integrated Products.
SpeedStep is a trademark of Intel Corp.
Pin Configuration appears at end of data sheet.
________________________________________________________________ Maxim Integrated Products
±
For free samples and the latest literature, visit www.maxim-ic.com or phone 1-800-998-8800.
For small orders, phone 1-800-835-8769.